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PMWS is an emerging viral disease of pigs that is being diagnosed with
increasing frequency in Canada, the United States, Europe and Asia. Pig
practitioners and diagnosticians in several countries began to recognise it in
the early 1990's, and Canadian scientists confirmed the disease in a
Saskatchewan pig herd in 1996.
PMWS is a multi-factorial disease associated with porcine circovirus type 2
(PCV2), porcine parvovirus (PPV), and porcine reproductive and respiratory
syndrome virus (PRRSV). Two of these agents – PPV and PCV2 – are endemic to
Diagnosis is dependent upon three criteria.
A definite diagnosis is confirmed by post-mortem examination of samples from
pigs showing the characteristic clinical signs, by finding histopathological
lesions in various internal organs and confirming the presence of viral material
using immunohistochemistry (IHC) staining.
PCV2 is an important part of the cause of Porcine Dermatitis Nephropathy
Syndrome. While PMWS remains the most important syndrome associated with PCV2,
this virus has been linked with a number of other syndromes in various parts of
the world, including certain types of Congenital Tremor in piglets, nervous
disease possibly leading to sudden death in weaners, Proliferative and
Necrotising Pneumonia (PNP), perinatal myocarditis, low-grade reproductive
problems and possibly Sow Abortion and Mortality Syndrome (SAMS).
The disease affects eight to16 week old piglets, often peaking at nine to 10
weeks. Clinical signs include loss of condition, failure to thrive, pallor and
possible diarrhoea. Some pigs may exhibit breathing difficulties and jaundice.
It is thought that the disease might be spread through the movement of pigs
or possible semen.
PMWS is a syndrome caused by a combination of infectious, pig, and
environmental factors. Hence clinical disease is often absent despite the
presence of infectious agents.
Currently, there is no vaccine to prevent PMWS and there is no treatment.
Mortality rates vary between 4 to 10% but farms with post-weaning mortality up
to 60% have been reported. Another feature is the persistent nature of the
syndrome – some farms are still affected for two or more years and still
experience similar levels of mortality.
PMWS is recognised as a world wide problem. Australia is free of the disease
and although an investigation is underway in New Zealand it has not yet be
There are numerous important management practices useful for mitigating the
spread of PMWS. Veterinarians, producers, industry and government
representatives from the European Commission met in September 2001 and put forth
"three golden rules" to control PMWS. These were?:
1. limiting litter to litter contact, both directly, through fostering and
multi-suckling, and indirectly from shared needles, equipment, mud, etc.,
2. reducing animal stress and susceptibility to disease by limiting exposure
to micro organisms, and
3. practising good management, hygiene and biosecurity on the farm. These
practices are common sense activities, which can minimise the spread of not only
PMWS, but many other diseases, as well.