Investigation of Cryptosporidium species in fecal samples obtained from humans and calves in the Siirt region by microscopy and molecular methods

The aim of this study is to investigate the prevalence of Cryptosporidium species and subtype in humans and calves in the Siirt region. Before the study commenced, approval was obtained from the Van Yüzüncü Yıl University Local Ethics Committee for Animal Experiments and the Non-Interventional Clinical Research Ethics Committee. The study was conducted between April 2024 and December 2024 on 200 volunteer patients and 200 calves. Fecal samples were collected from diarrheic patients aged 18 to 85 years who applied to various outpatient clinics of Siirt Training and Research Hospital with gastrointestinal complaints. Additionally, 200 fecal samples were directly collected from the rectum of calves in Siirt city center and its districts. All collected fecal samples were delivered to the Research Laboratory of the Department of Parasitology, Faculty of Medicine, Van Yüzüncü Yıl University. In the laboratory, all fecal samples were examined using the modified acid-fast staining (mAF), immunochromatographic cassette test (ICT), and molecular methods. Cryptosporidium parvum was detected in 10 (5%) of the human fecal samples and in 22 (11%) of the calf fecal samples. All samples in which Cryptosporidium spp. were detected by the modified acid-fast staining method were also found positive by ICT and nested PCR methods. However, in five samples where parasites were not observed with the mAF staining method, parasites were detected by ICT and nested PCR. PCR-RFLP analysis of the Cowp gene indicated that all Cryptosporidium spp. isolates from the positive samples were C. parvum. Subsequent sequencing of the gp60 gene region showed that the isolates obtained from calves belonged to the IIa subtype family, while those from humans were classified under the IId subtype family. As a result, the prevalence of Cryptosporidium spp. was determined for the first time in humans in the province of Siirt, and the effective species causing cryptosporidiosis in both humans and animals was identified as C. parvum. In addition, it was concluded that the routine use of nested PCR or ICT methods alongside the mAF staining method, which is used in hospitals for the diagnosis of Cryptosporidium spp., is of significant importance.