Porcine Respiratory Disease Complex (PRDC)

The vast majority of respiratory problems in swine are due to a combination of disease pathogens called PRDC, involving a mix of viral and bacterial pathogens. Signs of swine respiratory disease include coughing, sneezing, fever, labored breathing, nasal discharge, lethargy, and pigs that are off-feed.

Bacteria often involved in PRDC include Pasteurella multocida, Mycoplasma hyopneumoniae, Streptococcus suis, Haemophilus parasuis, Actinobacillus pleuropneumoniae, and Salmonella choleraesuis. Common viral components of PRDC include porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), pseudorabies virus (PRV), porcine circovirus type 2 (PCV-2), and porcine respiratory corona virus (PRCV).

By themselves, most bacterial infections are not that difficult to control, but a combination of these bacterial and viral pathogens in an intense management system often presents a serious and costly health challenge.

Mycoplasmal pneumonia is caused by Mycoplasma hyopneumoniae bacteria (M. hyo). Most infections result from nose-to-nose contact between infected pigs on a farm that are commingled with "clean" pigs, though airborne reinfection may occur among swine herds that are in close geographic proximity. M. hyo can also be transmitted from sows to pigs, and then from pigs to penmates by nose-to-nose contact.

Mycoplasmal pneumonia (sometimes called enzootic pneumonia) can severely hinder performance of pigs, reducing their rate of weight gain and feed efficiency. Onset of the disease is gradual, usually characterized by weeks or months of coughing, stunted growth, and hair lacking a normal “bloom.” In addition, a more obvious form can occur in some animals, evidenced by labored breathing (thumping), fever, loss of appetite, lethargy/lying down, and increased coughing. These effects are caused by secondary bacterial infection in the lungs (such as Pasteurella) and can lead to death losses. Most common and serious, however, is the association of M. hyo as a major component of a full-blown, costly PRDC outbreak that can devastate a herd (see left panel).

Lung lesions caused by M. hyo are often detected at slaughter and provide clear indication of infection in the herd. However, the negative impacts of M. hyo on weight gain and feed efficiency cannot be directly correlated with the severity of pneumonic lesions at slaughter.

Tetracycline antibiotics (such as Aureomycin®, Aureo S-P 250®, AureoZol®, ChlorMax®) have been historically used to treat M. hyo infections, though such antibiotics are not actually approved for M. hyo control.

Related Articles:

• Aureomycin® vs Mycoplasma Challenge: Thacker et al., 2006 (PDF)