One Health: A Study of Zoonotic Parasites in Cats

Feral and stray cats serve as reservoirs for pathogens that can be transmitted to humans. Researchers believe that better characterizing the parasites involved and the associated risk factors would help tailor strategies for controlling, preventing, and combating zoonotic parasitic diseases.   Feral and stray cats can carry numerous germs and parasites, including gastrointestinal protozoans and microsporidia, which pose a threat to both human and animal health. Cats that live outdoors can indeed contaminate the environment with fecal cysts, oocysts, spores, and eggs of pathogens that are pathogenic for humans. The growing population of feral cats worldwide is a topic of debate. Not only is their impact on public health and the environment a cause for concern, but disagreements over the best control measures to adopt are also sparking controversy. This is particularly true in South Korea, where stray cats have become the bane of residents’ existence. They cause traffic accidents, disrupt people’s sleep, and, most importantly, live in unsanitary conditions with little oversight. Without care or preventive treatments, some cats spread infections at high rates. Unfortunately, data on the prevalence of zoonotic agents in these populations vary widely depending on the samples, regions, and testing methods. Researchers therefore sought to characterize the parasitic reservoirs in shelter cats in South Korea, specifically on Jeju Island, to better understand the risks involved. Their study identified infection rates and risk factors (age and sex) associated with intestinal protozoans and microsporidia in cats. Of the 158 cats studied, 16 (10.1%) tested positive (via PCR test) for at least one protozoan or microsporidium. These results were well below expectations. In a previous study, 55.9% of shelter cats were infected with at least one intestinal pathogen, compared to 33.2% of pet cats. This difference may be explained by the small sample size, which was limited to the Korean island of Jeju. Larger-scale studies in other regions of the country—particularly on the mainland—would be more representative. Young cats, being more susceptible to parasitic infections, had a higher positivity rate for intestinal protozoans and microsporidia than adults, who were less frequently infected. Genomics of the pathogens identified five intestinal protozoans and microsporidia: Cryptosporidium felis (0.6%), Giardia duodenalis (3.8%), Blastocystis spp. (0.6%), Enterocytozoon bieneusi (3.8%), and Toxoplasma gondii (1.3%). Notably, this is the first time that the parasites C. felis, G. duodenalis assembly F, Blastocystis sp. subtype ST4, and E. bieneusi genotype Peru-11 have been described in cats in South Korea. Despite a limited number of positive samples, this study demonstrates the prevalence of zoonotic gastrointestinal protozoans and microsporidia in shelter cats and genetically characterizes the isolates found in infected animals. These results underscore the need for a better interdisciplinary strategy for the control, prevention, and management of feline intestinal parasitic diseases—tailored to field conditions—in order to protect animal and human health. At the heart of these measures, the researchers emphasize raising public awareness of the risks of zoonotic agent transmission by cats, as well as efforts to reduce feral or stray cat populations, for example through sterilization.