Update on the distribution of Mansonella perstans in the southern part of Cameroon: influence of ecological factors and mass drug administration with ivermectin. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Wanji, Samuel; Tayong, Dizzle; Layland, Laura; Datchoua Poutcheu, Fabrice; Ndongmo, Winston; Kengne-Ouafo, Jonas; Ritter, Manuel; Amvongo-Adjia, Nathalie; Fombad, Fanny; Njeshi, Charity; Nkwescheu, Armand; Enyong, Peter; Hoerauf, Achim
• Is Part Of: Parasites & vectors. Volume 9:Issue 1(2016)
• Page Start: 1
• Page End: 17
• Publication Date: 2016-12
• Subjects: Mansonellosis -- Mansonella perstans -- Microfilariae -- Distribution -- Prevalence -- Intensity -- Bioecological zones -- Ivermectin -- MDA -- Cameroon; Parasitism -- Periodicals; Parasites -- Periodicals; Vector-pathogen relationships -- Periodicals; Animals as carriers of disease -- Periodicals; Insects as carriers of disease -- Periodicals; 616.96
• DOI: 10.1186/s13071-016-1595-1
• Languages: English
• ISSNs: 1756-3305

Abstract

Abstract Background Mansonellosis remains one of the most neglected of tropical diseases and its current distribution in the entire forest block of southern Cameroon is unknown. In order to address this issue, we have surveyed the distribution ofMansonella perstans in different bioecological zones and in addition, elucidated the influence of multiple rounds of ivermectin (IVM) based mass drug administration (MDA). Methods A mixed design was used. Between 2000 and 2014, both cross-sectional and longitudinal surveys were carried out in 137 communities selected from 12 health districts belonging to five main bioecological zones of the southern part of Cameroon. The zones comprised of grassland savanna (GS), mosaic forest savanna (MFS), forested savanna (FS), deciduous equatorial rainforest (DERF) and the dense humid equatorial rainforest (DHERF). The survey was carried out in some areas with no treatment history as well as those currently under IVM MDA. Individuals within the participatory communities were screened for the presence ofM. perstans microfilariae (mf) in peripheral blood by the calibrated thick film method to determine both prevalence and geometric mean intensities at the community level. Results Apart from sporadic cases in savanna areas, distribution ofM. perstans was strongly linked to the equatorial rainforest zones. Before CDTI, the highest mean prevalence (70.0 %) and intensity (17, 382.2 mf/ml) were obtained in communities in Mamfes' DHERF areas followed by communities in the DHERF zone of Lolodorf (53.8 % and 7, 814.8 mf/ml, respectively). A longitudinal survey in Mamfe further showed thatM. perstans infections had reduced by 34.5 % in DERF (P < 0.001) but not DHERF zones after ten years of IVM MDA. Further data from the cross-sectional study revealed that there was a decrease in prevalence in DHERF zones only after ten years of MDA. In DERF zones however, the infection was relatively lower after four years of MDA. Conclusions The distribution ofM. perstans in the southern part of Cameroon varies with bioecological zones and IVM MDA history. The zones with high prevalence and intensities lie in forested areas while those with low endemicity are in the savanna areas. MDA with ivermectin induced significant reduction in the endemicity of mansonellosis in the decidious equatorial rainforest. In contrast, the prevalence and intensity remained relatively high and stable in the dense humid equatorial rainforest zones even after a decade of mass drug administration with ivermectin. Since it is known thatM. perstans down-regulates host's immune system, the findings from this work would be useful in designing studies to understand the impact ofM. perstans on host immune response to vaccination and co-infection with other pathogens such asMycobacterium spp. andPlasmodium spp. in areas of contrasting endemicities.