DISTRIBUTION OF VETERINARY AND MEDICAL IMPORTANT SNAILS AND THEIR TREMATODE INFECTION IN SELECTED DISTRICTS OF GAMO ZONE, SOUTH REGIONAL STATE, ETHIOPIA

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.