Pig wasting disease, initially called post-weaning multi-systemic wasting syndrome (PMWS) is a devastating pig disease that broke out on the North Island in 2003 and the South Island, in 2006 and it's still spreading. It's a cause of huge financial loss to pig farmers - and to the country. A conservative estimate is that the disease has now cost the nation's economy at least $44 million.
What does it do?
PWMS causes disease and a high death rate in pigs from 6 to 12 weeks old,
When it's first introduced to a farm, it can kill up to 40% of its weaners.
It causes continuing ill thrift for those that survive.
What causes it?
PMWS is associated with a virus, a circovirus, but other factors appear to be involved too. The disease is sometimes termed PCVAD - porcine circovirus-associated disease. It does not affect humans but attacks young pigs, causing emaciation, diarrhoea, and breathing problems.
The disease first appeared overseas only 10 years ago, but it has spread rapidly around the world. New Zealand is one of the last countries to be affected.
Here the disease was first found on a piggery in the central North Island in 2003, possibly after pigs were fed food scraps including pork that hadn't been cooked well before feeding it. (Pig swill must be boiled for at least an hour before it's fed to pigs - see "Feeding food scraps to pigs" in Lifestyle File).
Soon after its introduction, the disease spread like wildfire across farms that keep pigs outdoors, possibly distributed by such things as gulls, sparrows, flies, truck drivers and weaner pig movements. It now occurs nationwide.
What are the clinical signs?
- PMWS shows up as wasting in pigs from 6 to 14 weeks. Pigs lose their appetite, they lose weight and there is a high mortality
- Commonly they develop breathing difficulties and diarrhoea.
- There is a poor if any response to treatment.
Older pigs (sows, boars) and sucking piglets are not noticeably affected and it is uncommon for young pigs to be affected before 6 weeks of age.
Cases keep occurring in the herd for many months, reaching a peak at 6 to 12 months and then declining slowly after that.
There are other diseases that can look like PMWS (eg some forms of pneumonia or stomach ulcers), and your vet may need to do post-mortems and take samples for laboratory testing to confirm the diagnosis.
Control and prevention
There is no effective treatment for PMWS, but there is some good news for pig farmers! There is a very effective vaccine available. If you are concerned about PMWS, contact your vet for advice including the pros and cons of vaccination.
As with all diseases, the better the care of your animals the less likely the disease impact.
Reduce stress by:
- Ensuring good nutrition
- Keeping stocking rates low
- Providing good shelter
- Minimising exposure to other pigs, eg by segregating batches of pigs
- Ensuring scrupulous hygiene.
The bottom line
If you have pigs and are concerned about PMWS, contact your vet.