Prevalence, Environmental Loading, and Molecular Characterization of Cryptosporidium and Giardia Isolates from Domestic and Wild Animals along the Central California Coast

ABSTRACTThe risk of disease transmission from waterborne protozoa is often dependent on the origin (e.g., domestic animals versus wildlife), overall parasite load in contaminated waterways, and parasite genotype, with infections being linked to runoff or direct deposition of domestic animal and wildlife feces. Fecal samples collected from domestic animals and wildlife along the central California coast were screened to (i) compare the prevalence and associated risk factors for fecal shedding ofCryptosporidiumandGiardiaspecies parasites, (ii) evaluate the relative importance of animal host groups that contribute to pathogen loading in coastal ecosystems, and (iii) characterize zoonotic and host-specific genotypes. Overall, 6% of fecal samples tested during 2007 to 2010 were positive forCryptosporidiumoocysts and 15% were positive forGiardiacysts. Animal host group and age class were significantly associated with detection ofCryptosporidiumandGiardiaparasites in animal feces. Fecal loading analysis revealed that infected beef cattle potentially contribute the greatest parasite load relative to other host groups, followed by wild canids. Beef cattle, however, shed host-specific, minimally zoonoticCryptosporidiumandGiardia duodenalisgenotypes, whereas wild canids shed potentially zoonotic genotypes, includingG. duodenalisassemblages A and B. Given that the parasite genotypes detected in cattle were not zoonotic, the public health risk posed by protozoan parasite shedding in cattle feces may be lower than that posed by other animals, such as wild canids, that routinely shed zoonotic genotypes.