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Pneumonia is normally uncommon in mature acclimatised animals (unless exposed to a new organism), it occasionally it occurs in gilts but is very common in the growing animal. Mortality in naive animals can be as high as 10 to 15% (no immunity) if prompt treatment is not undertaken.

The onset of swine influenza is usually sudden and affects most pigs. The onset of enzootic pneumonia in a naive herd may be insidious although it may later develop rapidly affecting many sows severely. There is likely to be severe pneumonia and some mortality if the disease is not controlled in herds infected for the first time.

Of all the diseases that affect growing and finishing pigs, chronic respiratory disease is the most economically important. It is extremely common and can be difficult to prevent and control. Growth rates and feed-intake are depressed together with poor feed efficiency and in some herds there is heavy mortality. The control of respiratory disease requires an understanding of the complexities and interaction between the organisms that are present, the pig and the management of the environment.

Pneumonia is affected by:

  • The presence of respiratory pathogenic organisms.
  • The virulence of the pathogens present.
  • The level of the pathogens in the house environment.
  • The immunity of the pig and the time of exposure to the organisms
  • The presence of secondary opportunistic bacteria.
  • The interactions between management, environment, the diseases and the pig.


Weaners & Growers
  • Coughing.
  • Rapid breathing.
  • Dehydration.
  • Inappetence.
  • Discharges from the eyes - conjunctivitis.
  • Poor circulation.
  • Blue discoloration of the skin.
  • Loss of condition.
  • Huddling.
  • Fever.
  • Widespread coughing.
  • Some sows obviously very ill.
  • Respiratory rate is elevated, some showing acute respiratory distress.
  • Coughing.
  • Heavy breathing.
  • Loss of condition.
  • Dehydration.

Causes / Contributing factors

  • If pathogens such as influenza, PRRS virus, Mycoplasma hyopneumoniae or a virulent strain of Actinobacillus pleuropneumoniae enter a susceptible herd for the first time dramatic outbreaks may occur in sows.
  • Poor environments.
  • Incorrect ventilation and humidity.
  • High stocking densities.
  • Diseases are commonly transmitted through the movement of carrier pigs.
  • Incoming pigs.
Increased clinical disease is associated with the following;
  • Overcrowding and large group sizes.
  • Less than 3 cu.m. air space/pig and 0.7 sq.m. floor space/ pig.
  • Houses that are too wide for good air flow control.
  • Variable temperatures and poor insulation.
  • Variable wind speeds and chilling.
  • Low temperature, low humidity environments.
  • High levels of carbon dioxide and ammonia.
  • High dust and bacteria levels in the air.
  • Pig movement, stress and mixing.
  • Housing with a continuous throughput of pigs.
  • A combination of diseases, particularly PRRS, App, flu, and aujeszky's.
  • Poor nutrition and dietary changes at susceptible times.


This is based on the clinical signs and post-mortem examinations. Laboratory tests involving serology and microbiology are often necessary to identify the precise causes. See also the specific respiratory diseases.

Further Reading

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