Lymphatic filariasis transmission in Rufiji District, southeastern Tanzania: infection status of the human population and mosquito vectors after twelve rounds of mass drug administration

Detection of Wuchereria bancrofti infection in mosquitoes in areas co-endemic with Brugia malayi in Balasore district, Odisha, India

Lymphatic filariasis (LF) is a crippling and disfiguring parasitic condition. India accounts for 55% of the world's LF burden. The filarial parasite Wuchereria bancrofti is known to cause 99.4% of the cases while, Brugia malayi accounts for 0.6% of the issue occurring mainly in some pockets of Odisha and Kerala states. The Balasore (Baleswar) district of Odisha has been a known focus of B. malayi transmission. We employed molecular xenomonitoring to detect filarial parasite DNA in vectors. In six selected villages, Gravid traps were used to collect Culex mosquitoes and hand catch method using aspirators was followed for collection of mansonioides. A total of 2903 mosquitoes comprising of Cx. quinquefasciatus (n = 2611; 89.94%), Cx. tritaeniorhynchus (n = 100; 3.44%), Mansonia annuliferea (n = 139; 4.78%) and Mansonia uniformis (n = 53; 1.82%) were collected from six endemic villages. The species wise mosquitoes were made into 118 pools, each with a maximum of 25 mosquitoes, dried and transported to the laboratory at VCRC, Puducherry. The mosquito pools were subjected to parasite DNA extraction, followed by Real-time PCR using LDR and HhaI probes to detect W. bancrofti and B. malayi infections, respectively. Seven pools (6.66%) of Cx. quinquefasciatus, showed infection with only W. bancrofti while none of the pools of other mosquito species showed infection with either W. bancrofti or B. malayi. Although the study area is endemic to B. malayi, none of the vectors of B. malayi was found with parasite infection. This study highlights the ongoing transmission of bancroftian filariasis in the study villages of Balasore district of Odisha and its implications for evaluating LF elimination programme.

Efficacy of ivermectin and albendazole combination in suppressing transmission of lymphatic filariasis following mass administration in Tanzania: a prospective cohort study

BACKGROUND

Preventive chemotherapy with ivermectin and albendazole (IA) in mass drug administration (MDA) programs for all at-risk populations is the core public health intervention to eliminate lymphatic filariasis (LF). Achieving this goal depends on drug effectiveness in reducing parasite reservoirs in the community to halt transmission. We assessed the efficacy of ivermectin and albendazole in clearing microfilariae and circulating filarial antigens (CFA) following MDA.

METHODS

This community-based prospective study was conducted in Mkinga district, Tanga region, Tanzania, from November 2018 to June 2019. A total of 4115 MDA-eligible individuals were screened for CFA using Filarial test strips. CFA positives were re-examined for microfilariae by microscopy. CFA and microfilariae positive individuals were enrolled and received IA through MDA campaign. The status of microfilariae and CFA was monitored before MDA, and on day 7 and six-month following MDA. The primary efficacy outcomes were the clearance rates of microfilariae on day 7 and six-months, and CFA at 6 months of post-MDA. The McNemar test assessed the proportions of microfilariae positive pre- and post-MDA, while Chi-square tests were utilized to examine factors associated with CFA status six months post-MDA.

RESULTS

Out of 4115 individuals screened, 239 (5.8%) tested positive for CFA, of whom 11 (4.6%) were also positive for microfilariae. Out of the ten microfilariae-positive individuals available for follow-up on day 7, nine tested negative, yielding a microfilariae clearance rate of 90% [95% confidence interval (CI): 59.6-98.2%]. Participants who tested negative for microfilariae on day 7 remained free of microfilariae six months after MDA. However, those who did not clear microfilariae on day-7 remained positive six-months post-MDA. The McNemar test revealed a significant improvement in microfilariae clearance on day 7 following MDA (P = 0.02). Out of 183 CFA-positive individuals who were available at 6-month follow-up, 160 (87.4%) remained CFA positive, while 23 became CFA negative. The CFA clearance rate at 6 months post-MDA was 12.6% (95% CI: 8.5-8.5%). There was no significant association of variability in ivermectin plasma exposure, measured by maximum concentration or area under the curve, and the clearance status of microfilariae or CFA post-MDA.

