PRRS diagnostics: Matching your strategies with your scenarios
This article will review the different PRRS diagnostic options based on the different scenarios for which we complete PRRS sampling in the field.
The Porcine Reproductive and Respiratory Syndrome (PRRS) is the viral infection with the highest economical impact in North America and many European countries. The virus causes reproductive problems and affects the respiratory system.
Alternative names: Porcine respiratory and reproductive syndrome, Blue ear disease
The Porcine Reproductive and Respiratory Syndrome (PRRS) is caused by an arterivirus. The virus is classified in two types: North American and European (or Lelystad). The virus is very susceptible to the environment and disinfectants, and is characterized by its great capacity to mutate. The virus has a special affinity for alveolar macrophages found in the lung. Macrophages are part of the immune system ingesting and eliminating invading bacteria and viruses. The virus multiplies inside the macrophages producing more virus, and the cells die in the process. It destroys up to a 40% of macrophages, which eliminates most of the animal’s defense mechanisms and allows bacteria and other virus to proliferate and damage the respiratory system. The virus can cross the placenta and infect fetuses from 70 days of pregnancy, causing abortios in the third trimester and mummies or stillborn.
Once the virus has entered a farm, it stays in it and keeps active.
After an initial introduction of the virus, the infection of all breeding animals may take up to a year, especially in big farms. Although the virus appears to disseminate rapidly, positive seroconversion of at least 90% of the sows can take 4 to 5 months. Adult animals excrete the virus for shorter periods (14 days) than growing pigs, which excrete the virus during an average of 1 to 2 months (more than 5 months in some animals).
The clinical situation can vary a great deal from one farm to another due to the huge amount of different strains. Despite of the virus sequencing, it is impossible to predict the virulence, clinical presentation or crossed protection between each identified strain. Recent research has identified some swine genetics that are more resistant to the virus. Many modern farms based on their biosecurity system as their best PRRS prevention tool. The virus can be transmitted in semen.
Its chronic presentation is very variable. Clinical conditions are usually similar to the ones seen in the acute presentation, but it only affects a percentage of animals, especially gilts. The chronic form affects animals of all ages but with less severity.
Symptoms are very variable depending on the strain. North American strains are clinically more severe.
Acute disease
Sows
Lactating piglets
Boars
Nursery and fattening
Chronic disease
Sows
Piglets
Boars
Nursery and fattening
Common methods of spread:
This is based on the clinical signs, post mortem examinations and the known presence of the virus by PCR. There are several tests available, but ELISA is the standard test used. Currently, oral fluids are used to monitor farms. Virus sequencing can only be used epidemiologically to investigate the presence of a new strain and possibly its origin.
This article will review the different PRRS diagnostic options based on the different scenarios for which we complete PRRS sampling in the field.
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The Hungarian PRRS eradication program is based on a territorial approach as it is the only approach by which the infection or reinfection of PRRSV-free pig herds can be avoided with high probability.
The goal is set in Danish pig production - By 2025, 75% of all finishers will be PRRS seronegative at slaughter. This will be achieved by a close corporation between veterinary authorities, the pig industry, slaughter companies, veterinarians and producers.
Consider these factors when deciding to eliminate or control PRRSv.
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By May 2023, 85% of all Danish pig herds have a serological PRRS status. Area eradication programs have been established in regions with a high density of PRRS seropositive herds. The Danish Agriculture & Food Council has taken a range of initiatives with the purpose of paving the road for a national reduction of PRRS, including an implementation strategy, digital tools, common guidelines for the classification, monitoring, and eradication of PRRSV, and project funding resources.
In this article we will focus the discussion on the practical applications of the new monitoring systems.
PRRS creates frustrating challenges as it seems we have to keep learning the same lessons we already know, along with the occasional new chapter.
Are we using the best samples and techniques to monitor PRRS absence in boar studs?
Farmer profiling to understand their objections or willingness towards PRRS elimination using the ADKAR change management model.
This article describes the main characteristics of commercial vaccines to combat PRRS.