What's going on Blog Silent killers: Johne's Disease Johne’s disease, also known as Paratuberculosis, is a chronic, contagious bacterial disease of the intestinal tract that is most commonly seen in dairy cattle but also affects sheep and goats as well as other ruminant species. RBST has seen increasing numbers of cases of Johnes in certain rare sheep and goat breeds, and is particularly keen to highlight the disease to keepers who might be unaware of it – it is always worth getting an animal post-mortemed if it shows progressive and severe weight loss but seems to remain otherwise bright. Infected animals shed the bacterium in manure, colostrum, and milk. Infection is most commonly acquired in young animals through contamination of the environment or ingestion of contaminated milk from an infected cow. It can also be transmitted from an infected pregnant animal to its foetus. Faecal shedding of the bacteria begins before clinical signs are noticeable, so these ‘silent’ carrier animals are important sources of transmission. A non-infected herd generally becomes exposed through herd expansion or replacement purchases of animals that are carriers of the disease. Young animals are highly susceptible. Because of the slowly progressive nature of the infection in cattle, clinical signs usually first appear in young adulthood (4-7 years old), but the disease can occur in animals at any age over 1-2 years. The organism causes chronic enteritis (inflammation of the intestines) characterised by diarrhoea, unthrifty animals and progressive weight loss despite a good appetite and normal body temperature. In sheep, goats, and other ruminants, the diarrhoea may not be present. The single largest problem in Johne’s disease control is the difficulty of detecting infected animals that are not showing signs of illness. Faecal culture, although technically difficult and time-consuming, will detect infected animals 6 months or more before they have developed clinical signs, which is very important since this disease has a slow progression and many animals are non-clinical carriers of disease. There is no known treatment for the disease. Control involves good sanitation and management practices including screening tests for new animals to identify and eliminate infected animals and ongoing surveillance of adult animals. For more information, visit AHDB webpage on the disease.