Abstract: Paratuberculosis is a chronic infectious bacterial disease. The pathogen is Mycobacterium avium subsp. Paratuberculosis,which mainly infects cattle and sheep,causing damage to small intestine and other organs of sick animals,causing diarrhea,weight loss, malnutrition,anemia and even death. Paratuberculosis in dairy cows can lead to an increase in the death rate of dairy cows,a decrease in milk yield,a decrease in feed conversion efficiency,a decrease in reproductive capacity,a decrease in slaughter rate and an increase in the infection rate of other pathogens,thus causing significant economic losses to dairy farming. Mycobacterium paratuberculosis mainly spreads through the faecal-oral route,or vertically through the uterus. Mycobacterium paratuberculosis escapes the immune system by continuously infecting macrophages in the submucosa of the small intestine. In most cases,this recessive persistent infection lasts for at least two years,and then the bacteria begin to fall off and appear clinical symptoms. The slow progress of Mycobacterium paratuberculosis infection and the poor performance of diagnostic test and management system will make susceptible calves infected, which makes the prevention and control of bovine paratuberculosis very challenging,especially in seasonal calves. In this paper,the basic information,economic harm and diagnostic methods of bovine paratuberculosis were introduced,aiming at providing reference for clinical diagnosis and development of new diagnostic methods of bovine paratuberculosis.

Key words: cow, Paratuberculosis, diagnosis, review