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Mseti JJ, Maasayi MS, Lugenge AG, Mpelepele AB, Kibondo UA, Tenywa FC, Odufuwa OG, Tambwe MM, Moore SJ. Temperature, mosquito feeding status and mosquito density influence the measured bio-efficacy of insecticide-treated nets in cone assays. Parasit Vectors 2024; 17:159. [PMID: 38549097 PMCID: PMC10979578 DOI: 10.1186/s13071-024-06210-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 02/22/2024] [Indexed: 04/01/2024] Open
Abstract
BACKGROUND The WHO cone bioassay is routinely used to evaluate the bioefficacy of insecticide-treated nets (ITNs) for product pre-qualification and confirmation of continued ITN performance during operational monitoring. Despite its standardized nature, variability is often observed between tests. We investigated the influence of temperature in the testing environment, mosquito feeding status and mosquito density on cone bioassay results. METHODS Cone bioassays were conducted on MAGNet (alphacypermethrin) and Veeralin (alphacypermethrin and piperonyl butoxide (PBO)) ITNs, using laboratory-reared pyrethroid-resistant Anopheles funestus sensu stricto (FUMOZ strain) mosquitoes. Three experiments were conducted using standard cone bioassays following WHO-recommended test parameters, with one variable changed in each bioassay: (i) environmental temperature during exposure: 22-23 °C, 26-27 °C, 29-30 °C and 32-33 °C; (ii) feeding regimen before exposure: sugar starved for 6 h, blood-fed or sugar-fed; and (iii) mosquito density per cone: 5, 10, 15 and 20 mosquitoes. For each test, 15 net samples per treatment arm were tested with four cones per sample (N = 60). Mortality after 24, 48 and 72 h post-exposure to ITNs was recorded. RESULTS There was a notable influence of temperature, feeding status and mosquito density on An. funestus mortality for both types of ITNs. Mortality at 24 h post-exposure was significantly higher at 32-33 °C than at 26-27 °C for both the MAGNet [19.33% vs 7%; odds ratio (OR): 3.96, 95% confidence interval (CI): 1.99-7.87, P < 0.001] and Veeralin (91% vs 47.33%; OR: 22.20, 95% CI: 11.45-43.05, P < 0.001) ITNs. Mosquito feeding status influenced the observed mortality. Relative to sugar-fed mosquitoes, The MAGNet ITNs induced higher mortality among blood-fed mosquitoes (7% vs 3%; OR: 2.23, 95% CI: 0.94-5.27, P = 0.068) and significantly higher mortality among starved mosquitoes (8% vs 3%, OR: 2.88, 95% CI: 1.25-6.63, P = 0.013); in comparison, the Veeralin ITNs showed significantly lower mortality among blood-fed mosquitoes (43% vs 57%; OR: 0.56, 95% CI: 0.38-0.81, P = 0.002) and no difference for starved mosquitoes (58% vs 57%; OR: 1.05, 95% CI: 0.72-1.51, P = 0.816). Mortality significantly increased with increasing mosquito density for both the MAGNet (e.g. 5 vs 10 mosquitoes: 7% vs 12%; OR: 1.81, 95% CI: 1.03-3.20, P = 0.040) and Veeralin (e.g. 5 vs 10 mosquitoes: 58% vs 71%; OR 2.06, 95% CI: 1.24-3.42, P = 0.005) ITNs. CONCLUSIONS The results of this study highlight that the testing parameters temperature, feeding status and mosquito density significantly influence the mortality measured in cone bioassays. Careful adherence to testing parameters outlined in WHO ITN testing guidelines will likely improve the repeatability of studies within and between product testing facilities.
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Affiliation(s)
- Jilly Jackson Mseti
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania.
- School of Life Sciences and Bioengineering, The Nelson Mandela African Institution of Science and Technology (NM-AIST), 447, Arusha, Tanzania.
| | - Masudi Suleiman Maasayi
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- School of Life Sciences and Bioengineering, The Nelson Mandela African Institution of Science and Technology (NM-AIST), 447, Arusha, Tanzania
| | - Aidi Galus Lugenge
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- School of Life Sciences and Bioengineering, The Nelson Mandela African Institution of Science and Technology (NM-AIST), 447, Arusha, Tanzania
| | - Ahmadi B Mpelepele
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
| | - Ummi Abdul Kibondo
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
| | - Frank Chelestino Tenywa
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- Vector Biology Unit, Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, 4123, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Olukayode G Odufuwa
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- Vector Biology Unit, Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, 4123, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
| | - Mgeni Mohamed Tambwe
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- Vector Biology Unit, Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, 4123, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Sarah Jane Moore
- Vector Control Product Testing Unit, Environmental Health and Ecological Science Department, Ifakara Health Institute, 74, Bagamoyo, Tanzania
- School of Life Sciences and Bioengineering, The Nelson Mandela African Institution of Science and Technology (NM-AIST), 447, Arusha, Tanzania
- Vector Biology Unit, Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, 4123, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
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Abel L, Kimachas E, Omollo E, Nalianya E, Chepkwony T, Kipkoech J, Amunga M, Wekesa A, Namae J, Kahindi S, Mangeni J, Lapp Z, Markwalter C, Taylor SM, Obala A, O'Meara WP. Relationship between malaria vector survival, infectivity and insecticide treated net use in western Kenya. Res Sq 2024:rs.3.rs-4090984. [PMID: 38562697 PMCID: PMC10984022 DOI: 10.21203/rs.3.rs-4090984/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Background Much effort and resources have been invested to control malaria transmission in Sub-Saharan Africa, but it remains a major public health problem. For the disease to be transmitted from one person to another, the female Anopheles vector must survive 10-14 days following an infective bite for the Plasmodiumgametocytes to develop into infectious sporozoites which can be transmitted to the next person during a bloodmeal. The goal of this investigation was to assess factors associated with wild-caught Anopheles survival and infection following host-seeking and indoor resting. Methods The study was conducted in a longitudinal cohort of 75 households in 5 villages including a total of 755 household members in Bungoma County, Kenya. Monthly adult mosquito collection was conducted by attenuated aspiration in all the enrolled households, and the mosquitoes were reared in the insectary for 7 days. The daily mortality rate was determined through day 7, and all the mosquitoes were morphologically identified. Female Anopheline mosquitoes were dissected, and species-level members of the Anopheles gambiae complex were resolved by molecular methods. The abdomen for all samples were processed for P. falciparum detection by PCR. Results Within a period of 25 months, the total number of culex and Anopheles mosquitoes collected indoors were 12,843 and 712 respectively. Anopheles gambiaeand Anopheles funestus were the major vectors though their population varied between different villages. 61.2% (n=436/712) of the Anopheles species survived up to day 7 with the lowest mortality rate recorded on day 5 of captivity. The survival rate also varied between the different Anophelesspecies. 683 of 712 mosquito abdomens were tested for P. falciparumdetection and 7.8% (53/683) tested positive for P. falciparum with An. funestus having a higher (10%) prevalence than An. gambaie s.s.(6.0%, p=0.095, Pearson Chi square test). The proportion of household members sleeping under a bednet the night before mosquito collection varied across time and village. An. funestus survival times were refractory to household ITN coverage and An. gambaie s.s. survival was reduced only under very high (>95%) ITN coverage. Conclusion Despite ITN coverage, mosquitoes still acquired bloodmeals and P. falciparum infections. Survival differed across species and was inversely correlated with high ITN exposure in the household, but not oocyst development.
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Odufuwa OG, Bradley J, Ngonyani S, Mpelepele AB, Matanila I, Muganga JB, Bosselmann R, Skovmand O, Mboma ZM, Moore SJ. Time of exposure and assessment influence the mortality induced by insecticides against metabolic resistant mosquitoes. Parasit Vectors 2024; 17:103. [PMID: 38431631 PMCID: PMC10908098 DOI: 10.1186/s13071-024-06190-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 02/09/2024] [Indexed: 03/05/2024] Open
Abstract
BACKGROUND Increasing metabolic resistance in malaria vector mosquitoes resulted in the development of insecticide-treated nets (ITNs) with active ingredients (AI) that target them. Bioassays that accurately measure the mortality induced by these AIs on ITNs are needed. Mosquito metabolic enzyme expression follows a circadian rhythm. Thus, this study assessed (i) influence of the time of day of mosquito exposure and (ii) timing of assessment of mortality post exposure (24 and 72 h) to ITNs against vectors that are susceptible to pyrethroids and those with metabolic and knockdown resistance mechanisms. METHODS Two cone bioassay experiments were conducted following World Health Organization (WHO) guidelines. Firstly, on ITNs incorporated with 2 g AI/kg of deltamethrin (DM) alone, or combined with 8 g AI/kg piperonyl butoxide (PBO) synergist, during the day (9:00-14:00 h) and repeated in the evening (18:00-20:00 h). This was followed by a confirmatory experiment during the afternoon (12:00-14:00 h) and repeated in the night (22:00-24:00 h) using mosquitoes unexposed or pre-exposed to PBO for 1 h before exposure to DM ITNs. Each net piece was tested with a minimum of eight cones per time (N = 24). The outcome was mortality after 24 h (M24) or 72 h (M72) of holding. RESULTS The cone bioassays performed using metabolic resistant mosquitoes during the evening showed significantly lower M24 than those performed in the day for DM: odds ratio (OR) 0.14 [95% confidence interval (CI) 0.06-0.30, p < 0.0001] and DM PBO [OR 0.29 (95% CI 0.18-0.49, p < 0.0001). M72 was higher than M24 for metabolic resistant mosquitoes exposed to DM [OR 1.44 (95% CI 1.09-1.88), p = 0.009] and DM PBO [OR 1.82 (95% CI 1.42-2.34), p < 0.0001]. An influence of hour of experiment and time of assessment was not observed for mosquitoes that had knockdown resistance or that were pyrethroid-susceptible. CONCLUSIONS Time of day of experiment and hour of assessment of delayed mortality after exposure of mosquitoes are important considerations in evaluating insecticides that interact with mosquito metabolism to counter metabolic resistant mosquitoes. This is important when evaluating field-aged ITNs that may have lower concentrations of AI.
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Affiliation(s)
- Olukayode G Odufuwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, Allschwill, 4123, Basel, Switzerland.
