No evidence of lymphatic filariasis transmission in Bamako urban setting after three mass drug administration rounds.

Lymphatic filariasis (LF) elimination activities started in Mali in 2005 in the most endemic areas and reached countrywide coverage in 2009. In 2004, the district of Bamako was endemic for LF with a prevalence of 1.5%. The current study was designed to determine LF endemicity level in the urban area of Bamako after three rounds of ivermectin and albendazole mass drug administration (MDA). A cross-sectional study was conducted in 2011 in Bamako city, consisting of human prevalence and entomological surveys. Volunteers aged 14 years and above were invited to participate and tested for evidence of Wuchereria bancrofti using night time blood thick smear microfilarial count and blood spots for LF antibodies using the SD BIOLINE Oncho/LF IgG4 Biplex rapid test (Ov16/Wb123). Mosquitoes were collected using CDC light and gravid traps and tested using molecular methods. Poolscreen software v2.0 was used to estimate vector transmission potential. Of the 899 volunteers, one (0.11%) was found to be positive for LF using the Oncho/LF IgG4 Biplex rapid test, and none was found to have Wuchereria bancrofti microfilariae. No mosquitoes were found infected among 6174 Culex spp. (85.2%), 16 Anopheles gambiae s.l. (An. gambiae s.l.) (0.2%), 26 Aedes spp. (0.4%), 858 Ceratopogonidae (11.8%) and 170 other insects not identified (2.3%) tested. Our data indicate that there was no active LF transmission in the low prevalence urban district of Bamako after three MDA rounds. These data helped the National LF programme move forward towards the elimination goal.

Comparison of Different Sampling Methods to Catch Lymphatic Filariasis Vectors in a Sudan Savannah Area of Mali.

There is a need for better tools to monitor the transmission of lymphatic filariasis and malaria in areas undergoing interventions to interrupt transmission. Therefore, mosquito collection methods other than human landing catch (HLC) are needed. This study aimed to compare the Ifakara tent trap type C (ITTC) and the Biogents sentinel trap (BGST) to the HLC in areas with different vector densities. Mosquitoes were collected in two villages in Mali from July to December in 2011 and 2012. The three methods were implemented at each site with one ITTC, one BGST, and one HLC unit that consisted of one room with two collectors-one indoor and the other outdoor. The Anopheles collected in 2011 were individually dissected, whereas those from 2012 were screened in pools using reverse transcription-polymerase chain reaction (RT-PCR) to determine the maximum infection prevalence likelihood (MIPL) for Wuchereria bancrofti and Plasmodium falciparum. The dissection of the females also allowed to assess the parity rates, as well its results. Over the 2 years, the HLC method collected 1,019 Anopheles, yields that were 34- and 1.5-fold higher than those with the BGST and ITTC, respectively. None of the dissected Anopheles were infected. The RT-PCR results showed comparable MIPL between HLC and ITTC for W. bancrofti with one infected pool from each trap's yield (respectively 0.03% [0.0009-0.2%] and 0.04% [0.001-0.2%]). For P. falciparum, no infected pool was recovered from BGST. The ITTC is a good alternative to HLC for xenomonitoring of program activities.

Evaluation of mass drug administration for schistosomiasis and soil-transmitted helminths in school-aged children in Bankass, Mali.

BACKGROUND: In 2004, Mali implemented mass drug administration (MDA) aimed at controlling schistosomiasis and soil-transmitted helminths. Despite several rounds of MDA, the health district of Bankass reported low coverage (64.8%) for praziquantel and albendazole in 2017, meaning that this district was still facing challenges in accomplishing the targeted 75% coverage. This study aimed to explore the barriers and gaps that hindered MDA implementation in Bankass. METHODS: A cross-sectional study was performed. Questionnaires were administrated to all school-aged children in randomly selected villages. Technical directors of community health centers and community drug distributors in the selected villages were included in the interviews. RESULTS: A total of 2128 children and 52 health workers were interviewed. Coverage rates were 93.51% (1990/2128) for praziquantel and 95.25% (2027/2128) for albendazole. Among the untreated children, 31.63% (31/98) reported being unaware of the campaign and 26.53% (26/98) were unable to reach the distribution points. Most of the health workers suggested increasing incentives. CONCLUSION: The data showed satisfactory coverage >90%, in contrast with lower rates initially reported by the district health information system. These results raise concerns about the reliability of programmatic data and highlight the importance of population-based surveys for the evaluation of control interventions.

Lymphedema in three previously Wuchereria bancrofti-endemic health districts in Mali after cessation of mass drug administration.

