Occurrence and Genetic Diversity of Cryptosporidium spp. and Giardia intestinalis from Yaks (Bos grunniens) in Ganzi, Sichuan Province, China

<i>Cryptosporidium</i> spp. and <i>Giardia intestinalis</i> are important zoonotic protozoa that are closely related to diarrhea and cause considerable economic losses in the livestock breeding industry. Ganzi is one of the main production areas for yaks in China, but there have been few reports on the occurrence of <i>Cryptosporidium</i> spp. and <i>G. intestinalis</i> in yaks. This study used PCR-based sequencing techniques to survey the prevalence and species/genotypes of <i>Cryptosporidium</i> spp. and <i>G. intestinalis</i> in faecal samples from 223 yaks in Ganzi, Sichuan Province. The positive rate of <i>Cryptosporidium</i> spp. was 7.2% (16/223), with the highest positive rate of yaks found in Yajiang (37%, 10/27), which was significantly higher than that in Litang (3.1%, 4/130) and Seda (3%, 2/66). The positive rate of <i>Cryptosporidium</i> spp. in young animals aged <6 months (20.5%, 8/39) was significantly higher than that in older animals aged 12-23 months (0; 0/43) and >24 months (3.3%, 3/90). Three <i>Cryptosporidium</i> species were found by sequence analysis of <i>18S</i> rRNA locus, namely <i>C. andersoni</i>, <i>C. ryanae</i>, and <i>C. bovis</i>. The total positive rate of <i>G. intestinalis</i> was 15.7% (35/223), with significant differences identified between Yajiang (40.7%, 11/27), Litang (17.7%, 23/130), and Seda (1.5%, 1/66). One genotype (assemblage E) was found by analyzing the sequence of <i>gdh</i>, <i>bg</i>, and <i>tpi</i> loci. Meanwhile, co-infection of <i>Cryptosporidium</i> spp. and <i>Giardia intestinalis</i> was identified in five samples. The present study explores the infection of <i>Cryptosporidium</i> spp. and <i>G. intestinalis</i> from yaks in Ganzi, aiming to enrich our understanding of the occurrence of these protozoa in livestock.