Spatial Distribution and Habitat Characterisation Of Mosquitoes and Vector Snails, and Community Perceptions on Malaria and Schistosomiasis in Relation To Aquatic Habitats, In Lake Victoria Basin of Western Kenya
ONG'WEN, Samson Adoka
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Infections with vector-borne parasites are common in human populations inhabiting tropical regions of the world. Malaria and schistosomiasis are endemic along Kenyan Lake Victoria basin (LVB), and their vectors are fresh water breeders. However, much less is known about the current spatial distribution and habitat characterisation of mosquitoes including vectors of malaria and ~human schistosomiasis intermediate hosts snails in the Lake Victoria waters and adjacent terrestrial aquatic habitats. The current study was designed to determine differential mosquitoes and schistosomiasis snails' abundance in lake and land aquatic habitats; measure the aquatic habitats' (water) physico-chemical parameters and establish their effects on the abundance of Anopheles mosquitoes and schistosomiasis snails in lake and land habitats; enumerate the numbers of phytoplankton, zooplankton, and fish species, and determine the effects of their abundance on the abundance of Anopheles mosquitoes and schistosomiasis snails; carry out gut contents analysis of the different fish species to determine which ones are more insectivorous and can be used as biological agents against mosquito larvae in lake and land aquatic habitats; and lastly find out the community knowledge and perceptions regarding malaria and schistosomiasis transmission and control, and relationship with aquatic habitats in the Lake Victoria basin (LVB) of western Kenya. Mosquitoes and schistosomiasis intermediate-host snails were sampled to determine their abundance and distribution in the lake and land aquatic habitats using entomological and malacological techniques, respectively. Also,243 individuals randomly recruited from fish landing beaches in the Kenyan Lake Victoria basin were interviewed about their knowledge and perceptions regarding malaria and schistosomiasis. Data obtained was entered in Microsoft Excel, then cross-checked and transferred to SPSS for analysis. MSTAT-C software was used to determine whether there were significant variations between the locations, habitats or vegetation types. Descriptive statistics were carried out to determine relative frequencies, percentages and averages of variables. Chi-square test (X2) was used to determine relationships between level of education, age, gender and occupation, and correctness of responses of the study participants. P<0.05 was considered statistically significant. Results showed that Anopheles and Culex species of mosquitoes were absent in different locations in the lake but abundant in different aquatic habitats in different locations on land. There was heterogeneity in the relative abundance of Anopheles and Culex species in the aquatic habitats in different locations on land; p<O.OOI,Bartlett's test. There were significantly more Biomphalaria sudanica than Bulinus africanus . sampled in different locations in the lake and in land aquatic habitats, one way ANOVA, p<O.OOl. There were no significant correlations between abundance of Anopheles mosquitoes, Biomphalaria sudanica and Bulinus africanus snails, different physico-chemical parameters, and phytoplankton abundance, p > 0.05, Pearsons' correlation, but there was significant correlation between abundance of Biomphalaria sudanica and Bulinus africanus, and some phytoplankton in the lake and on land, p<0.03, Pearsons' correlation. There were significant correlations between abundance of Anopheles mosquitoes and Calanoid on land, p = 0.014, but no significant correlation with most zooplankton on land, p>0.05, Pearsons' correlation. There were no significant correlations between Biomphalaria sudanica and Bulinus africanus abundance with zooplankton in lake and on land though significant correlation between Bulinus africanus and Calanoid, copepoid in the lake were found, p<0.05, Pearsons' correlation. Clarias gariepinus were more insectivorous compared to other fish species. Most of the respondents (66.53%) were aware of symptoms of malaria and how it is transmitted (77.8%) but had poor knowledge on the breeding habitats of mosquitoes and aquatic plants harbouring schistosomiasis snails. The study results calls for removal of water hyacinth from the aquatic habitats both on land and in the lake as they harbour more schistosomiasis transmitting snails and recommends that concerted effort is needed to scale-up health education and improve the knowledge of the community about mosquitoes and snails and their breeding habitats, particularly malaria vectors which do not breed in deep lake waters. Introduction of Clarias gariepinus as a bio-control agent is suggested by the findings of this study.