An overview of calf diarrhea - infectious etiology, diagnosis, and intervention

Cho, Yong-il; Yoon, Kyoung-Jin

Cryptosporidium parvum is a protozoan parasite that is frequently associated with gastrointestinal tract disease in humans and neonatal cattle. Calves infected with C. parvum can be asymptomatic or develop severe diarrhea with dehydration [35, 36] . There are approximately 24 species of Cryptosporidium [34] . Cattle are commonly infected by C. parvum, C. bovis, C. ryanae, and C. andersoni. C. parvum is considered to be primary cause of calf diarrhea and is a potential zoonotic agent [15] . Once C. parvum is ingested, the oocyst excystation releases sporozoites that penetrate enterocytes. The excysted parasites undergo asexual (type I meront) and sexual (type II meront) reproduction to produce macrogametocytes and microgametocytes. Upon fertilization of the macrogametocytes by microgametes, zygotes are developed with sporulates (sporogony) generating thin-walled oocysts involved in autoinfection. Next, thick-walled oocysts pass out of the host. The oocysts can survive for more than a month in the environment under favorable conditions (e.g., high temperature and moisture with low UV radiation) and are resistant to most disinfectants [37] . Environments contaminated with oocysts can be an immediate source of infection for both animals and humans.