Managing PRRS by Assessing Antibiotic Intervention in Swine

swine health blackbelt Nov 28, 2023

Porcine Reproductive and Respiratory Syndrome (PRRS) remains one of the most economically significant diseases affecting the swine industry globally. Characterized by its dual impact on reproduction and respiratory health, PRRS continues to challenge even the most seasoned swine health professionals. The virus's ability to suppress the immune system of pigs not only exacerbates its direct effects but also opens the door to secondary bacterial infections, which can further impair health and productivity. In this context, the use of antibiotics, despite their targeted action against bacteria rather than viruses, has been explored to mitigate the clinical signs and performance impacts associated with PRRS.


The Immunological Challenge of PRRS

PRRS virus (PRRSV) has a well-documented capacity for immunomodulation, leading to increased susceptibility to secondary infections. The virus targets macrophages, critical cells in the immune response, leading to a compromised defense system. This immunosuppression is a central concern in managing PRRS, as it can lead to severe bacterial infections that compound the disease's impact.


Antibiotic Intervention: A Strategic Approach

In the face of PRRS, antibiotics have been considered for their potential to control secondary bacterial infections. This approach is not without controversy, as the misuse of antibiotics can lead to resistance. However, when used judiciously and strategically, antibiotics can play a role in comprehensive disease management plans.


A Focused Study on Antibiotic Efficacy

A recent project evaluated using two antibiotics, tilmicosin, and tulathromycin, in a sow farm experiencing a PRRS outbreak. The study was meticulously designed to assess the impact of these antibiotics on various reproductive parameters, including total born alive, pre-weaning mortality, and pigs weaned per sow.


Tilmicosin and Tulathromycin: A Comparative Analysis

Tilmicosin, with its potential antiviral properties against PRRSV, and tulathromycin, known for its immunomodulatory effects, were administered to different groups of sows. The study aimed to determine whether these antibiotics could improve outcomes by reducing the load of secondary bacterial infections and possibly by exerting direct or indirect antiviral effects.


Methodology and Treatment Groups

The trial was structured as a factorial experiment with four distinct groups: a control with no antibiotics, one receiving tilmicosin, another tulathromycin, and a final group receiving a combination of both. The sows were monitored throughout gestation and farrowing, with key performance indicators recorded and analyzed.


Results: Birth and Mortality Metrics

The administration of tilmicosin showed a statistically significant improvement in the number of pigs born alive. This finding suggests that the antibiotic may have contributed to a healthier gestational environment, possibly by reducing bacterial load or modulating the immune response in a manner favorable to embryo survival.

Conversely, the group treated with both antibiotics did not fare as well in pre-weaning mortality, indicating that the combination of tilmicosin and tulathromycin may not be synergistic and could be antagonistic.


Lactation and Weaning Outcomes

The study also revealed intriguing trends in lactation survival and weaning success. The tulathromycin group demonstrated the highest number of pigs weaned, suggesting that this antibiotic might have particular benefits during the lactation period, potentially by improving sow health or creating a more favorable environment for the piglets.


Implications for Swine Health Management

The implications of these findings are significant for swine health management. They suggest that antibiotics, when used thoughtfully and in the right context, can have a positive impact on managing PRRS. This is particularly relevant in the face of an outbreak, where the goal is to minimize losses and maintain productivity.


A Step Forward in PRRS Management

The study's outcomes offer a promising avenue for PRRS management, highlighting the potential role of antibiotics in a comprehensive disease control strategy. While antibiotics are not a panacea and should not be viewed as a standalone solution for PRRS, their judicious use can be a valuable component of an integrated approach to managing this complex disease.



Managing PRRS remains a multifaceted challenge that requires a nuanced understanding of the disease's pathogenesis and the interplay between viral and bacterial pathogens. The strategic use of antibiotics, as part of a broader management plan, can provide swine health professionals with an additional tool to combat the effects of PRRS. As the industry continues to evolve and adapt to the ever-changing landscape of swine health, such research provides critical insights that can inform best practices and improve outcomes for swine producers worldwide.



Managing PRRS by Assessing Antibiotic Intervention in Swine - Dr. Jessica Risser. Swine Campus, 2023. Available at: <>. Access on November 03th, 2023.