NCSU Extension Swine Husbandry1998

August, 1998 ^. Volume 21, Number 7

In response to the increasing number of cases Post-Weaning Multisystemic Wasting Syndrome (PMWS) diagnosed in the Midwest, the National Pork Producers Council (NPPC) has just issued a special call for research proposals to investigate this new disease. Thought to be caused by Porcine Circovirus (PCV), the disease was first identified in a small Saskatchewan herd in 1991. Since then it has been in numerous herds in Canada, Iowa, California, Illinois, Ohio, Nebraska, Indiana and Mississippi. It has also been suspected in herds in France, Spain and Britain.

As the name of the disease implies, the clinical signs include wasting with diarrhea, increased thirst and a pale skin. The disease hits herds that have active PRRS infections particularly hard. Monthly deaths may reach 10% but that usually decreases over time. As many as 50% of pigs may be sick. Unfortunately, the disease is hard to diagnose. Veterinarians must consider a combination of clinical signs, postmortem findings and complex laboratory work-up to arrive at a diagnosis.

Investigations are underway in many countries in an effort to understand this difficult disease and the recent decision by NPPC to fund research into the problem will assist in this effort. Until the mode of transmission of the disease is better understood managers should review their biosecurity programs and correct any deficiencies they find.

For preventing exposure of pigs to any disease, including PMWS, there are four basic areas to consider:

1. Source and handling of primary and replacement breeding stock.
2. Rules governing movement of people, vehicles, materials and pigs.
3. Layout of the farm.
4. Location of the new farm.

Of these, the source and handling of primary and replacement breeding stock is by far the most important.

Most swine diseases are transferred from one animal to the next by direct contact. Thus, the easiest and most frequent avenue for the introduction of diseases into a herd is via the replacement boar or gilt. Seedstock suppliers have a major responsibility in ensuring that the animals they sell are as free from economically damaging disease as practically possible.

What can the producer do to minimize the risk of "buying in" disease?

A. Buy replacement boars and gilts from as few sources as possible. Aim for only one or two supply herds at the most. The more seedstock herds supplying the herd, the greater the risk of introducing disease.

B. The producer's veterinarian should discuss health status with the veterinarian of the seedstock herd. In this way, the suitability of the herd as a supply herd can be assessed. Acclimatization procedures, vaccination and preventative drug treatment regimens must also be discussed so that the purchased stock are given every assistance to meet their full potential in the herd.

C. Isolate all stock for a minimum of 30 days before bring them into the herd. Within this quarantine period the animals will often show the signs of any disease they may be carrying. In addition, it is usually sufficient time for the supplying seedstock herd to experience any disease it may have recently contracted. The full benefit of this isolation period will not be realized unless:

1. The people caring for the stock in isolation do not go directly into the main herd. There must be a break that includes at least a complete change of clothing.
   
2. The veterinarians of the seedstock and commercial herd communicate and agree that nothing significant has happened in the seedstock herd during the isolation period that would preclude the isolated stock from entering the commercial herd.
   
3. Animals are blood tested for at least Pseudorabies before being admitted into the herd.
   
4. Appropriate medications and vaccinations, as agreed to by the seedstock and commercial herd veterinarian, are administered.
   
5. If producers diligently follow these rules, then they are more likely to keep PMWS out of their herd and avoid the cost of this difficult disease.
   

Morgan Morrow

Most nursery managers have felt the frustration of trying to prevent and stop the aesthetically unpleasing activities of piglets who consistently rub with their noses the flank or navel of their pen-mates. This activity, thought to extend from the udder-seeking or exploratory rooting behavior, can result in severe necrosis of the skin and development of ulcers at the site. The effect of this activity on average daily gain was recently reported by Jill Borgman and others at the American Association of Swine Practitioners meeting in Des Moines.

They weaned 315 pigs at age 16-18 days into pens of 20-25 animals in two rooms. They then observed them for six weeks and categorized some animals as either perpetrators or victims of these activities. They found that flank or belly rubbing did not occur until 10 days post-weaning, then it increased to a maximum at 20-25 days and then decreased. They observed lesions on 89% of the pigs, although most were mild. The attacking pigs were usually the smallest pigs and the victims were the biggest. In addition, gilts were more likely to be attackers then were barrows. Although there was some association between growth rate and lesions, particularly in the fourth, fifth and sixth week; overall, the effect on growth rate was not significant. However, because the biggest pigs tended to be victims, this probably biased the results, leading to an underestimation of the true effect.

In conclusion, early weaned, smaller pigs tend to be the attackers with bigger pigs the victims. These attacks probably decrease the growth rate of bigger pigs, but not enough for them grow at the slower rate of the smaller pigs in the pen that do most of the attacking.

Morgan Morrow

Number 50, July 6, 1998:

Last week, 2 positive animals were found on a gilt finisher in Sampson County. Breeding swine had been moved to 8 farms; however, only 3 boars had moved from the house with the positive animals.

All animals that had been shipped were immediately removed and sent to slaughter. Due to this prompt action, it does not appear that disease was moved to the other farms.

Progress is being made in herd clean-up and where only a few positives are found, the positives are being culled as quickly as possible.

All herds must be free of PRV and released from quarantine by December 31, 1998.

Morgan Morrow

Number of accesses to this file:
Last modified July 12, 2000.