Molecular characterisation of Cryptosporidium isolates from Swedish dairy cattle in relation to age, diarrhoea and region.

Cryptosporidium positive samples from 176 preweaned calves, young stock and cows of 48 herds were subjected to molecular characterisation of the 18S rRNA gene to determine which species are present in Swedish dairy cattle. In addition, samples characterised as Cryptosporidium parvum were further analysed at the GP60 gene to investigate distribution and zoonotic potential of subtypes. The 18S rRNA gene was successfully sequenced in 110 samples, with Cryptosporidium bovis in 83, C. parvum in 15, Cryptosporidium ryanae in 10, and Cryptosporidium andersoni in two samples. C. bovis was the most common species, being identified in 74% of calf samples, in 77% of young stock samples and in 100% of cow samples. The youngest calves infected with C. bovis were 7 days old, showing that the prepatent period is shorter than the previously stated 10 days. C. parvum was detected in 15 calves from nine farms, and samples were clustered in the southern parts of Sweden. Diarrhoeic calf samples contained C. parvum, C. bovis or C. ryanae. Sequencing of the GP60 gene was successful in 13 of the C. parvum samples. Eight subtypes, including three novel ones, were detected. Four of the subtypes have previously been identified in humans. This indicates that there is a zoonotic potential in C. parvum infected Swedish dairy calves.