Porcine Reproductive and Respiratory Syndrome (PRRS) is a widespread viral disease affecting pigs globally. It represents a significant concern for pig farmers due to its complex nature and varied impact on swine health. The disease can lead to substantial losses in pig production.
Understanding PRRS
PRRS is caused by the PRRS virus (PRRSV), a member of the Arteriviridae family of viruses. This virus specifically targets and destroys macrophages, which are immune cells found throughout the pig’s body, particularly in the lungs. The damage to these cells weakens the pig’s immune system, making it more susceptible to other infections.
The virus spreads through several main routes, including direct contact between infected and susceptible pigs. Airborne transmission can also occur over distances ranging from a few meters to several kilometers. Contaminated equipment, vehicles, and even semen used for artificial insemination can also facilitate the spread of PRRSV between farms and within herds.
Recognizing the Signs
The clinical signs of PRRS can vary widely, influenced by the pig’s age, the specific strain of PRRSV involved, and the presence of other concurrent infections. In breeding pigs, such as sows and boars, the disease often manifests as reproductive failure. This can include late-term abortions, premature farrowing, an increase in stillborn piglets, and the birth of mummified fetuses or weak, non-viable piglets.
Suckling piglets may show increased mortality before weaning and exhibit respiratory issues. For growing and finishing pigs, respiratory distress is a common sign, characterized by coughing and difficulty breathing. These pigs may also display fever, lethargy, and a noticeable reduction in their growth rates.
Managing and Preventing PRRS
Controlling and preventing PRRS relies on biosecurity measures. This involves strict hygiene protocols, such as regular cleaning and disinfection of facilities, equipment, and vehicles. Controlling access to farms and establishing quarantine procedures for new animals are also important steps to prevent the entry of PRRSV.
Vaccination plays a role in managing PRRS, with different types of vaccines available, including modified live virus (MLV) vaccines and inactivated vaccines. These vaccines are integrated into herd health programs to help reduce the severity of clinical signs and viral shedding, although they do not always prevent infection entirely. Diagnostic testing, such as PCR and ELISA, is used to monitor the disease status of a herd, guiding management decisions and identifying infected animals. In severe or persistent outbreaks, strategies like herd closure or even depopulation and repopulation of the farm, may be considered to eradicate the virus.
Impact on Pig Health and Industry
PRRS inflicts substantial economic losses on the global swine industry. These losses stem from increased mortality rates, reduced feed efficiency, slower growth rates, and decreased reproductive performance in affected herds. The disease also leads to higher veterinary costs and increased medication expenses for treating sick animals and managing outbreaks.
Beyond direct losses, PRRS can suppress the pig’s immune system, making animals more susceptible to other bacterial and viral infections, such as Mycoplasma hyopneumoniae, Streptococcus suis, and Haemophilus parasuis, which often lead to more severe disease outcomes. This phenomenon, often referred to as Porcine Respiratory Disease Complex (PRDC). The ability of PRRS to constantly evolve present an ongoing challenge to sustainable pork production worldwide.