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Joseph RN, Mwema T, Eiseb SJ, Maliti DV, Tambo M, Iitula I, Eloff L, Lukubwe O, Smith-Gueye C, Vajda ÉA, Tatarsky A, Katokele ST, Uusiku PN, Walusimbi D, Ogoma SB, Mumbengegwi DR, Lobo NF. Insecticide susceptibility status of Anopheles gambiae mosquitoes and the effect of pre-exposure to a piperonyl butoxide (PBO) synergist on resistance to deltamethrin in northern Namibia. Malar J 2024; 23:77. [PMID: 38486288 PMCID: PMC10941414 DOI: 10.1186/s12936-024-04898-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 03/02/2024] [Indexed: 03/17/2024] Open
Abstract
BACKGROUND Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO). METHODS This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly. RESULTS The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021. CONCLUSIONS Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region.
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Affiliation(s)
| | | | | | | | - Munyaradzi Tambo
- University of Namibia (UNAM), Windhoek, Namibia
- Washington University School of Medicine, St. Louis, MO, USA
| | - Iitula Iitula
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | - Lydia Eloff
- University of Namibia (UNAM), Windhoek, Namibia
| | - Ophilia Lukubwe
- Clinton Health Access Initiative (CHAI), Boston, MA, USA
- Namibia University of Science and Technology, Windhoek, Namibia
| | - Cara Smith-Gueye
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Élodie A Vajda
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Allison Tatarsky
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
| | - Stark T Katokele
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | - Petrina N Uusiku
- Ministry of Health and Social Services (MoHSS), Windhoek, Namibia
| | | | - Sheila B Ogoma
- Clinton Health Access Initiative (CHAI), Boston, MA, USA
| | | | - Neil F Lobo
- Malaria Elimination Initiative, University of California, san francisco, San Francisco, USA
- University of Notre Dame, Notre Dame, IN, USA
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Hadebe MT, Malgwi SA, Okpeku M. Revolutionizing Malaria Vector Control: The Importance of Accurate Species Identification through Enhanced Molecular Capacity. Microorganisms 2023; 12:82. [PMID: 38257909 PMCID: PMC10818655 DOI: 10.3390/microorganisms12010082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 12/08/2023] [Accepted: 12/20/2023] [Indexed: 01/24/2024] Open
Abstract
Many factors, such as the resistance to pesticides and a lack of knowledge of the morphology and molecular structure of malaria vectors, have made it more challenging to eradicate malaria in numerous malaria-endemic areas of the globe. The primary goal of this review is to discuss malaria vector control methods and the significance of identifying species in vector control initiatives. This was accomplished by reviewing methods of molecular identification of malaria vectors and genetic marker classification in relation to their use for species identification. Due to its specificity and consistency, molecular identification is preferred over morphological identification of malaria vectors. Enhanced molecular capacity for species identification will improve mosquito characterization, leading to accurate control strategies/treatment targeting specific mosquito species, and thus will contribute to malaria eradication. It is crucial for disease epidemiology and surveillance to accurately identify the Plasmodium spp. that are causing malaria in patients. The capacity for disease surveillance will be significantly increased by the development of more accurate, precise, automated, and high-throughput diagnostic techniques. In conclusion, although morphological identification is quick and achievable at a reduced cost, molecular identification is preferred for specificity and sensitivity. To achieve the targeted malaria elimination goal, proper identification of vectors using accurate techniques for effective control measures should be prioritized.
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Affiliation(s)
| | | | - Moses Okpeku
- Discipline of Genetics, School of Life Sciences, University of KwaZulu-Natal, Westville, Durban 4000, South Africa
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Beloconi A, Nyawanda BO, Bigogo G, Khagayi S, Obor D, Danquah I, Kariuki S, Munga S, Vounatsou P. Malaria, climate variability, and interventions: modelling transmission dynamics. Sci Rep 2023; 13:7367. [PMID: 37147317 PMCID: PMC10161998 DOI: 10.1038/s41598-023-33868-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 04/20/2023] [Indexed: 05/07/2023] Open
Abstract
Assessment of the relative impact of climate change on malaria dynamics is a complex problem. Climate is a well-known factor that plays a crucial role in driving malaria outbreaks in epidemic transmission areas. However, its influence in endemic environments with intensive malaria control interventions is not fully understood, mainly due to the scarcity of high-quality, long-term malaria data. The demographic surveillance systems in Africa offer unique platforms for quantifying the relative effects of weather variability on the burden of malaria. Here, using a process-based stochastic transmission model, we show that in the lowlands of malaria endemic western Kenya, variations in climatic factors played a key role in driving malaria incidence during 2008-2019, despite high bed net coverage and use among the population. The model captures some of the main mechanisms of human, parasite, and vector dynamics, and opens the possibility to forecast malaria in endemic regions, taking into account the interaction between future climatic conditions and intervention scenarios.
