Clinical signs in growers and finishing pigs

PRRSV infection alone is often subclinical. It is, however, indirectly responsible for huge economic losses in finishing herds due to its major role in the multifactorial Porcine Respiratory Disease Complex (PRDC).

PRRSV infection

Subclinical Infections

In growers and finishing pigs PRRSV infection is usually subclinical:

  • destruction of macrophages
  • thickening of the alveolar septa
  • occasional lesions in blood and lymphatic vessels
  • minor heart lesions

finishing pig

Clinical Infections

If clinical signs are present, they are usually respiratory:

  • fever
  • sneezing
  • hyperpnea
  • dyspnea
  • coughing
  • pneumonia
  • lethargy
  • periocular edema
  • oculonasal discharge.

Experimental challenge of SPF pigs with PRRSV usually produces no clinical signs.

Respiratory disease in growing and finishing pigs and Porcine Respiratory Disease Complex (PRDC)

Many terms are used to describe respiratory disease in growing and finishing pigs:

  • mixed respiratory infections
  • respiratory disease complex
  • porcine respiratory disease complex (PRDC)

PRDC was first defined by Halbur as:

Respiratory problems and poor growth in growing and finishing pigs with a multi-factorial aetiology involving PRRSV, SIV, PRCV and a variety of bacteria.

The term is now regularly used in reference to all mixed respiratory infections in growing and finishing pigs.

PRRSV is indirectly responsible for huge economic losses in finishing herds due to its major role in the multifactorial Porcine Respiratory Disease Complex (PRDC). The current view is that PRRSV causes an increased susceptibility to secondary bacterial and viral infections. See Interactions between PRRSV and other pathogens.

In many cases, mild pathogens or even non-pathogenic organisms can, in conjunction with PRRSV, cause severe problems in finishers. These problems appear as:

  • increased mortality
  • medication and treatments due to respiratory problems
  • reduced growth rate and feed efficiency
piglets

PRRSV is indirectly responsible for huge economic losses in finishing herds due to its major role in the multifactorial Porcine Respiratory Disease Complex.