- Faculty of Science, University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK.
| | - John Bradley
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
| | - Safina Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Ahmadi Bakari Mpelepele
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Isaya Matanila
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Joseph B Muganga
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | | | | | - Zawadi Mageni Mboma
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), Tengeru, P.O. Box 447, Arusha, Tanzania
| | - Sarah Jane Moore
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, Allschwill, 4123, Basel, Switzerland
- Faculty of Science, University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), Tengeru, P.O. Box 447, Arusha, Tanzania
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Madgwick PG, Wubs M, Kanitz R. Optimization of long-lasting insecticidal bed nets for resistance management: a modelling study and user-friendly app. Malar J 2023; 22:290. [PMID: 37773062 PMCID: PMC10543869 DOI: 10.1186/s12936-023-04724-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 09/25/2023] [Indexed: 09/30/2023] Open
Abstract
BACKGROUND Up until the present, pyrethroid-treated bed nets have been a key tool for vector control in the fight against malaria. A global system that sets standards and facilitates procurement has successfully driven down the price of these bed nets to enable more of them to be distributed. As a result of their mass rollout, malaria cases have been significantly reduced, but pyrethroid resistance is now widespread. Going forward, new insecticides have been and continue to be developed for use on bed nets, but it is unclear how to best deploy them for maximum impact. METHODS Here, an app for the optimization of bed nets based on their insecticide loading concentration and deployment lifespan is presented. Underlying the app are simple models that incorporate the chemical and physical properties of bed nets, and the genetic and ecological properties of resistance evolution in mosquitoes. Where possible, default parameter values are fitted from experimental data. The app numerically searches across a massive number of these simple models with variable loading and lifespan to find their optima under different criteria that constrain the options for vector control. RESULTS The app is not intended to provide a definite answer about the best bed net design, but allows for the quantative exploration of trade-offs and constraints under different conditions. Here, results for the deployment of a new insecticide are explored under default parameter values across public health budgets for the purchase of bed nets. Optimization can lead to substantial gains in the average control of the mosquito population, and these gains are comparatively greater with lower budgets. Whilst optimizing a bed net within the constraints of the incentives of the existing system of standards and procurement leads to substantially greater control than not optimizing the bed net, optimizing the bed net without constraints leads to yet substantially greater control. The most important factor in this optimization is coverage, which depends on the price per bed net. With this in mind, it is unsurprising that the optimization for plausible budgets suggests that a pyrethroid would be the preferred partner for a new insecticide under current constraints because it is cost-effective in the balance of being less expensive than the new insecticide but also less effective due to pre-existing resistance. Surprisingly, a pyrethroid is shown to be an effective partner for a new insecticide in this model because of its contribution to resistance management in delaying the onset of resistance to the new insecticide. CONCLUSIONS This study highlights the importance of trade-offs in the design of bed nets for vector control. Further, it suggests that there are challenges in the roll-out of bed nets with new insecticides because of the constraints imposed by the global system of standards and procurement, which currently fails to adequately incentivize important considerations in bed net design like resistance management.
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Affiliation(s)
- Philip G Madgwick
- Syngenta, Jealott's Hill International Research Centre, Bracknell, RG42 6EY, UK.
| | - Matthias Wubs
- Syngenta Crop Protection, Rosentalstrasse 67, CH-4058, Basel, Switzerland
| | - Ricardo Kanitz
- Syngenta Crop Protection, Rosentalstrasse 67, CH-4058, Basel, Switzerland.
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Ampofo GD, Ahiakpa AK, Osarfo J. Interventions for malaria prevention in pregnancy; factors influencing uptake and their effect on pregnancy outcomes among post-natal women in a tertiary facility in the Volta Region of Ghana. SAGE Open Med 2023; 11:20503121231199653. [PMID: 37719169 PMCID: PMC10503280 DOI: 10.1177/20503121231199653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 08/21/2023] [Indexed: 09/19/2023] Open
Abstract
Objectives Malaria in pregnancy is associated with adverse pregnancy outcomes including maternal anaemia and low birthweight. Uptake of preventive interventions is sub-optimal in sub-Saharan Africa including Ghana. Understanding local-level factors that influence uptake of these interventions can enhance control. The study assessed uptake of intermittent preventive treatment of malaria during pregnancy using sulphadoxine-pyrimethamine (IPTp-SP) and insecticide-treated net (ITN) use, their determinants and effects on pregnancy outcomes. Methods A cross-sectional study involving 349 post-partum women was conducted from 25 August 2022 to 9 October 2022 at the Ho Teaching Hospital. A structured questionnaire was used to collect data on participant socio-demographics, ITN use, number of doses of sulphadoxine-pyrimethamine received, knowledge of malaria in pregnancy, haemoglobin levels and birth weight among others. Summary statistics were reported as frequencies, percentages and means. Associations between exposure and outcome variables were assessed using logistic regression methods and odds ratios reported with 95% confidence intervals. Statistical significance was concluded at p < 0.05. Results More than 80% (291) of respondents received ⩾3 doses of intermittent preventive treatment using sulphadoxine-pyrimethamine and 64.8% (226) slept under ITNs the night before the survey. Age >25 years, employment, good knowledge of malaria in pregnancy, parity ⩾2 and initiating antenatal care visits in the first trimester facilitated the uptake of these interventions. Receiving ⩾3 doses of sulphadoxine-pyrimethamine was associated with having normal-weight babies (adjusted odds ratio 2.80, 95% CI: 1.07, 7.34; p = 0.036) while ITN use was associated with having term babies (adjusted odds ratio 2.72, 95% CI: 1.24, 5.90; p = 0.013) and normal maternal haemoglobin concentration at term (adjusted odds ratio 1.57, 95% CI: 1.01, 2.47; p = 0.044). Conclusions The interventions were beneficial against low birthweight and preterm births which predispose to neonatal deaths and poor cognitive function in children. Malaria in pregnancy health campaigns should be intensified, especially among younger-aged primigravidae, to increase their knowledge of the condition as a way to further improve uptake of these preventive interventions.
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Affiliation(s)
| | - Abraham Kwadzo Ahiakpa
- Department of Community Health, School of Medicine, University of Health and Allied Sciences, Ho, Ghana
| | - Joseph Osarfo
- Joseph Osarfo, Department of Community Health, School of Medicine, University of Health and Allied Sciences, PMB 31, Ho, Volta Region, Ghana.
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Kuetche MTC, Tabue RN, Fokoua-Maxime CD, Evouna AM, Billong S, Kakesa O. Prevalence and risk factors determinants of the non-use of insecticide-treated nets in an endemic area for malaria: analysis of data from Cameroon. Malar J 2023; 22:205. [PMID: 37407962 DOI: 10.1186/s12936-023-04510-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 02/21/2023] [Indexed: 07/07/2023] Open
Abstract
BACKGROUND Malaria is the main cause of morbidity and mortality in Cameroon. Insecticide-treated nets (ITNs) significantly reduce malaria transmission, but their use is not common in the population. This study aimed to estimate the nationwide prevalence of the non-use of ITNs and identify its major determinants. METHODS A cross-sectional study was conducted on interview data collected in households selected across all the regions of Cameroon through a non-probabilistic, random, 2-stage stratified sampling process. Descriptive statistics were used to describe the distribution of baseline characteristics across the households, and statistical tests assessed if the distribution of these characteristics differed significantly based on the non-use of ITNs, with 0.05 serving as a threshold of the p-value for statistical significance. The prevalence of the non-use of ITNs was estimated, and logistic regression models were used to tally the odds ratios of the associations between various factors and the non-use of ITNs, along with their 95% confidence intervals. The sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve (AUC) were determined, and the Hosmer Lemeshow test was used to measure the goodness of fit of each statistical model. RESULTS Of the 7593 households interviewed, 77% had at least one ITN and 59% of the population used ITNs. Only 72% of the population with at least one ITN used it. The logistic model of the multivariate analysis was significant at a 5% threshold. The AUC was 0.7087 and the error rate was 18.01%. The sensitivity and specificity of the model were 97.56% and 13.70%, respectively. The factors that were associated with ITN use were the presence of sufficient nets in the household (p < 0.0001), the region of residence (p < 0.0001), the level of education of the respondent (p < 0.0001), and the standard of living (p = 0.0286). Sex, age, colour preferences, as well as the shape and size of the nets were not associated with ITN use. CONCLUSIONS The use of ITNs in Cameroon was low and varied according to specific factors. These identified factors could be used as the foundations of effective sensitization campaigns on the importance of ITNs.
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Affiliation(s)
| | | | - C D Fokoua-Maxime
- School of Public Health, New York State University at Albany, Albany, NY, USA
| | - Armel M Evouna
- Cameroon Field Epidemiology Training Program, Yaoundé, Cameroon
| | - Serge Billong
- National Committee Against HIV-AIDS, Yaoundé, Cameroon
| | - Olivier Kakesa
- President's Malaria Initiative (PMI)-Measure Malaria Project, Yaoundé, Cameroon
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Natale G, Forte S, Messina G, Leonardi B, Mirra R, Leone F, Di Filippo V, Pica DG, Capasso F, Bove M, Noro A, Opromolla G, Martone M, De Angelis S, Fiorelli A. Intrathoracic neurogenic tumors ( ITNs): Management of solid and cystic lesions. Thorac Cancer 2023. [PMID: 37201908 DOI: 10.1111/1759-7714.14927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/20/2023] [Accepted: 04/22/2023] [Indexed: 05/20/2023] Open
Abstract
BACKGROUND Intrathoracic neurogenic tumors (INTs) are derived from nerve tissue and grow within the chest. Preoperative diagnosis can be challenging and only complete surgical exeresis enables confirmation of the suspected diagnosis. Here, we analyzed our experience on management of paravertebral lesions with solid and cystic patterns. METHODS A monocentric retrospective study was conducted, which included 25 consecutive cases of ITNs in the period from 2010 to 2022. These cases had been surgically treated by thoracoscopic resection alone, or in combination with neurosurgery in the case of dumbbell tumors. The demographic and operative data along with complications were recorded and analyzed. RESULTS Twenty-five patients were diagnosed with a paravertebral lesion of which 19 (76%) had solid features and six (24%) had cystic features. The most common diagnosis was schwannoma (72%), followed by neurofibroma (20%) and malignant schwannoma (8%). In four cases (12%) the tumor showed an intraspinal extension. None of the patients had recurrence until 6 months of follow-up. Comparison between the VATS and thoracotomy procedures showed that outcome of discharge on the postoperative day, on average, was 2.61 ± 0.5 versus 3.51 ± 0.53, respectively (p-value <0.001). CONCLUSION The treatment of choice for INTs is complete resection which is tailored to tumor size, location, and extension. In our study, paravertebral tumors with cystic characteristics were not associated with an intraspinal extension and did not show a different behavior from solid tumors.