CONCLUSIONS

Preventive chemotherapy with IA effectively clears microfilariae within a week. However, it is less effective in clearing CFA at six months of post-MDA. The low clearance rate for filarial antigenemia underscores the need for alternative drug combinations and additional preventive measures to achieve LF elimination by 2030.

Prevalence of Sarcoptes scabiei infestation and its associated factors among primary school children: A school-based cross-sectional survey in the Rufiji district, Tanzania

Objectives

This study aimed to investigate the prevalence of Sarcoptes scabiei infestation and its associated factors among primary school children (PSC) in the Rufiji district.

Methods

A quantitative school-based cross-sectional study was conducted among 447 PSC in the Rufiji district. The prevalence of scabies among PSC was determined by clinical examination and by microscopic examination of skin samples for the presence of S. scabiei. A structured questionnaire was used to gather data on factors associated with S. scabiei infestation. Descriptive analysis, Fisher's exact, chi-square tests, and logistic regression analysis were used to analyze the data.

Results

The prevalence of scabies was 2.0%. Of the assessed factors, only physical contact with a person having itchy skin lesions (Adjusted Odds Ratio [AOR]=4.04, 95%CI 4.39-12.50) and infrequency of changing clothes before laundry (AOR=2.99, 95%CI 1.35-4.94) were significantly associated with scabies. The majority of participants demonstrated low levels of knowledge, with half exhibiting poor attitudes and inappropriate healthcare-seeking behaviors.

Conclusions

There was an ongoing transmission of scabies among PSC in the Rufiji district, with the factors associated with the transmission being physical contact with a person who had an itchy skin lesion and the infrequency of changing clothes before laundry. Therefore, there is a need for regular clinical screening and treatment of positive cases with preventive measures on contact and provision of health education.

Mosquitoes, Lymphatic Filariasis, and Public Health: A Systematic Review of Anopheles and Aedes Surveillance Strategies

Lymphatic Filariasis (LF) affects over 120 million people in 72 countries, with sub-periodic filariasis common in the Pacific. Wuchereria bancrofti has three physiological races, each with a unique microfilarial periodicity, and each race is isolated to a specific geographical region. Sub-periodic W. bancrofti is transmitted by various Aedes mosquito species, with Aedes polynesiensis and Aedes samoanus being the primary vectors in Samoa. The Aedes scutellaris and Aedes kochi groups are also important vectors in the South Pacific Islands. Anopheles species are important vectors of filariasis in rural areas of Asia and Africa. The Anopheles gambiae complex, Anopheles funestus, and the Anopheles punctulatus group are the most important vectors of W. bancrofti. These vectors exhibit indoor nocturnal biting behaviour and breed in a variety of habitats, including freshwater, saltwater, and temporary water bodies. Effective vector surveillance is central to LF control and elimination programs. However, the traditional Human Landing Collection (HLC) method, while valuable, poses ethical concerns and risks to collectors. Therefore, this review critically analyses alternative trapping tools for Aedes and Anopheles vectors in LF-endemic regions. We looked at 14 research publications that discussed W. bancrofti vector trapping methods. Pyrethrum Spray Catches (PSC), one of the seven traps studied for Anopheles LF vectors, was revealed to be the second most effective strategy after HLC, successfully catching Anopheles vectors in Nigeria, Ghana, Togo, and Burkina Faso. The PSC method has several drawbacks, such as the likelihood of overlooking exophilic mosquitoes or underestimating Anopheles populations. However, exit traps offered hope for capturing exophilic mosquitoes. Anopheles populations could also be sampled using the Anopheles Gravid Trap (AGT). In contrast, the effectiveness of the Double Net Traps (DNT) and the CDC Light Trap (CDC LT) varied. Gravid mosquito traps like the OviArt Gravid Trap (AGT) were shown to be useful tools for identifying endophilic and exophilic vectors during the exploration of novel collection techniques. The Stealth trap (ST) was suggested for sampling Anopheles mosquitoes, although specimen damage may make it difficult to identify the species. Although it needs more confirmation, the Ifakara Tent Trap C design (ITT-C) showed potential for outdoor mosquito sampling in Tanzania. Furvela tent traps successfully captured a variety of Anopheles species and are appropriate for use in a variety of eco-epidemiological settings. By contrast, for Aedes LF vectors, no specific sampling tool was identified for Aedes niveus, necessitating further research and development. However, traps like the Duplex cone trap, Resting Bucket Trap (RB), and Sticky Resting Bucket trap (SRB) proved effective for sampling Aedes albopictus, offering potential alternatives to HLC. This review emphasises the value of looking into alternative trapping methods for Aedes and Anopheles vectors in the LF-endemic region. Further research is required to determine the efficacy of novel collection techniques in various contexts, even if PSC and AGT show promise for sampling Anopheles vectors. The identified traps, along with ongoing research, provide valuable contributions to vector surveillance efforts in LF-endemic regions, enabling LF control and elimination strategies to advance.

