Porcine Respiratory Disease Complex (PRDC) is a relatively new disease entity that is the result of our new production systems.

Most often, affected animals are from early weaning systems that have new genetics, are start-up herds and are finished in multi-site production units.

The syndrome usually presents itself as a mild to severe respiratory problem in finishing. The respiratory outbreaks occur frequently in late finishing (18 weeks into finishing) and don't usually respond to drug therapies.

Death loss and performance problems can vary from group to group. We usually find more than one pathogen involved. We may even see different pathogens isolated from different farms within the same production system.

With PRDC, it's not rare to find bacterial and viral pathogens on the same farm. The most common organisms we find are mycoplasmal pneumonia, pasteurella multocida, PRRS (Porcine Reproductive and Respiratory Syndrome), swine influenza virus, Streptococcus suis, Haemophilus parasuis and Actinobacillus pleuropneumonia. All these mixed infections can make isolating the cause of disease confusing.

When faced with a difficult respiratory problem, practitioners need to look at number of parameters. Many post- mortem evaluations need to be done at the start. Samples should be taken from affected animals, if possible, including grower and finisher hogs. For these tests:

* Do multiple postmortems and send in tissues for lab work. Compile the results. * Consider slaughter checks.

* Take paired serum samples and check for mycoplasmal pneumonia, PRRS and SIV.

To begin with, take the first samples before the problem starts. Take the second set of samples after the problem has started.

Case Study No. 1 A serious respiratory problem was hitting pigs at 6-8 weeks of age and then again at 18 weeks of age. At those two age groups, death loss was 20-30%.

In both nursery and finisher groups, postmortem examinations were done of various lung lesions. We then sent five affected live pigs to a diagnostic laboratory from both 8-week-old and 18-week-old age groups.

>From the nursery pigs, PRRS virus was isolated along with Haemophilus >parasuis and Streptococcus suis. In finishing, PRRS virus was found in the >lung, and lesions of mycoplasmal pneumonia were noted on the fluorescent >antibody exam. Pasteurella multocida was also isolated.

For treatment, a pulse water medication was given in the nursery along with mycoplasmal pneumonia vaccinations at 4 and 6 weeks of age. The nursery pulse medication (Lincocin) was run at 4-7 days and 11-14 days postweaning.

Replacement gilts were given a modified live virus PRRS vaccine a week after arrival and then isolated for 60 days. The sow herd was immunized with a killed PRRS vaccine.

After 2-3 months, nursery performance started to improve. Death loss came down to 2-3%.

To the treatment protocol, Lincocin was added to the finisher feed at a 100 gram/ton at 16-17 weeks of age for 2-3 weeks. The severe respiratory breaks in finishing subsided.

Case Study No. 2 A finisher facility was having difficulty with hogs continually coughing. Upon doing a slaughter check, we noted mostly chronic mycoplasma lesions in the lung with a few active lung lesions. Thirty pigs were evaluated in the slaughter check. We next selected 10 animals, tagged them and blood sampled them at 140-160 lb, resampling them at 200-240 lb.

Although we saw blood samples go positive to mycoplasma at 12-14 weeks of age, we were more concerned about animals that were SIV negative and then were positive by 220 lb. PRRS titers were high at the first bleeding and were beginning to go down at the second bleeding, so we felt that we had a mixed infection occurring.

We immunized the sow herd for SIV for six months to build high colostral protection in the farrowing house. We then began immunizing incoming gilts with mycoplasma and SIV vaccines.

Now the sow herd is being vaccinated for PRRS. Since we have installed the above programs in the sow and gilt herds we are experiencing fewer problems.

We believe the piglet vaccination program for mycoplasmal pneumonia has prevented major respiratory outbreaks from occurring at 18 weeks into the finishing period.

Six Summary Points 1. Pig respiratory problems can be difficult to diagnose. Postmortems are important.

2. Virus isolations are helpful to arrive at a diagnosis of PRRS.

3. Do slaughter checks.

4. Paired serum samples for various diseases should be evaluated for a four-fold increase in titer in the nursery and finisher hogs.

5. If SIV is involved, sow herd immunization may help reduce nursery and finisher problems.

6. Vaccination of incoming gilts for SIV and mycoplasmal pneumonia helps protect negative gilts from infection.

Arriving at a diagnosis and setting up prevention and control programs can eliminate many problems. These control procedures can be instituted after a diagnosis is made.