Molecular epidemiology of Cryptosporidium spp. in calves in Estonia: high prevalence of Cryptosporidium parvum shedding and 10 subtypes identified

We investigated the molecular epidemiology of Cryptosporidium spp. in Estonia by testing fecal samples from 486 calves aged <2 months, raised on 53 cattle farms, for the presence of Cryptosporidium DNA. The parasites were identified and characterized by sequencing of the 18S rRNA gene and of the 60 kDa glycoprotein (gp60) gene. Moreover, using a questionnaire, we surveyed factors that could be relevant for animal-to-human and human-to-animal transmission of Cryptosporidium spp. on the farms. Cryptosporidium spp. were shed by 23% of the investigated calves and at least one shedding calf was found on 66% of the farms. Cryptosporidium parvum was the most common species shed, while C. bovis and C. ryanae were also detected. More than half of the calves aged 8-14 days shed C. parvum. Nine previously described C. parvum subtypes (IIaA14G1R1, IIaA16G1R1, IIaA17G1R1, IIaA18G1R1, IIaA19G1R1, IIaA20G1R1, IIaA21G1R1, IIaA22G1R1 and IIaA16G2R1) and an apparently novel subtype IIlA21R2 were found. Calves from farms that reported spreading manure on fields during spring had 10 times higher odds to shed Cryptosporidium spp. in their feces than calves from farms that did not. Calves aged 8-14 days had higher odds to shed IIa18G1R1 as well as IIaA16G1R1 than younger calves.