Risk Factors of Noncompliance to Preventive Mass Drug Administration for Eliminating Lymphatic Filariasis: A Case-Control Study in Jawi District, Northwest Ethiopia

Background. High compliance is crucial for the success of a mass drug administration program to achieve lymphatic filariasis elimination. However, the presence of persistently noncompliant individuals might delay the elimination target. Besides, although context-based research is essential to designing effective strategies, only a few studies have focused on identifying factors that play a role in noncompliance with mass drug administration in Africa. Therefore, this study was conducted to identify the factors associated with noncompliance to prevent mass drug administration using ivermectin-with-albendazole for the elimination of lymphatic filariasis in Northwest Ethiopia. Methods. A case-control study was conducted in Jawi District, Northwest Ethiopia. All individuals who are permanently living in the study area and registered on the annual chemotherapy registration book since 2015 were included in this study. A two-proportion formula was used to estimate the required sample size and 348 cases and 348 controls were selected by identification number on the village chemotherapy registration book using a systematic sampling technique. Data were collected by face-to-face interviews using a structured questionnaire developed through an intensive literature review. Then, data were entered and cleaned by using the EPI DATA software, and analyses were conducted using SPSS version 26. Finally, a logistic regression analysis technique was applied to identify the risk factors using adjusted odds ratio as measures of effect. Results. A total of 690 (99.1%) participants, 345 cases and 345 controls, were included in the study. Younger age (AOR = 1.60; 95%CI: 1.10, 2.33), female sex (AOR = 1.56; 95%CI: 1.24, 3.93), thought of not being susceptible to the disease (AOR = 2.36, 95%CI: 1.80, 4.32), lack of disease knowledge (AOR = 1.88; 95% CI: 1.38, 3.81), fear of drug side effect (AOR = 2.45; 95% CI:1.23, 4.86), and not participating in community drug distributors selection (AOR = 2.58; 95% CI: 1.70, 3.91) were found to be the risk factors significantly associated with noncompliance. Conclusion. Noncompliance with lymphatic filariasis mass drug administration therapy was associated with specific demographic, individual, program, and drug delivery characteristics. This finding has important implications for program effectiveness and would be used to accelerate the elimination of lymphatic filariasis in the study area and other endemic settings.

Occurrence of Lymphatic Filariasis infection after 15 years of mass drug administration in two hotspot districts in the Upper East Region of Ghana

Background

Lymphatic filariasis (LF) causes chronic morbidity, which usually manifests as lymphedema or hydrocele. Mass drug administration (MDA) began in Kassena Nankana East Municipal (KNEM) and Nabdam, two hotspot districts in the Upper East Region in Ghana, in 2000 and 2005, respectively. This cross-sectional study evaluated the impact of 15 years of MDA on the control of LF as determined by circulating filarial antigen (CFA) and microfilariae assessment in the KNEM and the Nabdam districts.

Methodology/Principal findings

A total of 7,453 participants from eight sub-districts in the two hotspot districts (KNEM: N = 4604; Nabdam: N = 2849) were recruited into the study. The overall CFA prevalence as determined by the FTS was 19.6% and 12.8% in the KNEM and Nabdam districts, respectively. Manyoro, a sub-district on the border with Burkina Faso, recorded the highest CFA prevalence of 26% in the KNEM. Assessment of microfilariae and Og4C3 antigen was done from 1009 (KNEM: N = 799 (79.2%); Nabdam: N = 210 (20.8%)) randomly selected FTS-positive (N = 885) and FTS-negative (N = 124) individuals. The Og4C3 antigen was found in 22.6%/23.0% of the selected individuals (KNEM/Nabdam), whereas the night blood revealed microfilariae in only 0.7%/0.5%.

