In animals, streptococcal diseases usually occur following infection by another agent (influenza, for example), or when the animal’s immune system is weakened. Streptococcal infections can cause a range of mild to severe symptoms in many different species of animals.
The diseases caused by the bacteria Streptococcus suis and Streptococcus equi ssp zooepidemicus are zoonotic, meaning that they can be transmitted to humans by animals such as pigs and horses. However, cases in humans are rare.
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Streptococcus suis settles in the snout, amygdala and reproductive system of pigs. Streptococcus equi ssp zooepidemicus is commonly present in the upper respiratory tract of healthy horses. It has also been found in many other animal species, including cows, sheep, goats, cats and dogs.
Many other mammals and birds can sometimes be infected by these bacteria.
Signs of the disease
Animals like pigs and horses may be carriers of Streptococcus and spread the bacteria throughout their environment, even if they show no symptoms of illness.
Pigs infected by Streptococcus suis may show symptoms such as:
Neurological and respiratory issues
Horses infected by Streptococcus equi ssp zooepidemicus may show symptoms such as:
Pneumonia (common as a secondary agent)
Reproductive system infection
Embryonic mortality, abortion or premature birth
Swollen and infected lymph nodes in the throat, leading to abscesses in the lymph nodes and guttural pouch (similar to strangles [equine distemper] (in French only), but less common)
Animals are most commonly infected by direct contact with other animals that are carriers of streptococcal bacteria.
Piglets may be infected during birth if the sow’s birth canal is contaminated.
Sick animals may be treated with antibiotics.
Protection and prevention
The best way to prevent streptococcal diseases in animals is by good management and hygiene practices to maintain ideal livestock conditions in stables and farm buildings. This means controlling other diseases and being careful about introducing new animals to the farm or group, with attention to their state of health.
If an outbreak is affecting multiple horses in a stable, cats and dogs must not be allowed to enter the building, or at least must be prevented from coming into contact with sick horses.
This disease is rare in humans, but can be serious. It generally occurs, when it does occur, in people who come into direct contact with infected animals, such as farmers, veterinarians and slaughterhouse workers.
A human can be infected through direct contact with carrier animals. Handling pig carcasses is also an infection risk. The bacteria can enter the body through broken skin (wounds).
Most pig-related human cases are caused by Streptococcus suis type 2. Human cases involving Streptococcus equi ssp zooepidemicus are generally connected to contact with sick or healthy horses or with sick dogs or cats.
The most common symptoms seen in infected humans are:
Symptoms appear approximately 60 hours after infection. Meningitis is the most common form of the infection. Over 50% of meningitis cases result in hearing loss. Some people may experience widespread blood poisoning.
Preventing transmission to humans
To protect yourself from transmission of streptococcal disease:
Wash your hands with soap and hot water after having contact with an animal or visiting a farm, and before eating or touching your mouth with your hands.
Immediately wash all wounds (including scratches or bites) and protect them with a bandage.
Do not kiss animals.
Follow recommendations for preventing food poisoning (in French only).
Workers in the pork industry can help prevent the disease by wearing protective equipment. Some types of work with horses also require precautions. For example, wearing gloves and protective clothing is recommended for anyone coming into contact with pork meat or caring for an infected wound. Goggles and a mask should also be used to protect the mucous membranes when doing a task that may produce droplets (for example, taking a sample may make an animal sneeze).