First report of contamination of public water system by Giardia duodenalis and Cryptosporidium spp. in Bahia, northeastern Brazil

Waterborne diseases such as cryptosporidiosis and giardiasis are among the leading public health problems worldwide because these protozoa are more resistant to water disinfection methods. This study aimed to evaluate the presence of oocysts of Cryptosporidium spp. and cysts of Giardia spp. in samples of raw and treated water. During one year, 24 raw and treated water samples were collected from the public water supply system in Canavieiras, Bahia, Brazil. Cysts and oocysts were concentrated using membrane filtration and visualized through Direct immunofluorescence assay (DFA). DNA isolated with a commercial kit was subjected to nested PCR (nPCR). The DFA obtained a better result than the nPCR in detecting both protozoa. By DFA, Cryptosporidium spp. was present in 25% (6/24) of the raw water and 4.2% (1/24) of the treated water samples. Giardia spp. was detected in 41.6% (10/24) of the raw water and 16.6% (4/24) of the treated water samples. In nPCR, Giardia spp. was detected in treated and raw water at 16.6% (4/24) and 16.6% (4/24), respectively. Cryptosporidium spp. was detected in raw water at 8.3% (2/24). The DFA and nPCR results differed despite the molecular analysis having greater sensitivity. Many inhibitors in the samples may have influenced the result. The physicochemical parameters pH and turbidity were not under the standards established by the legislation. In raw water, microbiological parameters were above the required legal standard. Precipitation and pH correlated with Cryptosporidium nPCR results in raw water. The presence of these protozoa in the water samples constitutes a potential risk for transmitting diarrheal diseases to this municipality's human and animal populations.