Species diversity and distribution of schistosome intermediate snail hosts in The Gambia

Joof, Ebrima; Sanneh, Bakary; Sambou, Sana M.; Wade, Christopher M.

Abstract

There is a need for recent information on intermediate snail hosts of schistosomes in The Gambia; the previous studies were conducted over three decades ago. This study assessed the incidence, species diversity, distribution and infection status of schistosome intermediate snail hosts in the country. Malacological surveys were conducted in all 5 regions of The Gambia: Central River Region (CRR), Upper River Region (URR), Western Region (WR), Lower River Region (LRR) and North Bank Region (NBR). Sampling of snails was under-taken at 114 sites that included permanent water bodies such as streams (bolongs), rice fields, irrigation canals and swamps; and temporal (seasonal) laterite pools. Ecological and physicochemical factors of sites were recorded. Snails were identified morphologically and screened for schistosome infections using molecular techniques. Freshwater snails were found at more than 50% (60/114) of sites sampled. While three species of Bulinus were col-lected, no Biomphalaria snails were found in any of the sites sampled. Of the total 2877 Buli-nus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. Seasonal pools produced the largest number of snails, and CRR was the region with the largest number of snails. Bulinus senegalensis was found more in seasonal pools as opposed to permanent sites, where B. forskalii and B. trun-catus were observed to thrive. Bulinus snails were more common in seasonal sites where aquatic vegetation was present. In permanent sites, the abundance of snails increased with increase in water temperature and decrease in water pH. Bulinus senegalensis was found infected with both S. haematobium and S. bovis, while B. forskalii and B. truncatus had only S. bovis infection. While the human parasite S. haematobium was restricted to just four sites, the livestock parasite S. bovis had a much more widespread geographical distribution across both CRR and URR. This new information on the distribution of intermediate snail hosts of schistosomes in The Gambia will be vital for the national schistosomiasis control initiative.

Citation

Joof, E., Sanneh, B., Sambou, S. M., & Wade, C. M. (2021). Species diversity and distribution of schistosome intermediate snail hosts in The Gambia. PLoS Neglected Tropical Diseases, 15(10), Article e0009823. https://doi.org/10.1371/journal.pntd.0009823

• Journal Article Type: Article
• Acceptance Date: Sep 20, 2021
• Online Publication Date: Oct 4, 2021
• Publication Date: Oct 4, 2021
• Deposit Date: Aug 8, 2022
• Publicly Available Date: Aug 9, 2022
• Journal: PLoS Neglected Tropical Diseases
• Electronic ISSN: 1935-2735
• Publisher: Public Library of Science
• Peer Reviewed: Peer Reviewed
• Volume: 15
• Issue: 10
• Article Number: e0009823
• DOI: https://doi.org/10.1371/journal.pntd.0009823
• Keywords: Infectious Diseases; Public Health, Environmental and Occupational Health
• Public URL: https://nottingham-repository.worktribe.com/output/6739578
• Publisher URL: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0009823