Molecular Epidemiology of Cryptosporidium spp. in an Agricultural Area of Northern Vietnam: A Community Survey

BackgroundCryptosporidium spp. is a protozoan parasite with worldwide distribution that causes cryptosporidiosis in humans and other animals. In the countryside of northern Vietnam, where free-roaming livestock are widespread, cryptosporidiosis is an important zoonotic disease. However, there have been few studies of cryptosporidiosis in Southeast Asia from the perspective of zoonotic disease epidemiology. The purpose of this study was to investigate the occurrence of Cryptosporidium infection in both humans and animals and to gain an awareness of the potential threat posed by this zoonotic infection in northern Vietnam.Methods We conducted a community survey to collect information about cases of diarrhea in an agricultural area of northern Vietnam. For this study, a total of 2715 samples (2120 human diarrheal samples, 471 non-diarrheal human samples, and 124 animal stool samples) were collected. A direct immunofluorescence assay (DFA) was used to detect Cryptosporidium spp. oocysts in concentrated stool samples by observation under a fluorescent microscope. DNA extraction, PCR amplification of the three genes (COWP, SSU-rRNA, and GP60), and sequencing analysis were performed to identify Cryptosporidium spp.Results Of 2715 samples, 15 samples (10 diarrheal samples, 2 non-diarrheal samples, and 3 animal stool samples) tested positive by PCR for the COWP gene. Three species of Cryptosporidium spp. were detected; C. canis (from six human diarrheal samples, two human non-diarrheal samples, and one dog sample); C. hominis (from four human diarrheal samples); and C. suis (from two pig samples). In terms of C. hominis, the GP60 subtype IeA12G3T3 was detected in all four human diarrheal samples.Conclusions Although the number of positive samples was very small, our epidemiological data showed that the emerging pattern of each of the three species (C. canis, C. hominis, and C. suis) was different at this study site. For example, zoonotic transmission of C. canis, between dogs and humans was suspected. Further studies are needed to assess the risk of oocyst contamination in the wider environment, including water, in this study area.