Abstract
The parasitic protozoan Cryptosporidium parvum causes cryptosporidiosis in young calves, leading to diarrhoea and financial losses in the farming industry. This study aimed to examine the occurrence of C. parvum in preweaning calves suffering from diarrhoea in Sulaymaniyah, Iraq, using both enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) methods. Faecal samples were obtained from 80 young calves categorised into various groups according to age, breed, sex, and geographic origin. Notably, a greater occurrence of C. parvum infection was observed in female calves, those in the 5-30 days age group, and those of the Friesian breed. Furthermore, the highest infection rate was reported in the Zarayan region. A strong correlation was observed between the ELISA and PCR findings. The molecular analysis detected both C. parvum and C. ryanae, with C. ryanae documented for the first time in Iraq. C. parvum infection considerably affects physiological indicators, particularly in younger calves, including body temperature, heart rate, and respiratory rate. PCR positivity in our study was substantially correlated with dehydration. Overall, this study highlights the need for prompt identification and intervention for the management of C. parvum infections in young calves.