Paratuberculosis (Johne`s disease) in ruminants - an ongoing story

Paratuberculosis or JOHNE´s disease is one of the most important diseases in ruminants today. Mycobacterium avium subspecies paratuberculosis (MAP), the cause of paratuberculosis, has a broad host range. Although mainly considered a disease of cattle, sheep and goats, all ruminants, including a large number of wild and exotic species of ruminants, are susceptible. The reported prevalence of infected animals varies by country and region and reaches up to 84.7 % MAP positive dairy herds in some aereas. Although calves are most susceptible to paratuberculosis, older heifers and adult cattle can also become infected. In newborn calves the infection mostly takes place soon after birth by oral ingestion of the organism but MAP can also be found in colostrum and milk of asymptomatic infected cows. Although shedding of MAP is considered not to start before 1.5 years of age, it has been shown, that also young calves can shed MAP and thereby pass infection to other calves in the same environment. The vast majority of herds that acquire MAP do so through purchase of infected animals. The first clinical sign in cattle can usually be seen after calving as a chronic or intermittent diarrhea alternating with periods of normal consistency of faces. In sheep and goats diarrhea is usually absent. Subclinically infected adult animals do not show visible signs of paratuberculosis, although they carry MAP. The prognosis is poor, the disease leads to emaciation and ends with the death of the affected animal. If clinical symptoms are missing laboratory tests have to be used to confirm or rule out the diagnosis. Many different test systems are available for the detection of MAP, such as Ziehl-Neelsen Staining, faecal culture and Polymerase Chain Reaction (PCR) or the evaluation of antibody levels by Enzyme Linked Immuno Sorbent Essays (ELISA). Because paratuberculosis is difficult to diagnose and untreatable control and reduction in MAP positive herds and prevention of spreading the disease to negative herds is very important. Hygienic precautionary measures have to be taken to prevent further spreading of the disease in a herd. The mayor aim of this hygienic precaution is to prevent infection of calves and young stock and to purchase MAP- free animals only. In this article a review about infection, diagnosis and control of this disease is given. New aspects of current researches are combined with