Porcine reproductive and respiratory syndrome (PRRS)Clinical signs, differential diagnosis, treatment and prevention in pigs.

Overview

A major viral disease of pigs causing reproductive failure in sows/boars and respiratory disease in growing pigs. PRRS virus, an enveloped RNA virus of the genus Arterivirus, family Arteriviridae.

Clinical signs

Highly variable clinical syndrome.
(a) Reproductive failure phase: Late-gestation abortions (typically occurring near the end of gestation, usually after 90 days as the virus does not readily cross the placenta until the third trimester) 10-14
Stillbirths and mummies may increase to 25%–35% (stillbirths can reach 35%–40% in severe farrowing storms).
Sows often exhibit anorexia, mild fever, lethargy, and agalactia, resulting in high preweaning mortality of 30%–50%.
(b) Postweaning respiratory phase: Characterized by anorexia, fever (generalized febrile response of 41°–42°C), dyspnea, polypnea, thumping respiratory pattern ("thumps" in suckling piglets), coughing, unthriftiness…
Morbidity in weanling pigs can be up to 30% with a mortality of 5%–10% (nursery mortality can reach up to 10%–25%).
Bluish discoloration of the ears, abdomen, snout, tail, or vulva ("blue-eared disease") can occur in up to 5% of pigs (more common in European outbreaks, uncommon in North America).
(c) Highly Pathogenic PRRS (HP-PRRS): Causes severe clinical signs, marked inappetence, high fever, severe respiratory signs, thymus atrophy, and extremely high morbidity and mortality rates of 50% to 100% across all…

Predisposing factors

Nursery piglets infected from older infected pigs 1; slatted floors, storage of slurry under floors, exposure to transport vehicles, and lack of quarantine facilities for imported pigs 5
Environmental stressors such as cold weather 5 and housing of all age groups in one building.
Dual infection or synergism with other respiratory pathogens: Mycoplasma hyopneumoniae (the dual infection of PRRS and M.

Look-alikes to rule out

Classical Swine Fever Pseudorabies

Treatment

There is no specific antiviral treatment against the virus.
Outbreaks of respiratory disease are managed by improving environmental conditions in barns and pens, keeping stocking density low, monitoring feed programs, and providing supplemental heat for neonatal pigs.
Delay or avoid routine procedures (such as tail docking, iron injections, castrations, teeth clipping, and cross-fostering) during the acute phase of the disease.
Sows that have aborted their litters should not be bred until the normal time of weaning.
This will reduce the incidence of infertility common at the first estrus after the abortion or farrowing.
Treat secondary bacterial infections using appropriate parentally administered antibiotics (e.g., administering ceftiofur injection for 3 consecutive days to minimize disease associated with PRRS and S. suis).

Drugs mentioned: Aspirin

Prevention

1. Strict biosecurity and quarantine of replacement stock are the primary means of control. 2. Understancing the PRRS status of replacement gilts and boars, as well as proper isolation and acclimatization of incoming stock, are critical measures to prevent viral introduction. 3.

Source

A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Pages 1792–1813); The Merck Veterinary Manual 11th Edition (Pages 885–890).

MSD Veterinary Manual — Porcine Reproductive and Respiratory Syndrome (accessed 2026-08-11)

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