Postweaning multisystemic wasting syndrome--PMWS. the first year with the disease in Sweden

Postweaning multisystemic wasting syndrome (PMWS) is causally associated with porcine circovirus type 2 (PCV2) infection of pigs. PCV2 has been present in the Swedish pig population for at least ten years. Despite this, no signs of PMWS were observed in pigs of Sweden until 2003. Since then the disease has spread slowly in Sweden. The pig population of Sweden is geographically isolated, the density of pigs and the pathogen load in the country is low and the trade of animals is organised in a restricted way. To date, there has been little information placed in the peer-reviewed literature on the study of the spread of PMWS in a country during the early phase of the disease outbreak, mainly because diagnosis of PMWS has only occurred after the disease has been recognised on a number of farms. This manuscript documents the studies to date on the PMWS outbreak in Sweden which has been closely monitored since the initial outbreak of diseases on a single farm in 2003 was diagnosed. In Sweden PMWS was officially reported for the first time at a progeny test station during December 2003. One year later sixteen herds have been diagnosed and reported to the authorities: one progeny test station, one nucleus herd, thirteen piglet producers or integrated herds and one specialised fattening herd. Fifteen suspected cases have been deemed negative for PMWS with disease scenarios associated with Lawsonia intracellularis, Brachyspira pilosicoli, Mycoplasma hyopneumoniae, shortcomings in feed composition etc. To date, one year after the index case was reported ten other herds suspected for PMWS are under observation. The PMWS cases are concentrated into the southern part of Sweden. However, the disease is spreading slowly, and in general there are no obvious physical links between affected herds. The data generated to date in Sweden suggest that introduction of a new contagious microbe into the country that is responsible for the PMWS outbreaks appears unlikely, as does the spread of PMWS via semen.