Serious limitations of the current strategy to control Soil-Transmitted Helminths and added value of Ivermectin/Albendazole mass administration: A population-based observational study in Cameroon

Abstract

Background Soil-transmitted helminth (STH) infections remain a public health concern in sub-Saharan Africa. School-based mass drug administration (MDA) using the anthelminthic drug Mebendazole/Albendazole have succeeded in controlling morbidity associated to these diseases but failed to interrupt their transmission. In areas were filarial diseases are co-endemic, another anthelminthic drug (Ivermectin) is distributed to almost the entire population, following the community-directed treatment with ivermectin (CDTI) strategy. Since Ivermectin is a broad spectrum anthelmintic known to be effective against STH, we conducted cross-sectional surveys in two health districts with very contrasting histories of Ivermectin/Albendazole-based PC in order to investigate whether CDTI might have contributed in STH transmission interruption. Methodology Cross-sectional surveys were conducted in two health districts with similar socio-environmental patterns but with very contrasting CDTI histories (Akonolinga health district where CDTI was yet to be implemented vs. Yabassi health district where CDTI has been ongoing for two decades). Stool samples were collected from all volunteers aged >2 years old and analyzed using the Kato-Katz technique. Infections by different STH species were compared between Akonolinga and Yabassi health districts to decipher the impact of Ivermectin/Albendazole-based MDA on STH transmission. Principal findings A total of 610 and 584 participants aged 2–90 years old were enrolled in Akonolinga and Yabassi health districts, respectively. Two STH species (Ascaris lumbricoides and Trichuris trichiura) were found, with prevalence significantly higher in Akonolinga health district (43.3%; 95% CI: 38.1–46.6) compared to Yabassi health district (2.5%; 95% CI: 1.1–5.1) (chi-square: 90.8; df: 1; p < 0.001). Conclusion/significance These findings (i) suggest that Mebendazole- or Albendazole-based MDA alone distributed only to at-risk populations might not be enough to eliminate STH, (ii) support the collateral impact of Ivermectin/Albendazole MDA on A. lumbricoides and T. trichiura infections, and (iii) suggest that Ivermectin/Albendazole-based PC could accelerate STH transmission interruption.

Transmission of Soil Transmitted Helminthiasis in the Mifi Health District (West Region, Cameroon): Low Endemicity but Still Prevailing Risk

“…The three-year retrospective survey revealed that the overall prevalence of STH was quite low (4.9%), suggestive of low endemicity levels, as was previously demonstrated during a cross-sectional prospective survey, both in the human population and the environment, conducted in the Bangangte Health District (West Region, Cameroon), located about 50 km from the Mifi Health District [17]. In fact, a continuing decreasing trend has been observed since 1987 (prior to intervention in the Mifi Division, with prevalence of 68.2% and 82.9% for A. lumbricoides and T. trichiura, respectively), suggesting a good momentum towards elimination [5,6,[10][11][12]. This could be the result of the public health interventions (Mebendazole-based deworming campaigns) that have been implemented since 2007 by the Ministry of Public Health through its National Program for Schistosomiasis and Soil-Transmitted Helminthiasis Control [18].…”

“…The control of STH in Cameroon, as recommended by the World Health Organization (WHO) [8,9], is principally based on large-scale deworming through annual mass drug administration (MDA) of mebendazole to at-risk populations, especially pre-school and school-age children [7]. This strategy has significantly reduced the prevalence and intensity of infection, indicative of transmission interruption in certain foci [10][11][12]. However, this intervention approach, targeting only a subset of the population, even though at high risk for infestation, does not prevent re-infestation as prevalence may return to baseline levels 6-8 months after treatment [13], and the disease was found to be persisting in some foci [14,15].…”

Limitations of PCR detection of filarial DNA in human stools from subjects non-infected with soil-transmitted helminths

“…This situation probably results from the fact that (a) the health areas neighboring the TaNT villages have been treated with ivermectin for about two decades to fight onchocerciasis; (b) most of the people living in the TaNT villages benefitted from annual treatment with ivermectin between 2015 and 2018 (subjects excluded from this treatment represent less than 3% of those tested with the LoaScope); and (c) school-aged children of the whole health district have received regular mebendazole treatment since 2007. Of note, it has been shown recently that, in areas where ivermectin is administered as a mass treatment, the impact is greater on STH transmission compared to where only mebendazole has been administered [4]. Given the absence of hookworm infection, the low proportion of participants infected with T. trichiura or A. lumbricoides, and the low egg counts recorded (Table 2), STH-related blood loss in the intestine was probably minimal.…”

Responsiveness of fecal immunoglobulin A to HPA‐axis activation limits its use for mucosal immunity assessment

“…Anthelmintic treatment is carried out routinely as a veterinary care procedure to remove helminth infections in the Barbary macaques living at Affenberg Salem. All monkeys individually received Ivermectin (Diapec, Albrecht), a broad‐spectrum anthelmintic compound (Djune‐Yemeli et al, 2020; Heukelbach et al, 2004; Müller et al, 2017). The study animals were divided into two groups, a treatment group (eight females, five males) which received Ivermectin treatment in August 2015, and a control group (six females, four males) which did not receive the treatment at this time.…”