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Affiliation(s)
- Giovanni Natale
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Stefano Forte
- Genomics and Experimental Oncology Unit, IOM Ricerca, Viagrande, Italy
| | - Gaetana Messina
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Beatrice Leonardi
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Rosa Mirra
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Francesco Leone
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Vincenzo Di Filippo
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Davide Gerardo Pica
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Francesca Capasso
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Mary Bove
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Antonio Noro
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Giorgia Opromolla
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Mario Martone
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Sabrina De Angelis
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
| | - Alfonso Fiorelli
- Department of Translation Medicine, Thoracic Surgery Unit, Università della Campania "Luigi Vanvitelli", Naples, Italy
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Kouassi BL, Edi C, Ouattara AF, Ekra AK, Bellai LG, Gouaméné J, Kacou YAK, Kouamé JKI, Béké AO, Yokoli FN, Gbalegba CGN, Tia E, Yapo RM, Konan LY, N'Tamon RN, Akré MA, Koffi AA, Tanoh AM, Zinzindohoué P, Kouadio B, Yepassis-Zembrou PL, Belemvire A, Irish SR, Cissé NG, Flatley C, Chabi J. Entomological monitoring data driving decision-making for appropriate and sustainable malaria vector control in Côte d'Ivoire. Malar J 2023; 22:14. [PMID: 36635720 DOI: 10.1186/s12936-023-04439-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 01/03/2023] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Entomological surveillance provides critical information on vectors for appropriate malaria vector control and strategic decision-making. The widely documented insecticide resistance of malaria vectors in Côte d'Ivoire requires that any vector control intervention deployment be driven by entomological data to optimize its effectiveness and appropriate resource allocations. To achieve this goal, this study documents the results of monthly vector surveillance and insecticide susceptibility tests conducted in 2019 and a review of all previous entomological monitoring data used to guide vector control decision making. Furthermore, susceptibility to pirimiphos-methyl and clothianidin was assessed in addition to chlorfenapyr and pyrethroids (intensity and piperonyl butoxide (PBO) synergism) tests previously reported. Vector bionomic data were conducted monthly in four sites (Sakassou, Béoumi, Dabakala and Nassian) that were selected based on their reported high malaria incidence. Adult mosquitoes were collected using human landing catches (HLCs), pyrethrum spray catches (PSCs), and human-baited CDC light traps to assess vector density, behaviour, species composition and sporozoite infectivity. RESULTS Pirimiphos-methyl and clothianidin susceptibility was observed in 8 and 10 sites, respectively, while previous data reported chlorfenapyr (200 µg/bottle) susceptibility in 13 of the sites, high pyrethroid resistance intensity and increased mortality with PBO pre-exposure at all 17 tested sites. Anopheles gambiae sensu lato was the predominant malaria vector collected in all four bionomic sites. Vector density was relatively higher in Sakassou throughout the year with mean biting rates of 278.2 bites per person per night (b/p/n) compared to Béoumi, Dabakala and Nassian (mean of 48.5, 81.4 and 26.6 b/p/n, respectively). The mean entomological inoculation rate (EIR) was 4.44 infective bites per person per night (ib/p/n) in Sakassou, 0.34 ib/p/n in Beoumi, 1.17 ib/p/n in Dabakala and 1.02 ib/p/n in Nassian. The highest EIRs were recorded in October in Béoumi (1.71 ib/p/n) and Nassian (3.22 ib/p/n), in July in Dabakala (4.46 ib/p/n) and in May in Sakassou (15.6 ib/p/n). CONCLUSION Based on all results and data review, the National Malaria Control Programme developed and implemented a stratified insecticide-treated net (ITN) mass distribution in 2021 considering new generation ITNs. These results also supported the selection of clothianidin-based products and an optimal spraying time for the first indoor residual spraying (IRS) campaign in Sakassou and Nassian in 2020.
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Miller JE, Malm K, Serge AA, Ateba MJ, Gitanya P, Sene D, Kooma EH, Kandeh B, Gerberg L, Nuñez L. Multi-country review of ITN routine distribution data: are ANC and EPI channels achieving their potential? Malar J 2022; 21:366. [PMID: 36461005 PMCID: PMC9719175 DOI: 10.1186/s12936-022-04373-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/07/2022] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Routine continuous distribution (CD) of insecticide-treated nets (ITNs) has been an important part of an overall ITN strategy to complement mass campaigns since the early 2000s. The backbone of CD implementation for many sub-Saharan African countries is distribution through antenatal care (ANC) and Expanded Programme for Immunizations (EPI) channels. Performance of these channels is often not monitored closely at the national level, nor is it reviewed globally, unlike the oversight provided to mass campaigns. The question as to why every eligible pregnant woman and child attending these services does not get an ITN remains important and yet, unanswered. METHODS ANC and EPI issuing rates from seven countries were reviewed with the aim of conducting a blinded multi-country analysis. Monthly data from January to December 2021 was extracted from each country's health management information system and analysed jointly with a National Malaria Control Programme (NMCP) focal point. VectorLink CD assessment reports were also reviewed to glean key findings. RESULTS ITN issuing rates varied across countries at ANC (31% to 93%) and EPI (39% to 92%). Across the seven countries, the median ITN issuing rate was 64% at ANC and 78% at EPI. Results varied greatly across months per country at both ANC and EPI. NMCP focal points are aware that mass campaigns often negatively affect implementation of ITN distribution through ANC and EPI, even though global and national guidelines emphasize sustaining CD during campaigns. Concerns were also raised about the standard ITN issuing rate indicator at ANC and even more so at EPI due to the denominator. Findings from CD assessments were similar across countries: ITN stock was inconsistent and sometimes inadequate, and updated guidelines on ITN distribution and utilization and funding for social behaviour change activities were lacking at the facility level. CONCLUSION The importance of optimizing ANC and EPI routine channels cannot be underscored enough. They are at the frontline to protect the most biologically vulnerable populations, i.e., pregnant women and unborn and young children. Although there are encouraging signs of improvement in issuing rates with some countries reaching optimal rates, further improvements are needed to ensure that every pregnant woman and young child receives the ITN to which they are entitled.
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Affiliation(s)
- Jane E. Miller
- grid.423224.10000 0001 0020 3631PMI VectorLink, PSI, Washington, DC USA
| | - Kezia Malm
- National Malaria Control Programme, Accra, Ghana
| | | | | | - Peter Gitanya
- grid.415734.00000 0001 2185 2147National Malaria Control Programme, Dodoma, Tanzania
| | - Doudou Sene
- National Malaria Control Programme, Dakar, Senegal
| | | | - Balla Kandeh
- National Malaria Control Programme, Banjul, The Gambia
| | - Lilia Gerberg
- grid.507606.2U.S. President’s Malaria Initiative, USAID, Washington, DC USA
| | - Luigi Nuñez
- grid.423224.10000 0001 0020 3631PMI VectorLink, PSI, Washington, DC USA
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Kahamba NF, Finda M, Ngowo HS, Msugupakulya BJ, Baldini F, Koekemoer LL, Ferguson HM, Okumu FO. Using ecological observations to improve malaria control in areas where Anopheles funestus is the dominant vector. Malar J 2022; 21:158. [PMID: 35655190 PMCID: PMC9161514 DOI: 10.1186/s12936-022-04198-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/19/2022] [Indexed: 11/10/2022] Open
Abstract
The most important malaria vectors in sub-Saharan Africa are Anopheles gambiae, Anopheles arabiensis, Anopheles funestus, and Anopheles coluzzii. Of these, An. funestus presently dominates in many settings in east and southern Africa. While research on this vector species has been impeded by difficulties in creating laboratory colonies, available evidence suggests it has certain ecological vulnerabilities that could be strategically exploited to greatly reduce malaria transmission in areas where it dominates. This paper examines the major life-history traits of An. funestus, its aquatic and adult ecologies, and its responsiveness to key interventions. It then outlines a plausible strategy for reducing malaria transmission by the vector and sustaining the gains over the medium to long term. To illustrate the propositions, the article uses data from south-eastern Tanzania where An. funestus mediates over 85% of malaria transmission events and is highly resistant to key public health insecticides, notably pyrethroids. Both male and female An. funestus rest indoors and the females frequently feed on humans indoors, although moderate to high degrees of zoophagy can occur in areas with large livestock populations. There are also a few reports of outdoor-biting by the species, highlighting a broader range of behavioural phenotypes that can be considered when designing new interventions to improve vector control. In comparison to other African malaria vectors, An. funestus distinctively prefers permanent and semi-permanent aquatic habitats, including river streams, ponds, swamps, and spring-fed pools. The species is therefore well-adapted to sustain its populations even during dry months and can support year-round malaria transmission. These ecological features suggest that highly effective control of An. funestus could be achieved primarily through strategic combinations of species-targeted larval source management and high quality insecticide-based methods targeting adult mosquitoes in shelters. If done consistently, such an integrated strategy has the potential to drastically reduce local populations of An. funestus and significantly reduce malaria transmission in areas where this vector species dominates. To sustain the gains, the programmes should be complemented with gradual environmental improvements such as house modification to maintain biting exposure at a bare minimum, as well as continuous engagements of the resident communities and other stakeholders.
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Affiliation(s)
- Najat F Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
| | - Marceline Finda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Betwel J Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heather M Ferguson
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa.
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania.
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Kibondo UA, Odufuwa OG, Ngonyani SH, Mpelepele AB, Matanilla I, Ngonyani H, Makungwa NO, Mseka AP, Swai K, Ntabaliba W, Stutz S, Austin JW, Moore SJ. Influence of testing modality on bioefficacy for the evaluation of Interceptor ® G2 mosquito nets to combat malaria mosquitoes in Tanzania. Parasit Vectors 2022; 15:124. [PMID: 35410250 PMCID: PMC8996609 DOI: 10.1186/s13071-022-05207-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 02/15/2022] [Indexed: 12/02/2022] Open
Abstract
Background Insecticide-treated net (ITN) durability is evaluated using longitudinal bioefficacy and fabric integrity sampling post-distribution. Interceptor® G2 was developed for resistance management and contains two adulticides: alpha-cypermethrin and chlorfenapyr; it is a pro-insecticide that is metabolized into its active form by mosquito-detoxifying enzymes and may be enhanced when the mosquito is physiologically active. To elucidate the impact of bioassay modality, mosquito exposures of the alphacypermethrin ITN Interceptor® and dual adulticide Interceptor® G2 were investigated. Methods This study evaluated the performance of Interceptor® G2 compared to Interceptor® against local strains of mosquitoes in Tanzania. Unwashed and 20× times washed nets were tested. Efficacy of ITNs was measured by four bioassay types: (1) World Health Organisation (WHO) cone test (cone), (2) WHO tunnel test (tunnel), (3) Ifakara ambient chamber test (I-ACT) and (4) the WHO gold standard experimental hut test (hut). Hut tests were conducted against free-flying wild pyrethroid metabolically resistant Anopheles arabiensis and Culex quinquefasciatus. Cone, tunnel and I-ACT bioassays used laboratory-reared metabolically resistant An. arabiensis and Cx. quinquefasciatus and pyrethroid susceptible Anopheles gambiae sensu stricto and Aedes aegypti. Results Against resistant strains, superiority of Interceptor® G2 over Interceptor® was observed in all “free-flying bioassays”. In cone tests (which restrict mosquito flight), superiority of Interceptor® over Interceptor® G2 was recorded. Mortality of unwashed Interceptor® G2 among An. arabiensis was lowest in hut tests at 42.9% (95% CI: 37.3–48.5), although this increased to 66.7% (95% CI: 47.1–86.3) by blocking hut exit traps so mosquitoes presumably increased frequencies of contact with ITNs. Higher odds of mortality were consistently observed in Interceptor® G2 compared to Interceptor® in “free-flying” bioassays using An. arabiensis: tunnel (OR = 1.42 [95% CI:1.19–1.70], p < 0.001), I-ACT (OR = 1.61 [95% CI: 1.05–2.49], p = 0.031) and hut (OR = 2.53 [95% CI: 1.96–3.26], p < 0.001). Interceptor® and Interceptor® G2 showed high blood-feeding inhibition against all strains. Conclusion Both free-flying laboratory bioassays (WHO Tunnel and I-ACT) consistently measured similarly, and both predicted the results of the experimental hut test. For bioefficacy monitoring and upstream product evaluation of ITNs in situ, the I-ACT may provide an alternative bioassay modality with improved statistical power. Interceptor G2® outperformed Interceptor ® against pyrethroid-resistant strains, demonstrating the usefulness of chlorfenapyr in mitigation of malaria. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05207-9.