BACKGROUND: Lymphedema is a public health problem in countries with lymphatic filariasis (LF) including Mali. We studied the epidemiology and clinical presentation of lymphedema in three previously LF-endemic health districts of Mali after at least five consecutive rounds of mass drug administration (MDA) with albendazole and ivermectin. METHODS: From 2016 to 2018, we used passive and active case finding methods to identify lymphedema cases in three health districts with high pre-MDA LF prevalence: Kolondieba (66%), Bougouni (44%) and Kolokani (34%). RESULTS: Three hundred and thirty nine cases of lymphedema were identified, 235 (69.32%) through active case finding. Their median age was 56 years (range 2-90) and 286 (84.36%) were women. Lymphedema was reported in 226 (78.5%) people aged 41 years and older compared to 73 (21.5%) people below the age of 41 years (Chi2 = 17.28, df = 5, p = 0.004). One hundred and seventy five cases of lymphedema were found in Kolondieba (66 per 100,000 people), 116 in Bougouni (19 per 100,000) and 48 in Kolokani (16 per 100,000). Stage III lymphedema was observed in 131 (38.64%), stage II in 108 (31.86%), stage IV in 46 (13.57%), stage I in 23 (6.78%), stage V in 21 (6.19%) and stage VI in ten (2.95%). In the three study districts, lymphedema affected the legs in 281 (82.89%), the arms in 42 (12.39%) and both in 16 (4.72%) (Chi2 = 13.63, p = 0.008). CONCLUSION: Health districts in Mali with the highest pre-MDA LF prevalences had the highest prevalence of lymphedema. Efforts to actively identify lymphedema cases should be scaled up in previous LF-endemic areas, and should be supplemented by a morbidity management and disability prevention plan at the peripheral health system level.

Integrated seroprevalence-based assessment of Wuchereria bancrofti and Onchocerca volvulus in two lymphatic filariasis evaluation units of Mali with the SD Bioline Onchocerciasis/LF IgG4 Rapid Test.

BACKGROUND: Mali has become increasingly interested in the evaluation of transmission of both Wuchereria bancrofti and Onchocerca volvulus as prevalences of both infections move toward their respective elimination targets. The SD Bioline Onchocerciasis/LF IgG4 Rapid Test was used in 2 evaluation units (EU) to assess its performance as an integrated surveillance tool for elimination of lymphatic filariasis (LF) and onchocerciasis. METHODOLOGY/PRINCIPAL FINDINGS: A cross sectional survey with SD Bioline Onchocerciasis/LF IgG4 Rapid Test was piggy-backed onto a transmission assessment survey (TAS) (using the immunochromatographic card test (ICT) Binax Filariasis Now test for filarial adult circulating antigen (CFA) detection) for LF in Mali among 6-7 year old children in 2016 as part of the TAS in two EUs namely Kadiolo-Kolondieba in the region of Sikasso and Bafoulabe -Kita-Oussoubidiagna-Yelimane in the region of Kayes. In the EU of Kadiolo- Kolondieba, of the 1,625 children tested, the overall prevalence of W. bancrofti CFA was 0.62% (10/1,625) [CI = 0.31-1.09]; while that of IgG4 to Wb123 was 0.19% (3/1,600) [CI = 0.04-0.50]. The number of positives tested with the two tests were statistically comparable (p = 0.09). In the EU of Bafoulabe-Kita-Oussoubidiagna-Yelimane, an overall prevalence of W. bancrofti CFA was 0% (0/1,700) and that of Wb123 IgG4 antibody was 0.06% (1/1,700), with no statistically significant difference between the two rates (p = 0.99). In the EU of Kadiolo- Kolondieba, the prevalence of Ov16-specific IgG4 was 0.19% (3/1,600) [CI = 0.04-0.50]. All 3 positives were in the previously O. volvulus-hyperendemic district of Kolondieba. In the EU of Bafoulabe-Kita-Oussoubidiagna-Yelimane, an overall prevalence of Ov16-specific IgG4 was 0.18% (3/1,700) [CI = 0.04-0.47]. These 3 Ov16 IgG4 positives were from previously O.volvulus-mesoendemic district of Kita. CONCLUSIONS/SIGNIFICANCE: The SD Bioline Onchocerciasis/LF IgG4 Rapid test appears to be a good tool for integrated exposure measures of LF and onchocerciasis in co-endemic areas.

Factors Associated with Wuchereria bancrofti Microfilaremia in an Endemic Area of Mali.

