**1. Introduction**

*Cryptosporidium* spp. are major pathogens that mainly parasitize the gastrointestinal epithelium, causing moderate-to-severe diarrhea in humans and animals [1,2]. They are responsible for significant mortality in both young children [1,3] and neonatal farm animals [4–8]. In addition, cryptosporidiosis has been associated with retarded growth in humans and farm animals [9–12].

*Cryptosporidium* spp. are especially common in rodents [13]. Among the >40 established *Cryptosporidium* species and an equal number of genotypes of unknown species status [14], *C. parvum* is commonly found in various rodents in China [15]. Other *Cryptosporidium* spp. from rodents have more limited host ranges, such as *C. meleagridis* and *Cryptosporidium* deer mouse genotypes I, II, III, and IV in deer mice [16–19]; *Cryptosporidium* chipmunk genotypes I and II in chipmunks [16]; and *Cryptosporidium* ferret genotype, *C. rubeyi* and several squirrel genotypes in squirrels [20–23].

Bamboo rats are widely farmed in southern China. They are commonly infected with *Cryptosporidium* spp. Several *Cryptosporidium* species and genotypes have been identified in these animals, including *C. parvum*, *C. parvum*-like genotype, *C. occultus*, and *Cryptosporidium* bamboo rat genotypes I and II [24,25]. Thus, the distribution of *Cryptosporidium* spp. in bamboo rats appears to be different from other rodents. At the subtype level, *C. parvum* subtypes found in bamboo rats also differ from those in other rodents. In China, rodents such as hamsters, chipmunks, and rats are mostly infected with the IId subtype family of *C. parvum*, with IIdA15G1 and IIdA19G1 as the most common subtypes [26]. In contrast, bamboo rats in southern China are seemingly infected with rare IIo and IIp subtype families of *C. parvum* [25,27]. Most of data on these two *C. parvum* subtype families in bamboo rats, however, were from a study of animals in Jiangxi, Guangxi, and Hainan [24].

In this study, we examined the occurrence of *Cryptosporidium* spp. and *C. parvum* subtypes in bamboo rats in Guangdong Province. The distributions of *Cryptosporidium* spp. and *C. parvum* subtypes were compared among farms, age groups and reproduction statuses. The oocyst shedding intensity was compared among *Cryptosporidium* species and genotypes for the first time.

#### **2. Results**

#### *2.1. Occurrence of Cryptosporidium spp. in Bamboo Rats*

The overall detection rate of *Cryptosporidium* spp. in bamboo rats in Guangdong was 12.2% (88/724). The detection rate of *Cryptosporidium* spp. on farm 1 (35.9% or 33/92) was significantly higher than on farm 2 (3.5% or 5/142; χ<sup>2</sup> = 42.95, *df* = 1, *p* < 0.0001; *df*: degrees of freedom), farm 3 (1.0% or 2/205; χ<sup>2</sup> = 74.38, *df* = 1, *p* < 0.0001), farm 5 (0% or 0/56; χ<sup>2</sup> = 25.85, *df* = 1, *p* < 0.0001), and farm 6 (19.7% or 37/188; χ<sup>2</sup> = 8.63, *df* = 1, *p* = 0.0033). The difference in detection rate between farms 4 (26.8% or 11/41) and 1 was not significant (χ<sup>2</sup> = 1.05, *df* = 1, *p* = 0.3062; Table 1).

By age, the detection rates of *Cryptosporidium* spp. in bamboo rats ranged from 0.0% (0/8) in animals of 6–8 months to 23.2% (13/56) in animals under 2 months. The detection rate of *Cryptosporidium* spp. in animals under 2 months of age was significantly higher than in older animals (11.2% or 75/668; χ<sup>2</sup> = 6.95, *df* = 1, *P* = 0.0084; Table 2). By reproduction status of adult animals (1–3 years in age), nursing animals had a significantly higher detection rate (23.1% or 27/117) than breeding animals (4.9% or 10/205; χ<sup>2</sup> = 24.26, *df* = 1, *p* < 0.0001), pregnant animals (6.8% or 4/59; χ<sup>2</sup> = 7.18, *df* = 1, *p* = 0.0074), and nonpregnant animals (10.6% or 21/198; χ<sup>2</sup> = 8.86, *df* = 1, *p* = 0.0029; Table 3).




