Streptococcal infections

Streptococcus suis is the most important streptococcus of pigs causing pneumonia, septicemia, arthritis and encephalitis in pigs and is also of great public importance for its zoonotic potential.

Alternative names: Streptococcus suis, Streptococcus equisimilis, Streptococcus porcinus


The streptococci are common organisms in all animals. Generally, but not always, they are specie specific. The main species present in pigs is Streptococcus suis which is widespread through all swine populations. It is associated with a variety of diseases including meningitis, septicemia, polyserositis, arthritis, endocarditis and pneumonia. It has also been isolated in cases of abortion and rhinitis. The pattern and the relative importance of different syndromes varies by country.

S. suis is subdivided into at least thirty five serotypes. They vary in pathogenicity and clinical signs they produce, between and within the different types. Some types appear to be non-pathogenic and have been isolated mainly from healthy animals, some are mainly associated with pulmonary lesions and some have been isolated from other animals besides swine. Some types, especially type 2, can cause meningitis in humans in addition to pigs. Fortunately human cases are rare.

For a farmer it is important and of concern the endemic meningitis caused by type 2. Clinically healthy animals may carry the organism in their tonsils for many months and there are sows that are carriers. There is still no technique available to eradicate a serotype once it has entered the farm and sets itself as part of the normal flora. S. suis is rapidly eliminated through disinfectants used in farms, including phenolic disinfectants, with chlorine and iodophors. Detergents also eliminate the organism in thirty minutes.

The sow passes antibodies through the colostrum to nursing piglets and therefore the disease is rare in this group unless it is entering into the farm for the first time. It is much more common to see it starting 2 or 3 weeks after weaning and it continues until 16 weeks of age. In farrowing almost 100% of pigs become carriers in three weeks.

PRRS can also increase the incidence of meningitis caused by pathogenic strains when it first enters in the farm.

Other Streptococcus species other than S. suis can cause diseases in pigs. For example, Streptococcus equisimilis produces sporadic cases of septicemia and arthritis in lactating piglets, heart valve infections in growing pigs and ascending infection of the uterus in sows. In the USA Streptococcus porcinus causes abscesses in the throat and septicemia, and sometimes is isolate from cases of pneumonia. However, cases of throat abscesses due to streptococcus have become rare in modern swine production facilities.



  • Rare.
  • Abortion.
  • Septicemia.

Lactating piglets, nursery and fattening

  • Occasional arthritis.
  • Sudden death.
  • Seizures.
  • Lateralized head.
  • Lateral twitching eye movements (nystagmus).
  • Animal is sideways, it has a pedaling movement and produces foam in the mouth.
  • Lameness.
  • Abscesses.
  • Septicemia.
  • Polyserositis.

Causes / Contributing Factors

  • S. suis is mainly transmitted during farrowing via the birth canal.
  • Carrier gilts or boars.
  • It can also be transmitted within the farm by indirect contact.
  • High density of animals in the nurseries.
  • Continuous production.
  • Concurrent infection with PRRS.
  • Mixing animals after weaning.
  • Poor ventilation and high humidity.
  • Stress.


  • A history of recurrent presence of meningitis in weaned pigs is very indicative; it is confirmed by isolation of the organism from the brain.
  • Isolation of S. suis from joints, heart, liver, spleen, kidney, or polyserositis.
  • Due to the existence of strains that are not pathogenic or only moderately pathogenic; isolation of S. suis type 2 from tonsils of a pig is difficult to assess.



  • Treatment should be started as soon as the disease is diagnosed.
  • Give intramuscular injections of penicillin, cephalosporin or other antibiotics.
  • The strategic use of medication may be applied through drinking water.
  • Use of vaccines may be useful especially in sows before farrowing.