Herd history over a 2 month period

PMWS is a disease that affects group after group. A single group with wasting is not PMWS. Such pigs have occurred for as long as pigs have been farmed.

To give some indication of the severity of PMWS on a farm, the graph below indicates the post-weaning mortality numbers for a single farm.

Each farm’s mortality profile is unique. The pattern above is from a South Korean 2000 sow farm. While there were problems on the farm starting in February and March 2004, changes in management and treatment routines appeared to correct the problems. With the heat of the summer, problems returned in August and rapidly escalated until the farm reported a full blown PMWS outbreak with the loss of 70% of the weaners/growers (30-50 lbs) in November 2004. Changes in the farm management resulted in a reduction of clinical signs and a feeling that the problems were resolving in the later spring of 2005. Unfortunately, following personnel problems in the summer 2005 and failure of all-in/all-out, PMWS reappeared in September 2005. Currently a restoration of all-in/all-out and other management changes, the post-weaning mortality is being stabilized at 6-12%.

This case has been selected because it emphasizes the severity of PMWS on a farm’s production and also illustrates the continual vulnerability of the farm if management falters.

The epidemiological history of the infected area

The clinical signs of PMWS move through a population of pig units. In the UK, illustrated on the left, the disease moved from the south of England in 1999, into East Anglia in 2000 (red area). Over the next 18 months it moved from East Anglia to most of the pig areas of England (green area). By July 2002 the clinical signs were first recognized in Scotland (purple area). In North America, the condition was first recognized in the pig dense area of Montreal, Quebec. It has then moved west into Ontario and North. It is progressively moving west and south into the United States. Problems are now being reported in North Carolina and probably most of the northern states. PMWS has also been reported in Mexico.

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Introduction	Diagnosis	Clinical findings
		Gross pathological findings
		Laboratory findings
Herd History	Epidemiology
Treatment and control	PMWS negative	PMWS positive