Abstract:
Freshwater snails, aside from being a valuable food source, are considered one of the negatively
affecting invertebrates on the natural environment. They share intimate relationship with
parasitic trematodes because they serve as resource for development and vehicle for
transmission to its next definite host. A cross-sectional study was designed to establish the
distribution and, abundance of veterinary/medical importance snails in the area and also to
examine the infection rate of snails with trematode cercariae. In this study, freshwater snails
were collected during dry and wet seasons from ten different aquatic sites of selected districts in
Gamo Zone, using a scoop net or handpicking. Snails were identified and counted on the basis of
their shell morphology and each snail was then examined for cercarial infection by shedding
method under artificial light. Cercariae were identified morphologically by referring body and
tail structure under microscopy. Accordingly, a total of 1,349 snails were collected that
comprised of five medical/veterinary important genera/species in the study area. The most
abundant snail was Radix natalensis, accounting for 48.6% (655/1349) of the total count, which
is followed by Biomphalaria spp. 18.9% (255/1349), Galba truncatula 17.5% (236/1349),
Melanoides spp. 12.1% (163/1349) and Bulinus spp. 2.9% (40/1349). The distribution of the
snails was highest in dry season 55.3% (746/1349) than rainy season 44.7% (603/1349). The
abundance of Biomphalaria and R.natalensis was positively associated with water temperature,
G. truncatula with dissolved oxygen and Melanoides with pH. The overall prevalence of
trematode infection in the snails collected was 7.64% (103/1349). Four trematode cercariae;
gymnocephalous cercariae, amphistome cercaria, furcocercous cercariae and xiphidiocercariae
were found to infect various snail population. A descriptive statistics shows that 25%, 12.1%,
7.6%, 3.7% and 2.5% of Bulinus spp., Biomphalaria spp., R. natalensis, Melanoides spp. and G.
truncatula respectively were infected with at least one type of cercariae. In conclusion, the
occurrence of medical and veterinary significant snails and also the presence of fluke larva in
their tissue suggest the likelihood of trematodiasis of human and livestock population in the
study sites. Thus, the status of trematode infections in human and domestic animals should be
established in these sites.
