| Abstrakt: |
Background: Cryptosporidiumis a gastrointestinal pathogen. The oocysts are transmitted through the environment, and drinking contaminated water is one particular route. There is heavy pollution of Cryptosporidiumin Njoro River, the main source of drinking water for humans and animals around the watershed. However, there is no information on the parasite concentration and estimated health risk exposed to these populations. This study determined the level of contamination and risk of infection by Cryptosporidiumparasites in Njoro River. Water samples were collected monthly from three ecological sites along Njoro River for twelve months. Cryptosporidiumoocysts were concentrated from these water samples using calcium carbonate flocculation method, examined and counted using epifluorescent microscopy. Quantitative microbial risk assessment was applied to estimate the health risk of Cryptosporidiuminfection in Njoro River using a beta-Poisson dose–response model. Results: The concentration of Cryptosporidiumparasites in Njoro River is 0.936 ± 0.73 oocysts/litre. However, this concentration fluctuates with ecological site of the river; highest concentration occurs at downstream (1.325 ± 0.73), followed by midstream (0.917 ± 0.74) and least at upstream (0.567 ± 0.54). Concentration of Cryptosporidiumin the river is higher during wet than dry seasons, with the difference in mean concentrations between the two seasons being significant (t(34)= − 6.101, p< 0.01). There was a negative correlation between Cryptosporidiumconcentration, temperature and pH, while a strong positive correlation existed between Cryptosporidiumconcentration and turbidity. The daily probability of infection by Cryptosporidiumin Njoro River watershed is 0.25, while the annual risk is 0.99. Conclusions: Njoro River is heavily polluted with Cryptosporidiumparasites. This exposes both the humans and animals that drink water from this river to a high risk of cryptosporidiosis, a potentially fatal infection particularly in immunocompromised individuals. |
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