Respiratory Diseases

By James McKean.

Respiratory diseases of swine cause major economic losses. In many cases, respiratory disease losses are not recognized because death losses are low and reduced feed efficiencies are the primary effect.

The major infectious organisms currently associated with swine pneumonias are:

Mycoplasma hyopneumoniae, Pasteurella multocida, Bordetella bronchiseptica, Hemophilus pleuropneumoniae, Hemophilus parasuis, swine influenza and pseudorabies viruses. Other disease conditions such as salmonella, streptococcus may cause pneumonia as a secondary problem. Roundworm and lung-worm migration may intensify the severity of pneumonia by their movement through lung tissues.

A brief description of the major swine pneumonia diseases will be given. Each disease will be treated as a singular event, but the diseases usually occur together producing a more severe problem than when alone.

Mycoplasma pneumonia of swine (MPS), also known as virus pig pneumonia (VPP), or enzootic pneumonia is a chronic disease of growing finishing swine. The causative agent, Mycoplasma hyopneumoniae, is a small bacteria found only in swine. Exposure to this organism is estimated as high as 65 to 80 percent for all U.S. swine.

Clinical signs are a dry, persistent cough, labored breathing and slow or uneven growth. Pigs are infected by aerosol transmission (fine misty particles as a result of breathing, sneezing, coughing) from their mothers or by other pigs when grouped at weaning. Severity of signs may depend on the presence of secondary infectious agents and environmental conditions.

Respiratory diseases of swine cause major economic losses in the form of reduced feed efficiencies. A key to preventing respiratory diseases is clean, dry housing with adequate ventilation and air space per pig.

Treatment of mycoplasmal pneumonia is centered on reducing the effects of secondary bacterial infections and reduction of lung lesion development. Tylosin, lincomycin tiamulin, sulfonamides and tetracylcines administered either by injection or orally will reduce lesion development. Control of economic losses involves feeding growth-promoting levels of the above drugs and improving environmental conditions.

Prevention requires a complete break between infected and uninfected herds. Movement of swine between herds is dangerous. The specific-pathogen-free (SPF) management scheme, embryo transfers, and artificial insemination are all relatively safe methods of adding breeding stock to MPS-free herds.

Pasteurella Infections

Pasteurella pneumonias are common secondary pneumonia infections following MPS, Bordetella, influenza and environmental stresses. Pasteurella multocida occurs in apparently healthy swine but is rarely the initiating factor in pneumonia. Spread is by aerosol transmission from pig to pig. Cold, damp, poorly ventilated, drafty, or overcrowded conditions make Pasteurella infections more serious. Clinical signs of pasteurellosis include a sudden onset of coughing, fever of 104 to 107 F, labored breathing and poor growth affecting a large percentage of the group.

Tetracyclines and sulfonamides in feed or water will reduce clinical severity of an outbreak. Individual animal treatment by injection may be needed for severely affected pigs.

Control of Pasteurella infections involves improved environment, reducing dust and aerosol bacterial contamination, treatment of visibly affected pigs, reducing stocking rate, adequate nutrition, and parasite migration control. Vaccines currently available may reduce the severity of lesion development but do not prevent disease.

HPP or Hemophilus pleuropneumoniae (parahemolyticus) causes a sudden to chronic pneumonia in pigs generally from 30 lbs. to adult- When it is first introduced into a group of swine, common signs are sudden death without signs of coughing, labored breathing, high temperatures-104 to 107 F, listlessness and loss of appetite. Some pigs die with a bloody froth coming from their mouth. Mortality can range from 5 to 50 percent of a group.

As the disease becomes more chronic, the sudden deaths are reduced but the chronic cough, labored breathing, slow growth and lung adhesions become more prominent. Sudden changes in temperature or management can cause a reappearance of the acute form. Spread of infection is by aerosol droplets from infected swine.

Treating Acute HPP

Treatment of acute HPP requires immediate action. The bacterium generally is susceptible to penicillin or tetracyclines injected at the higher treatment levels. Besides medical treatments, efforts should be made to increase ventilation rates, reduce numbers of pigs/air space, and avoid adding new animals until the disease is controlled.

After the sudden deaths are controlled, high levels of sulfas or tetracyclines given orally may help increase feedlot performance. Preventive measures including vaccination or oral medication are indicated.