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Affiliation(s)
- Ummi Abdul Kibondo
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
| | - Olukayode G Odufuwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, England
| | - Saphina H Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Ahmadi B Mpelepele
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Issaya Matanilla
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Hassan Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Noel O Makungwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Antony P Mseka
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Kyeba Swai
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
| | - Watson Ntabaliba
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Susanne Stutz
- Professional & Specialty Solutions, BASF SE, Public Health, 67117, Limburgerhof, Germany
| | - James W Austin
- Professional & Specialty Solutions, BASF Corporation, Public Health Global Development, Research Triangle Park, NC, 27709, USA
| | - Sarah Jane Moore
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.,Nelson Mandela African Institute of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
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12
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Madgwick PG, Kanitz R. Modelling new insecticide-treated bed nets for malaria-vector control: how to strategically manage resistance? Malar J 2022; 21:102. [PMID: 35331237 PMCID: PMC8944051 DOI: 10.1186/s12936-022-04083-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 02/11/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The program to eradicate malaria is at a critical juncture as a new wave of insecticides for mosquito control enter their final stages of development. Previous insecticides have been deployed one-at-a-time until their utility was compromised, without the strategic management of resistance. Recent investment has led to the near-synchronous development of new insecticides, and with it the current opportunity to build resistance management into mosquito-control methods to maximize the chance of eradicating malaria. METHODS Here, building on the parameter framework of an existing mathematical model, resistance-management strategies using multiple insecticides are compared to suggest how to deploy combinations of available and new insecticides on bed nets to achieve maximum impact. RESULTS Although results support the use of different strategies in different settings, deploying new insecticides ideally together in (or at least as a part of) a mixture is shown to be a robust strategy across most settings. CONCLUSIONS Substantially building on previous works, alternative solutions for the resistance management of new insecticides to be used in bed nets for malaria vector control are found. The results support a mixture product concept as the most robust way to deploy new insecticides, even if they are mixed with a pyrethroid that has lower effectiveness due to pre-existing resistance. This can help deciding on deployment strategies and policies around the sustainable use of these new anti-malaria tools.
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Affiliation(s)
- Philip G Madgwick
- Syngenta, Jealott's Hill International Research Centre, Bracknell, RG42 6EY, UK
| | - Ricardo Kanitz
- Syngenta Crop Protection, Rosentalstrasse 67, 4058, Basel, Switzerland.
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Ateba FF, Doumbia S, ter Kuile FO, Terlouw DJ, Lefebvre G, Kariuki S, Small DS. The effect of malaria on stunting: an instrumental variables approach. Trans R Soc Trop Med Hyg 2021; 115:1094-1098. [PMID: 33493346 PMCID: PMC8578805 DOI: 10.1093/trstmh/traa183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 11/05/2020] [Accepted: 12/24/2020] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Previous studies have found mixed evidence for an effect of malaria on stunting, but have suffered from concerns about confounding and/or power. Currently, an effect of malaria on stunting is not included in the Lives Saved Tool (LiST) model. METHODS We used instrumental variables regression with the sickle cell trait and random assignment to bednets as instruments in the analysis of data on children aged 0-2 y from a bednet trial in western Kenya. RESULTS We estimated that one additional clinical malaria episode per year increases the odds of a child being stunted by 6% (OR estimate: 1.06, 95% CI 1.01 to 1.11). CONCLUSIONS Our finding that malaria affects stunting suggests that an effect of malaria on stunting in young children should be considered in the LiST model.
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Affiliation(s)
- François Freddy Ateba
- Malaria Research and Training Center & Department of Public Health Education and Research of the Faculty of Medicine and Odonto-Stomatology, University of Sciences, Techniques and Technologies of Bamako, BP 1805 Point G Bamako, Mali
- Department of Mathematics, University of Quebec at Montreal (UQAM), Montréal, QC H2X 3Y7, Canada
| | - Seydou Doumbia
- Malaria Research and Training Center & Department of Public Health Education and Research of the Faculty of Medicine and Odonto-Stomatology, University of Sciences, Techniques and Technologies of Bamako, BP 1805 Point G Bamako, Mali
| | - Feiko O ter Kuile
- Liverpool School of Tropical Medicine, Department of Clinical Sciences, Pembroke Place, Liverpool L3 5QA, UK
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P.O. Box 1578, 40100 Kisumu, Kenya
| | - Dianne J Terlouw
- Liverpool School of Tropical Medicine, Department of Clinical Sciences, Pembroke Place, Liverpool L3 5QA, UK
- Malawi-Liverpool Wellcome Trust Clinical Research Programme (MLW), P.O. Box 30096 Blantyre, Malawi
| | - Genevieve Lefebvre
- Department of Mathematics, University of Quebec at Montreal (UQAM), Montréal, QC H2X 3Y7, Canada
| | - Simon Kariuki
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P.O. Box 1578, 40100 Kisumu, Kenya
| | - Dylan S Small
- Department of Statistics, Wharton School, University of Pennsylvania, 464 Jon M. Huntsman Hall 3730 Walnut Street Philadelphia, PA 19104 Philadelphia, PA, USA
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Zemene E, Belay DB, Tiruneh A, Lee MC, Yewhalaw D, Yan G. Malaria vector dynamics and utilization of insecticide-treated nets in low-transmission setting in Southwest Ethiopia: implications for residual transmission. BMC Infect Dis 2021; 21:882. [PMID: 34454443 PMCID: PMC8403392 DOI: 10.1186/s12879-021-06592-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 08/20/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Understanding the behaviour of local malaria vectors is essential as effectiveness of the commonly used vector-targeted malaria control tools heavily relies on behaviour of the major malaria vectors. This study was conducted to determine species composition, biting behaviour, host preference and infectivity of anopheline mosquitoes, and assess utilization of insecticide-treated nets (ITNs) in a low transmission setting in Southwest Ethiopia. METHODS Adult anopheline mosquitoes were collected using human landing catches (HLCs), Centers for Disease Control and Prevention (CDC) light traps (LTs) and Pyrethrum Spray Catches (PSCs) from June 2016 to May 2018 in Kishe, Jimma Zone, Southwest Ethiopia. The anopheline mosquitoes were morphologically identified. Moreover, sub-sample of An. gambiae s.l. was identified to species using polymerase chain reaction (PCR). Circum-sporozoite proteins (CSPs) and blood meal sources of the anopheline mosquitoes were tested using enzyme-linked immunosorbent assay (ELISA). In addition, a cross-sectional survey was conducted to assess ITN utilization by the inhabitants. RESULTS A total of 3659 anopheline mosquitoes comprising An. coustani complex (84.4%), An. gambiae s.l. (11.3%), and An. pharoensis and An. squamosus comprising less than 5% were collected. The anopheline mosquitoes showed marked outdoor (67%) and early evening (63%) biting behaviour. An. coustani complex and An. gambiae s.l. were predominantly zoophilic and anthropophilic, respectively. None of the sampled anopheline were CSP-positive. Most of the households (97.8%) owned at least one ITN, with modest usage by the inhabitants (73.4%). ITN usage was significantly higher among under-five children (AOR = 7.9, 95% CI: 4.41-14.03), household heads and spouses (AOR = 4.8, 95% CI: 3.0-7.59), those with sufficient access to ITNs (AOR = 1.8, 95% CI: 1.39-2.35), and who were not utilizing alternative mosquito repellents (AOR = 2.2, 95% CI: 1.58-2.99). CONCLUSION The anopheline mosquito species exhibited predominantly outdoor and early evening biting activity. Household ITN coverage was high with slight gap in usage. Vector control interventions should target outdoor and early biting vectors to further suppress the local mosquito population. Moreover, sensitization of the community on consistent use of ITNs is required.
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Affiliation(s)
- Endalew Zemene
- School of Medical Laboratory Sciences, Institute of Health, Jimma University, Jimma, Ethiopia
| | - Denekew Bitew Belay
- Department of Statistics, College of Science, Bahir Dar University, Bahir Dar, Ethiopia
| | - Abebaw Tiruneh
- School of Medical Laboratory Sciences, Institute of Health, Jimma University, Jimma, Ethiopia
| | - Ming-Chieh Lee
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Institute of Health, Jimma University, Jimma, Ethiopia
- Tropical and Infectious Diseases Research Center, Jimma University, Jimma, Ethiopia
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
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Kouassi BL, Edi C, Tia E, Konan LY, Akré MA, Koffi AA, Ouattara AF, Tanoh AM, Zinzindohoue P, Kouadio B, Andre M, Irish SR, Armistead J, Dengela D, Cissé NG, Flatley C, Chabi J. Susceptibility of Anopheles gambiae from Côte d'Ivoire to insecticides used on insecticide-treated nets: evaluating the additional entomological impact of piperonyl butoxide and chlorfenapyr. Malar J 2020; 19:454. [PMID: 33298071 PMCID: PMC7725118 DOI: 10.1186/s12936-020-03523-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 11/25/2020] [Indexed: 11/29/2022] Open
Abstract
Background Pyrethroid-treated mosquito nets are currently the mainstay of vector control in Côte d’Ivoire. However, resistance to pyrethroids has been reported across the country, limiting options for insecticide resistance management due to the paucity of alternative insecticides. Two types of insecticide-treated nets (ITNs), ITNs with pyrethroids and the synergist piperonyl butoxide (PBO), and Interceptor®G2 nets, a net treated with a combination of chlorfenapyr and alpha-cypermethrin, are believed to help in the control of pyrethroid-resistant mosquitoes. Methods The susceptibility of Anopheles gambiae sensu lato (s.l.) to pyrethroid insecticides with and without pre-exposure to PBO as well as to chlorfenapyr was investigated in fifteen sites across the country. Susceptibility tests were conducted on 2- to 4-day old adult female An. gambiae s.l. reared from larval collections. The resistance status, intensity, and effects of PBO on mortality after exposure to different concentrations of deltamethrin, permethrin and alpha-cypermethrin were determined using WHO susceptibility test kits. In the absence of a WHO-recommended standard protocol for chlorfenapyr, two interim doses (100 and 200 µg/bottle) were used to test the susceptibility of mosquitoes using the CDC bottle assay method. Results Pre-exposure to PBO did not result in full restoration of susceptibility to any of the three pyrethroids for the An. gambiae s.l. populations from any of the sites surveyed. However, PBO pre-exposure did increase mortality for all three pyrethroids, particularly deltamethrin (from 4.4 to 48.9%). Anopheles gambiae s.l. from only one site (Bettie) were susceptible to chlorfenapyr at the dose of 100 µg active ingredient (a.i.)/bottle. At the dose of 200 µg (a.i.)/bottle, susceptibility was only recorded in 10 of the 15 sites. Conclusion Low mosquito mortality was found for pyrethroids alone, and while PBO increased mortality, it did not restore full susceptibility. The vector was not fully susceptible to chlorfenapyr in one third of the sites tested. However, vector susceptibility to chlorfenapyr seems to be considerably higher than for pyrethroids alone or with PBO. These data should be used cautiously when making ITN procurement decisions, noting that bioassays are conducted in controlled conditions and may not fully represent field efficacy where the host-seeking behaviours, which include free-flying activity are known to enhance pro-insecticide chlorfenapyr intoxication to mosquitoes.
