There is a relatively new syndrome in swine that is still being defined. Postweaning multisystemic wasting syndrome (PMWS) was recognized in the late 1990s and is still being described today.
Initial reports of PMWS problems began in Canada, and soon after were seen in the U.S. PMWS is also recognized in Europe and elsewhere. Mortality is variable and can be up to 25% or more in some units.
The clinical condition is basically synonymous with the name:
Postweaning — it almost always strikes pigs after they are weaned;
Multisystemic — many organ systems are involved;
Wasting — pigs appear to waste away; and
Syndrome — diseases associated with PMWS include porcine circovirus type 2 (PCV2), pneumonia linked to porcine respiratory disease complex and, to a lesser extent, diarrhea associated with enteritis.
The clinical picture in most cases involves late nursery pigs and growing hogs (5 to 16 weeks of age). Generally, the first thing that is noticed is that pigs are falling behind the rest of the group, thus the term “wasting.” Weight loss is the most common, consistent finding of PMWS.
Since this syndrome involves many organ systems (typically lungs and less often liver, kidney and pancreas), clinical signs can be variable. Other signs can include listlessness, anorexia, diarrhea and respiratory symptoms.
Postmortem examination can reveal gross lesions, the most striking of which is the presence of greatly enlarged lymph nodes. Lymph nodes are part of the pig's immune system. We often see enlarged livers and in some pigs icterus (yellow color). Thickening of lungs that do not collapse at the time of postmortem is also common.
Diagnostic laboratory submissions are essential to finding a diagnosis. Tests should include virology, bacteriology and histopathology (fixed tissues).
There appears to be a common theme in that PCV2 is often involved in these cases.
Some pigs test positive for porcine circovirus, but show no clinical signs.
Bacterial secondary invaders are common. The secondary invaders are the usual ones that we see with other viral diseases in swine, including Pasteurella multocida, Streptococcus suis and Hemophilus parasuis.
Histopathology often reveals lesions in the lymph nodes, liver, kidneys and lungs.
No control measures are available for the most common PCV2 concern of this syndrome. Researchers are working on possible farm-specific vaccines that would immunize against PCV2.
Since PCV2 immunity can't be enhanced at this time, producers must manage it with good husbandry practices. We advise:
Decrease exposure by cleaning and disinfecting between groups;
Implement and maintain all-in, all-out pig flow throughout;
Control secondary infections by having your veterinarian conduct antibiotic sensitivity testing on your farm and treat animals appropriately; and
Lower stress and maintain a good environment by using proper stocking density. Establish sick pens and consider trying gruel feeding to encourage feed consumption.
A 500-sow, farrow-to-finish farm, using single-site production, began to see nursery pigs fall behind. The first signs were seen in 5-week-old gaunt pigs with a slight cough. This condition continued until about 12 weeks of age. Mortality ranged from 5 to 12%.
Postmortem examination revealed greatly enlarged lymph nodes in affected pigs.
Laboratory work yielded a PCV2 isolate. Other secondary organisms were isolated and antibiotic sensitivity patterns recorded. Streptococcus suis types 2 and 7 and Haemophilus parasuis were commonly isolated from nursery pigs. Pasteurella multocida type A was commonly seen in finishers.
Management revolves around providing a good environment in buildings, emphasizing airflow and humidity control. Purging medication based on antibiotic sensitivities to control secondary invaders was instituted. In the nursery, water medication was used at 5 and 6¼ weeks postweaning for two days. In grow-finish, the farm uses a rotation of 10 mg./lb. of chlortetracycline during Weeks 1 and 3 in the finisher, and 100 grams/ton of tylosin during Week 2. From there, the farm uses bacitracin as a growth promoter.
Mortality has decreased to 3 to 5% in recent groups. We believe this improvement is due to environmental management and the therapy program.