A seedstock producer engages a new protocol for cleaning up Actinobacillus pleuropneumonia (APP).

For many years, APP has plagued pork producers. High death loss, treatment and control costs got so expensive that many chose to depopulate/repopulate their herds, says Paul Yeske, DVM, Swine Vet Center, St. Peter, MN.

“Highly pathogenic strains 1 and 5 produced a very rapid onset of clinical signs in adult hogs that would progress to death very rapidly,” he observes.

Co-infections make outbreaks worse. “Certainly, porcine reproductive and respiratory syndrome, porcine circovirus-associated disease and swine influenza virus would make APP much more difficult to deal with today,” warns Yeske.

Good environmental management is also needed to control APP.

“APP will teach you the lesson that overcrowding doesn't pay. Ventilation must also be carefully controlled, especially in the fall, where in places like Minnesota you can get 10-degree or more temperature shifts that can trigger stress and onset of disease. Inside hog buildings, you want to keep temperature variations to just 1-3 degrees during the day,” he notes.

Different Picture Today

New, more sensitive tests can help producers stay vigilant against new, low-pathogenic strains of APP.

Those new tests will identify all types of APP. The Chekit APP APXIV Antibody ELISA test from IDEXX eliminates time-consuming individual testing and/or culturing the organism, comments Yeske. The test, performed routinely at the University of Minnesota Veterinary Diagnostic Lab, costs $6.25/sample.

Treatment options are also much improved with Excede (ceftiofur) and Draxxin (tulathromycin), both from Pfizer Animal Health; Nuflor (florfenicol) from Schering-Plough Animal Health; and Pulmotil (tilmicosin) from Elanco Animal Health, providing antibiotic answers in injectable, water and feed-grade formulations.

Disease Cleanup

An APP-positive seedstock operation Yeske consults with has experienced barriers to sales because of test status, not because of disease symptoms.

“This disease can be very expensive to live with, even if it is not a big clinical problem,” he adds.

“This herd has had a low virulent strain of APP. The offspring would uniformly test positive at the end of the finishing phase,” Yeske says. A cross-section of the herd indicated there were three active serotypes in the herd, with seroconversion occurring in the finisher. The sows and replacement gilts were uniformly positive.

Because the producer couldn't locate negative sources of similar genetics to use as replacement stock, eradication and repopulation weren't feasible.

Fortunately, a new, wean-to-finish facility located on a separate site provided the opportunity to attempt a modified, medicated early weaning (MMEW) program to clean up APP, says Yeske.

The protocol was as follows:

  • Offspring were taken from Parity 2 and older sows only.

  • Offspring were only taken for use in genetic repopulation of the herd.

  • All sows, whether in the project or not, were fed 363 g./ton of Pulmotil for 21 days prior to farrowing and during lactation.

  • Sows were injected with Draxxin (1 ml/88 lb.) at Day 100 of gestation.

  • Sows were redosed with Draxxin (1 ml/88 lb.) at Day 110 of gestation.

  • Piglets were weaned at less than 14 days of age.

  • Piglets were injected with Draxxin (1 ml/88 lb.), diluted to 1 ml/4.4 lb. at birth, at 7 days of age and at weaning.

  • Project sows and pigs were held in isolation in separate farrowing rooms.

  • Personnel for the project pigs only entered the rooms containing project pigs at the beginning of each day and wore separate clothing and boots assigned to the project rooms. Personnel did not reenter the project rooms until the next day if they'd worked in the non-project rooms that day. All equipment used in the project rooms was kept separate.

Testing, Repopulation

To avoid maternal immunity, 30 pigs more than 12 weeks of age were randomly sampled using the APXIV antibody test. In addition, all animals sold in the project were tested. Postmortems were done on all suspects and deads.

MMEW pigs are still growing and being monitored.

Sows bred off-site at the wean-to-finish facility, used to repopulate the herd, are also tested.

There have been a few unexpected positive test results, but those suspects have been resolved by use of PCR (polymerase chain reaction) in tissue or tonsil, and negative pig flows are being regenerated, says Yeske.

He notes while the project is not completed, results have provided some confidence.

With the new screening test, he expects more APP-positive herds will be found, and new eradication programs will get underway.

Yeske's report was given in mid-September at the Carlos Pijoan International Symposium on Swine Disease Eradication in St. Paul, MN.