Bovine cysticercosis in Denmark. A study of possible causes of infection in farms with heavily infected animals.

Epidemiological studies were made on 14 farms from which, during a 2 year period, 38 cattle had been condemned at slaughter, due to massive infections with Cysticercus bovis. By on-site investigations and interviews, attempts were made to identify the transmission routes of Taenia saginata eggs from human faeces into the environment and further on to cattle. The most frequent sources of infection were found to be sludge from septic tanks illegally applied on pasture or crops, in some cases after having been mixed with animal slurry. Animals in permanently housed herds were infected through the fodder or by contamination of the indoor environment by such slurry containing Taenia eggs. Other herds were infected by grazing pastures in close proximity to municipal sewage treatment plants. In contrast to earlier Danish observations, application on farmland of sewage sludge from municipal treatment plants was not involved in any of the reported outbreaks. This apparent change coincides with the implementation of more restrictive legislation for the agricultural use of sewage sludge in Denmark.