Conclusions/Significance

Using the WHO endorsed FTS, CFA prevalence exceeded the long-standing <2% threshold—which may need revision and validation. Surprisingly, the Og4C3 ELISA showed positive results in only about one-fifth of the FTS positive samples. However, even this result would not have met the <2% CFA criteria for LF elimination. In contrast, projections from the microfilariae results revealed a halt in LF transmission. The global elimination target was due in 2020 but has been extended to 2030 since this could not be met. Focused MDA intervention intensification on seasonal migrants and non-compliers, and implementation of alternative treatment strategies may suffice for the elimination of the disease.

Lymphatic filariasis (LF) is a major neglected tropical disease (NTD) affecting over 120 million individuals worldwide and identified as one of WHO’s 20 NTDs targeted for elimination. It has strong links with poverty and is associated with significant clinical morbidity, which impose considerable socio-psychological and economic burdens on the affected individuals. One of the main goals of the Global Programme to Eliminate Lymphatic Filariasis (GPELF) is the use of mass drug administration (MDA) to interrupt LF transmission. The initial 2020 elimination target year set by the GPELF could not be met, with 2030 now the new proposed year targeted for global elimination. The study evaluated the impact of 15 years of MDA on the control of LF in two hotspot districts in Ghana. The results from this study are indicative of a halt in LF transmission in the districts, with microfilaria detected in <1% of those sampled. However, the antigenemia prevalence is still above the recommended level. MDA should be intensified especially at the border towns or alternative treatment strategies should be employed to finally eliminate the disease as some people who are still with the active infection can serve as a reservoir for recrudescence and transmission in already “LF-free” areas.

The viability of utilising phone-based text messages in data capture and reporting morbidities due to lymphatic Filariasis by community health workers: a qualitative study in Kilwa district, Tanzania

Background

Globally, there is recognition of the value of using mobile phones among health providers in improving health systems performance. However, in many Low- and Middle-income countries where there is shortage of health providers, Community Health Workers have assumed some responsibilities especially relating to identifying and reporting on health problems within their communities. Despite the known benefits of using mobile phone technology to deliver health services, there is limited information on the extent to which Community Health Workers are able to effectively use the technology in data collection and reporting. The aim of this study was to determine the feasibility of utilizing phone-based text messages on Lymphatic Filariasis morbidity surveillance by Community Health Workers.

Methods

This was a cross sectional study whose data was collected through key informant interviews and focused group discussions among community health workers, health providers and staff of neglected tropical diseases control program. Collected transcripts were analysed through Thematic content analysis as it allowed for the identification of data codes through inductive reasoning.

Results

The use of mobile phone-based text messages in data collection and reporting lymphatic filariasis morbidity cases by Community Health Workers was perceived by study participants to be a relevant tool and feasible due to the ease of use of the technology. The tool was reported by end-users to significantly increase their performance and efficiency was gained in terms of reduced paper work, increased the number of patients accessing health care services and the ability to report in real-time. All respondents were confident that Community Health Workers were the right persons to interact with communities in tracking and reporting morbidity cases using mobile technology.

Conclusion

Mobile phone-based text messages have proven to be effective in routine workflows such as, data collection and reporting on Lymphatic Filariasis morbidity cases, patient to provider communication, decision making and supportive supervision. Mobile phones have also improved efficiency and general performance of end users in terms of increased number of cases identified and efficiency gained in terms of reduced paper work and the ability to collect and report in real-time.

Prevalence and management of filarial lymphoedema and its associated factors in Lindi district, Tanzania: A community-based cross-sectional study

OBJECTIVE

To determine the burden and management of filarial lymphoedema and its associated factors in Lindi district, Tanzania.

METHODS

Cross-sectional study involving 954 community members who were screened for filarial lymphoedema by using a checklist. Moreover, lymphoedema patients were examined for the presence of entry lesions, staging of disease, and interviewed on acute dermatolymphangioadenitis (ADLA) attacks, and their current practices on lymphoedema management. Descriptive statistics and logistic regression analyses were performed. A p < 0.05 was considered statistically significant.

RESULTS

The prevalence of filarial lymphoedema was 7.8%, with the majority in the early stage of lymphoedema (78.4%). The large majority (98.6%) of the patients had lower limb lymphoedema and 46% of lymphoedema patients had entry lesions. More than a half (60.8%) of those lymphoedema patients had experienced ADLA attacks; close to two-thirds (64.8%) had one or two attacks in the past 6 months. Generally, patients had inappropriate hygiene care practices for filarial lymphoedema management. Inappropriate hygiene care practice for lymphoedema management was associated with an increased risk for the development of advance stage of lymphoedema (adjusted odds ratio = 7.379, 95%, confidence interval: 3.535-16.018, p = 0.04).