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Affiliation(s)
| | - Constant Edi
- Swiss Center of Scientific Research in Côte d'Ivoire, Abidjan, Côte d'Ivoire
| | - Emmanuel Tia
- Centre of Veterinary and Medical Entomology, Abidjan, Côte d'Ivoire
| | - Lucien Y Konan
- National Institute of Public Hygiene, Abidjan, Côte d'Ivoire
| | - Maurice A Akré
- National Institute of Public Health/Pierre Richet Institute, Bouake, Côte d'Ivoire
| | - Alphonsine A Koffi
- National Institute of Public Health/Pierre Richet Institute, Bouake, Côte d'Ivoire
| | | | | | | | - Blaise Kouadio
- U.S. President's Malaria Initiative, USAID, Abidjan, Côte d'Ivoire
| | - McKenzie Andre
- National Malaria Control Programme, Abidjan, Côte d'Ivoire
| | - Seth R Irish
- U.S. President's Malaria Initiative, Entomology Branch, U.S. Centers for Disease Control and Prevention, Atlanta, GA, USA
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Odufuwa OG, Ross A, Mlacha YP, Juma O, Mmbaga S, Msellemu D, Moore S. Household factors associated with access to insecticide-treated nets and house modification in Bagamoyo and Ulanga districts, Tanzania. Malar J 2020; 19:220. [PMID: 32576180 PMCID: PMC7313165 DOI: 10.1186/s12936-020-03303-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 06/18/2020] [Indexed: 08/29/2023] Open
Abstract
BACKGROUND Insecticide-treated nets (ITNs) and house modifications are proven vector control tools, yet in most regions, full coverage has not been achieved. This study investigates household factors associated with access to ITNs and house modification in Tanzania. METHODS Baseline cross-sectional survey data from previous studies on spatial repellants and indoor residual spray evaluation was analysed from 6757 households in Bagamoyo (60 km north of Dar es Salaam) and 1241 households in Ulanga (a remote rural area in southeast Tanzania), respectively. Regression models were used to estimate the associations between the outcomes: population access to ITNs, access to ITN per sleeping spaces, window screens and closed eaves, and the covariates household size, age, gender, pregnancy, education, house size, house modification (window screens and closed eaves) and wealth. RESULTS Population access to ITNs (households with one ITN per two people that stayed in the house the previous night of the survey) was 69% (n = 4663) and access to ITNs per sleeping spaces (households with enough ITNs to cover all sleeping spaces used the previous night of the survey) was 45% (n = 3010) in Bagamoyo, 3 years after the last mass campaign. These findings are both lower than the least 80% coverage target of the Tanzania National Malaria Strategic Plan (Tanzania NMSP). In Ulanga, population access to ITNs was 92% (n = 1143) and ITNs per sleeping spaces was 88% (n = 1093), 1 year after the last Universal Coverage Campaign (UCC). Increased household size was significantly associated with lower access to ITNs even shortly after UCC. House modification was common in both areas but influenced by wealth. In Bagamoyo, screened windows were more common than closed eaves (65% vs 13%), whereas in Ulanga more houses had closed eaves than window screens (55% vs 12%). CONCLUSION Population access to ITNs was substantially lower than the targets of the Tanzania NMSP after 3 years and lower among larger households after 1 year following ITN campaign. House modification was common in both areas, associated with wealth. Improved access to ITNs and window screens through subsidies and Behaviour Change Communication (BCC) strategies, especially among large and poor households and those headed by people with a low level of education, could maximize the uptake of a combination of these two interventions.
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Affiliation(s)
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Yeromin P Mlacha
- Ifakara Health Institute, Bagamoyo, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Omary Juma
- Ifakara Health Institute, Bagamoyo, Tanzania
| | | | - Daniel Msellemu
- Ifakara Health Institute, Bagamoyo, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Sarah Moore
- Ifakara Health Institute, Bagamoyo, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
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17
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Bashir IM, Nyakoe N, van der Sande M. Targeting remaining pockets of malaria transmission in Kenya to hasten progress towards national elimination goals: an assessment of prevalence and risk factors in children from the Lake endemic region. Malar J 2019; 18:233. [PMID: 31299976 PMCID: PMC6624951 DOI: 10.1186/s12936-019-2876-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 07/08/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND With an overall decline of malaria incidence, elimination of malaria is gradually becoming the next target for many of countries affected by the disease. In Kenya the national malaria control strategy is aiming to reach pre-elimination for most parts of the country. However, considerable heterogeneity in prevalence of the disease within the country and especially the remaining high prevalent region of the Lake endemic region is likely to slow progress towards this target. To achieve a sustained control and an eventual elimination, a clear understanding of drivers of ongoing malaria transmission in remaining hotspots is needed. METHODS Data from the 2015 Malaria Indicator Survey (MIS) were analysed for prevalence of malaria parasitaemia in children (6 months to 14 years) of different countries within the highly endemic Lake region. Univariate and multivariate logistic regression analysis were preformed to explore associations between selected risk factors and being parasitaemic. A predictive model was built for the association between malaria and the risk factors with the aim of identifying heterogeneities of the disease at the lower administrative levels. RESULTS Overall, 604/2253 (27%, 95% CI 21.8-32.2) children were parasitaemic. The highest prevalence was observed in Busia County (37%) and lowest in Bungoma County (18%). Multivariate logistic regression analysis showed that the 10-14 years age group (OR = 3.0, 95% CI 2.3-4.1), households in the poorest socio-economic class (OR = 2.1, 95% CI 1.3-3.3), farming (OR = 1.4, 95% CI 1.2-2.5) and residence in Busia (OR = 4.6, 95% CI 2.1-8.2), Kakamega (OR = 2.6, 95% CI 1.3-5.4), and Migori counties (OR = 4.6 95% CI 2.1-10.3) were associated with higher risk of parasitaemia. Having slept under a long-lasting insecticide-treated bed net (LLIN) was associated with a lower risk (OR = 0.7, 95% CI 0.6-0.9). No association were found between malaria infection and the gender of the child, the household head, and the education status of the household head. DISCUSSION AND CONCLUSION Detailed analysis of malaria prevalence data in a hotspot area can identify new threats and avail opportunities for directing intervention. In the Lake endemic region of Kenya, interventions should be focused more on counties with the highest prevalence, and should target older children as well as children from the lower socio-economic strata. Precisely targeting interventions in remaining hotspots and high-risk populations will likely make impact and accelerate progress towards pre-elimination targets.
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Affiliation(s)
- Ismail Mahat Bashir
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.
| | - Nancy Nyakoe
- Walter Reed Project, Kenya Medical Research Institute, Kisumu, Kenya
| | - Marianne van der Sande
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,Julius Global Health Center, Julius Center for Health Sciences and Primary Care, Utrecht University, Utrecht, The Netherlands
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18
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Talipouo A, Ngadjeu CS, Doumbe-Belisse P, Djamouko-Djonkam L, Sonhafouo-Chiana N, Kopya E, Bamou R, Awono-Ambene P, Woromogo S, Kekeunou S, Wondji CS, Antonio-Nkondjio C. Malaria prevention in the city of Yaoundé: knowledge and practices of urban dwellers. Malar J 2019; 18:167. [PMID: 31072344 PMCID: PMC6509831 DOI: 10.1186/s12936-019-2799-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 05/03/2019] [Indexed: 01/26/2023] Open
Abstract
Background Malaria prevention in Cameroon mainly relies on the use of ITNs. Although several free distribution campaigns of treated nets have been conducted across the country, bed net usage remains very low. A household survey was conducted to assess knowledge of the population and practices affecting treated net usage in the city of Yaoundé. Methods A community-based descriptive cross-sectional survey was conducted in January 2017 in 32 districts of the city of Yaoundé. Parents (household head, spouse or an elder representative) who consented to the study, were interviewed using a structured pre-tested questionnaire. Interviews were conducted in French or English. A questionnaire consisting of 22 questions was administered to know (i) people’s knowledge and attitude on preventive measures; and, (ii) attitudes concerning the treatment of malaria and estimated amount spent for malaria prevention and treatment. Results A total of 1643 household heads were interviewed. Over 94% of people interviewed associated malaria transmission to mosquito bites. The main methods used against mosquito bites were: treated bed nets (94%; n = 1526) and insecticide spray or coils (32.2%; n = 523). The majority of people interviewed reported using bed nets mainly to prevent from mosquito bites (84.4%, n = 1257), rather than for malaria prevention (47.3%). Knowledge and attitude analysis revealed that people with university or secondary level of education have better knowledge of malaria, prevention and treatment measures compared to those with the primary level (OR = 7.03; P < 0.001). Also, wealthy households were more aware of good practices concerning malaria prevention and treatment compared to poor ones. In the majority of districts of Yaoundé, over 50% of people interviewed per district, had good knowledge of malaria and prevention measures but less than 50% applied good practices concerning malaria treatment and prevention. The amount spent annually by a household for vector control was CFAF 11,589 ± 1133 (US$21.87 ± 2.14) and CFAF 66,403 ± 4012 (US$125.29 ± 7.57) for malaria treatment. Conclusion The study indicated that, despite good knowledge of malaria and prevention measures, few people apply good practices. More sensitization needs to be done to improve adherence to good practices concerning malaria prevention and treatment. Electronic supplementary material The online version of this article (10.1186/s12936-019-2799-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Abdou Talipouo
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Yaoundé 1, P.O. Box 337, Yaoundé, Cameroon
| | - Carmene S Ngadjeu
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Yaoundé 1, P.O. Box 337, Yaoundé, Cameroon
| | - Patricia Doumbe-Belisse
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Yaoundé 1, P.O. Box 337, Yaoundé, Cameroon
| | - Landre Djamouko-Djonkam
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Dschang, P.O. Box 337, Dschang, Cameroon
| | - Nadege Sonhafouo-Chiana
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Health Sciences, University of Buea, P.O. Box 456, Buea, Cameroon
| | - Edmond Kopya
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Yaoundé 1, P.O. Box 337, Yaoundé, Cameroon
| | - Roland Bamou
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Dschang, P.O. Box 337, Dschang, Cameroon
| | - Parfait Awono-Ambene
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Sylvain Woromogo
- Centre Inter Etats d'Enseignement Supérieur en Santé Publique d'Afrique Centrale (CIESPAC), P.O. Box 1536, Brazzaville, Congo
| | - Sevilor Kekeunou
- Faculty of Sciences, University of Yaoundé 1, P.O. Box 337, Yaoundé, Cameroon
| | - Charles S Wondji
- Vector Biology Liverpool School of Tropical Medicine Pembroke Place, Liverpool, L3 5QA, UK
| | - Christophe Antonio-Nkondjio
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon. .,Vector Biology Liverpool School of Tropical Medicine Pembroke Place, Liverpool, L3 5QA, UK.