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Affiliation(s)
- Anton Beloconi
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Bryan O Nyawanda
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - Godfrey Bigogo
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - Sammy Khagayi
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - David Obor
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - Ina Danquah
- Heidelberg Institute of Global Health (HIGH), Medical Faculty and University Hospital, Heidelberg University, Heidelberg, Germany
| | - Simon Kariuki
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - Stephen Munga
- Kenya Medical Research Institute - Centre for Global Health Research, Kisumu, Kenya
| | - Penelope Vounatsou
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
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4
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Okiring J, Gonahasa S, Nassali M, Namuganga JF, Bagala I, Maiteki-Sebuguzi C, Opigo J, Nabende I, Nangendo J, Kabami J, Ssewanyana I, Kiwuwa SM, Nankabirwa JI, Dorsey G, Briggs J, Kamya MR, Staedke SG. LLIN Evaluation in Uganda Project (LLINEUP2)-Factors associated with coverage and use of long‑lasting insecticidal nets following the 2020-21 national mass distribution campaign: a cross-sectional survey of 12 districts. Malar J 2022; 21:293. [PMID: 36261818 PMCID: PMC9580445 DOI: 10.1186/s12936-022-04302-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 09/26/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND In 2020-2021, long-lasting insecticidal nets (LLINs) were distributed nationwide in Uganda during the COVID-19 pandemic. A cross-sectional survey was conducted in 12 districts to evaluate the impact of the campaign 1-5 months after LLIN distribution. METHODS During April-May 2021, households were randomly selected from target areas (1-7 villages) surrounding 12 government-run health facilities established as Malaria Reference Centres; at least 50 households were enrolled per cluster. Outcomes included household ownership of LLINs distributed through the universal coverage campaign (UCC) (at least one UCC LLIN), adequate coverage of UCC LLINs (at least one UCC LLIN per 2 residents), and use of LLINs (resident slept under a LLIN the previous night). Multivariate logistic regression models were used to identify household- and individual-level factors associated with outcomes, controlling for clustering around health facilities. RESULTS In total, 634 households, with 3342 residents and 1631 bed-nets, were included. Most households (93.4%) owned at least 1 UCC LLIN, but only 56.8% were adequately covered by UCC LLINs. In an adjusted analysis, the factor most strongly associated with adequate coverage by UCC LLINs was fewer household residents (1-4 vs 7-14; adjusted odds ratio [aOR] 12.96, 95% CI 4.76-35.26, p < 0.001; 5-6 vs 7-14 residents; aOR 2.99, 95% CI 1.21-7.42, p = 0.018). Of the 3166 residents of households that owned at least one UCC LLIN, only 1684 (53.2%) lived in adequately covered households; 89.9% of these used an LLIN the previous night, compared to 1034 (69.8%) of 1482 residents living in inadequately covered households. In an adjusted analysis, restricted to residents of inadequately covered households, LLIN use was higher in children under-five than those aged 5-15 years (aOR 3.04, 95% CI 2.08-4.46, p < 0.001), and higher in household heads than distantly-related residents (aOR 3.94, 95% CI 2.38-6.51, p < 0.001). CONCLUSIONS Uganda's 2021-21 campaign was successful, despite the COVID-19 pandemic. In future campaigns, strategies should be adopted to ensure high LLIN coverage, particularly for larger households. A better understanding of the drivers of LLIN use within households is needed to guide future interventions, educational messages, and behaviour change communication strategies; school-aged children and distantly-related residents appear vulnerable and could be targeted.
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Affiliation(s)
- Jaffer Okiring
- Clinical Epidemiology Unit, School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda.
