There used to be lots of pneumonia outbreaks due to Actinobacillus pleuropneumonia (APP).
Today those numbers have dropped. But when APP does strike, from 2% to 10% death loss in 2-3 weeks is common. Death loss often strikes 60- to 120-lb. animals. But it can also hit market-age animals.
Commonly, a respiratory outbreak is preceded by coughing and animals off-feed along with sudden death. If it is linked with other diseases, pseudorabies (PRV) or Porcine Reproductive and Respiratory Syndrome (PRRS), it lingers on.
Current thinking targets disease elimination through negative selection of breeding stock or movement in three-site production systems. In a three-site system, weaning under 18 days of age, nursery pigs will be negative as they are moved off site still under maternal protection.
That protection may be due to active infection and/or sow immunization. Often, nursery pigs on infected sow farms are put on water and feed medication during the move. Denagard (BI/NOBL) is a common water medication and Pulmotil (Elanco) is often used in the feed.
When an APP outbreak occurs at a later age, feed and water medications often don't help due to animal flow or environment. Thus, we need to look at disease elimination.
APP serology or blood testing is done by drawing blood samples and having them analyzed for antibodies to APP. There are 12 serotypes. The three most common in the U.S. are 1, 5 and 7. Type 1 tends to be severe and causes acute death loss. Type 5 causes death loss, but is less severe. Type 7 tends to be non-clinical.
When selecting seedstock from units where there may be a concern about APP, blood tests should be run on the serum from the parent herd along with an evaluation of the clinical history. Tests include the complement fixation test, which is done at certain university diagnostic labs. The ELISA blood test tends to be more sensitive and specific. Cross-reactions can occur with certain ELISA tests.
Case Study No. 1 A producer reported an outbreak in the finishing unit. It killed 18 of 230 head in 24 hours. The dead hogs were found with blood running from their noses. The outbreak was confined mostly to 2 to 3 pens. Animals were feverish and coughing.
The number affected reached 30%. Animals weighing 200-240 lb. were overcrowded in an open-front building. We immediately moved a third of them to an open lot. We injected them with penicillin and gave follow-up injections the next few days to problem animals. The animals recovered well.
Case Study No. 2 A producer called with an outbreak in a finisher. The animals had just been moved from nursery to finisher. One finisher room of four began to break with APP symptoms. Animals were put on water and feed medications. All pigs were immunized with an APP oil-in-water vaccine. Excenel (Pharmacia & Upjohn) was injected.
All postmortem tests showed APP Type 1 to be the cause. The first room was boostered with vaccine two weeks after the first immunization. A second room began to break two weeks after the first room. We then began to immunize the last two rooms ahead of the break. All rooms were immunized twice. The animals responded well for a time but then broke down again. We found they were positive for PRV. After vaccination for PRV and continued treatment, the animals finally recovered.
Case Study No. 3 Replacement gilts were brought onto a farm. They were negative for APP but the sow farm was positive. These new gilts were isolated, immunized twice and added to the herd. They broke with respiratory problems and were treated.
Animals ran fevers. In most cases, it was the gilts that were sick. But a few sows developed respiratory problems. The problem stemmed from bringing 90 vaccinated animals into a positive herd.
Even though animals were put on an immunization program, it wasn't 100% protective. APP immunizations aren't the total answer.
During the respiratory outbreak, gestating sows were given Pulmotil in the feed for a short time. The feed antibiotic was removed after two weeks.
In all, it took 45 days for the disease to quiet down. We treated a lot of gilts and sows. There was some death loss. All incoming gilts were vaccinated three times. Re-breaks occurred one month later and continued to be a sporadic problem. The system was depopulated after six months of battling the problem.
Summary There are different APP vaccines on the market. Most of the vaccines contain killed bacteria with an oil-in-water emulsion, which tends to give a better immunization than the killed bacterins with aluminum salt carriers.
This is an acute respiratory disease. The success of immunization depends on the amount of challenge organisms and if other diseases are present.
The best way to avoid APP is don't buy the problem when purchasing new gilts. Screening new gilts serologically is extremely important.