Clinical signs of PRRS in sows and piglets

PRRS infection causes reproductive problems in sows and stillborn or weak piglets that die soon after birth.

Reproductive syndrome

PRRSV infection can cause severe reproductive damage:

  • premature farrowings
  • stillborn or mummified piglets
  • weak PRRSV-positive piglets (50% die soon after birth)
  • delayed return to service

PRRSV in sows

In acute PRRS outbreaks, abortions may occur in 1-3% of sows that are between 21 and 109 days of gestation.

After approximately 1 week after onset of acute illness, the second phase of the disease begins. This is a consequence of transplacental transmission of the virus and is characterized by late-term reproductive failure. At any time between 100 and 118 days of gestation, 5% - 80% of sows may have reproductive failure. Experimentally, it has been found that inoculation of sows at 45 days of gestation does not result in the virus crossing the placenta. After infection at 70 and 85 days of gestation, the virus crosses the placenta in 33% and 80% of cases, respectively.

In addition to reproductive failure, sows and gilts may show:

  • anorexia
  • fever
  • lethargy
  • pneumonia
  • agalactica
  • red/blue discolouration of the ears and vulva
  • subcutaneous and hind limb oedema
  • delayed return to oestrus after weaning
  • in rare cases, death

Swine abortion and mortality syndrome (SAMS)

In the USA, from late 1996, increased disease outbreaks described as severe PRRS, atypical PRRS or "Swine abortion and mortality syndrome (SAMS)" were reported to diagnostic laboratories. The clinical outbreaks are characterized by an abortion rate of 10% - 50% within a 4- to 6-week period. Sows and gilts are anorexic and have a fever. The mortality rate of the breeding herd can be up to 5-10% during an outbreak (Halbur PG et al. 1997). The same syndrome was described later in Europe (Martelli et al. 2003; Garcia et al. 2004).

Neonatal piglets

Neonatal piglets can display a variety of clinical signs. The most characteristic are dyspnea, tachypnea and death (up to 100% mortality).

stillborn piglets

Stillborn and weak piglets.

weak piglet

Neonatal piglet infected with PRRSV