CONCLUSION

Though lymphatic filariasis transmission has drastically declined, chronic manifestations of lymphoedema persist in Lindi district. The recommended disease management practices are deficient, which calls for a programmatic approach for mapping the burden of lymphoedema and implementing its management.

The role of anthropogenic container habitats as mosquito oviposition habitats in rural settlements in northern Tanzania

In many areas, the main sources of mosquito vectors are not natural habitats but small artificial water bodies that are provided unintentionally by humans. Such container habitats have been linked to outbreaks of dengue fever and other arboviral diseases. However, in many parts of the world the possible risks associated with container habitats have not been assessed. Here, we focused on a human population expansion area in northern Tanzania with a high incidence of dengue and other cases of high fever. We explored the importance of anthropogenic container habitats for mosquito production in the Lake Manyara Basin. We also assessed how biotic and physicochemical habitat characteristics limit mosquito abundance in containers. Results showed that Aedes aegypti (Linnaeus), vector of dengue and other arboviruses, and Culex quinquefasciatus (Say), vector of filarial worms, were the dominant mosquitoes ovipositing in large numbers in different containers. Old tires were the dominant and most productive container habitat for mosquitoes in the region. However, there were strong differences among villages, illustrating that the mosquito burden associated with container habitats varies locally. We concluded that in this region, removal of artificial container habitats could be a simple strategy to reduce the mosquito-mediated disease burden within the local population.

Lymphatic filariasis elimination status: Wuchereria bancrofti infections in human populations and factors contributing to continued transmission after seven rounds of mass drug administration in Masasi District, Tanzania

BACKGROUND

Lymphatic filariasis (LF) affects more than 120 million people globally. In Tanzania, nearly six million people are estimated to live with clinical manifestations of the disease. The National LF control program was established in 2000 using Mass drug administration (MDA) of Ivermectin and Albendazole to individuals aged 5years and above. This study assessed the infection status in individuals aged 15 years and above who are eligible for participation in MDA. The level of compliance to MDA and the reasons for non-compliance to MDA were also assessed.

METHODS

A community based cross-sectional study was conducted in two villages of Masasi District. A total of 590 participants aged 15 years and above were screened for the circulating filarial antigen (CFA) using the rapid diagnostic test. Night blood samples from CFA positive individuals were further analyzed for detection and quantification of Wuchereria bancrofti microfilaria (Mf) using the counting chamber technique. A pre-tested questionnaire was administered to collect information on compliance to MDA and the factors affecting continued transmission. Data were analyzed using SPSS Version 20. Chi-square test was used to compare the prevalence of CFA by gender and village where a P-value ≤0.05 was considered statistically significant.

RESULTS

Out of 590 participants, 30 (5.1%) were positive for CFA and one (0.2%) was found positive for microfilaria of Wuchereria bancrofti. Compliance during the last round of MDA, in the year 2019 was 56% which is below the minimum coverage recommended by WHO. Absence from home during MDA and perceptions of being free from hydrocele or elephantiasis were the major reasons for non-compliance.

CONCLUSION

There is a significant decline in LF transmission in Masasi District after seven rounds of MDA. However, the presence of individuals who are persistently non-compliant may delay elimination of LF in the District.

Keep your natural enemies close - native predators can maintain low mosquito densities in temporary ponds in a malaria expansion area in Northern Tanzania

Mosquitoes and the diseases they transmit are a global public health threat that affects most human populations. Mosquito abundances are strongly linked to the number of suitable larval habitats available. However, it is still not well understood how different land uses impact larval habitat quality in different parts of the world. We investigated links between land use practices and abundance of mosquito larvae in temporary ponds located in different land uses in a malaria expansion zone in Tanzania. Temporary ponds are often cited as important sources of mosquitoes but are also of substantial conservation concern being home to a unique fauna and flora. Often, they also have high socio-economic importance. Overall, encountered mosquito larval abundances were very low, both for the collected Anopheles gambiae s.l. and Culex quinquefasciatus. Although temporary ponds are important mosquito larval habitats in other parts of Africa, currently they are unlikely to be an important factor affecting the prevalence of mosquito borne diseases in the Manyara study region. Larval abundances in temporary ponds were higher in agricultural areas where more eutrophic conditions were found and minimal in residential areas. Overall, even though temporary ponds are often modified as rice paddies in the rainy season, they were in a good ecological condition and hosted a diverse assemblage of aquatic predators that likely prevented larval mosquitoes from reaching high densities. Maintaining this good condition by preventing pesticide and nutrient input as much as possible, can be important to prevent pond degradation that is likely to make these habitats more suitable for mosquitoes in the future.