Although Wuchereria bancrofti (Wb), the causative agent of lymphatic filariasis, is endemic throughout Mali, the prevalence of Wb microfilaremia (Mf) can vary widely between villages despite similar prevalence of infection as assessed by circulating antigen. To examine this variation, cross-sectional data obtained during screening prior to an interventional study in two neighboring villages in Mali were analyzed. The overall prevalence of Wb, as assessed by Wb CAg (circulating antigen), was 50.3% among 373 participants, aged 14-65. Wuchereria bancrofti Mf-positive and negative individuals appeared randomly distributed across the two villages (Moran's I spatial statistic = -0.01, Z score =0.1, P>0.05). Among the 187 subjects positive for Wb CAg, 117 (62.5%) had detectable Mansonella perstans microfilaremia (Mp Mf) and 64 (34.2%) had detectable Wb microfilaremia. The prevalence of Mp microfilaremia was 73.4% in the Wb Mf-positive group (as compared to 56.9% in the Wb Mf-negative group; p=0.01), and median Wb Mf load was increased in co-infected subjects (267Mf/ml vs 100 Mf/ml; p<0.001). In multivariate analysis, village of residence, Mp Mf positivity and gender were significantly associated with Wb Mf positivity. After controlling for age, gender, and village of residence, the odds of being Wb Mf positive was 2.67 times higher in Mp positive individuals (95% confidence interval [1.42-5.01]). Given the geographical overlap between Mp and Wb in Africa, a better understanding of the distribution and prevalence of Mp could assist national lymphatic filariasis control programs in predicting areas of high Wb Mf prevalence that may require closer surveillance.

The Impact of Six Annual Rounds of Mass Drug Administration on Wuchereria bancrofti Infections in Humans and in Mosquitoes in Mali.

Wuchereria bancrofti prevalence and transmission were assessed in six endemic villages in Sikasso, Mali prior to and yearly during mass drug administration (MDA) with albendazole and ivermectin from 2002 to 2007. Microfilaremia was determined by calibrated thick smear of night blood in adult volunteers and circulating filarial antigen was measured using immunochromatographic card test in children < 5 years of age. Mosquitoes were collected by human landing catch from July to December. None of the 686 subjects tested were microfilaremic 12 months after the sixth MDA round. More importantly, circulating antigen was not detected in any of the 120 children tested, as compared with 53% (103/194) before the institution of MDA. The number of infective bites/human/year decreased from 4.8 in 2002 to 0.04 in 2007, and only one mosquito containing a single infective larva was observed 12 months after the final MDA round. Whether this dramatic reduction in transmission will be sustained following cessation of MDA remains to be seen.

Wuchereria bancrofti transmission pattern in southern Mali prior to and following the institution of mass drug administration.

BACKGROUND: The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the goal of stopping transmission of lymphatic filariasis (LF) through yearly mass drug administration (MDA). Although preliminary surveys of the human population in Mali suggested that Wuchereria bancrofti infection was highly endemic in the Sikasso district, baseline entomological data were required to confirm high levels of transmission prior to the selection of villages in this region for a study of the impact of MDA on transmission of LF by anopheline vectors. METHODS: W. bancrofti transmission was assessed in 2001 (pre-MDA) and 2002 (post-MDA) in the Central District of Sikasso in southern Mali by dissection of Anopheles mosquitoes caught using the human landing catch (HLC) method. The relative frequencies and molecular forms of An. gambiae complex were determined. RESULTS: The majority (86%) of the anopheline vectors captured were identified as An. gambiae complex, and these accounted for >90% of the entomological inoculation rate (EIR) during both years of the study. There was a dramatic decrease in the number of An. gambiae complex mosquitoes captured and in the An. gambiae complex infectivity rates following MDA, accounting for the observed decrease in EIR in 2002 (from 12.55 to 3.79 infective bites per person during the transmission season). An. funestus complex mosquitoes were responsible for a low level of transmission, which was similar during both years of the study (1.2 infective bites per person during the transmission season in 2001 and 1.03 in 2002). CONCLUSIONS: Based on the entomological data from this study, the district of Sikasso was confirmed as an area of high W. bancrofti transmission. This led to the selection of this area for a multi-national study on the effects of MDA on LF transmission by anopheline vectors. Comparison of vector transmission parameters prior to and immediately following the first round of MDA demonstrated a significant decrease in overall transmission. Importantly, the dramatic variability in EIR over the transmission season suggests that the efficacy of MDA can be maximized by delivering drug at the beginning of the rainy season (just prior to the peak of transmission).