Freshwater Snails in Schistosomiasis Endemic Communities in Ovia South-West Local Government Area in Edo State, Nigeria

Background

Malacological surveys are crucial for determining vectors transmitting the Schistosoma species responsible for schistosomiasis in endemic communities. Ovia South-West Local Government Area of Edo State in Nigeria is one of the localities endemic for urogenital schistosomiasis. However, there is no report of the snail host of the disease in any community.

Method

A year-long freshwater snail survey was conducted in seven localities (Aden, Igbogor, Ikoha, Okopon, Okponha, Siluko, and Ugbogui) in Ovia South-West to determine the snail diversity and identify species that are intermediate hosts for schistosomiasis.

Result

A total of 468 snails, representing species in four genera ( Bulinus, Lanistes, Melanoides , and Radix ) were collected. Based on the morphological appearances of shells, five snails, B. forskalii, B. globosus ,

B. truncatus, L. varicus , and M. tuberculata were identified at the species level. A snail, Radix , could not be identified at the species level. Melanoides tuberculata was the most abundant snail and the only species identified in all sampled locations (n = 284, 60.68%). The next abundant species was Radix sp. (n = 106, 22.65%), followed by B. globosu s (n = 42, 8.97%). The least abundant snail was B. truncatus (n = 5, 1.07%). At Siluko, all species of snails were present, and only M. tuberculata in Ugbogui. In both dry and wet seasons, all species of snails were present (wet, n = 297) (dry, n = 171). Similar snail diversity occurred in each sampling location in both seasons, with more individuals of each species collected during the wet season. The only infected snail was a single Radix sp. in Siluko that shed brevifurcate-apharyngeate distome furcocercariae. All other snail species were uninfected.

Conclusion

For the first time in Edo State, snail vectors of schistosomiasis were reported but were uninfected with Schistosoma parasite. The brevifurcate-apharyngeate distome furcocercariae from the Radix sp. had conspicuous eye spots that suggest it is not a Schistosoma sp.