Abstract

Bivalve molluscs are filter feeders and can bioaccumulate oocysts of Cryptosporidium. Tiga Lake in Kano State Nigeria is used for recreational, domestic and agricultural purposes by humans and also serves as a source of drinking water for animals. Bivalve molluscs from the lake are consumed by people. This study was conducted to assess the occurrence of Cryptosporidium spp. in Tiga Lake using edible Anodonta sp., (fresh water mussels) a bivalve mollusc as sentinel. The samples were examined using modified acid fast staining technique and micrometery of the oocysts. 169 and 150 samples of the molluscs were collected from two locations namely Tashan Idi and Rurum, respectively. The organs examined from each of the molluscs were the gastrointestinal tracts (GIT), gills and haemolymph. The mean oocysts load was higher in the GIT (192.50 ± 173.03) than in the other organs, although the difference was not statistically significant (P > 0.05). Of the two sampling sites, 60 (35.50%) and 40 (26.67%) of the molluscs from Tashan Idi and Rurum respectively were positive for the oocysts. However, the difference was not statistically significant (P > 0.05).The micrometry of the oocysts showed that most of them fell within the size range of 4.0 to 4.3 µm and 4.4 to 4.7 µm suggesting that the oocysts encountered in this work might be those of Cryptosporidium parvum and C. meleagridis which infect a wide range of animals and also humans. The result of this study reveals that 27.59% of the bivalve molluscs harboured Cryptosporidium oocysts and this may have public health implications if undercooked molluscs are consumed by humans.

Key words: Cryptosporidium, bivalve molluscs, Tiga Lake, bioaccumulate, public health.