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Mohammed-Awel J, Agusto F, Mickens RE, Gumel AB. Mathematical assessment of the role of vector insecticide resistance and feeding/resting behavior on malaria transmission dynamics: Optimal control analysis. Infect Dis Model 2019; 3:301-321. [PMID: 30839928 PMCID: PMC6326232 DOI: 10.1016/j.idm.2018.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Revised: 10/06/2018] [Accepted: 10/24/2018] [Indexed: 12/22/2022] Open
Abstract
The large-scale use of insecticide-treated bednets (ITNs) and indoor residual spraying (IRS), over the last two decades, has resulted in a dramatic reduction of malaria incidence globally. However, the effectiveness of these interventions is now being threatened by numerous factors, such as resistance to insecticide in the mosquito vector and their preference to feed and rest outdoors or early in the evening (when humans are not protected by the bednets). This study presents a new deterministic model for assessing the population-level impact of mosquito insecticide resistance on malaria transmission dynamics. A notable feature of the model is that it stratifies the mosquito population in terms of type (wild or resistant to insecticides) and feeding preference (indoor or outdoor). The model is rigorously analysed to gain insight into the existence and asymptotic stability properties of the various disease-free equilibria of the model namely the trivial disease-free equilibrium, the non-trivial resistant-only boundary disease-free equilibrium and a non-trivial disease-free equlibrium where both the wild and resistant mosquito geneotypes co-exist). Simulations of the model, using data relevant to malaria transmission dynamics in Ethiopia (a malaria-endemic nation), show that the use of optimal ITNs alone, or in combination with optimal IRS, is more effective than the singular implementation of an optimal IRS-only strategy. Further, when the effect of the fitness cost of insecticide resistance with respect to fecundity (i.e., assuming a decrease in the baseline birth rate of new resistant-type adult female mosquitoes) is accounted for, numerical simulations of the model show that the combined optimal ITNs-IRS strategy could lead to the effective control of the disease, and insecticide resistance effectively managed during the first 8 years of the 15-year implementation period of the insecticides-based anti-malaria control measures in the community.
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Affiliation(s)
- Jemal Mohammed-Awel
- Department of Mathematics, Valdosta State University, Valdosta, GA 31698, USA
- Corresponding author.
| | - Folashade Agusto
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS USA
| | - Ronald E. Mickens
- Department of Physics, Clark Atlanta University, Atlanta, GA 30314, USA
| | - Abba B. Gumel
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ, 85287, USA
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Nofal SD, Peto TJ, Adhikari B, Tripura R, Callery J, Bui TM, von Seidlein L, Pell C. How can interventions that target forest-goers be tailored to accelerate malaria elimination in the Greater Mekong Subregion? A systematic review of the qualitative literature. Malar J 2019; 18:32. [PMID: 30709399 PMCID: PMC6359845 DOI: 10.1186/s12936-019-2666-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/27/2019] [Indexed: 11/26/2022] Open
Abstract
Background Despite decreases in incidence and related mortality, malaria remains a major public health challenge in the Greater Mekong Sub-region (GMS). The emergence of artemisinin resistance threatens these gains and has prompted efforts to accelerate elimination in the region. In the GMS, transmission now clusters in hotspots along international borders and among high-risk populations, including forest-goers. To eliminate malaria in the region, interventions must target such hard-to-reach populations. This review provides a comprehensive overview of the qualitative research on behaviours and perceptions that influence uptake of and adherence to malaria interventions among forest-goers in the GMS. Methods A systematic search strategy was used to identify relevant sources, including database (OVID SP, PubMed, ISI Web of Knowledge) and bibliographic searches. Relevant findings from qualitative research methods were extracted and thematic analysis undertaken. Results Of 268 sources retrieved in searches twenty-two were reviewed. Most reported studies were conducted in Cambodia (n = 10), and were published after 2014 (n = 16). Four major themes emerged that are particularly relevant to the design of intervention packages targeted at forest-goers: (1) understanding of malaria and perceived risk; (2) preventive measures used when visiting the forest; (3) behaviours that put forest-goers at risk of infection; and, (4) malaria-related treatment seeking. There were notable differences across the reviewed articles that suggest the need for a locally tailored approach. Conclusion A more detailed characterization of forest activities is needed but research on this topic raises methodological challenges. Current vector control measures have limitations, with use of insecticidal-treated nets, hammocks and repellents influenced by the type of forest activities and the characteristics of these measures. In contrast, anti-malarial drugs, for example, as chemoprophylaxis, hold promise but require further evaluation. Electronic supplementary material The online version of this article (10.1186/s12936-019-2666-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephanie D Nofal
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Thomas J Peto
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. .,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
| | - Bipin Adhikari
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Rupam Tripura
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - James Callery
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Thanh Mai Bui
- Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Lorenz von Seidlein
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Christopher Pell
- Centre for Social Sciences and Global Health, University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Institute for Global Health and Development, Amsterdam, The Netherlands
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Kamau A, Mwangangi JM, Rono MK, Mogeni P, Omedo I, Midega J, Scott JAG, Bejon P. Variation in the effectiveness of insecticide treated nets against malaria and outdoor biting by vectors in Kilifi, Kenya. Wellcome Open Res 2019; 2:22. [PMID: 30542660 DOI: 10.12688/wellcomeopenres.11073.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2017] [Indexed: 11/20/2022] Open
Abstract
Background: Insecticide treated nets (ITNs) protect humans against bites from the Anopheles mosquito vectors that transmit malaria, thereby reducing malaria morbidity and mortality. It has been noted that ITN use leads to a switch from indoor to outdoor feeding among these vectors. It might be expected that outdoor feeding would undermine the effectiveness of ITNs that target indoors vectors, but data are limited. Methods: We linked homestead level geospatial data to clinical surveillance data at a primary healthcare facility in Kilifi County in order to map geographical heterogeneity in ITN effectiveness and observed vector feeding behaviour using landing catches and CDC light traps in six selected areas of varying ITN effectiveness. We quantified the interaction between mosquitoes and humans to evaluate whether outdoor vector biting is a potential explanation for the variation in ITN effectiveness. Results: We observed 37% and 46% visits associated with positive malaria slides among ITN users and non-ITN-users, respectively; ITN use was associated with 32% protection from malaria (crude OR = 0.68, 95% CI: 0.64, 0.73). We obtained modification of ITN effectiveness by geographical area (p=0.016), and identified 6 hotspots using the spatial scan statistic. Majority of mosquitoes were caught outdoor (60%) and were of the An. funestus group (75%). The overall propensity to feed at times when most people were asleep was high; the vast majority of the Anopheles mosquitoes were caught at times when most people are indoors asleep. Estimates for the proportion of human-mosquito contact between the first and last hour when most humans were asleep was consistently high across all locations, ranging from 0.83 to 1.00. Conclusion: Our data do not provide evidence of an epidemiological association between microgeographical variations in ITN effectiveness and variations in the microgeographical distribution of outdoor biting.
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Affiliation(s)
- Alice Kamau
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Joseph M Mwangangi
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Integrated Vector and Disease Management Cluster, International Centre of Insect Physiology and Ecology, Nairobi, Kenya.,Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Martin K Rono
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Polycarp Mogeni
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Irene Omedo
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Janet Midega
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Genomics and Global Health, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, WC1E 7HT, UK
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, OX3 7FZ, UK
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22
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Kamau A, Mwangangi JM, Rono MK, Mogeni P, Omedo I, Midega J, Scott JAG, Bejon P. Variation in the effectiveness of insecticide treated nets against malaria and outdoor biting by vectors in Kilifi, Kenya. Wellcome Open Res 2018; 2:22. [PMID: 30542660 PMCID: PMC6281023 DOI: 10.12688/wellcomeopenres.11073.4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2018] [Indexed: 12/27/2022] Open
Abstract
Background: Insecticide treated nets (ITNs) protect humans against bites from the
Anopheles mosquito vectors that transmit malaria, thereby reducing malaria morbidity and mortality. It has been noted that ITN use leads to a switch from indoor to outdoor feeding among these vectors. It might be expected that outdoor feeding would undermine the effectiveness of ITNs that target indoors vectors, but data are limited. Methods: We linked homestead level geospatial data to clinical surveillance data at a primary healthcare facility in Kilifi County in order to map geographical heterogeneity in ITN effectiveness and observed vector feeding behaviour using landing catches and CDC light traps in six selected areas of varying ITN effectiveness. We quantified the interaction between mosquitoes and humans to evaluate whether outdoor vector biting is a potential explanation for the variation in ITN effectiveness. Results: We observed 37% and 46% visits associated with positive malaria slides among ITN users and non-ITN-users, respectively; ITN use was associated with 32% protection from malaria (crude OR = 0.68, 95% CI: 0.64, 0.73). We obtained modification of ITN effectiveness by geographical area (p=0.016), and identified 6 hotspots using the spatial scan statistic. Majority of mosquitoes were caught outdoor (60%) and were of the
An. funestus group (75%). The overall propensity to feed at times when most people were asleep was high; the vast majority of the
Anopheles mosquitoes were caught at times when most people are indoors asleep. Estimates for the proportion of human-mosquito contact between the first and last hour when most humans were asleep was consistently high across all locations, ranging from 0.83 to 1.00. Conclusion: Our data do not provide evidence of an epidemiological association between microgeographical variations in ITN effectiveness and variations in the microgeographical distribution of outdoor biting.
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Affiliation(s)
- Alice Kamau
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Joseph M Mwangangi
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Integrated Vector and Disease Management Cluster, International Centre of Insect Physiology and Ecology, Nairobi, Kenya.,Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Martin K Rono
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Pwani University Bioscience Research Centre, Pwani University, Kilifi, Kenya
| | - Polycarp Mogeni
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Irene Omedo
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Janet Midega
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Genomics and Global Health, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - J Anthony G Scott
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, WC1E 7HT, UK
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, OX3 7FZ, UK
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23
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Levitz L, Janko M, Mwandagalirwa K, Thwai KL, Likwela JL, Tshefu AK, Emch M, Meshnick SR. Effect of individual and community-level bed net usage on malaria prevalence among under-fives in the Democratic Republic of Congo. Malar J 2018; 17:39. [PMID: 29347953 PMCID: PMC5774036 DOI: 10.1186/s12936-018-2183-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 01/10/2018] [Indexed: 11/10/2022] Open
Abstract
Background Understanding the contribution of community-level long-lasting, insecticidal net (LLIN) coverage to malaria control is critical to planning and assessing intervention campaigns. The Democratic Republic of Congo (DRC), which has one of the highest burdens of malaria cases and deaths and has dramatically scaled up LLIN ownership in recent years thus it is an ideal setting to evaluate the effect of individual versus community-level use to prevent malaria among children under the age of 5. Results Data were derived from the 2013–2014 DRC Demographic and Health Survey. Community-level LLIN usage was significantly associated with protection against malaria, even when individual-level LLIN usage was included in the model. In stratified analysis, higher levels of community LLIN coverage enhanced the protective effect of individual LLIN usage, resulting in lower malaria prevalence among individuals who used a LLIN. A sub-analysis of individual LLIN usage by insecticide type revealed deltamethrin-treated nets were more protective than permethrin-treated nets, suggesting that mosquitoes in the DRC are more susceptible to deltamethrin. Conclusions This study examines the effects of individual and community-level LLIN usage in young children in an area of high ITN usage. Individual and community LLIN usage were significantly associated with protection against malaria in children under 5 in the DRC. Importantly, the protective effect of individual LLIN usage against malaria is enhanced when community LLIN coverage is higher, demonstrating the importance of increasing community-level LLIN usage. LLINs treated with deltamethrin were shown to be more protective against malaria than LLINs treated with permethrin. Demographic and Health Surveys are thus a novel and important means of surveillance for insecticide resistance.
