Diagnosing and treating the Suis-ide Diseases

Wednesday, August 1, 2012

Streptococcus suis, Haemophilus parasuis and Actinobacillus suis have similar profiles and are common in recently weaned nursery pigs. Some guidelines on how to identify and deal with them

by ERNEST SANFORD

Three bacteria with similar disease profiles have earned the colloquial name "Suis-ide Diseases." The three bacteria, Streptococcus (Strep) suis, Haemophilus parasuis and Actinobacillus suis cause a wide range of clinical conditions, most commonly in recently weaned nursery pigs, often in but not restricted to higher health herds. These bacteria are "early colonizers," meaning they colonize piglets at birth or in the first few days of life, making them difficult to control by management practices like segregated early weaning (SEW).

Streptococcus (Strep) suis
Diseases caused by Strep suis occur primarily in suckling or more commonly in recently weaned pigs, although all age groups can be affected.

Epidemiology. There are more than 35 serotypes or "strains" of Strep suis with types 2, 1/2, 3, 4 and 7 being most prevalent across North America and type 2 being the most common and most virulent in most locations, including Ontario.

Most serotypes can be found in the upper respiratory tract of normal healthy pigs, usually causing no harm. Disease outbreaks are often triggered by stressors such as overcrowding, poor ventilation and sudden changes in temperature. Transmission may be through ingestion, inhalation or nose-to-nose contact. Flies and rodents can transmit the organism. Strep suis survives on flies for at least five days. Healthy carrier swine usually introduce infection. Sows infect piglets at or shortly after birth. Once a few piglets are infected, they transmit the infection to cohorts in the farrowing room and when commingled in the nursery after weaning.

Clinical signs. Acute Strep suis infection can cause sudden death without exhibiting clinical signs. Lateral recumbency and paddling are the usual signs in young pigs with central nervous system (CNS) lesions. Older pigs exhibit CNS signs, including convulsions, head tilt, incoordination and tremors. Pigs with arthritis have swollen joints and are lame.

Haemophilus parasuis
Haemophilus parasuis is the bacterium that causes Glässer's disease, an infectious disease characterized by meningitis, polyserositis, polyarthritis and pneumonia. It is a sporadic disease seen in pigs three weeks to four months old, usually subsequent to stresses. More than 20 serovars (strains) of H. parasuis have been identified and additional untypable strains are common. Individual pigs can harbour several different serovars without developing clinical disease. Serotypes 4 and 5 are common in Canada.

Clinical signs. Signs of H. parasuis disease include sudden death, anorexia, difficult breathing, fever, CNS signs, lameness, swollen joints, reluctance to move, lateral recumbency, short coughing episodes and blue discolouration (cyanosis). Gross lesions at postmortem consist of fibrinous pleuritis, peritonitis, meningitis, arthritis and polyserositis.

Epidemiology. H. parasuis is ubiquitous throughout the swine world, usually with no clinical disease. Similar to Strep suis, pigs are colonized by H. parasuis soon after birth. Colostral antibodies usually protect pigs from disease while exposure to the organism allows them to develop their own active immunity over time.

Pigs without passive or active immunity are subject to developing severe Glässer's disease when exposed to H. parasuis. Stressors such as weaning, overcrowding, poor ventilation, prolonged transport or concomitant diseases such as PRRS, PCV2, influenza and mycoplasmal pneumonia may trigger outbreaks.

Diagnosis. History, clinical signs and gross lesions give a good indication of H. parasuis (Glässer's) disease. Confirmation and differentiation from Strep suis and A. suis depend on isolation of the organism from lesions.

Actinobacillus suis
Actinobacillus suis causes an infectious disease characterized by hemorrhages in multiple organs. Outbreaks occur predominantly in immunologically naïve pigs and thus are most commonly seen in high-health herds and SEW production units. Most outbreaks are in recently weaned pigs and in grow-finish pigs in SEW systems or other high-health operations, less often in conventional herds.

Epidemiology. Carrier pigs probably introduce A. suis into herds. It resides in the tonsils and upper respiratory tracts of many pigs, although it is not readily isolated from conventionally-reared pigs. It is found in the reproductive tract of healthy sows and is another "early colonizer."

Clinical signs. Sudden death of young pigs is often the first sign of an outbreak. Fever, rapid breathing, cough, lameness, weakness, wasting, abscesses, CNS signs, abortion, cyanosis or congested extremities in various combinations are all signs of A. suis disease. Mortality in affected litters can approach 50 per cent. Older growing pigs and adults can have similar signs but may also have signs of acute respiratory distress, lethargy, anorexia and erysipelas-like skin lesions. At postmortem, lung lesions in grow-finish pigs can be confused with Actinobacillus pleuropneumoniae pneumonia.

Treatment and control
As these Suis-ide diseases often have an acute onset, sick animals must be identified quickly and treated promptly with an injectable antibiotic to which the organism is sensitive. The organisms are usually sensitive to a large number of antibiotics. Some strains, however, are resistant especially to tetracyclines.

Affected pigs should be treated individually. Your veterinarian may decide to pulse the entire population or a section of the population experiencing high morbidity (for example, a pen or pens with many affected pigs) with a systemically absorbed antibiotic in the water for a few days.  

Attention to elimination of stresses such as overcrowding, poor ventilation, high humidity and other stressors should be implemented to reduce the chances of future outbreaks. Commercial vaccines are available for Strep suis and H. parasuis and can be useful. They do not cover all strains and it might be necessary to get herd-specific autogenous bacterins to cover the specific organisms in your herd.  Furthermore, the predominant strains undergo change over time, so it is necessary to keep checking to determine if the previous strains are still the ones causing renewed outbreaks.

Autogenous bacterins can be made for A. suis. Independent efficacy has not been determined for A. suis bacterins. BP

S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) in Burlington. Email: ernest.sanford@boehringer-ingelheim.com