Abstract
Major progress has been made in understanding the epidemiology of bovine Cryptosporidium in China in the past 30 years. The overall infection rate in that period was 14.50% (5265/36316), with different prevalence being observed among dairy cattle, yaks, beef cattle, and buffalo. The infection rate declined as the animals’ ages increased and the lowest prevalence occurred in winter. Ten Cryptosporidium species and two genotypes have been found in cattle, with Cryptosporidium parvum, C. andersoni, C. bovis, and C. ryanae being the commonest species. Cryptosporidium bovis rather than C. parvum predominated in preweaned dairy cattle, and C. parvum IIdA15G1 and IIdA19G1 were the only subtypes detected in dairy cattle. Two subtype families, IIa and IId, were found in yaks. Population genetic analysis detected an epidemic population structure in C. andersoni, which suggested that the prevalence of C. andersoni in China is not attributable to the introduction of dairy cattle. Moreover, C. parvum IId subtypes probably dispersed from western Asia to other geographic regions based on population genetic analysis of isolates from China, Sweden, and Egypt. Therefore, we hypothesize that Cryptosporidium was introduced into China in the past, and different populations formed progressively in various hosts in response to diverse factors, including the transmission dynamics, geographic isolation, host specificity, and large-scale farming. More epidemiological studies are required to test this hypothesis and to clarify the prevalence and transmission of Cryptosporidium species in China.
Highlights
Cryptosporidium spp. are important zoonotic agents infecting a wide spectrum of vertebrate hosts (Xiao et al, 2004; Wang et al, 2011b)
Epidemiological data suggest that Cryptosporidium infections are commonly found in cattle in China
Similar to the species distributions reported in other countries and areas of the world, C. parvum, C. bovis, C. andersoni and C. ryanae are the four commonest Cryptosporidium species in cattle
Summary
Cryptosporidium spp. are important zoonotic agents infecting a wide spectrum of vertebrate hosts (Xiao et al, 2004; Wang et al, 2011b). Following ingestion by a suitable host, the motile, infective sporozoites are released through a suture in the oocyst wall and parasitize epithelial cells of the gastrointestinal tract or other tissues (Reduker et al, 1985; O’Hara and Chen, 2011). In these cells, the parasites undergo asexual multiplication, which produces Type-I and Type-II merozoites (Current and Reese, 1986). Cattle are the mammals in which Cryptosporidium infection is most commonly found, and preweaned calves are considered the most important reservoir for zoonotic infection (Wang et al, 2011b; Li F. et al, 2016). The present paper focuses on the advances in the molecular epidemiology of bovine Cryptosporidium that have occurred in China in the past 30 years
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