Distribution and abundance of schistosomiasis and fascioliasis host snails along the Mara River in Kenya and Tanzania

Abstract

We purposively selected 39 sampling sites along the Mara River and its two perennial tributaries of Amala and Nyangores and sampled snails. In addition, water physicochemical parameters (temperature, turbidity, dissolved oxygen, conductivity, alkalinity, salinity and pH) were taken to establish their influence on the snail abundance and habitat preference. Out of the 39 sites sampled, 10 (25.6%) had snails. The snail species encountered included Biomphalaria pfeifferi Krauss – the intermediate host of Schistosoma mansoni Sambon, Bulinus africanus – the intermediate host of Schistosoma haematobium, and Lymnaea natalensis Krauss – the intermediate host of both Fasciola gigantica and F. hepatica Cobbold. Ceratophallus spp., a non-vector snail was also encountered. Most (61.0%) of the snails were encountered in streamside pools. Schistosomiasis-transmitting host snails, B. pfeifferi and B. africanus, were fewer than fascioliasis-transmitting Lymnaea species. All the four different snail species were found to be attached to different aquatic weeds, with B. pfeifferi accounting for over half (61.1%) of the snails attached to the sedge, followed by B. africanus and Lymnaea spp., accounting for 22.2 and 16.7%, respectively. Ceratophallus spp. were non-existent in sedge. The results from this preliminary study show that snails intermediate hosts of schistosomiasis and fascioliasis exists in different habitats, in few areas along the Mara River, though their densities are still low to have any noticeable impacts on disease transmission in case they are infected. The mere presence of the vector snails in these focal regions calls for their immediate control and institution of proper regulations, management, and education among the locals that can help curtail the spread of the snails and also schistosomiasis and fascioliasis within the Mara River basin.

Prevalence and Intensity of Schistosomiasis in Communities around Water Reservoirs in Malawi

“…This is because the water temperature, the water levels and water currents are more conducive than during the rainy season when the rains are heavy and wash away many of the snails [27,28]. Similar patterns of higher schistosomiasis prevalence in the dry season than the rainy season have also been reported in [25][26][27][28][29].…”

“…Anto, Asoala [25] reported similar findings in Ghana. Additionally, dry season presents conducive environment for buildup of snail populations [26]. This is because the water temperature, the water levels and water currents are more conducive than during the rainy season when the rains are heavy and wash away many of the snails [27,28].…”

Effects of land use on intermediate snail host fauna, abundance, distribution and cercariae infection rate in Omo-Gibe river basin, Ethiopia

“…There is positive correlation between snail richness and built-up area class [9]. Gabriel et al [10] also reported activities associated with agricultural irrigation can cause adverse impacts on wetland ecological resources. Land-use change due to human settlement and his domesticated animals can affect water quality [11].…”

“…The other medically important snails collected was L.natalensis and is second dominant and abundant species. Moreover, studies of Gabriel et al[10] showed that L. natalensis was the dominant species followed by B. pfeifferi in river habitat. L. natalensis accounted for 16.45% of the snail collection and encountered 29.2% of the surveyed sites with prevalence of 69.6%, 24.7% and 2.1% in wetlands, rivers and irrigation ditches, respectively.…”

Shell Morphology of Three Medical Important Tropical Freshwater Pulmonate Snails from Five Sites in South-Western Nigeria

“…Some of the snails transmitting the above infections like B. pfeifferi and B. globosus transmit Schistosoma parasites to man causing human Schistosomiasis (Brown, 1980;Gryseels, 1989;Jordan et al, 1993;Opisa et al, 2011;Dida et al, 2014) while, L. natalensis transmits Fasciola parasites to animals and man causing fascioliasis (Utzinger and Tanner, 2000;Dida et al, 2014). Biomphalaria pfeifferi is mainly found in tropical regions of Africa and Southwest Arabia.…”