Giardia duodenalisisolates recovered from humans and dogs living in the same locality in a remote tea-growing community of northeast India were characterized at 3 different loci; the SSU-rDNA, elongation factor 1-alpha (ef1-α) and triose phosphate isomerase (tpi) gene. Phylogenetic analysis of the SSU-rDNA and ef1-α genes provided poor genetic resolution of the isolates within various assemblages, stressing the importance of using multiple loci when inferring genotypes toGiardia. Analysis of the tpi gene provided better genetic resolution and placed canineGiardiaisolates within the genetic groupings of human isolates (Assemblages A and B). Further evidence for zoonotic transmission was supported by epidemiological data showing a highly significant association between the prevalence ofGiardiain humans and presence of aGiardia-positive dog in the same household (odds ratio 3·01, 95% CI, 1·11, 8·39,P=0·0000).

Little is known of the prevalence ofCryptosporidiumandGiardiaparasites in sheep and the genotypes that they harbor, although potentially sheep may contribute significantly to contamination of watersheds. In the present study, conducted in Western Australia, a total of 1,647 sheep fecal samples were screened for the presence ofCryptosporidiumandGiardiaspp. using microscopy, and a subset (n= 500) were screened by PCR and genotyped. Analysis revealed that although both parasites were detected in a high proportion of samples by PCR (44% and 26% forGiardiaandCryptosporidiumspp., respectively), with the exception of oneCryptosporidium hominisisolate, the majority of isolates genotyped are not commonly found in humans. These results suggest that the public health risk of sheep-derivedCryptosporidiumandGiardiaspp. in catchment areas and effluent may be overestimated and warrant further investigation.

Cryptosporidium is an enteric parasite that is transmitted via the faecal-oral route, water and food. Humans, wildlife and domestic livestock all potentially contribute Cryptosporidium to surface waters. Human encroachment into natural ecosystems has led to an increase in interactions between humans, domestic animals and wildlife populations. Increasing numbers of zoonotic diseases and spill over/back of zoonotic pathogens is a consequence of this anthropogenic disturbance. Drinking water catchments and water reservoir areas have been at the front line of this conflict as they can be easily contaminated by zoonotic waterborne pathogens. Therefore, the epidemiology of zoonotic species of Cryptosporidium in free-ranging and captive wildlife is of increasing importance. This review focuses on zoonotic Cryptosporidium species reported in global wildlife populations to date, and highlights their significance for public health and the water industry.