This disease is caused by a small organism (a protozoa called cryptosporidium), which can multiply in the cells of the gut and cause diarrhoea. It is considered to be self-limiting and is found in normally healthy animals, however it will overwhelm immuno-suppressed animals and in association with other infectious agents can cause high death rates. In the early days of deer farming cryptosporidium wasnt much of a problem, probably because the animals were not farmed so intensively. But in the past few years there has been a noticeable increase in cases, particularly in wet areas. During the peak of an outbreak cryptosporidium can kill 20% of the fawns in a herd. The year after an outbreak the losses are likely to be about 10% and the next year about 2%. The main cause of the disease seems to be stress. Bad weather, a lack of shelter or change in diet can make the fawn susceptible. The disease tends to cause sudden outbreaks and lots of deaths. In the face of an outbreak deer farmers have to decide whether to leave stock alone or to come in at frequent intervals to locate any weak or scouring fawns and to treat them. Farmers should attempt to minimise the stress on fawns, by changing fawning paddocks, limiting the number of hinds fawning in a paddock reducing disturbances and providing shelter. It is important to be careful when dealing with cryptosporidium because transmission to humans is possible and can result in severe disease in some individuals. Extract from an article in Country Practice.