title: Update on the distribution of Mansonella perstans in the southern part of Cameroon: influence of ecological factors and mass drug administration with ivermectin.
abstract: 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 of Mansonella perstans in different bioecological zones and in addition, elucidated the influence of multiple rounds of ivermectin (IVM) based mass drug administration (MDA).
  
  
  
  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 of M. perstans microfilariae (mf) in peripheral blood by the calibrated thick film method to determine both prevalence and geometric mean intensities at the community level.
  
  
  
  Apart from sporadic cases in savanna areas, distribution of M. 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 that M. 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.
  
  
  
  The distribution of M. 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 that M. perstans down-regulates host's immune system, the findings from this work would be useful in designing studies to understand the impact of M. perstans on host immune response to vaccination and co-infection with other pathogens such as Mycobacterium spp. and Plasmodium spp. in areas of contrasting endemicities.
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon. swanji@yahoo.fr.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon. swanji@yahoo.fr.
authors.forename: Samuel
authors.initials: S
authors.lastname: Wanji
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Dizzle Bita
authors.initials: DB
authors.lastname: Tayong
authors.affiliation: Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University Hospital of Bonn, Bonn, Germany.|German Centre for Infection Research (DZIF), partner site, Bonn-Cologne, Bonn, Germany.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Layland
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Fabrice R
authors.initials: FR
authors.lastname: Datchoua Poutcheu
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Winston Patrick Chounna
authors.initials: WP
authors.lastname: Ndongmo
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Jonas Arnaud
authors.initials: JA
authors.lastname: Kengne-Ouafo
authors.affiliation: Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University Hospital of Bonn, Bonn, Germany.|German Centre for Infection Research (DZIF), partner site, Bonn-Cologne, Bonn, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Ritter
authors.affiliation: Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Amvongo-Adjia
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Fanny Fri
authors.initials: FF
authors.lastname: Fombad
authors.affiliation: Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Charity Nya
authors.initials: CN
authors.lastname: Njeshi
authors.affiliation: Scientific Networks and Ethics Promotion, Division of Health Operations Research, Ministry of Public Health, Yaoundé, Republic of Cameroon.
authors.forename: Armand Seraphin
authors.initials: AS
authors.lastname: Nkwescheu
authors.affiliation: Parasite and Vector Research Unit (PAVRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.|Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Enyong
authors.affiliation: Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University Hospital of Bonn, Bonn, Germany.|German Centre for Infection Research (DZIF), partner site, Bonn-Cologne, Bonn, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Hoerauf
mesh_terms: D000818:Animals; D002163:Cameroon / Q000453:epidemiology; D003430:Cross-Sectional Studies; D019353:Endemic Diseases; D005260:Female; D065928:Forests; D005843:Geography; D006801:Humans; D007306:Insecticides / Q000008:administration & dosage*; D007559:Ivermectin / Q000008:administration & dosage*; D008137:Longitudinal Studies; D008297:Male; D008366:Mansonella / Q000187:drug effects / Q000254:growth & development*; D008368:Mansonelliasis / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control; D008842:Microfilariae; D058069:Neglected Diseases; D011156:Population Density; D015995:Prevalence; D065947:Rainforest
chemical_list: D007306:Insecticides; D007559:Ivermectin
keywords: Bioecological zones; Cameroon; Distribution; Intensity; Ivermectin; MDA; Mansonella perstans; Mansonellosis; Microfilariae; Prevalence