Schistosomiasis in school-age children in Burkina Faso after a decade of preventive chemotherapy.

OBJECTIVE: To assess the impact of a decade of biennial mass administration of praziquantel on schistosomiasis in school-age children in Burkina Faso. METHODS: In 2013, in a national assessment based on 22 sentinel sites, 3514 school children aged 7-11 years were checked for Schistosoma haematobium and Schistosoma mansoni infection by the examination of urine and stool samples, respectively. We analysed the observed prevalence and intensity of infections and compared these with the relevant results of earlier surveys in Burkina Faso. FINDINGS: S. haematobium was detected in 287/3514 school children (adjusted prevalence: 8.76%, range across sentinel sites: 0.0-56.3%; median: 2.5%). The prevalence of S. haematobium infection was higher in the children from the Centre-Est, Est and Sahel regions than in those from Burkina Faso's other eight regions with sentinel sites (P < 0.001). The adjusted arithmetic mean intensity of S. haematobium infection, among all children, was 6.0 eggs per 10 ml urine. Less than 1% of the children in six regions had heavy S. haematobium infections - i.e. at least 50 eggs per 10 ml urine - but such infections were detected in 8.75% (28/320) and 11.56% (37/320) of the children from the Centre-Est and Sahel regions, respectively. Schistosoma mansoni was only detected in two regions and 43 children - i.e. 1 (0.31%) of the 320 from Centre-Sud and 42 (8.75%) of the 480 from Hauts Bassins. CONCLUSION: By mass use of preventive chemotherapy, Burkina Faso may have eliminated schistosomiasis as a public health problem in eight regions and controlled schistosome-related morbidity in another three regions.

Exposition of Intermediate Hosts of Schistosomes to Niclosamide (Bayluscide WP 70) Revealed Significant Variations in Mortality Rates: Implications for Vector Control.

(1) Background: Schistosomiasis remains a public health issue in Cameroon. Snail control using Niclosamide can prevent schistosome transmission. It is safe to determine lethal concentrations for the population. This study aimed at assessing the toxicity of Niclosamide on different developmental stages of snail populations; (2) Methods: Snails were collected, identified, and reared in the laboratory. Egg masses and adult snails were exposed to Niclosamide, at increasing concentrations (0.06, 0.125, 0.25, 0.5, 1 mg/L for egg embryos and 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 mg/L for adults). After 24 h exposure, egg masses and snails were removed from Niclosamide solutions, washed with source water and observed; (3) Results: Snail susceptibility was species and population dependent. For egg embryos, Biomphalaria pfeifferi was the most susceptible (LC50: 0.1; LC95: 6.3 mg/L) and Bulinus truncatus the least susceptible (LC50: 4.035; LC95: 228.118 mg/L). However, for adults, B. truncatus was the most susceptible (mortality rate: 100%). The LC50 and LC95 for Bi. camerunensis eggs were 0.171 mg/L and 1.102 mg/L, respectively, and were higher than those obtained for adults (0.0357 mg/L and 0.9634 mg/L); (4) Conclusion: These findings will guide the design of vector control strategies targeting these snail species in Cameroon.

Biomphalaria camerunensis as a viable alternative intermediate host for Schistosoma mansoni in southern Cameroon.

BACKGROUND: Intestinal schistosomiasis due to Schistosoma mansoni was mapped in Cameroon in the 1990s and preventive chemotherapy launched since 2005. A situation analysis conducted in 2011 revealed an increase in schistosomiasis transmission, especially in the equatorial part of the country, despite the fact that Biomphalaria pfeifferi, the main intermediate host of this parasite, is now scarce in many foci. Biomphalaria camerunensis, restricted to the equatorial part of the country, is considered as a less suitable host for S. mansoni due to it resistance to the parasite, although exhibiting a better survival than B. pfeifferi. In a context where human migration is quite frequent as a consequence of terrorism, war in neighboring countries, as well as development of hydraulic projects, it seems appropriate to evaluate the current epidemiological role of B. camerunensis to estimate the risk of extension of S. mansoni distribution in Cameroon. To do this, the susceptibility of three B. pfeifferi and five B. camerunensis populations to a strain of S. mansoni was assessed. Juvenile snails (G1) of each population were infected with S. mansoni miracidia, and prepatent period, infection and survival rates of infected snails, as well as cercarial production were recorded and compared between snail species and populations. RESULTS: Compatibility tests were performed on a total of 827 snails: 344 B. pfeifferi and 483 B. camerunensis. Infection rates were quite heterogeneous, higher in B. pfeifferi (61.5%) as compared to B. camerunensis (7.8%) (Chi-square test: χ2 = 258.88, df = 1, P < 0.0001). All the three B. pfeifferi-infected populations were susceptible to S. mansoni. However, among the five B. camerunensis populations tested, four were susceptible to S. mansoni, with 21.9% as the highest infection rate. The prepatent period was, on average, shorter in B. pfeifferi than in B. camerunensis (P < 0.0001), but the cercarial production was significantly higher in B. camerunensis as compared to B. pfeifferi (P < 0.001). CONCLUSION: These findings indicate that B. camerunensis populations might substantially contribute to S. mansoni transmission and dissemination in Cameroon, their low susceptibility being compensated by their high cercariae production. More attention and surveillance towards this species are required to achieve intestinal schistosomiasis elimination in Cameroon.

Successful Control of Soil-Transmitted Helminthiasis in School Age Children in Burkina Faso and an Example of Community-Based Assessment via Lymphatic Filariasis Transmission Assessment Survey.

BACKGROUND: Burkina Faso is endemic with soil-transmitted helminth infections. Over a decade of preventive chemotherapy has been implemented through annual lymphatic filariasis (LF) mass drug administration (MDA) for population aged five years and over, biennial treatment of school age children with albendazole together with schistosomiasis MDA and biannual treatment of pre-school age children through Child Health Days. Assessments were conducted to evaluate the current situation and to determine the treatment strategy for the future. METHODOLOGY/PRINCIPAL FINDINGS: A cross-sectional assessment was conducted in 22 sentinel sites across the country in 2013. In total, 3,514 school age children (1,748 boys and 1,766 girls) were examined by the Kato-Katz method. Overall, soil-transmitted helminth prevalence was 1.3% (95% CI: 1.0-1.8%) in children examined. Hookworm was the main species detected, with prevalence of 1.2% (95% CI: 0.9-1.6%) and mean egg counts of 2.1 epg (95% CI: 0-4.2 epg). Among regions, the Centre Ouest region had the highest hookworm prevalence of 3.4% (95% CI: 1.9-6.1%) and mean egg counts of 14.9 epg (95% CI: 3.3-26.6 epg). A separate assessment was conducted in the Centre Nord region in 2014 using community-based cluster survey design during an LF transmission assessment survey (TAS). In this assessment, 351 children aged 6-7 years and 345 children aged 10-14 years were examined, with two cases (0.6% (95% CI: 0.2-2.1%)) and seven cases (2.0% (95% CI: 1.0-4.1%)) of hookworm infection was identified respectively. The results using both age groups categorized the region to be 2% to <10% in STH prevalence according to the pre-defined cut-off values. CONCLUSIONS/SIGNIFICANCE: Through large-scale preventive chemotherapy, Burkina Faso has effectively controlled STH in school age children in the country. Research should be conducted on future strategies to consolidate the gain and to interrupt STH transmission in Burkina Faso. It is also demonstrated that LF TAS provides one feasible and efficient platform to assess the STH situation for post LF MDA decision making.