Porcine Respiratory Disease Complex (PRDC), caused by a group of diseases, produces a respiratory syndrome in hogs. We quickly recognized Mycoplasmal pneumonia, swine influenza virus (SIV) and porcine reproductive and respiratory syndrome (PRRS) virus as the common pathogens.
Although in varying combinations, there was more than one organism involved in most cases. We recognize that Pasteurella multocida plays a key role as a secondary invader. We also recognize circovirus and parvovirus as playing a role in limited cases.
The complex varies from farm to farm. Factors that affect the onset of disease include exposure, challenge level, disease load, vaccination program and the feed grade antibiotic program.
We used to speak of an 18- to 20-week window in which disease would seem to come on suddenly and growth rates and other parameters would suddenly change within a group of pigs. The different control measures have made the onset of disease less predictable.
The disease complex looks similar on many farms. The most common signs include coughing, reduced feed intake, pneumonia, thumping and death. PRDC can affect from 10% to nearly 100% of a group of finishers.
In many cases, the pigs are fairly unresponsive to treatment. This is mostly due to the combination of organisms involved. Viral organisms normally found in this syndrome are by nature unresponsive to antibiotics. Viruses must run their course.
We usually treat the bacterial pathogens involved, such as mycoplasma and other secondary organisms.
Laboratory work is a must in identifying organisms involved. We use bacterial culture, virus isolation and tissue examination. Blood samples can be used to measure antibody levels. These are used to decide the timing of control programs. Water or feed purge medication programs control mycoplasma and secondary organisms.
Prevention is the key to PRDC control. Learn which organisms are a concern on each farm, primary organisms as well as secondary invaders. Of the common organisms listed above, it appears that mycoplasma and Pasteurella are the most suitable for control. Prevention revolves around the use of feed and/or water medication programs and vaccination programs. Each farm will use different vaccination and medication protocols.
Case Study No. 1
We were called to a 180-sow, one-site, farrow-to-finish farm with unattached buildings. The farm uses a 28-day batch farrowing system. This farm uses artificial insemination, all-in, all-out (AIAO) in all phases of production and split-sex feeding.
The complaint of respiratory problems occurred in the finisher. The facility had a double curtain, totally slotted floor design with two rooms, end to end. The building had a common working/sorting area between rooms. One room always contained pigs.
The pigs began to cough nine weeks after placement — at approximately 17 weeks of age. Clinical signs included coughing, thumping, reduced feed intake and mortality. Tissues were submitted to the diagnostic laboratory for analysis. The pigs were positive for mycoplasma and SIV and negative for PRRS and pseudorabies virus.
Treatment included vaccination for mycoplasma at 6 and 8 weeks of age. The groups were purge-medicated at 40 days after entry into the finisher with lincomix at 100 g./ton.
Clinical disease decreased in subsequent groups. Slaughter checks were performed to monitor the program. Lung lesions were minimal. This treatment remains in place.
Case Study No. 2
A unit receives weaned pigs from a single-source, multiple-owner sow farm. Pigs are delivered in groups of 1,200 pigs every eight weeks. Pigs arrive weighing about 10 lb. and are placed into AIAO nurseries.
The sow unit is considered a high-health source. Pigs are vaccinated with two doses of mycoplasma vaccine.
The respiratory problem begins at about 20 weeks of age, similar to the previous case. Mortality was high in some groups. Growth rate is severely reduced and is poor throughout finishing.
Treating individual pigs with antibiotics hasn't worked. Laboratory work detected mycoplasma and Pasteurella organisms in the lungs. No other isolations were obtained. A modified-live-virus Pasteurella vaccine was added.
Clinical signs subsided, and slaughter checks improved.
We have better diagnostic tools and understanding of PRDC than a few years ago.
If you are concerned about PRDC, contact your veterinarian to determine the cause. Using a good diagnostic workup, you can develop a program for prevention, treatment and control.