Emergence of novel subtypes of Cryptosporidium parvum in calves in Poland

The aim of the study was to identify the Cryptosporidium parvum subtypes circulating in Polish cattle and their distribution in relation to the age and health status of tested animals. In total, 779 fecal samples were obtained from young cattle originating from 237 farms. C. parvum strains were identified at the 18 small-subunit ribosomal RNA (SSU rRNA), COWP, and LIB13 loci and were subsequently analyzed by sequencing at the 60-kDa glycoprotein (GP60) locus for subtype determination. The presence of 71 C. parvum strains belonging to IIa, IId, or IIl subtype families was shown. The strains from the IIa allele family prevailed with IIaA17G1R1, IIaA17G2R1, and IIaA15G2R1 subtypes occurring frequently. Two novel subtypes IIaA10G1R1 and IIlA19R3 were detected for the first time in a bovine host. The highest C. parvum prevalence (22.5 %, confidence interval (CI) = 2.5 %) was observed among the youngest animals up to 2 weeks of age, followed by the prevalence among those aged 2 to 4 weeks (6.6 %, CI = 2.6 %) and then among older cattle (4.9 %, CI = 2.1). The occurrence of diarrhea in animals was associated with the presence of the IIaA16G1R1b subtype, while infections caused by IIaA15G2R1 strains were more likely to be asymptomatic. The geographical distribution of subtypes revealed that strains from the IIa subtype family were detected all over the country frequently compared to the IId and IIl subtypes, the sporadic appearances of which confirmed their endemic occurrence. Subtype analysis revealed the presence of zoonotic strains indicating cattle as a reservoir for human cryptosporidiosis.