Epidemiology of helminth infections in adults in rural rainforest communities of the Nkam-Wouri River Basin, Littoral Region of Cameroon: Implications for NTDs elimination using preventive chemotherapies

Background Chronic helminth infections cause serious health problems; however, limited data on prevalence and distribution hinder effective control interventions. This study assessed the prevalence, distribution, and risk factors of helminth infections in adults across four health districts (HD) in the Littoral Region of Cameroon, while hypothesizing that helminth infection prevalences are significantly higher in densely forested and wetland forest plantation districts compared to degraded and mosaic plantation forest districts despite over more than two decades of preventive chemotherapy. Methodology/Principal Findings Adults aged 18 – 65 years residing in the community for ≥ 5 years were recruited across four HDs. Skin snips, thick blood films, and stool samples were examined using the Kato Katz method (stool) and microscopy. Demographic data were analyzed in R. Participants were mainly farmers (79.9%), male (52.9%) and aged 18–49 years (50.7%). Yabassi HD, a densely forested area, recorded the highest prevalence of Loa. loa and Mansonella. perstans , while Loum HD, a wetland forest plantation area, showed higher prevalence for other helminth groups. Overall infection prevalence was 41.9%, dominated by filariasis (33.3%), with Onchocerca volvulus (23.9%) most common, followed by M. perstans (11.9%) and L. loa (8.9%). Intestinal nematode prevalence was 9.9%, led by Capillaria spp. (4.6%), Ascaris lumbricoides (2.9%) and Trichuris trichiura (2.7%). Trematode infections included Dicrocoelium dendriticum (6.9%) and Paragonimus spp. (3.5%), while Taenia spp. (3.1%) was the most common cestode. Infections were more frequent in males and individuals over 40 years. Strong associations were observed among parasites with similar life cycles, Filariasis risk increased with age ≥ 50 years and longer residence, whereas recent deworming and higher education reduced the odds. Conclusions/Significance Adult helminth infections pose a public health risk and may serve as transmission reservoirs in child-centred programs. Monitoring and including adults in preventive chemotherapy programs, promoting regular deworming and awareness and using a multi-parasite, multi-pathway strategy will strengthen control and elimination efforts in persistently endemic areas.