b'Johnes Diseasesurveys suggest it is closer to 17.5 per cent 96 . HistoryJohnes disease was first noted in 1826 but not officially recognised as an infectious disease until 1894 97 . The last 100 years have seen a steady increase in the number of infected animals within a species, the number of different species infected, and the number of countries in which it has taken root 98 . Routes of transmissionWhat is it? Infected animals shed Johnes disease is an infectious wastingthe bacteria in manure, colostrum and condition caused by Mycobacterium aviummilk. Infection is most commonly acquired subspecies paratuberculosis (MAP). Thein young animals through ingestion of contaminated milk from an infected cow or bacterium causes a chronic and sometimesthrough the environment 99 . (Just one cow fatal infection in cows, sheep, goats andwith diarrhoea could potentially thoroughly other ruminants. In infected flocks of sheep,contaminate her surroundings 100 .) It can the annual ewe mortality rate is estimatedalso be transmitted from an infected to be between 5 and 10 per cent 94 . Johnespregnant animal to her foetus. is endemic in the UK 95but it is not known just how prevalent it is. One 2006 studyConfining large numbers of animals in small estimated that around 35 per cent of herdsareas helps to spread the disease and is one are affected, while more recent small-scalereason that it is such a growing threat 101 . 18'