Genotypes of Cryptosporidium Species Infecting Fur-Bearing Mammals Differ from Those of Species Infecting Humans

Abstract

Of 471 specimens examined from foxes, raccoons, muskrats, otters, and beavers living in wetlands adjacent to the Chesapeake Bay, 36 were positive for five types of Cryptosporidium, including the C. canis dog and fox genotypes, Cryptosporidium muskrat genotypes I and II, and Cryptosporidium skunk genotype. Thus, fur-bearing mammals in watersheds excreted host-adapted Cryptosporidium oocysts that are not known to be of significant public health importance.The enteric parasites in the genus Cryptosporidium can be transmitted through ingestion of contaminated water (5). However, the sources of contamination are not clearly identified. Cryptosporidium spp. have been reported to infect a wide range of wild mammals (15). Among them, wild rodents have received particular attention, and it has been suggested that they may serve as reservoirs of Cryptosporidium infection for domestic animals and humans (1-6, 13-15, 18). Since the 1993 cryptosporidiosis outbreak in Milwaukee, Wis., the water industry in the United States has been striving to provide Cryptosporidium-free drinking water through stringent treatment practices and source water protection. Although there has been speculation that wild mammals serve as potential sources of watershed contamination with Cryptosporidium oocysts infectious for humans (1-3, 7), the actual role of wildlife in the contamination of source water with human-pathogenic Cryptosporidium spp. remains unknown.Results of recent studies indicate a strong host adaptation for Cryptosporidium (22). Eight species of Cryptosporidium have been identified as pathogens in humans: C. parvum, C. hominis, C. meleagridis, C. felis, C. canis, C. muris, and Cryptosporidium pig and cervine species (8-12, 20, 21). Of these, C. hominis, C. parvum, and C. meleagridis have been found most frequently, whereas the others have been identified mostly in clinical case reports involving a few persons. Thus, unless wild mammals can be shown to be a source of these three species, they do not represent a significant risk as a source of water contamination affecting humans under normal circumstances. The present study was conducted to determine if Cryptosporidium infections are present in wild mammals (beavers, muskrats, otters, raccoons, and foxes) living in Chesapeake Bay watersheds and, if so, to determine the prevalence and species of Cryptosporidium by molecular methods. Results of the study provide the first genetically based data on the role of wildlife in Cryptosporidium contamination in watersheds.Wildlife fecal specimen collection and genomic DNA extraction. A total of 471 fecal specimens were collected during January 2001 and January 2002 from 87 beavers, 237 muskrats, 20 otters, 51 raccoons, and 76 foxes trapped in the Caroline (Marshy Hope Creek, Federalsburg), Charles (Clifton Creek, Newburg), Dorchester (Hunting Creek, Hurlock), and Talbot (Choptank River, Easton) counties of Maryland. With few exceptions, most of the trapped animals were older than 12 months. Details of the animal sources were described previ...

Sheep May Not Be an Important Zoonotic Reservoir forCryptosporidiumandGiardiaParasites

“…These results highlight the importance of genotyping analysis as there are significant differences in the zoonotic risk between genotypes and therefore hazard analysis critical control point analysis based on data from microscopy alone could significantly overestimate the risk of human cryptosporidiosis and giardiasis from sheep-derived protozoan contamination of catchments, effluents, and abattoirs. This is further supported by recent studies in the United States and Australia which reported that mammals and marsupials in watersheds excreted host-adapted Cryptosporidium oocysts not known to be of significant public health importance and that the potential role of wildlife in the transmission of human Cryptosporidium infection had been overestimated (30,43). This is also in agreement with the previous finding of only wildlife Cryptosporidium genotypes in runoff (storm water) in feral areas in the United States (40).…”

UnusualCryptosporidiumGenotypes in Human Cases of Diarrhea

“…data), but the source is unknown. Since many isolates have yet to be found in humans and although little is actually known about them, they are assumed to be insignifi cant to public health (6,15). The importance of unusual genotypes in humans who seek treatment for diarrheal disease warrants further investigation.…”

Tracking Host Sources of Cryptosporidium spp. in Raw Water for Improved Health Risk Assessment

“…Caution needs to be used when extrapolating molecular data from water samples to concretely determine host sources of contamination. In studies that examine the host specificity of Cryptosporidium parasites, there is a direct association between the host being studied and the fecal material used for typing parasites (30,37,55). This direct association does not exist for isolates from water samples.…”