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda.
| | - Samuel Gonahasa
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Martha Nassali
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Jane F Namuganga
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Irene Bagala
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Catherine Maiteki-Sebuguzi
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
- National Malaria Control Division, Ministry of Health, Kampala, Uganda
| | - Jimmy Opigo
- National Malaria Control Division, Ministry of Health, Kampala, Uganda
| | - Isaiah Nabende
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Joanita Nangendo
- Clinical Epidemiology Unit, School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Jane Kabami
- Clinical Epidemiology Unit, School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Isaac Ssewanyana
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Steven M Kiwuwa
- Department of Child Health and Development Centre, School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Joaniter I Nankabirwa
- Clinical Epidemiology Unit, School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
| | - Grant Dorsey
- Department of Medicine, University of California San Francisco, San Francisco, USA
| | - Jessica Briggs
- Department of Medicine, University of California San Francisco, San Francisco, USA
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
- Department of Medicine, Makerere University, Kampala, Uganda
| | - Sarah G Staedke
- Infectious Diseases Research Collaboration, PO Box 7475, Kampala, Uganda
- Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
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5
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Otambo WO, Onyango PO, Ochwedo K, Olumeh J, Onyango SA, Orondo P, Atieli H, Lee MC, Wang C, Zhong D, Githeko A, Zhou G, Githure J, Ouma C, Yan G, Kazura J. Clinical malaria incidence and health seeking pattern in geographically heterogeneous landscape of western Kenya. BMC Infect Dis 2022; 22:768. [PMID: 36192672 PMCID: PMC9528858 DOI: 10.1186/s12879-022-07757-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 09/27/2022] [Indexed: 12/03/2022] Open
Abstract
Background Malaria remains a public health problem in Kenya despite sustained interventions deployed by the government. One of the major impediments to effective malaria control is a lack of accurate diagnosis and effective treatment. This study was conducted to assess clinical malaria incidence and treatment seeking profiles of febrile cases in western Kenya. Methods Active case detection of malaria was carried out in three eco-epidemiologically distinct zones topologically characterized as lakeshore, hillside, and highland plateau in Kisumu County, western Kenya, from March 2020 to March 2021. Community Health Volunteers (CHVs) conducted biweekly visits to residents in their households to interview and examine for febrile illness. A febrile case was defined as an individual having fever (axillary temperature ≥ 37.5 °C) during examination or complaints of fever and other nonspecific malaria related symptoms 1–2 days before examination. Prior to the biweekly malaria testing by the CHVs, the participants' treatment seeking methods were based on their behaviors in response to febrile illness. In suspected malaria cases, finger-prick blood samples were taken and tested for malaria parasites with ultra-sensitive Alere® malaria rapid diagnostic tests (RDT) and subjected to real-time polymerase chain reaction (RT-PCR) for quality control examination. Results Of the total 5838 residents interviewed, 2205 residents had high temperature or reported febrile illness in the previous two days before the visit. Clinical malaria incidence (cases/1000people/month) was highest in the lakeshore zone (24.3), followed by the hillside (18.7) and the highland plateau zone (10.3). Clinical malaria incidence showed significant difference across gender (χ2 = 7.57; df = 2, p = 0.0227) and age group (χ2 = 58.34; df = 4, p < 0.0001). Treatment seeking patterns of malaria febrile cases showed significant difference with doing nothing (48.7%) and purchasing antimalarials from drug shops (38.1%) being the most common health-seeking pattern among the 2205 febrile residents (χ2 = 21.875; df = 4, p < 0.0001). Caregivers of 802 school-aged children aged 5–14 years with fever primarily sought treatment from drug shops (28.9%) and public hospitals (14.0%), with significant lower proportions of children receiving treatment from traditional medication (2.9%) and private hospital (4.4%) (p < 0.0001). There was no significant difference in care givers' treatment seeking patterns for feverish children under the age of five (p = 0.086). Residents with clinical malaria cases in the lakeshore and hillside zones sought treatment primarily from public hospitals (61.9%, 60/97) traditional medication (51.1%, 23/45) respectively (p < 0.0001). However, there was no significant difference in the treatment seeking patterns of highland plateau residents with clinical malaria (p = 0.431).The main factors associated with the decision to seek treatment were the travel distance to the health facility, the severity of the disease, confidence in the treatment, and affordability. Conclusion Clinical malaria incidence remains highest in the Lakeshore (24.3cases/1000 people/month) despite high LLINs coverage (90%). The travel distance to the health facility, severity of disease and affordability were mainly associated with 80% of residents either self-medicating or doing nothing to alleviate their illness. The findings of this study suggest that the Ministry of Health should strengthen community case management of malaria by providing supportive supervision of community health volunteers to advocate for community awareness, early diagnosis, and treatment of malaria. Supplementary Information The online version contains supplementary material available at 10.1186/s12879-022-07757-w.
