# Mapping and phylogeny of Biomphalaria snail in the Adamawa Region of Cameroon: A step towards vector control and schistosomiasis elimination

## TL;DR

This study maps Biomphalaria snails in Cameroon's Adamawa Region, identifying new species and genetic patterns to aid in controlling schistosomiasis.

## Contribution

The first report of Biomphalaria camerunensis in northern Cameroon above 6° latitude and genetic insights into Biomphalaria pfeifferi populations.

## Key findings

- Biomphalaria snails were found in 13 out of 43 water contact sites in Adamawa Region.
- Biomphalaria camerunensis was identified for the first time in northern Cameroon above 6° latitude.
- Genetic analysis showed stable populations with slight intraspecific variation in Biomphalaria pfeifferi.

## Abstract

Schistosomiasis is the world’s second-most important parasitic disease affecting humans. Among the two main forms of the disease, intestinal schistosomiasis due to Schistosoma mansoni is predominant in Cameroon, where its intermediate host Biomphalaria spp. is widely distributed, particularly in the Adamawa plateau. As a prerequisite to targeted vector control for effective elimination of intestinal schistosomiasis infection, we mapped the geographical distribution of Biomphalaria snails in the Adamawa Region.

A total of 43 human-water contact sites were visited across the Adamawa Region for snail collection. Snail species were identified morphologically and with PCR-RFLP technique at the ITS2 rDNA region using the HpaII restriction enzyme. The genus Biomphalaria was identified at 13 sites (30.2%), four sites (9,3%) harboured Gyraulus species firstly identified as Biomphalaria with shell morphology, and 22 sites (51,16%) were free from any snail species. Two Biomphalaria species were identified, Biomphalaria pfeifferi in 12 water contact sites, and Biomphalaria camerunensis was found only in one site (Djalingo, Vina Division), and it was the first report of this species in the Northern Cameroon (above the 6° latitude North). Morphologic identification was supported by PCR-RFLP results and sequencing revealed three haplotypes for Biomphalaria pfeifferi and one haplotype for Biomphalaria camerunensis. The studied populations were stable according to neutrality tests (Tajima’s D and Fu Fs) and no signal of gene flow was observed between them.

This study confirmed the presence of Biomphalaria pfeifferi in the Adamawa Region and reported for the first time B. camerunensis above 6° of Latitude North, thus deserving further monitoring to assess its current distribution in Cameroon.

The transmission of schistosomiasis depends on the distribution of specific freshwater snails that act as intermediate hosts for the parasite’s larval form. The World Health Organization recently recognised that efforts to interrupt schistosomiasis transmission through mass drug administration solely have not been sufficient in some regions to eliminate the infection and encouraged the control of these intermediate hosts as a complementary intervention. In this study, we mapped the distribution of Biomphalaria snails throughout the Adamawa Region of Cameroon and assessed the phylogenetical relationship between different populations as a prerequisite to snail control. Biomphalaria snails were found in four of the five Divisions of the Adamawa Region. In addition to B. pfeifferi that was the only species reported in previous studies, B. camerunensis was identified in the region for the first time. Genetic analysis revealed a slight intraspecific variation in B. pfeifferi and, that snail populations are stable on the field.