Evaluating the Diagnostic Test Accuracy of Molecular Xenomonitoring Methods for Characterizing Community Burden of Lymphatic Filariasis

Background

Molecular xenomonitoring (MX), the detection of pathogen DNA in mosquitoes, is a recommended approach to support lymphatic filariasis (LF) elimination efforts. Potential roles of MX include detecting presence of LF in communities and quantifying progress towards elimination of the disease. However, the relationship between MX results and human prevalence is poorly understood.

Methods

We conducted a systematic review and meta-analysis from all previously conducted studies that reported the prevalence of filarial DNA in wild-caught mosquitoes (MX rate) and the corresponding prevalence of microfilaria (mf) in humans. We calculated a pooled estimate of MX sensitivity for detecting positive communities at a range of mf prevalence values and mosquito sample sizes. We conducted a linear regression to evaluate the relationship between mf prevalence and MX rate.

Results

We identified 24 studies comprising 144 study communities. MX had an overall sensitivity of 98.3% (95% confidence interval, 41.5–99.9%) and identified 28 positive communities that were negative in the mf survey. Low sensitivity in some studies was attributed to small mosquito sample sizes (<1000) and very low mf prevalence (<0.25%). Human mf prevalence and mass drug administration status accounted for approximately half of the variation in MX rate (R² = 0.49, P < .001). Data from longitudinal studies showed that, within a given study area, there is a strong linear relationship between MX rate and mf prevalence (R² = 0.78, P < .001).

Conclusions

MX shows clear potential as tool for detecting communities where LF is present and as a predictor of human mf prevalence.

Lymphatic filariasis, infection status in Culex quinquefasciatus and Anopheles species after six rounds of mass drug administration in Masasi District, Tanzania

Background

Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. Evidence shows a persistent LF transmission despite more than a decade of mass drug administration (MDA). It is advocated that, regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely. This study was therefore designed to assess the status of Wuchereria bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District, South Eastern Tanzania.

Methods

Mosquitoes were collected between June and July 2019 using Center for Diseases Control (CDC) light traps and gravid traps for indoor and outdoor respectively. The collected mosquitoes were morphologically identified into respective species. Dissections and PCR were carried out to detect W. bancrofti infection. Questionnaire survey and checklist were used to assess vector control interventions and household environment respectively. A Poisson regression model was run to determine the effects of household environment on filarial vector density.

Results

Overall, 12 452 mosquitoes were collected of which 10 545 (84.7%) were filarial vectors. Of these, Anopheles gambiae complex, An. funestus group and Cx. quinquefasciatus accounted for 0.1%, 0.7% and 99.2% respectively. A total of 365 pools of Cx. quinquefasciatus (each with 20 mosquitoes) and 46 individual samples of Anopheles species were analyzed by PCR. For Cx. quinquefasciatus pools, 33 were positive for W. bancrofti, giving an infection rate of 0.5%, while the 46 samples of Anopheles species were all negative. All 1859 dissected mosquitoes analyzed by microscopy were also negative. Households with modern latrines had less mosquitoes than those with pit latrines [odds ratio (OR) = 0.407, P < 0.05]. Houses with unscreened windows had more mosquitoes as compared to those with screened windows (OR = 2.125, P < 0.05). More than 80% of the participants own bednets while 16.5% had no protection.

Conclusions

LF low transmission is still ongoing in Masasi District after six rounds of MDA and vector control interventions. The findings also suggest that molecular tools may be essential for xenomonitoring LF transmission during elimination phase.

