PRDC shows up in many different pork production systems with varying management styles and health statuses.

Other contributors to PRDC are environmental and management practices. Large temperature swings, poor air quality, overcrowding and poor nutrition are all factors.

Diagnostic Tools Veterinarians, producers and diagnosticians have all been frustrated pursuing a consistent, definitive diagnosis of PRDC. The presence of multiple pathogens makes the conventional approach of doing individual postmortems change depending on the day, week or month.

Improved diagnostic tools, including serology, helps us more definitively diagnose and identify primary vs. secondary pathogens.

We use serology to help clarify the involvement of the three primary pathogens involved in PRDC: Mycoplasmal pneumonia, swine influenza virus (SIV) and porcine reproductive and respiratory syndrome (PRRS).

Serology also improves our ability to detect diseases crucial to vaccine timing and recommendations. Serology is combined with postmortems using specific lung tests and other diagnostic procedures.

Case Study No. 1 I was called to a farm experiencing PRDC. The pigs were about 18 weeks old and had been in the finisher for 10 weeks. Pigs were coughing, had high fevers and were off feed. These symptoms plagued the last three groups that had gone through this finishing barn.

We decided to try serum profiling. Ten blood samples were collected from pigs that were 6, 10, 14, 18 and 22 weeks of age.

The blood samples were tested for PRRS, mycoplasma and SIV (both H3N2 and H1N1). All of the PRRS samples were positive by 10 weeks of age; 25% of the SIV samples became positive by 22 weeks. The mycoplasma test showed 20% of the pigs tested positive in the 6-week-old group and 80% of the pigs were positive at 22 weeks of age.

At this same time, we sacrificed pigs and sent them to a diagnostic laboratory. Multiple bacteria were isolated, including Streptococcus suis, Pasteurella multocida type A and Haemophilus parasuis. Histopathology lesions indicated that mycoplasma was involved.

In combining all of the diagnostic information, I felt that mycoplasma was the primary contributor. The fact that mycoplasma titers were low or nonexistent in early phases, but were highly positive at 22 weeks of age, and the fact that histopathology lesions were positive, all led us to focus on mycoplasma as the primary control point.

In response to the mycoplasma diagnosis, we placed Lincomycin (Pharmacia & Upjohn) in the feed at 100 grams/ton for three weeks, starting at nine weeks into the finisher. In addition, future groups of finishing hogs were vaccinated for mycoplasma.

There were no control methods put into play to control PRRS or SIV on this farm. The combination of Lincomycin and mycoplasma vaccination has helped eliminate problems on this farm.

Case Study No. 2 Pigs at this farm, too, were experiencing PRDC symptoms - severe respiratory problems through late finishing. Multiple diagnostic methods had shown mycoplasma, SIV (H3N2), PRRS and bacteria such as Streptococcus suis, Haemophilus parasuis and Pasteurella multocida type A were all present at various times.

The producer knew he couldn't vaccinate for all of these problems. He asked me to help pinpoint which bug was causing the most problem.

A serological profile was implemented. Ten blood samples were taken at 6, 10, 14, 18 and 22 weeks of age. The laboratory testing allowed us to develop a composite picture and graph to help prioritize which pathogens were causing most of the problems.

Swine influenza and mycoplasma were the two pathogens that had significant increases in blood antibody titers following the clinical disease outbreak. The traditional methods of diagnosis indicated multiple organisms were present. But this serological picture helped us emphasize that mycoplasma and SIV were the two pathogens we would attempt to control.

A mycoplasma vaccine and an autogenous SIV vaccine were used. A pulse medication program was set up utilizing Lincomycin and tetracycline in the finishing phase.

Both farms responded well to the combination of vaccine and feed additive medications.