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Affiliation(s)
- Wilfred Ouma Otambo
- Department of Zoology, Maseno University, Kisumu, Kenya. .,International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya.
| | | | - Kevin Ochwedo
- International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya
| | - Julius Olumeh
- School of Natural and Environmental Science, Newcastle University, Newcastle Upon Tyne, UK
| | - Shirley A Onyango
- International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya
| | - Pauline Orondo
- International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya
| | - Harrysone Atieli
- International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya
| | - Ming-Chieh Lee
- Program in Public Health, University of California Irvine, Irvine, CA, USA
| | - Chloe Wang
- Program in Public Health, University of California Irvine, Irvine, CA, USA
| | - Daibin Zhong
- Program in Public Health, University of California Irvine, Irvine, CA, USA
| | - Andrew Githeko
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Guofa Zhou
- Program in Public Health, University of California Irvine, Irvine, CA, USA
| | - John Githure
- International Centre of Excellence for Malaria Research, Tom Mboya University College-University of California Irvine Joint Lab, Homa Bay, Kenya
| | - Collins Ouma
- Department of Biomedical Sciences and Technology, Maseno University, Kisumu, Kenya
| | - Guiyun Yan
- Program in Public Health, University of California Irvine, Irvine, CA, USA
| | - James Kazura
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Ujuju CN, Okoronkwo C, Okoko OO, Akerele A, Okorie CN, Adebayo SB. Use of insecticide treated nets in children under five and children of school age in Nigeria: Evidence from a secondary data analysis of demographic health survey. PLoS One 2022; 17:e0274160. [PMID: 36174025 PMCID: PMC9521839 DOI: 10.1371/journal.pone.0274160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 08/23/2022] [Indexed: 11/18/2022] Open
Abstract
Background and objective Use of insecticide treated nets (ITN), one of the most cost-effective malaria interventions contributes to malaria cases averted and reduction in child mortality. We explored the use of ITN in children under five (CU5) and children of school age to understand factors contributing to ITN use. Methods A cross-sectional study analyzed 2018 Nigeria Demographic and Health Survey data. The outcome variable was CU5 or children of school age who slept under ITN the night before the survey. Independent variables include child sex, head of household’s sex, place of residence, state, household owning radio and television, number of household members, wealth quintile, years since ITN was obtained and level of malaria endemicity. Multi-level logistic regression model was used to access factors associated with ITN use among children. Results In total, 32,087 CU5 and 54,692 children of school age were examined with 74.3% of CU5 and 57.8% of children of school age using ITN the night before the survey. While seven states had more than 80% of CU5 who used ITN, only one state had over 80% of school children who used ITN. ITN use in CU5 is associated with living in rural area (aOR = 1.20, 95% CI 1.14 to 1.26) and residing in meso endemic area (aOR = 3.1, 95% CI 2.89 to 3.54). While In children of school age, use of ITN was associated with female headed households (aOR = 1.14, 95% CI 1.09 to 1.19), meso (aOR = 3.17, 95% CI 2.89 to 3.47) and hyper (aOR = 14.9, 95% CI 12.99 to 17.07) endemic areas. Children residing in larger households were less likely to use ITN. Conclusions This study demonstrated increased use of ITN in CU5 from poor households and children living in rural and malaria endemic areas. Findings provide some policy recommendations for increasing ITN use in school children.