A cross-sectional survey on parasitic infections in schoolchildren in a rural Tanzanian community

Infectious diseases remain the leading cause of death in children in low- and middle-income countries. Infection with helminths and intestinal protozoa cause considerable morbidity. The aim of this study was to assess the health status of schoolchildren in nine villages of the Kilombero district in Tanzania. We conducted a cross-sectional survey and subjected 427 children aged 6-12 years to standardized diagnostic tests. We found that 15% of children were infected with Entamoeba histolytica/Entamoeba dispar/Entamoeba moshkovskii, 12% with Schistosoma mansoni, and 5% with Plasmodium falciparum. The most common soil-transmitted helminth species was Trichuris trichiura (7%). Strongyloides stercoralis, Schistosoma haematobium, Giardia intestinalis and lymphatic filariasis were rare. Having a latrine inside the house was associated with a lower odds of parasite infections (odds ratio (OR) 0.51, 95% confidence interval (CI) 0.27-0.96, p = 0.04). Children from households with goats were at higher odds of E. histolytica/E. dispar/E. moshkovskii infection (OR 3.03, 95%%CI 1.29-7.10, p = 0.01).When compared to a cross-sectional survey conducted in the same district in the 1980s, there seems to have been a substantial reduction in the prevalence and intensity of parasitic infections, except for T. trichiura, which showed a similar prevalence. Our data suggest that the general development, coupled with infectious disease control programmes improved children's health markedly. However, continued efforts to control parasitic diseases, including new approaches of drug combinations, stronger intersectoral collaboration, rigorous surveillance and public health responses tailored to the local settings are needed to move from control to elimination.

A systematic review of alternative surveillance approaches for lymphatic filariasis in low prevalence settings: Implications for post-validation settings

Due to the success of the Global Programme to Eliminate Lymphatic Filariasis (GPELF) many countries have either eliminated the disease as a public health problem or are scheduled to achieve this elimination status in the coming years. The World Health Organization (WHO) recommend that the Transmission Assessment Survey (TAS) is used routinely for post-mass drug administration (MDA) surveillance but it is considered to lack sensitivity in low prevalence settings and not be suitable for post-validation surveillance. Currently there is limited evidence to support programme managers on the design of appropriate alternative strategies to TAS that can be used for post-validation surveillance, as recommended by the WHO. We searched for human and mosquito LF surveillance studies conducted between January 2000 and December 2018 in countries which had either completed MDA or had been validated as having eliminated LF. Article screening and selection were independently conducted. 44 papers met the eligibility criteria, summarising evidence from 22 countries and comprising 83 methodologically distinct surveillance studies. No standardised approach was reported. The most common study type was community-based human testing (n = 42, 47.2%), followed by mosquito xenomonitoring (n = 23, 25.8%) and alternative (non-TAS) forms of school-based human testing (n = 19, 21.3%). Most studies were cross-sectional (n = 61, 73.5%) and used non-random sampling methods. 11 different human diagnostic tests were described. Results suggest that sensitivity of LF surveillance can be increased by incorporating newer human diagnostic tests (including antibody tests) and the use of mosquito xenomonitoring may be able to help identify and target areas of active transmission. Alternative sampling methods including the addition of adults to routine surveillance methods and consideration of community-based sampling could also increase sensitivity. The evidence base to support post-validation surveillance remains limited. Further research is needed on the diagnostic performance and cost-effectiveness of new diagnostic tests and methodologies to guide policy decisions and must be conducted in a range of countries. Evidence on how to integrate surveillance within other routine healthcare processes is also important to support the ongoing sustainability of LF surveillance.

Lymphatic filariasis (LF) is a mosquito-borne disease, which can result in complications including swelling affecting the limbs (lymphoedema) or scrotum (hydrocele). LF can be eliminated by mass drug administration (MDA) which involves whole communities taking drug treatment at regular intervals. After MDA programmes, country programmes conduct the Transmission Assessment Survey (TAS), which tests school children for LF. It is important to continue testing for LF after elimination because there can be a 10-year period between becoming infected and developing symptoms, but it is thought that the use of TAS in such settings is likely to be too expensive and also not sensitive enough to detect low-level infections. Our study assesses the results from 44 studies in areas of low LF prevalence that have investigated methods of surveillance for LF which differ from the standardised TAS approach. These include both human and mosquito studies. Results show that there is currently no standardised approach to testing, but that surveillance can be made more sensitive through the use of new diagnostic tests, such as antibody testing, and also by targeting higher risk populations. However, further research is needed to understand whether these approaches work in a range of settings and whether they are affordable on the ground.

