Oocistos de Cryptosporidium e cistos de Giardia: circulação no ambiente e riscos à saúde humana

Abstract

The presence of protozoa in drinking water is recognised as an important public health hazard in many countries; nevertheless the knowledge about this issue in Brazil is still sparse. In this regard, this paper gathers information that help to explain the environmental circulation and epidemiological importance of Giardia and Cryptosporidium (oo)cysts, including: their occurrence in surface water (source water), sewage, human and animal faeces; their occurrence in commercial crops; the evaluation of protozoa removal by water treatment; and presence in filtered effluents. High protozoa concentration in source waters were found, as well as its presence in filtered effluent of existing water treatment plants and pilot slow sand filters, regardless of a general high removal efficiency. Protozoa cysts and oocysts were also found, in high densities, in wastewater and in faeces of contaminated animals. In addition, a relatively high prevalence in faeces of an urban population studied. The study shows evidence of the expressive human health risk represented by the occurrence of this protozoa in several environments and brings unpublished information to strengthen health risk evaluation, and the discussion about the validation of premises adopted in the Brazilian drinking water guidelines (Decree No 518/2004)