Scientists model Map transmission
Map, or Mycobacterium avium subspecies paratuberculosis is a chronic bacterial infection of the intestine. Symptoms are diarrhoea, weight loss and possible loss of life in domestic ruminants and some wild animals, notably the rabbit. This is obviously a serious situation as regards farm animals susceptible to the disease, including cattle, sheep and goats. Worryingly, the infection begins in young animals but does not always manifest itself until they become adult. The disease is readily passed on through contaminated faeces and milk. PARA-TB TRANSMISSION, an EC funded project, aimed to study the epidemiology of the disease. All available research results were then used as data to model the progression of the disease in domestic and wild hosts. Project partners at the University of Thessaly in Greece used the models to assess the potential impact of control practices in different production systems ranging from dairy farming to bull production. Using variable parameters over a 30 year period, the expected results within herd prevalence were predicted. Analysis of the models showed no impact if the only means of control involved wildlife infection. However, reduction of the average time between signs of infection and culling had a significant effect on disease prevalence. Pathology of the disease and its transmission via faeces infers that any modifications in husbandry would limit Map levels. The risk profile of a production system then could be improved by implementing better neonatal management and hygiene. Wildlife transmission was also investigated and from ecological studies and modelling, it would appear that the systems most under threat are where grazing resources and feed stuff are exposed to wild rodents. It seems then that the main instruments of control for Map are routine testing, culling infected animals, improved hygiene and targeting wildlife to herd transmission wherever possible. Dissemination of these results to veterinarians and government agricultural bodies has led to their incorporation in national control programmes across Europe.
