**1. Introduction**

*Cryptosporidium* spp. are important apicomplexan parasites inhabiting the gastrointestinal tract of humans and other vertebrates, causing severe diarrhea [1]. Human cryptosporidiosis has been associated with over 20 *Cryptosporidium* species, but *C. hominis*, *C. parvum*, *C. meleagridis*, *C. felis*, and *C. canis* are the most common ones [2]. Among them, *C. felis* mainly infects cats and is therefore considered a host-adapted species [3]. Human *C. felis* infections, however, are common in developing countries [4–7], and at least one possible zoonotic transmission of *C. felis* between a household cat and the owner has been reported [8]. Nevertheless, the limited number of reports of zoonotic infections with this species has raised questions on the importance of zoonotic transmission in the epidemiology of human *C. felis* infections [9].

Subtyping tools based on sequence analysis of the 60-kDa glycoprotein (*gp60*) gene have been developed for human-pathogenic *Cryptosporidium* spp. to track infection sources [10]. Currently, the *gp60*-based subtyping tools are available for *C. hominis*, *C. parvum*, *C. meleagridis*, *C. ubiquitum*, *C. viatorum*, *Cryptosporidium* skunk genotype, and *Cryptosporidium* chipmunk genotype I [11–16]. These subtyping methods have been used in characterizing the transmission of these *Cryptosporidium* spp. in humans and animals [3].

A *gp60* subtyping tool has been developed recently for genetic characterizations of *C. felis* [17]. Thus far, nearly 200 *C. felis* isolates have been examined, which has led to the

Guo, S.; Guo, Y.; Li, N.; Feng, Y.; Xiao, L. Subtype Characterization and Zoonotic Potential of *Cryptosporidium felis* in Cats in Guangdong and Shanghai, China. *Pathogens* **2021**, *10*, 89. https://doi.org/10.3390/pathogens10020089

**Citation:** Li, J.; Yang, F.; Liang, R.;

Academic Editor: David Carmena Received: 25 December 2020 Accepted: 19 January 2021 Published: 20 January 2021

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identification of approximately 100 subtypes in five subtype families (XIXa, XIXb, XIXc, XIXd, and XIXe) worldwide [17,18]. Most of the isolates, however, were from humans, and only two isolates from a human and a rhesus macaque have been characterized from China [18]. As *C. felis* has been identified in children and immunocompromised patients in China [19–22], we sought to examine the subtype identity of cat-derived *C. felis* isolates from Guangdong and Shanghai for assessment of their zoonotic potential.
