24 May 2002

PMWS answers still to be revealed

How to cope with costly pig wasting diseases was the

key topic at this years Pig and Poultry Fair. But the

event also featured a debate on whether pigs should be

reared to heavier weights, the option of going organic,

welfare and the latest research results. Richard Allison

kicks off the FW livestock teams event report

PIG wasting diseases are proving to be confusing to producers.

With the cause still unknown, many are struggling to find practical, effective solutions while facing a lack of research to prevent its spread.

But a straw poll by farmers weekly at the Pig and Poultry Fair found that reducing other stress factors helped cut the high mortality resulting from post-weaning multi-systemic wasting syndrome (PMWS) on several units.

Norfolk producer Graham Taylor saw grower mortality rates peak at 20% on his 340-sow unit. "After trying many different strategies, the only one which seems to work is cutting stocking rates."

Lowering stocking rates by 15% is also part of Andy Bartletts tactics for his 1500 growers. On his Somerset unit, mortality has fallen from 20% to 4% over the past 12 months. "Cutting stress, avoiding delays when moving animals and putting smaller pigs in hospital pens were also part of the strategy."

Another producer, facing a 7% rise in mortality on his unit near Thirsk, North Yorks, recently discovered Glassers disease. Since treating for this, mortality seems to be back under control.

Once a plan had been proven to work on your unit, stick to it, Norfolk vet Roger Harvey told producers at a PMWS seminar. "Successful plans are all based on the same basic actions aimed at minimising stress, limiting mixing and ensuring good hygiene, particularly around weaning."

But what is confusing for producers is that the cause remains unknown. However, it is believed to be due to Porcine Circovirus Type-2 (PCV2) infection plus some other factor such as diet, pasteurella or swine flu. Mr Harvey believed parvovirus was a strong contender for the unknown factor with higher levels seen in East Anglia.

That was supported by a survey of infected farms, said MLC vet Derek Armstrong. "One risk factor identified by research is changing parvovirus vaccination product, compared with sticking with the same brand. This may suggest mixing brands may reduce its effectiveness.

"Another risk factor is salmonella infection. Units with PMWS are 2.7 times more likely to have reported salmonella compared with uninfected herds."

But those units still free of PMWS were found to be fighting to keep it out. Staffs-based producer Trevor Digby told farmers weekly that he had managed to keep his 400-sow multiplier herd free of the disease, despite other units in the area being infected. This had been achieved by stepping up biosecurity and closing the herd, with only boars brought in.

That highlighted the difficult task of sourcing replacements without introducing wasting diseases, said Mr Harvey. "Ideally, they should buy animals from PMWS-free herds and quarantine them. But it takes about six months before animals show symptoms, making this approach difficult."

He believed using AI was just as risky as buying in boars, as semen often contained PCV2, thought to be the underlying cause of PMWS. "More than 95% of semen in France was found to contain the virus."

The risk of bringing in PMWS with replacements was also highlighted in the MLC survey, added Mr Armstrong. "Infected units are 4.5 times more likely to be buying in more than 400 pigs a year, compared with units without the disease."

Despite the gloom, Mr Harvey believed the future lay in moving to a higher health status, closing herds and breeding from parent gilts on farm. There is a vaccine for PCV2, but it is still 2-3 years away, he added.

New hope was also emerging from a National Pig Association and MLC scheme which has been launched to gather and sift on-farm experiences via 10 regional self-help groups. Ian Campbell of NPA believes these groups might help find practical solutions for combating these diseases.

"This could answer many questions, such as whether having smaller groups of pigs with solid divisions between them reduced mortality," he added.

lTwo MLC booklets to help combat pig wasting diseases were also launched at the fair. Copies are available from MLC (01908-844271, fax 01908-609826).

&#8226 20 producers questioned.

&#8226 12 herds infected.

&#8226 17 altered management in response.

Minimising stress, limiting mixing, and good hygiene can help reduce PMWS mortality, says Roger Harvey.