Porcine reproductive and respiratory syndrome virus

PRRSV

Changed on: 29.07.2021
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Animal disease categories: D E

Profile

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important swine infectious diseases worldwide.

Occurrence

Worldwide; only a few countries (including Switzerland, Finland, Sweden, Norway) are currently considered PRRSV-free.

Host animals

Domestic pigs, wild boars

Mode of transmission

Direct contact (droplet infection) from infected pigs; indirectly via stable dust, equipment, hands, clothing and shoes. The virus can also be transmitted via semen.

Symptoms

There are two main clinical manifestations, which have given the virus its name:1. respiratory symptoms at weaning and fattening age2. reproductive symptoms in the form of late abortions and the birth of weak piglets.

Therapy

A specific therapy is not possible

Prevention

In infected herds, the occurrence of clinical symptoms can be prevented by the use of vaccines and the excretion of the pathogen can be reduced. Protection against infection cannot be achieved by vaccination.

Situation in Austria

PRRSV also causes economic damage in pig herds in Austria. In infected herds, the occurrence of clinical symptoms can be prevented by the use of vaccines and the excretion of the pathogen can be reduced.

An infection with PRRSV is currently not notifiable or reportable.

Professional information

PRRSV is an enveloped single-stranded RNA virus of the genus Arterivirus. It is divided into the two species PRRSV 1 (formerly European genotype) and PRRSV 2 (formerly North American genotype). Both species are highly mutagenic and have innumerable subtypes and strains. A highly pathogenic (HP) variant was detected in China in 2007 and resulted in high mortality, including in sows.

Within hours of infection, the virus is detectable in its target cells, the alveolar macrophages. In addition to colonising macrophages in the nose, throat and tonsils, the virus is detectable in the blood within 12 hours. The viraemic phase lasts an average of 28 days. Purchased infected pigs as well as transport vehicles and visitors can transmit the virus from herd to herd.

Symptoms

The clinical symptoms are very varied and strongly depend on the virus strain or strains in the respective herd, the immunity status of the pigs, the age group affected and concomitant diseases. PRRSV infected animals may become infected with other bacterial and viral diseases that may be more severe due to the existing infection with PRRS.

Respiratory symptoms occur mainly at weaning (and fattening) age and are due to interstitial pneumonia. They manifest as dyspnea, increased respiratory rate, increased susceptibility to other infectious diseases, and increased mortality. Initially, conjunctivitis, decreased general condition and inappetence may occur.

Abortions occur mostly after infections in the last third of gestation. There may be increased stillbirths, birth of weak piglets, and increased piglet mortality.Clinical signs in boars are moderate and can be easily overlooked. At times, semen quality is decreased.

Particularly virulent and HP strains can cause outbreaks with high mortality in all age groups. Clinical signs include respiratory signs and abortions, as well as erythema, petechiae, fever, anorexia and tremors, and skin cyanosis, especially of the ears, proboscis disc, tail, scrotum and distal limbs.

Since PRRSV has been categorized as a D + E disease by the European Animal Health Law (AHL), measures must be taken to prevent its spread in connection with the movement of animals and animal products. No specific therapy is available. Priority is given to minimising the risk of pathogen introduction into farms through appropriate monitoring and surveillance programmes and hygiene and biosecurity measures. Eradication of stocks is costly and only promising if a new pathogen introduction can be avoided.

Diagnostic

To maintain PRRSV-negative herds (especially breeding herds and boar stations), targeted monitoring in the herds as well as quarantine and examination of newly housed pigs is necessary.

Due to the viraemia lasting about 28 days, blood samples are equally suitable for virus genome detection by PCR and for antibody detection by ELISA. Frequent testing (at least quarterly) of a representative number of samples (approx. 13 samples per herd, irrespective of herd size) can lead to rapid detection of pathogen introduction into the herd, even if no clinical symptoms occur.

To clarify the cause of respiratory symptoms in weaners and fattening pigs as well as gilts, blood samples of typically sick pigs can also be examined by PCR. Antibody testing in older groups of piglets can confirm the diagnosis. In case of dissections, tonsils, lungs as well as lung lymph nodes can be used for detection by PCR. Longer-standing infections can be detected by PCR from tonsillar scrapings, as the virus can be detected in the tonsils for the longest time.

In the case of abortions, detection by PCR from the placenta and fetal organs is suitable for establishing the diagnosis.

PRRSV RNA can also be detected in semen, but a negative result does not mean that an infection can be ruled out, as excretion in semen is intermittent.

Contact, Forms

Institute for Veterinary Investigations Mödling Robert Koch-Gasse 172340 MödlingTel: +43 50 555-38112Fax: +43 50 555-38529E-mail: vetmed.moedlingno@Spam@agesno.Spam.at

Further reading

Sattler T, Pikalo J, Wodak E, Schmoll F (2016): Ability of ELISAs to detect antibodies against porcine respiratory and reproductive syndrome virus in serum of pigs after inacti-vated vaccination and subsequent challenge. BMC Veterinary Research 12, 259

Sattler T, Pikalo J, Revilla-Fernández S, Steinrigl A, Bagó Z, Entenfellner F, Claude JP, Pez F, Francilette M, Schmoll F (2018): Efficacy of live attenuated porcine reproductive and respiratory syndrome virus 2 strains to protect pigs from challenge with a heterologous Vietnamese PRRSV 2 field strain. BMC Veterinary Research 14, 133

Steinrigl A, Revilla-Fernandéz S, Schmoll F, Sattler T (2016): Detection of Porcine Re-productive and Respiratory Syndrome virus and Porcine Cirovirus type 2 in blood and oral fluid collected with GenoTube swabs. Berl Münch Tierärztl Wsch. 129, 437-443

Kopacka I, Fuchs K, Schmoll F, Sattler T (2016): Vergleich verschiedener Stichprobenverfahren zum Nachweis des Porzinen Reproduktiven und Respiratorischen Syndrom-Virus in einem Schweinezuchtbetrieb mithilfe von Simulationsmethoden. Berl Münch Tierärztl Wsch. 129, 258-268

More J, et al (2017): Assessment of listing and categorisation of animal diseas-es within the framework of the Animal Health Law (Regulation (EU) No 2016/429): porcine reproductive and respiratory syndrome (PRRS). EFSA Journal, DOI: 10.2903/j.efsa.2017.4949

OIE Terrestrial Manual: Chapter 3.8.6: Porcine reproductive and respiratory syndrome.

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