Cryptosporidium species from common edible bivalves in Manila Bay, Philippines

Manila Bay is one of the major propagation sites of edible bivalves in the Philippines. Studies have shown that bivalves might be contaminated with human pathogens like the protozoan parasite Cryptosporidium, one of the major causes of gastroenteritis in the world. In this study, Cryptosporidium from four species of edible bivalves were isolated using a combination of sucrose flotation and immunomagnetic separation. Using direct fluorescent antibody test, Cryptosporidium oocysts were found in 67 out of 144 samples collected. DNA sequence analysis of the 18S rRNA gene of the isolates detected C. parvum and C. hominis (major causes of human cryptosporidiosis) and C. meleagridis (causes infection in avian species). Analysis of the 60 kDa glycoprotein gene further confirmed the genotypes of the Cryptosporidium isolates. This study is the first to provide baseline information on Cryptosporidium contamination of Manila Bay where bivalves are commonly cultured.