Porcine Respiratory Disease Complex (PRDC): What is it and how do we prevent it?

A good biosecurity program is essential for the improvement and maintenance of the genetic potential and productivity of farm animals.

Disease outbreaks on farms affect productivity in numerous undesirable ways, such as reducing productivity, increasing mortality and reducing daily gain. Not only does this affect herd health but it also affects producers' bottom lines. Disease also can cause production costs to jump as efficiency decreases. All of this can cause severe strain on a facility, as the demand to do more with less increases.Given the economic repercussions, it is important to discuss respiratory challenges in post-weaning pigs. One of the biggest concerns is porcine respiratory disease complex (PRDC), which is caused by a dangerous combination of multiple infectious agents, environmental stress and issues in the production system. 

Respiratory disease in pigs very rarely is the result of a lone pathogen. Rather, when a pig presents with respiratory illness, multiple pathogens are most likely affecting the pig simultaneously, such as swine influenza and porcine reproductive and respiratory syndrome (PRRS). When environmental factors provide an opportunity for these infectious agents, such as viruses or bacteria, to infect the pigs, these agents act as "door openers". That is, these primary infections clear the way for other viruses and bacteria to infect the animal, making its illness worse.

A combination of viral and bacterial pathogens, along with environmental factors, can culminate in PRDC, with Pasteurella spp. and Haemophilus parasuis almost always being involved as they are nearly ubiquitous in swine populations. Viral agents include the PRRS virus, porcine circovirus type 2 (PCV2) and swine influenza virus, while bacterial agents include Mycoplasma hyopneumoniae and Salmonella choleraesuis, among others.

Environmental factors also can affect the likelihood of an animal contracting respiratory illness. High stress environments caused by overcrowding or inappropriate ventilation, for example, can have a negative effect on swine and make them more susceptible to the infections that cause PRDC. Likewise, an inadequate or nonexistent biosecurity program can also contribute to PRDC, especially if surfaces, feed troughs and other common areas and objects aren't properly cleaned.

As Dr. Lawrence Firkins points out, once PRDC affects a unit, anywhere from 30 to 70 percent of pigs typically are affected with about 4 to 6 percent mortality. 

The symptoms and severity of PRDC can vary depending on age of the animal, the types and numbers of pathogens causing the illness and pathogenicity. However, the most common symptoms include coughing, difficulty breathing, anorexia, fever, nasal and/or ocular discharge and depression. These symptoms can vary in severity, with the most dire cases ending in death.

Unfortunately, since PRDC is an amalgam of varying pathogens and environmental stressors, it can be difficult to diagnose (importantly, lung lesions are not enough for a diagnosis). One of the most important methods of diagnosis is collection and submission of the proper tissue samples to a veterinary diagnostic lab. Additionally, a detailed clinical history is essential for diagnosis, Cary Honnold of Purdue University notes. 

Since PRDC is caused by a range of factors (remember, bacterial, viral and environmental), treatment will vary depending on the case. Antibiotics are available, but can only be properly administered once you know what you're dealing with (again, proper diagnosis is critical). Vaccines for viral pathogens also are available.

It also is important to monitor for illness; the sooner it is caught, the sooner it can be treated (and prevented from spreading throughout the herd).

From an environmental standpoint, stressors such as overcrowding and improper ventilation should be avoided. Proper ventilation will exchange enough air to keep the facility dry and the air fresh and will maintain a comfortable barn temperature for the pigs.

Finally, biosecurity is of paramount importance, especially proper sanitation procedures. Facilities and objects that come in contact with the pigs and their environment should be subject to a rigorous cleaning and disinfection program. 

A good biosecurity program is essential to reducing devastating illnesses such as PRDC. However, if infection occurs, proper and quick diagnosis and treatment is vital, along with an evaluation of preventive strategies to ensure illness is prevented in the future.