Isolation and characterisation of Cyclospora cayetanensis oocysts in an equatorial polysaprobic hydrosystem, Central Africa
Little information is available on the distribution of enteropathogenic apicomplexa of the human digestive apparatus, these agents being responsible for endemic diarrheic diseases. A study carried out in the Olézoa water course in Yaoundé (Cameroon) revealed that this water contains the oocysts of Cyclospora cayetanensis. Samples for the analysis of biological and physico-chemical characteristics were obtained upstream and downstream with respect to the strongly human polluted zone. The identification of Cyclospora cayetanensis oocysts by direct observation and Ziehl-Neelsen techniques revealed that these oocysts contain two sporocysts, each having two sporozoïtes. Statistically, turbidity, temperature and pH have a significant effect (p<0.01) on the population dynamics of these microorganisms. The highest mean concentration of oocysts identified upstream was 407 oocysts•L-1 in the month of August. The non sporulated forms of oocysts are more abundant than the sporulated forms in the environment and are strongly linked to dissolved oxygen levels, oxygen being a parameter that is very important for the process of sporulation and viability. Non sporulated forms of oocysts, 8 μm in size, are dominant in the ecosystem analyzed in our investigations. These resistant forms of parasites that are present in the surface and wastewater represent a considerable health risk to the inhabitants of the study zone who could easily be exposed to cyclosporiasis.The two methods which have been carried out are complementary in the characterisation of the resistant forms of these enteropathogens.