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Review
. 2023 Nov 30:4:100158.
doi: 10.1016/j.crpvbd.2023.100158. eCollection 2023.

Cryptosporidium and Giardia in cats and dogs: What is the real zoonotic risk?

Amanda D Barbosa  1   2 , Siobhon Egan  1 , Yaoyu Feng  3 , Lihua Xiao  3 , Una Ryan  1
Affiliations
Review

Cryptosporidium and Giardia in cats and dogs: What is the real zoonotic risk?

Amanda D Barbosa et al. Curr Res Parasitol Vector Borne Dis. .

Abstract

Due to the close bond between humans and companion animals, a thorough understanding of the diversity of Cryptosporidium species and Giardia assemblages in cats and dogs is essential to determine the potential zoonotic risks. Analysis of molecular studies shows that C. felis and C. canis are the main species infecting cats and dogs, respectively. These species are largely host-specific, as despite intense association with humans, prevalence of C. felis and C. canis in humans is low and predominantly in immunocompromised individuals and low-income countries. There have been reports of C. parvum in cats and dogs and two reports of C. hominis in dogs. In most studies conducted to date, however, the prevalence of zoonotic species was low and may be associated with coprophagy and or/spillback, but this remains to be determined. Results of subtyping studies suggest that for C. felis and C. canis, some zoonotic transmission may occur but host-adapted subtypes also exist. Giardia duodenalis assemblages C and D are commonly reported in dogs, with assemblages F and A most common in cats. Assemblages C, D and F are largely host-specific as there are only a handful of reports of them in humans. Reports of assemblage A and B in cats and dogs may be due to coprophagy or spillback from owners. Despite the extent of pet ownership and the close contact between humans and companion animals worldwide, the overall risk of zoonotic transmission from cats and dogs to humans is uncertain but thought to be low due to C. canis, C. felis and G. duodenalis assemblages C, D and F being predominantly host-specific, the relatively low prevalence of C. parvum (and C. hominis) in cats and dogs (which may be due to mechanical carriage), and low oo/cyst shedding. Carefully designed epidemiological studies of cats and dogs and their owners using subtyping tools are essential to better quantify the extent of spillover and spillback of Cryptosporidium and Giardia between pets and their owners.

Keywords: Cats; Cryptosporidium; Dogs; Giardia; Molecular typing; Zoonosis; Zoonotic potential.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Given their role as Guest Editor, Amanda D. Barbosa had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Dr Frank Katzer (Co-Editor) and Professor Aneta Kostadinova (Editor-in-Chief).

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