macrophyte cover and algal mass were scored visually and recorded as percentages of the area covered within the sampling sites. Environmental and physical factors assumed to affect the presence of snails were recorded i.e. Sampling of the snails was carried out using a scoop made of an iron frame supporting a wire mesh. Snails and trematodes were collected monthly from January 2004 to December 2005 from canals of an irrigation system of the Blue Nile River, in the East Nile locality, Khartoum. Rain falls during the summer season from June to September, which is followed by a long dry season, extending from October to May. There are two seasons in Sudan: summer (May to September) and winter (October to April). Therefore, the present longitudinal study followed seasonal density fluctuations in populations of freshwater snails and determined the prevalence of associated trematode infections in relation to various environmental factors, in the East Nile locality of Khartoum state, Sudan. Likewise, some attention has been given to the control of their snail intermediate hosts, but no studies have been undertaken on snail abundance and host relationships of other trematode species, which are either not of medical and/or veterinary importance. In Sudan specifically, research has been done on the epidemiology and distribution of Schistosoma mansoni, S. However, relatively few studies have dealt with the total snail and trematode fauna even though it has been suggested that other snail and trematode species may significantly affect transmission patterns of the aforementioned diseases. Whereas many studies have been conducted on intermediate host snails, most of these have focused on the specific intermediate host species infected with particular trematode. In Sudan, these are most notably schistosomiasis and fascioliasis. Further studies should be conducted to determine whether some of these trematodes could be manipulated for the biological control of schistosomiasis.įreshwater snails receive considerable attention as they are intermediate hosts of several trematodes that cause diseases in humans and domestic animals. The findings of this study indicate that besides schistosomes, other larval trematodes are found, and some use the same intermediate hosts as the schistosomes. tuberculata snails, which were not affected by seasonal changes. The density of snails tended to be lower during the summer months than the winter months, except for M. Xiphidiocercariae type 1 was the most common type of cercariae recovered, accounting for 44.3 % of all infections. Twenty different morphotypes of cercariae were recorded, seven of which appeared not to conform to previously described cercariae from Africa. truncatus snails and one Cleopatra bulimoides snail. Double infections were recorded in only two B. Five species were found to have infections among these the Bulinus truncatus species was found to be the most heavily infected, with an overall prevalence of 46.2 %. Overall, 14.1 % of the snails were found to be shedding some type of cercariae. The most abundant species was Biomphalaria pfeifferi, representing 48.6 % of the sample. ResultsĪ total of 10,493 snails, representing seven species, were collected. Vegetation cover in the study sites as well as the physicochemical characteristics of the water, including temperature, were also recorded. The snails were examined for trematode infections by cercarial emergence immediately after collection and then weekly for an additional four weeks to allow for the maturation of prepatent infections. Methodsįreshwater snails from irrigation canals ( abueshreens) were sampled monthly from January 2004 to December 2005. This study explored the coexistence of other species of freshwater snails and the two genera along with their trematode infections in relation to a number of environmental factors in the East Nile locality, Khartoum state, Sudan. In Sudan specifically, most studies have focused on the chemical and ecological control of the two genera, but few studies have looked at their biological control. The planorbid freshwater snails of the two genera, Biomphalaria and Bulinus -have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis.
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