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Affiliation(s)
| | - Chukwu Okoronkwo
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Okefu Oyale Okoko
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Adekunle Akerele
- Department of Medical Statistics and Epidemiology, University of Ibadan, Ibadan, Nigeria
| | - Chibundo N. Okorie
- Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Enugu, Nigeria
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Otambo WO, Omondi CJ, Ochwedo KO, Onyango PO, Atieli H, Lee MC, Wang C, Zhou G, Githeko AK, Githure J, Ouma C, Yan G, Kazura J. Risk associations of submicroscopic malaria infection in lakeshore, plateau and highland areas of Kisumu County in western Kenya. PLoS One 2022; 17:e0268463. [PMID: 35576208 PMCID: PMC9109926 DOI: 10.1371/journal.pone.0268463] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/29/2022] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Persons with submicroscopic malaria infection are a major reservoir of gametocytes that sustain malaria transmission in sub-Saharan Africa. Despite recent decreases in the national malaria burden in Kenya due to vector control interventions, malaria transmission continues to be high in western regions of the country bordering Lake Victoria. The objective of this study was to advance knowledge of the topographical, demographic and behavioral risk factors associated with submicroscopic malaria infection in the Lake Victoria basin in Kisumu County. METHODS Cross-sectional community surveys for malaria infection were undertaken in three eco-epidemiologically distinct zones in Nyakach sub-County, Kisumu. Adjacent regions were topologically characterized as lakeshore, hillside and highland plateau. Surveys were conducted during the 2019 and 2020 wet and dry seasons. Finger prick blood smears and dry blood spots (DBS) on filter paper were collected from 1,777 healthy volunteers for microscopic inspection and real time-PCR (RT-PCR) diagnosis of Plasmodium infection. Persons who were PCR positive but blood smear negative were considered to harbor submicroscopic infections. Topographical, demographic and behavioral risk factors were correlated with community prevalence of submicroscopic infections. RESULTS Out of a total of 1,777 blood samples collected, 14.2% (253/1,777) were diagnosed as submicroscopic infections. Blood smear microscopy and RT-PCR, respectively, detected 3.7% (66/1,777) and 18% (319/1,777) infections. Blood smears results were exclusively positive for P. falciparum, whereas RT-PCR also detected P. malariae and P. ovale mono- and co-infections. Submicroscopic infection prevalence was associated with topographical variation (χ2 = 39.344, df = 2, p<0.0001). The highest prevalence was observed in the lakeshore zone (20.6%, n = 622) followed by the hillside (13.6%, n = 595) and highland plateau zones (7.9%, n = 560). Infection prevalence varied significantly according to season (χ2 = 17.374, df = 3, p<0.0001). The highest prevalence was observed in residents of the lakeshore zone in the 2019 dry season (29.9%, n = 167) and 2020 and 2019 rainy seasons (21.5%, n = 144 and 18.1%, n = 155, respectively). In both the rainy and dry seasons the likelihood of submicroscopic infection was higher in the lakeshore (AOR: 2.71, 95% CI = 1.85-3.95; p<0.0001) and hillside (AOR: 1.74, 95% CI = 1.17-2.61, p = 0.007) than in the highland plateau zones. Residence in the lakeshore zone (p<0.0001), male sex (p = 0.025), school age (p = 0.002), and living in mud houses (p = 0.044) increased the risk of submicroscopic malaria infection. Bed net use (p = 0.112) and occupation (p = 0.116) were not associated with submicroscopic infection prevalence. CONCLUSION Topographic features of the local landscape and seasonality are major correlates of submicroscopic malaria infection in the Lake Victoria area of western Kenya. Diagnostic tests more sensitive than blood smear microscopy will allow for monitoring and targeting geographic sites where additional vector interventions are needed to reduce malaria transmission.
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Affiliation(s)
- Wilfred Ouma Otambo
- Department of Zoology, Maseno University, Kisumu, Kenya
- International Centre of Excellence for Malaria Research, Tom Mboya University College of Maseno University, Homa Bay, Kenya
| | - Collince J. Omondi
- International Centre of Excellence for Malaria Research, Tom Mboya University College of Maseno University, Homa Bay, Kenya
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
| | - Kevin O. Ochwedo
- International Centre of Excellence for Malaria Research, Tom Mboya University College of Maseno University, Homa Bay, Kenya
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
| | | | - Harrysone Atieli
- International Centre of Excellence for Malaria Research, Tom Mboya University College of Maseno University, Homa Bay, Kenya
| | - Ming-Chieh Lee
- Department of Population Health and Disease Prevention, University of California, Irvine, CA, United States of America
| | - Chloe Wang
- Department of Population Health and Disease Prevention, University of California, Irvine, CA, United States of America
| | - Guofa Zhou
- Department of Population Health and Disease Prevention, University of California, Irvine, CA, United States of America
| | - Andrew K. Githeko
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - John Githure
- International Centre of Excellence for Malaria Research, Tom Mboya University College of Maseno University, Homa Bay, Kenya
| | - Collins Ouma
- Department of Biomedical Sciences and Technology, Maseno University, Kisumu, Kenya
| | - Guiyun Yan
- Department of Population Health and Disease Prevention, University of California, Irvine, CA, United States of America
| | - James Kazura
- Centre for Global Health & Diseases, Case Western University Reserve, Cleveland, Ohio, United States of America
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