Cryptosporidium spp. in wild rats (Rattus spp.) from the Hainan Province, China: Molecular detection, species/genotype identification and implications for public health

Abstract

Wild rats (<i>Rattus</i> spp.) carry many zoonotic pathogens including <i>Cryptosporidium.</i> Due to the close proximity of rats to humans in urban environments, the potential for disease transmission is high. <i>Cryptosporidium</i> is a protozoan parasite which when ingested causes serious human illness. Despite its importance, genetic characterization of <i>Cryptosporidium</i> in wild rats in the Hainan province of China has not been performed. In this study, we analyzed the occurrence and genetics of <i>Cryptosporidium</i> in wild rats from Hainan, China. From December 2017 to October 2018, 150 wild rats were captured and fresh fecal material was collected from intestinal sections. Rat species were identified by PCR-based amplification and analysis of the vertebrate cytochrome <i>b</i> (<i>cytb</i>) gene. <i>Cryptosporidium</i> was examined by PCR amplification of the partial small subunit of ribosomal DNA (SSU rDNA). <i>C. viatorum</i> were subtyped by PCR analysis of the gp60 gene. A total of four rat species were identified including Asian house rats (<i>Rattus tanezumi</i>) (n = 46), brown rats (<i>Rattus norvegicus</i>) (n = 56), Edward's long-tailed rats (<i>Leopoldamys edwardsi</i>) (n = 38) and muridae (<i>Niviventer fulvescens</i>) (n = 10), with <i>Cryptosporidium</i> positive rates of 73.9%, 28.6%, 55.3% and 40.0%, respectively (average infection rate: 50.0%, 75/150. Sequence analysis confirmed the presence of four <i>Cryptosporidium</i> species and two genotypes including <i>C. viatorum</i> (n = 11); <i>C. occultus</i> (n = 2); <i>C. muris</i> (n = 1); and <i>C. erinacei</i> (n = 1); rat genotypes III (n = 13) and IV (n = 47). Three novel subtypes of <i>C. viatorum</i> were identified in 6 of the 11 infected Edward's long-tailed rats: XVcA2G1a (n = 4), XVcA2G1b (n = 1) and XVdA3 (n = 1). The identification of human pathogenic <i>C. viatorum</i> and zoonotic <i>C. occultus</i>, <i>C. muris</i> and <i>C. erinacei,</i> suggested that wild rats infected with <i>Cryptosporidium</i> pose a threat to human health. Taken together, these findings highlight the need to control the rat population in Hainan, China. The need to improve the public awareness of the risk of disease transmission from wild rats to humans is also highlighted.