Avaliação da contaminação de ostras (Crassostrea rhizophorae) por especies de Cryptosporidium e Giardia em um ambiente de estuario do litoral de São Paulo / Evaluation of the contamination of oysters (Crassostrea rhizophorae) by species of Cryptosporidium and Giardia in a estuarine environment from São Paulo coast

Diego Averaldo Guiguet Leal

Bivalve molluscs are great filter feeders that may accumulate and concentrate substances, particles and even pathogens in their tissues, if the places that they inhabit or are cultivated receive contaminated effluents dispose. These animals, which serve as biological indicators of faecal contamination, may transmit the protozoa accumulated in their tissues, whenever they are ingested in a raw or lightly cooked form. Several studies in different countries reported the presence of parasite protozoa like Cryptosporidium and Giardia in bivalve molluscs destined for human consumption, however, in Brazil, these data are non-existent. For this reason, it is interesting and relevant the investigation of the occurrence of these protozoan in this type of food, consumed in different regions of the country. The aim of this study was to evaluate the natural contamination of oocysts and cysts of parasite protozoan in bivalve molluscs located in an estuarine environment in the Northern coast of São Paulo State; detect this protozoan in river and seawater; verify if there is a correlation between climatic, microbiological, physical and chemical factors with the natural occurrence of parasites in aquatic environments and verify if there is a correlation between water quality and the contamination of bivalve molluscs present at the region. Bivalve molluscs were processed through the homogenization of specific tissues and submitted to centrifugal concentration with ether-PBS, and water samples were analyzed by membrane filtration technique. Protozoa were visualized with direct immunofluorescence antibody test and to confirm the morphology of the parasites, contrast-phase microscopy and the incorporation of a vital dye (DAPI) were used. Giardia cysts were detected in 8 of 12 samples of river water and one sample contained Cryptosporidium oocysts. Both pathogens were detected in marine water where Cryptosporidium were present in 40,0% and Giardia in 20,0% of all samples analyzed. Gill pools homogenates of oysters were positive for oocysts and cysts in two periods with a mean concentration of 12 oocysts/oyster and 50 cysts/oyster. There was no significant association between the climatic, physical, chemical and microbiological factors with the number of oocysts detected in river water and in seawater; for cysts, it was found a high association only with thermotolerant coliforms (p = 0,007) in seawater. Moreover, it was not possible to establish correlation between water quality and the number of oocysts and cysts detected in oysters tissues. This is the first time that Cryptosporidium oocysts and Giardia cysts were found in oysters from the coastal region of Brazil, and it is also the first report in Latin America to date. These findings might be of public health importance, reflecting the extension of the contamination in marine environment and on seafood, requiring a need for quality control standards. Key-words: Cryptosporidium spp.; Giardia spp.; bivalve molluscs; Crassostrea rhizophorae; seawater; river water; estuary; sewage.

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