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Affiliation(s)
- Lauren Levitz
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA
| | - Mark Janko
- Department of Geography, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, 27599, USA
| | | | - Kyaw L Thwai
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA
| | - Joris L Likwela
- Programme National de la Lutte contre le Paludisme, Kinshasa, Democratic Republic of Congo
| | - Antoinette K Tshefu
- University of Kinshasa School of Public Health, Kinshasa, Democratic Republic of Congo
| | - Michael Emch
- Department of Geography, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, 27599, USA
| | - Steven R Meshnick
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA.
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Nsakashalo-Senkwe M, Mwase E, Chizema-Kawesha E, Mukonka V, Songolo P, Masaninga F, Rebollo M, Thomas B, Bockarie M, Betts H, Stothard J, Kelly-Hope L. Significant decline in lymphatic filariasis associated with nationwide scale-up of insecticide-treated nets in Zambia. Parasite Epidemiol Control 2017; 2:7-14. [PMID: 29774291 PMCID: PMC5952671 DOI: 10.1016/j.parepi.2017.08.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/25/2017] [Accepted: 08/26/2017] [Indexed: 11/29/2022] Open
Abstract
Lymphatic filariasis (LF) is a mosquito-borne disease, broadly endemic in Zambia, and is targeted for elimination by mass drug administration (MDA) of albendazole and diethylcarbamazine citrate (DEC) to at-risk populations. Anopheline mosquitoes are primary vectors of LF in Africa, and it is possible that the significant scale-up of malaria vector control over the past decade may have also impacted LF transmission, and contributed to a decrease in prevalence in Zambia. We therefore aimed to examine the putative association between decreasing LF prevalence and increasing coverage of insecticide-treated mosquito nets (ITNs) for malaria vector control, by comparing LF mapping data collected between 2003-2005 and 2009-2011 to LF sentinel site prevalence data collected between 2012 and 2014, before any anti-LF MDA was started. The coverage of ITNs for malaria was quantified and compared for each site in relation to the dynamics of LF. We found a significant decrease in LF prevalence from the years 2003-2005 (11.5% CI95 6.6; 16.4) to 2012-2014 (0.6% CI95 0.03; 1.1); at the same time, there was a significant scale-up of ITNs across the country from 0.2% (CI95 0.0; 0.3) to 76.1% (CI95 71.4; 80.7) respectively. The creation and comparison of two linear models demonstrated that the geographical and temporal variation in ITN coverage was a better predictor of LF prevalence than year alone. Whilst a causal relationship between LF prevalence and ITN coverage cannot be proved, we propose that the scale-up of ITNs has helped to control Anopheles mosquito populations, which have in turn impacted on LF transmission significantly before the scale-up of MDA. This putative synergy with vector control has helped to put Zambia on track to meet national and global goals of LF elimination by 2020.
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Affiliation(s)
- M. Nsakashalo-Senkwe
- Ministry of Health, P.O. Box 30205, Lusaka, Zambia
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - E. Mwase
- School of Veterinary Medicine, University of Zambia, P.O. Box 32379, Lusaka, Zambia
| | | | - V. Mukonka
- Ministry of Health, P.O. Box 30205, Lusaka, Zambia
| | - P. Songolo
- WHO Country Office, World Health Organisation, P.O. Box 32346, Ridgeway, Lusaka, Zambia
| | - F. Masaninga
- WHO Country Office, World Health Organisation, P.O. Box 32346, Ridgeway, Lusaka, Zambia
| | - M.P. Rebollo
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - B. Thomas
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - M.J. Bockarie
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - H. Betts
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - J.R. Stothard
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - L.A. Kelly-Hope
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
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Ssempiira J, Nambuusi B, Kissa J, Agaba B, Makumbi F, Kasasa S, Vounatsou P. The contribution of malaria control interventions on spatio-temporal changes of parasitaemia risk in Uganda during 2009-2014. Parasit Vectors 2017; 10:450. [PMID: 28964263 PMCID: PMC5622426 DOI: 10.1186/s13071-017-2393-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 09/19/2017] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND In Uganda, malaria vector control interventions and case management with Artemisinin Combination Therapies (ACTs) have been scaled up over the last few years as a result of increased funding. Data on parasitaemia prevalence among children less than 5 years old and coverage of interventions was collected during the first two Malaria Indicator Surveys (MIS) conducted in 2009 and 2014, respectively. In this study, we quantify the effects of control interventions on parasitaemia risk changes between the two MIS in a spatio-temporal analysis. METHODS Bayesian geostatistical and temporal models were fitted on the MIS data of 2009 and 2014. The models took into account geographical misalignment in the locations of the two surveys and adjusted for climatic changes and socio-economic differentials. Parasitaemia risk was predicted over a 2 × 2 km2 grid and the number of infected children less than 5 years old was estimated. Geostatistical variable selection was applied to identify the most important ITN coverage indicators. A spatially varying coefficient model was used to estimate intervention effects at sub-national level. RESULTS The coverage of Insecticide Treated Nets (ITNs) and ACTs more than doubled at country and sub-national levels during the period 2009-2014. The coverage of Indoor Residual Spraying (IRS) remained static at all levels. ITNs, IRS, and ACTs were associated with a reduction in parasitaemia odds of 19% (95% BCI: 18-29%), 78% (95% BCI: 67-84%), and 34% (95% BCI: 28-66%), respectively. Intervention effects varied with region. Higher socio-economic status and living in urban areas were associated with parasitaemia odds reduction of 46% (95% BCI: 0.51-0.57) and 57% (95% BCI: 0.40-0.53), respectively. The probability of parasitaemia risk decline in the country was 85% and varied from 70% in the North-East region to 100% in Kampala region. The estimated number of children infected with malaria declined from 2,480,373 in 2009 to 825,636 in 2014. CONCLUSIONS Interventions have had a strong effect on the decline of parasitaemia risk in Uganda during 2009-2014, albeit with varying magnitude in the regions. This success should be sustained by optimizing ITN coverage to achieve universal coverage.
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Affiliation(s)
- Julius Ssempiira
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Makerere University School of Public Health, Kampala, Uganda
| | - Betty Nambuusi
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Makerere University School of Public Health, Kampala, Uganda
| | | | | | | | - Simon Kasasa
- Makerere University School of Public Health, Kampala, Uganda
| | - Penelope Vounatsou
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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26
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Sutcliffe J, Ji X, Yin S. How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets. Malar J 2017; 16:304. [PMID: 28764726 PMCID: PMC5540337 DOI: 10.1186/s12936-017-1951-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 07/20/2017] [Indexed: 11/18/2022] Open
Abstract
Background Insecticide-treated bed nets (ITNs) have played an integral role in malaria reduction but how insecticide depletion and accumulating physical damage affect ITN performance is poorly understood. More accurate methods are needed to assess damage to bed nets so that they can be designed, deployed and replaced optimally. Methods Video recordings of female Anopheles gambiae in near approach (1–½ cm) to occupied untreated rectangular bed nets in a laboratory study were used to quantify the amount of mosquito activity (appearances over time) around different parts of the net, the per-appearance probability of a mosquito coming close to holes of different sizes (hole encounter) and the per-encounter probability of mosquitoes passing through holes of different sizes (hole passage). Results Appearance frequency on different parts of the net reflected previously reported patterns: the area of the net under greatest mosquito pressure was the roof, followed by the bottom 30 cm of the sides, followed by the 30 cm area immediately above this, followed by the upper two-thirds of the sides. The ratio of activity in these areas was (respectively) 250:33:5:1. Per-appearance probability of hole encounter on all parts of the net was strongly predicted by a factor combining hole perimeter and area. Per-encounter probability of hole passage, in turn, was strongly predicted by hole width. For a given width, there was a 20% greater risk of passage through holes on the roof than holes on the sides. Discussion Appearance, encounter and passage predictors correspond to various mosquito behaviours that have previously been described and are combined into a prototype mosquito entry risk tool that predicts mosquito entry rates for nets with various amounts of damage. Scenarios that use the entry risk tool to test the recommendations of the WHOPES proportionate hole index (pHI) suggest that the pHI hole size categories and failure to account for hole location likely sometimes lead to incorrect conclusions about net serviceability that could be avoided by using an entry risk tool of the form presented here instead. Practical methods of collecting hole position, shape and size information for bed net assessments using the tool in the field are discussed and include using image analysis and on-line geometric analysis tools. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1951-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- James Sutcliffe
- Department of Biology, Trent University, Peterborough, ON, Canada. .,Entomology Branch, US Centers for Disease Control and Prevention, Atlanta, GA, USA.
| | - Xin Ji
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, USA
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27
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Njunda AL, Njumkeng C, Nsagha SD, Assob JCN, Kwenti TE. The prevalence of malaria in people living with HIV in Yaounde, Cameroon. BMC Public Health 2016; 16:964. [PMID: 27619013 PMCID: PMC5376676 DOI: 10.1186/s12889-016-3647-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Accepted: 09/06/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Coinfection with malaria and HIV is common in Sub-Saharan Africa. In the advent of a decline in the global incidence of malaria, it is important to generate updated data on the burden of malaria in people living with HIV (PLWHIV). This study was designed to determine the prevalence of malaria in PLWHIV in Yaounde, Cameroon, as well determine the association between CD4 (+) T cell count and malaria in the study population. METHODS In a cross sectional study performed between April 2015 and June 2016, 355 PLWHIV were enrolled and blood samples were collected for analysis. Complete blood count was performed using an automated haematology analyser (Mindray®, BC-2800) and CD4 (+) T cell count was performed using a flow cytometer (BD FASCount™). Giemsa-stained blood films were examined to detect malaria parasite. The Pearson's chi-square, student's T-test, ANOVA, and correlation analysis were all performed as part of the statistical analyses. RESULTS The prevalence of malaria observed in the study was 7.3 % (95 % CI: 4.8-10.6). No significant association was observed between the prevalence of malaria and age or gender. The prevalence of malaria was higher in participants who were not sleeping in insecticide treated bed nets, ITNs (p < 0.001); and in participants who were not on cotrimoxazole prophylaxis (p = 0.002). The prevalence of malaria (p < 0.001) and malaria parasite density (p = 0.005) were observed to be progressively higher in participants with CD4 (+) T cell count below 200cells/μl. Furthermore, the mean CD4 (+) T cell count was observed to be lower in participants coinfected with malaria compared to non-coinfected participants (323.5 vs 517.7) (p < 0.001). In this study, a negative correlation was observed between malaria parasite density and CD4 (+) T cell count (p = 0.019). CONCLUSIONS A low prevalence of malaria was observed in the study population. Some of the factors accounting for the low prevalence of malaria in this study population may include the health seeking habit of PLWHIV, the use of cotrimoxazole based chemoprophylaxis, and their cautious use of ITNs.
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Affiliation(s)
- Anna Longdoh Njunda
- Department of Medical Laboratory Sciences, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Charles Njumkeng
- Department of Medical Laboratory Sciences, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Shey Dickson Nsagha
- Department of Public Health and Hygiene, University of Buea, P.O. Box 63, Buea, Cameroon
| | | | - Tebit Emmanuel Kwenti
- Department of Medical Laboratory Sciences, University of Buea, P.O. Box 63, Buea, Cameroon.
