Strategies for PRRS Control

Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the most challenging diseases for the global swine industry. Since its emergence in the late 1980s, the genetic variability of the virus has led to multiple epidemics caused by emerging and re-emerging strains, complicating its control and eradication. Its ability to mutate and recombine not only facilitates its persistence in production systems but also enables it to evade acquired immunity, whether through vaccination or previous infection. Given this scenario, farmers must be prepared to face the constant evolution of PRRS with strategies that combine advanced biosecurity, efficient health management, epidemiological monitoring, research into new vaccines, and the development of innovative production management models.

PRRSV evolution and its impact on production

Since its emergence, PRRSV has evolved significantly, leading to multiple strains with varying levels of virulence. In the 1990s, the VR-2385 and SDSU 73 variants caused the first severe outbreaks in North America. Later, during the 2000s, more pathogenic strains such as JA142 and MN184 emerged. In recent years, variants like NADC30 and NADC34 have spread globally, affecting farms in Europe, America, and Asia.

In Europe, the "Rosalía" variant, detected in Spain in 2020, and the Lena strain in Belarus have shown a strong ability to spread. These strains have been responsible for severe outbreaks, characterized by reproductive failures, severe interstitial pneumonia in piglets, and increased viral shedding, facilitating virus transmission within farms.

The effects of PRRS on pig production are devastating. In pregnant sows, infection causes abortions, premature births, and reduced farrowing rates. In piglets and growing pigs, the virus compromises immune function, making them more susceptible to secondary infections such as bacterial pneumonia. This results in increased mortality, lower weight gain, and reduced feed efficiency.

Since PRRSV can persist in the body for long periods and transmit subclinically, eradication in infected farms is challenging. Therefore, a comprehensive approach based on multidimensional control strategies is essential.

Strategies for PRRS control

Controlling PRRS requires a combination of measures that reduce virus circulation and minimize its impact on production. Key strategies include:

1. Biosecurity

Biosecurity is the first line of defense against PRRS. Virus transmission can occur through direct contact between infected and susceptible animals, as well as via fomites, aerosols, and mechanical vectors. To reduce virus introduction and spread, strict biosecurity measures must be implemented, such as:

• Access control and movement restrictions for animals, people, and vehicles.
• Installation of air filters in farms located in high-density swine areas.
• Strict cleaning and disinfection protocols for facilities and equipment.
• Animal flow management within the farm to prevent contact between different age groups.
• Risk assessment using quantitative methodologies to measure biosecurity effectiveness.

 2. Health management and epidemiological control

Continuous PRRS monitoring on farms is crucial for detecting the virus and preventing its spread. Strategies include:

• Early diagnosis using real-time PCR, ELISA, and genetic sequencing to identify circulating strains.
• Farm closure and opening strategies to reduce virus transmission within pig populations.
• Immune homogenization of the herd through controlled exposures and replacement management strategies.
• Coordination between producers and veterinarians to share epidemiological data and improve decision-making in the industry.

 3. Research on pathogenesis and immunology

PRRS remains difficult to control due to the complexity of the host immune response. More investment is needed in studying the virus’s pathogenesis and persistence in infected individuals to develop more effective therapeutic strategies. Additionally, understanding the factors behind the emergence of virulent strains will help anticipate new variants and design more efficient prevention measures.

4. Development of new vaccines

Current vaccines have shown variable efficacy due to PRRSV’s high genetic diversity. However, advances in biotechnology are opening new possibilities for improving immunization. Promising research lines include:

• mRNA vaccines, which could offer more specific and adaptable protection against virus variability.
• CRISPR/Cas9 gene editing to develop genetically resistant pigs.
• Viral vector vaccines that enhance immune responses without the risk of recombination with field strains.

Combining these strategies will help advance the fight against PRRS and improve farm protection.

Future perspectives

PRRS is a global problem that requires a collaborative and multidisciplinary approach. The virus’s evolution will continue to pose challenges, but implementing advanced biosecurity measures, improving diagnostics, and developing innovative vaccines will help reduce its impact on pig production. The key to effective control lies in epidemiological surveillance, investment in technology, and adopting stricter management practices. The industry must continue exploring new strategies and strengthening cooperation among all sector stakeholders to minimize losses and improve disease control in the coming years.