Historical cases of anthrax in Sweden 1916-1961.

As in most European countries, anthrax was common in Swedish livestock during the centuries leading up to the mid-twentieth century. After 1957, the disease was regarded as practically extinct. However, in the past 7 years, three outbreaks have caused public alarm because of the risk of environmental contamination. Properly buried carcasses should present little risk of spore contamination, and instructions were in place to ensure this since the 1890s. However, as has been demonstrated in recent outbreaks, carcasses were not always adequately buried and viable spores may remain in some sites. This study was prompted by the lack of historical information to assess the geographical risk of old anthrax spores. The aim was to obtain sufficient information to map old anthrax outbreaks, to study clusters and variation between years. Historical data were retrieved from Official National and Regional Veterinary Archives. In the years 1916 to 1961, anthrax was reported from more than 3000 farms and all 24 counties in Sweden were affected. Most cases were single animals, but there were also some larger outbreaks mainly involving cattle. Anthrax in horses was mostly reported before the mid-twentieth century, and the same was seen for pigs and wildlife. A ban in 1957, on the import of bone meal for animal feed led to a drastic reduction of outbreaks. The majority of cases were reported during the summer months in animals on pasture. Historical records proved useful for the investigation of current outbreaks. If handled properly, old carcasses pose no substantial risk, but if not, they may present a risk to grazing animals in some areas. Historical information is useful for all planning of work that involves digging or relocation of soil masses. Anthrax can be regarded as one of the diseases where history is a key to present knowledge.