Interactions between PRRSV and other pathogens

PRRSV interacts with other pathogens to cause severe respiratory symptoms in finishing pigs.

Mechanism of interactions

The mechanism by which PRRSV interacts with other pathogens is still under investigation. However, it has been demonstrated experimentally that:

• Mycoplasma enhances the pathological effects of PRRSV
• PRRSV enhances the pathological effects of Porcine Influenza virus
• PRRSV predisposes pigs to infection and disease caused by Streptococcus suis
• PRRSV can cause a loss of the bactericidal function of pulmonary intravascular macrophages.

The role of PRRSV

It is still not possible to conclude which are the most important combinations of pathogens or to define the importance of PRRSV in the severity of respiratory disease in finishing pigs. This is difficult to prove experimentally due to pathogenicity of virus strains used, timing of infections, serological status of pigs used and the lack of predisposing or stress factors due to housing and/or management. Clinical experience in the field has shown that the occurence of new respiratory pathogens result in increasingly complex respiratory problems and improved performance has been observed in PRRSV-vaccinated herds.