Cryptosporidium spp. is recognized globally as an important cause of intestinal diarrhea-related diseases in humans and animals(Pumipuntu and Piratae 2018). Mithun is distributed in the deep mountains of the N'Mai River and Nujiang River basins in Nujiang Prefecture, Yunnan Province, southwestern China. A previous study has shown that remote areas are more prone to infection with Cryptosporidium(Ma et al. 2019), therefore, this is one of the reasons to investigate the prevalence of Cryptosporidium spp. in mithun in this region. The prevalence of Cryptosporidium spp. was 6.24% in mithun in Yunnan Province in this study, to our knowledge, this is the initial time that the prevalence of Cryptosporidium spp. has been found in mithun in Yunnan Province, southwestern China. Compared with other cattle breeds previously studied in Yunnan Province, the Cryptosporidium prevalence was higher in mithun than in Yunling cattle (0.77%) and dairy buffalo (1.1%) and lower than that in Holstein cows (14.7%)(Liang et al. 2021; Meng et al. 2022). In other regions of China, the prevalence of Cryptosporidium spp. in dairy cattle, yellow cattle, and buffaloes was 2.1%, 3.1%, and 1.9%, respectively in Anhui Province, 3.4% in cattle in Shaanxi Province, 2.53% in yaks in Qinghai Province and 2.55% in dairy cattle in Beijing(Li et al. 2016; Liu et al. 2022; Ren et al. 2019; Zhao et al. 2013). The Cryptosporidium prevalence in this study was found higher than the prevalence in all of the above areas. The prevalence of Cryptosporidium spp. in white yaks in Gansu Province was 5.26%, and the prevalence in dairy cows in both Gansu and Ningxia was 5.09%(Qin et al. 2014; Zhang et al. 2015), similar to the prevalence in our study. However, the prevalence of Cryptosporidium spp. in this study was lower than that in Heilongjiang, Jilin, Taiwan, Xinjiang Uygur Autonomous Region, Shandong, Henan, and Hunan, with the prevalence ranging from 16–32.6%(Huang et al. 2014; Ma et al. 2015; Qi et al. 2015; Tao et al. 2018). The findings of this study differ from the prevalence of Cryptosporidium spp. in the different regions mentioned above, and in combination with those studies, the reasons for these prevalence differences may be associated with regional geographic location, environment, climate, sanitary conditions, sampling conditions, sampling season and number of samples examined. In our study, we found that the prevalence of Cryptosporidium spp. in mithun was significantly different among seasons, with the highest prevalence in spring. However, in a previous study, the prevalence of Cryptosporidium spp. in Egyptian cattle was highest in winter owing to the cold season in Egypt is more suitable for Cryptosporidium to reproduce(Abdelaziz et al. 2022). And Cryptosporidium spp. is more likely to spread among yaks during autumn in Qinghai Province, China(Ren et al. 2019). Owing to the unique lifestyle and habits of mithun, which are wild and mostly raised in the deep mountains on a small scale, the prevalence of Cryptosporidium spp. may be relatively low. Therefore, group feeding may also be the main cause of high prevalence of Cryptosporidium spp. As mithun in Yunnan Province are herded in the mountains, basic data such as sex and age are not available, so the prevalence of Cryptosporidium in mithun of different ages and sexes was not reported in our study. However, previous studies have indicated that the prevalence of Cryptosporidium spp. in younger cattle is higher than that in adult cattle(Geng et al. 2021; Li et al. 2020).
As the host of Cryptosporidium spp., cattle are usually primarily infected by C. bovis, C. parvum, C. andersoni and C. ryanae(Gong et al. 2017). However, four Cryptosporidium spp. in mithun were identified in this study, known as C. struthionis, C. andersoni, C. ryanae, and Cryptosporidium sp., The prevalence of C. struthionis is highest in mithun, followed by C. andersoni, Cryptosporidium sp., and C. ryanae. It is rare that C. struthionis is reported to be prevalent in cattle, but there has been a former study found that C. struthionis is prevalent in yaks in Qinghai Province, China(Wang et al. 2018). In addition, no C. bovis was found and three different species of C. andersoni were identified in this study. Besides being the main cause of cryptosporidiosis in cattle, the C. andersoni has also been isolated from diarrhea patients in Jiangsu Province, China, and from pediatric patients in England and Malawi(Jiang et al. 2014; Leoni et al. 2006; Morse et al. 2007).
The two basins in Nujiang Prefecture, Yunnan Province, southwestern China, are remote and surrounded by mixed agricultural and pastoral areas, where a great number of wild animals exist, and the infected mithun share water with those, making it very convenient to spread Cryptosporidium between each other. The zoonotic parasite C. andersoni in mithun may have a risk to the health of the local population as well as to public health. Therefore, the health-related departments in Nujiang Prefecture, Yunnan Province, should prepare for the prevention of cryptosporidiosis and assess the public health risk. This study was the initial to report the prevalence of Cryptosporidium spp. in mithun and to identify C. andersoni in mithun, the findings could provide basic data for locally prevented Cryptosporidiosis.