AUTHOR=Jang Dong-Hun , Cho Hyung-Chul , Park Yu-Jin , Park Jinho , Choi Kyoung-Seong 

TITLE=First report of Cryptosporidium andersoni and risk factors associated with the occurrence of Cryptosporidium spp. in pre-weaned native Korean calves with diarrhea

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1145096

DOI=10.3389/fvets.2023.1145096

ISSN=2297-1769

ABSTRACT=<p><italic>Cryptosporidium</italic> spp. are important enteric protozoan parasites that infect humans and other animals throughout the world. <italic>Cryptosporidium</italic> infection in cattle industry leads to substantial economic losses due to diarrhea, growth retardation, weight loss, and possibly death. Most studies have focused on <italic>C. parvum</italic>, and studies on other <italic>Cryptosporidium</italic> spp. and calf diarrhea are limited. Therefore, this study aimed to investigate the occurrence of <italic>Cryptosporidium</italic> spp. in pre-weaned calves, to determine the risk factors for <italic>Cryptosporidium</italic> spp. infection such as age and season, and to identify subtypes of <italic>C. parvum</italic> circulating in the Republic of Korea (ROK). A total of 510 fecal samples were collected from calves with diarrhea and divided by age and season. <italic>Cryptosporidium</italic> spp. were first screened using PCR targeting the small subunit (SSU) rRNA gene and further the 60-kDa glycoprotein gene for subtyping of <italic>C. parvum</italic>. Out of 510 fecal samples, 71 (13.9%) were positive for <italic>Cryptosporidium</italic> spp. in pre-weaned calves with diarrhea. <italic>C. andersoni</italic> (2.8%), <italic>C. bovis</italic> (30.9%)<italic>, C. parvum</italic> (29.6%), and <italic>C. ryanae</italic> (36.6%) were identified. <italic>C. ryanae</italic> was the most predominant in calves in the ROK. Calf age was a significant risk factor for <italic>C. bovis</italic> (χ<sup>2</sup> = 13.83, <italic>P</italic> = 0.001)<italic>, C. parvum</italic> (χ<sup>2</sup> = 7.57, <italic>P</italic> = 0.023), and <italic>C. ryanae</italic> (χ<sup>2</sup> = 20.18, <italic>P</italic> = 0.000) occurrence. Additionally, <italic>C. parvum</italic> was detected 3.1-fold more frequently in pre-weaned calves with diarrhea in fall (95% CI: 1.23–7.81; <italic>P</italic> = 0.016) than in spring, whereas <italic>C. ryanae</italic> was 8.9-fold more frequently detected in summer (95% CI: 1.65–48.68; <italic>P</italic> = 0.011) than in spring. Three subtypes (IIaA17G4R1, IIaA18G3R1, and IIaA20G3R1) of <italic>C. parvum</italic> were identified. Of them, IIaA17G4R1 was the most common, whereas IIaA20G3R1 was not previously detected in calves in the ROK. To our knowledge, this is the first report of <italic>C. andersoni</italic> in pre-weaned calves in the ROK. The occurrence of <italic>Cryptosporidium</italic> spp. appears to be age-dependent in calves. Season had a significant effect on the occurrence of <italic>C. parvum</italic> and <italic>C. ryanae</italic>. Taken together, <italic>C. bovis</italic> and <italic>C. ryanae</italic> along with <italic>C. parvum</italic> are detected in pre-weaned calves with diarrhea and these two pathogens should not be overlooked in the diagnosis of calf diarrhea.</p>