Low transmission of Wuchereria bancrofti in cross-border districts of Côte d'Ivoire: A great step towards lymphatic filariasis elimination in West Africa

BACKGROUND

Lymphatic filariasis (LF) is widely endemic in Côte d'Ivoire, and elimination as public health problem (EPHP) is based on annual mass drug administration (MDA) using ivermectin and albendazole. To guide EPHP efforts, we evaluated Wuchereria bancrofti infection indices among humans, and mosquito vectors after four rounds of MDA in four cross-border health districts of Côte d'Ivoire.

METHODOLOGY

We monitored people and mosquitoes for W. bancrofti infections in the cross-border health districts of Aboisso, Bloléquin, Odienné and Ouangolodougou, Côte d'Ivoire. W. bancrofti circulating filarial antigen (CFA) was identified using filariasis test strips, and antigen-positive individuals were screened for microfilaremia. Moreover, filarial mosquito vectors were sampled using window exit traps and pyrethrum sprays, and identified morphologically at species level. Anopheles gambiae s.l. and Culex quinquefasciatus females were analyzed for W. bancrofti infection using polymerase chain reaction (PCR) technique.

PRINCIPAL FINDINGS

Overall, we found a substantial decline in W. bancrofti infection indices after four rounds of MDA compared to pre-MDA baseline data. CFA prevalence fell from 3.38-5.50% during pre-MDA to 0.00-1.53% after MDA interventions. No subjects had detectable levels of CFA in Ouangolodougou. Moreover, post-MDA CFA prevalence was very low, and below the 1% elimination threshold in Aboisso (0.19%) and Odienné (0.49%). Conversely, CFA prevalence remained above 1% in Bloléquin (1.53%). W. bancrofti microfilariae (Mf) were not found in Aboisso, Bloléquin, and Ouangolodougou, except for Odienné with low prevalence (0.16%; n = 613) and microfilaremia of 32.0 Mf/mL. No An. gambiae s.l. and Cx. quinquefasciatus pools were infected with W. bancrofti in Bloléquin and Ouangolodougou, while they exhibited low infection rates in Aboisso (1% and 0.07%), and Odienné (0.08% and 0.08%), respectively.

CONCLUSIONS

In cross-border areas of Côte d'Ivoire, LF infection indices in humans and mosquito vectors substantially declined after four rounds of MDA. CFA prevalence fell under the World Health Organization (WHO)-established threshold (1%) in Aboisso, Ouangolodougou and Odienné. Moreover, W. bancrofti prevalence in mosquitoes was lower than WHO-established threshold (2%) in all areas. This might suggest the interruption of W. bancrofti transmission, and possible MDA cessation. However, a formal transmission assessment survey (TAS) and molecular xenomonitoring in mosquito vectors should be implemented before eventual MDA cessation. However, MDA should pursue in Bloléquin where W. bancrofti infection prevalence remained above 1%. Our results provided important ramifications for LF control efforts towards EPHP in Côte d'Ivoire.

Assessing the Presence of Wuchereria bancrofti Infections in Vectors Using Xenomonitoring in Lymphatic Filariasis Endemic Districts in Ghana

Mass drug administration (MDA) is the current mainstay to interrupt the transmission of lymphatic filariasis. To monitor whether MDA is effective and transmission of lymphatic filariasis indeed has been interrupted, rigorous surveillance is required. Assessment of transmission by programme managers is usually done via serology. New research suggests that xenomonitoring holds promise for determining the success of lymphatic filariasis interventions. The objective of this study was to assess Wuchereria bancrofti infection in mosquitoes as a post-MDA surveillance tool using xenomonitoring. The study was carried out in four districts of Ghana; Ahanta West, Mpohor, Kassena Nankana West and Bongo. A suite of mosquito sampling methods was employed, including human landing collections, pyrethrum spray catches and window exit traps. Infection of W. bancrofti in mosquitoes was determined using dissection, conventional and real-time polymerase chain reaction and loop mediated isothermal amplification assays. Aedes, Anopheles coustani, An. gambiae, An. pharoensis, Culex and Mansonia mosquitoes were sampled in each of the four study districts. The dissected mosquitoes were positive for filarial infection using molecular assays. Dissected An. melas mosquitoes from Ahanta West district were the only species found positive for filarial parasites. We conclude that whilst samples extracted with Trizol reagent did not show any positives, molecular methods should still be considered for monitoring and surveillance of lymphatic filariasis transmission.