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Infectious diseases come in many forms. Some produce chronic health problems and poor performance, such as Mycoplasmal pneumonia. Erysipelas and Strep suis can kill pigs without warning. Haemophilus parasuis is unique in that it can produce both sudden death and chronic poor growth. Often lameness and pleuritis (infection of the chest cavity) are responsible for the long-term effects, but might be mistaken for other problems.

Haemophilus parasuis is a normal companion to many pigs, lining the nasal cavity without any associated disease. A few biotypes, or genetic types, of Hps have the ability to enter a pig's body and grow in the blood stream and on the surfaces lining body cavities. These biotypes can be identified from clinical pigs and evaluated genetically. This information helps producers know if they are dealing with repeat problems from one type, or if they have new/multiple types of the bacteria on the farm.

Sudden death in growing pigs

In late nursery and growing pigs, signs of Central Nervous System, or CNS, disease are often the result of Hps infection. The bacteria attack the tissue lining the brain, causing it to become inflamed (meningitis). Pigs may be seen down on their side, “paddling”, or simply found dead. Other body cavity linings are attacked, including those in the chest (pleuritis), around the heart (pericarditis), and within the abdomen (peritonitis) and joints (arthritis). The resulting damage can be painful, producing pigs that are reluctant to move or eat.

High fever often accompanies this infection. When the lungs are involved, a mild, wet, productive cough may be heard. Rapid treatment of affected pigs is critical. Based on antibacterial sensitivity information, treatment with antibiotics such as penicillin G, ampicillin or tiamulin can be effective if started immediately. If left untreated, mortality of 20% or more may occur.

Chronic lameness, lung lesions

The long term effects of Haemophilus parasuis infection may be more costly than the acute losses. Reduced appetite and growth rate may follow pleuritis. Lameness can also slow performance and lead to trim loss at harvest. Sudden death, especially in warm weather or stressful conditions, can be the result of pericarditis. All these signs are due to scar tissue formed after the intial infection and inflammation produced by Hps. The affected tissues can no longer glide over one another due to the binding of scar tissue or adhesions. These lesions can affect more than 20% of all pigs that survive to market.

Identify the culprit

Culture the bacteria from pigs that have just become infected to have the best chance to diagnose infection with Hps. Swab locations like the brain or brain stem, heart sac/pericardium or a swollen joint. The bacteria can be grown in the veterinary clinic locally, or sent to a diagnostic laboratory for culture.

Once recovered, have the isolate saved back for future reference. Also submit a duplicate sample for genetic typing — today this is done at the University of Minnesota (see sidebar page 3).

Application

Diagnostic Benefits

Finding out if Hps is the problem.

Many types of Haemophilus parasuis can be found in the nasal cavity of healthy pigs, producing no apparent problems. However, certain types have the ability to enter the pig's body, probably through the tonsil or lungs. These isolates are responsible for clinical disease and should be the target of interventions. Be sure to collect isolates from brain swabs or pericardial fluids when investigating suspect Hps cases.

More information

Solano G, et al. Effect of Porcine Reproductive and Respiratory Syndrome Virus Infection on the clearance of Haemophilus parasuis by porcine alveolar macrophages. Can J Vet Res 1998; 62: 251-256.

Zucker BA, Abolghasem B, Traux R, O'Rielly KL, Storz J. Detection of strain-specific antigenic epitopes on the lipo-oligosaccharide of Haemophilus parasuis by use of monoclonal and polyclonal antibodies, AJVR (57) No 1, Jan 1996. pp 63 - 67

Blackall PJ, et al. Analysis of Haemophilus parasuis by multilocus enzyme electrophoresis. Vet Micro (1997) 56; 125-134.