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28
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Zhou Z, Mitchell RM, Kariuki S, Odero C, Otieno P, Otieno K, Onyona P, Were V, Wiegand RE, Gimnig JE, Walker ED, Desai M, Shi YP. Assessment of submicroscopic infections and gametocyte carriage of Plasmodium falciparum during peak malaria transmission season in a community-based cross-sectional survey in western Kenya, 2012. Malar J 2016; 15:421. [PMID: 27543112 PMCID: PMC4992329 DOI: 10.1186/s12936-016-1482-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 08/10/2016] [Indexed: 11/10/2022] Open
Abstract
Background Although malaria control intervention has greatly decreased malaria morbidity and mortality in many African countries, further decline in parasite prevalence has stagnated in western Kenya. In order to assess if malaria transmission reservoir is associated with this stagnation, submicroscopic infection and gametocyte carriage was estimated. Risk factors and associations between malaria control interventions and gametocyte carriage were further investigated in this study. Methods A total of 996 dried blood spot samples were used from two strata, all smear-positives (516 samples) and randomly selected smear-negatives (480 samples), from a community cross-sectional survey conducted at peak transmission season in 2012 in Siaya County, western Kenya. Plasmodium falciparum parasite presence and density were determined by stained blood smear and by 18S mRNA transcripts using nucleic acid sequence-based amplification assay (NASBA), gametocyte presence and density were determined by blood smear and by Pfs25 mRNA-NASBA, and gametocyte diversity by Pfg377 mRNA RT-PCR and RT-qPCR. Results Of the randomly selected smear-negative samples, 69.6 % (334/480) were positive by 18S-NASBA while 18S-NASBA detected 99.6 % (514/516) smear positive samples. Overall, 80.2 % of the weighted population was parasite positive by 18S-NASBA vs 30.6 % by smear diagnosis and 44.0 % of the weighted population was gametocyte positive by Pfs25-NASBA vs 2.6 % by smear diagnosis. Children 5–15 years old were more likely to be parasitaemic and gametocytaemic by NASBA than individuals >15 years old or children <5 years old while gametocyte density decreased with age. Anaemia and self-reported fever within the past 24 h were associated with increased odds of gametocytaemia. Fever was also positively associated with parasite density, but not with gametocyte density. Anti-malarial use within the past 2 weeks decreased the odds of gametocytaemia, but not the odds of parasitaemia. In contrast, recent anti-malarial use was associated with lowered parasite density, but not the gametocyte density. Use of ITNs was associated with lower odds for parasitaemia in part of the study area with a longer history of ITN interventions. In the same part of study area, the odds of having multiple gametocyte alleles were also lower in individuals using ITNs than in those not using ITNs and parasite density was positively associated with gametocyte diversity. Conclusion A large proportion of submicroscopic parasites and gametocytes in western Kenya might contribute to the stagnation in malaria prevalence, suggesting that additional interventions targeting the infectious reservoir are needed. As school aged children and persons with anaemia and fever were major sources for gametocyte reservoir, these groups should be targeted for intervention and prevention to reduce malaria transmission. Anti-malarial use was associated with lower parasite density and odds of gametocytaemia, but not the gametocyte density, indicating a limitation of anti-malarial impact on the transmission reservoir. ITN use had a protective role against parasitaemia and gametocyte diversity in western Kenya. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1482-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhiyong Zhou
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA.
| | - Rebecca M Mitchell
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Simon Kariuki
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Christopher Odero
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Peter Otieno
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Kephas Otieno
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Philip Onyona
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Vincent Were
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Ryan E Wiegand
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - John E Gimnig
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Edward D Walker
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Meghna Desai
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Ya Ping Shi
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA.
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Abstract
BACKGROUND Malaria is the leading cause of morbidity in Uganda with 90-95 % of the population at risk and it contributing to approximately 13 % of under-five mortality. The aim of this study was to investigate the relationship between the malaria status of children under the age of 5 years old in Uganda and selected socio-economic, demographic and environmental factors, as well as to identify significant risk factors associated with malaria. METHODS This study made use of data collected from the 2014 Malaria Indicator Survey conducted in Uganda. Two test procedures for malaria in children under the age of 5 years old were carried out. Due to the complex survey design, a generalized linear mixed model was used to test for associations between several independent variables and the response variable, which was whether a child tested positive or negative for malaria according to the microscopy test. RESULTS The sample in this study was made up of 4939 children. Of those children, 974 tested positive for malaria, resulting in an observed malaria prevalence of 19.7 %. The socio-economic factors closely related to the risk of malaria were main floor material, main wall material and availability of electricity in the household. The event of indoor residual spraying (IRS) significantly reduced a child's risk of malaria. An older child was associated with a higher risk of malaria, however their risk decreased with an increase in cluster altitude and an increase in their caregiver's education level. CONCLUSION Although there has been a significant increase in the use of mosquito nets since the previous Malaria Indicator Survey done in 2009, particularly in the use of insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs), these control measures alone may not be sufficient. IRS will be a key strategy in reaching the malaria goals set by the government of Uganda. Supplementing these control measures with education of appropriate and consistent use of ITNs and LLINs, as well as education of practicing safe living habits, such as reducing outdoor activities during peak biting hours of a mosquito, can go a long way in aiding the reduction of the burden of malaria in Uganda.
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Affiliation(s)
- Danielle Roberts
- School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Westville, Private Bag X 54001, 4000, Durban, South Africa.
| | - Glenda Matthews
- School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Westville, Private Bag X 54001, 4000, Durban, South Africa
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Fokam EB, Ngimuh L, Anchang-Kimbi JK, Wanji S. Assessment of the usage and effectiveness of intermittent preventive treatment and insecticide-treated nets on the indicators of malaria among pregnant women attending antenatal care in the Buea Health District, Cameroon. Malar J 2016; 15:172. [PMID: 26987387 PMCID: PMC4794838 DOI: 10.1186/s12936-016-1228-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 03/11/2016] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Malaria in pregnancy is an immense public health problem with at least 50 million pregnant women living in malaria endemic areas. To prevent malaria and its complications in pregnancy the World Health Organization recommends the use of intermittent preventive treatment sulfadoxine-pyrimethamine (IPTp-SP), the use of insecticide-treated nets (ITNs), and effective case management. In most malaria endemic countries in Africa, 40% of pregnant women sleep under ITNs. In Cameroon, about 90% of pregnant women receive the first dose of SP, while 64% take the complete dose. Following the 2011 mass-campaign of free distribution of ITNs coupled with routine ANC distribution of ITN and adoption of IPTp in Cameroon, little has been done to assess the effectiveness of both interventions outside of Yaoundé, the capital city. This study sought to assess the usage and effectiveness of IPTp-SP and ITNs on malaria in pregnancy. METHODS The research was a cross-sectional hospital-based study that included 410 pregnant women attending antenatal clinics in the Buea Health District. Capillary blood samples were collected to check malaria parasite by microscopy and haemoglobin levels by microhaematocrit technique. RESULTS A prevalence of 13.4 and 41.7% was detected for malaria and anaemia, respectively. The Overall coverage of ITN was 32.4% while that of ITPp was 63.2%. Malaria prevalence was least (7.2%) amongst women using both IPTp-SP and ITN while those with no intervention had the highest malaria prevalence of 18.6% (χ2 = 6.188; P = 0.103). Of the women with malaria, 12.73% were using ITN and had taken at least one dose of SP, 38.18% had taken at least one dose IPTp only, 10.91% were using only ITN and 38.18% were not using any preventive measure. There was a difference in anaemia status within the different intervention groups (χ2 = 8.673; P = 0.034). Pregnant women using both interventions were less associated to malaria (OR = 0.341, 95% CI = 0.138-0.841) compared to those using only one control method. CONCLUSION Repeated doses of SP in combination with ITN use are effective in reducing malaria parasitaemia and improving haemoglobin level of pregnant women.
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Affiliation(s)
- Eric Bertrand Fokam
- />Department of Zoology and Animal Physiology, University of Buea, 63, Buea, Cameroon
| | - Leonard Ngimuh
- />Department of Microbiology and Parasitology, University of Buea, 63, Buea, Cameroon
| | | | - Samuel Wanji
- />Department of Microbiology and Parasitology, University of Buea, 63, Buea, Cameroon
- />Research Foundation in Tropical Diseases and Environment, P.O. Box 474, Buea, Cameroon
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Stephens JK, Ofori MF, Quakyi IA, Wilson ML, Akanmori BD. Prevalence of peripheral blood parasitaemia, anaemia and low birthweight among pregnant women in a suburban area in coastal Ghana. Pan Afr Med J 2014; 17 Suppl 1:3. [PMID: 24624240 PMCID: PMC3946255 DOI: 10.11694/pamj.supp.2014.17.1.3541] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 12/02/2013] [Indexed: 11/06/2022] Open
Abstract
Introduction Malaria and anaemia have adverse effects in pregnant women and on the birth weight of infants in malaria endemic areas. P. falciparum malaria, the most virulent species continues to be a major health problem in sub-Saharan Africa. This study was carried out to establish the prevalence of pregnancy-associated malaria and its associated consequences including maternal anaemia and low birthweight (LBW) deliveries and placental malaria among pregnant women in a sub-urban area in coastal Ghana. Methods A facility-based investigation was carried out among 320 pregnant women seeking antenatal care in a hospital in suburban coastal Ghana. Information on the use of Insecticide Treated Nets (ITNs) and Intermittent Preventive Treatment in pregnancy (IPTp) were collected using a structured questionnaire at enrolment. Venous blood was collected for microscopy and screening for Glucose 6-phosphate dehydrogenase (G6PD) deficiency. Haemoglobin concentration was obtained from an automatic blood analyzer. Placental smears and birth weight measurements were taken at delivery. Resuls The prevalence of Plasmodium falciparum parasitaemia was 5%. The mean haemoglobin (Hb) level at registration was 11.44g/dL (95% CI 11.29 – 11.80). Placental blood parasitaemia and low birthweight were 2.5% and 3% respectively. ITN possession was 31.6% with 5.4% usage. The IPTp coverage was 55%. Conclusion The prevalence of malaria and anaemia among the pregnant women were low at enrolment. Placental blood parasitaemia and LBW at delivery were also low. These are clear indications of the high coverage of the IPTp. Increase in ITN use will further improve birthweight outcomes and reduce placental malaria.
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Affiliation(s)
- Judith Koryo Stephens
- Biological, Environmental and Occupational Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. BOX LG 13 Legon, Accra, Ghana
| | - Michael F Ofori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of H College of Health Sciences, University of Ghana, P. O. BOX LG 581 Legon, Accra, Ghana
| | - Isabella Akyinbah Quakyi
- Biological, Environmental and Occupational Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. BOX LG 13 Legon, Accra, Ghana
| | - Mark Lee Wilson
- Department of Epidemiology, School of Public Health II, The University of Michigan, 109 Observatory Street, M5507, Ann Arbor, MI 48109-2029, USA
| | - Bartholomew Dicky Akanmori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of H College of Health Sciences, University of Ghana, P. O. BOX LG 581 Legon, Accra, Ghana ; Vaccine Research and Development, Immunization and Vaccines Development Cluster, Office of the Regional Director, WHO regional Office for Africa, Box 06 Djoue, Brazzaville, Congo
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