Dr Andrew Tucker – Charles Street Veterinary Consultancy
What is Streptococcal Meningitis?
Streptococcus suis (most commonly type 2) is a fairly hardy bacteria, which can survive in nutrient medium at 4°C for up to nine months. It is recorded to survive in faeces for eight days at 22-25°C and in dust at the same temperature for 24 hours.
It spreads mainly via direct contact but also via aerosol and ingestion. If present, most pigs will become infected but not all will develop the disease. Other diseases and environmental factors (overcrowding, poor ventilation, mixing) contribute to the initiation of the disease. S.suis can spread from sows to offspring or from one piglet to another. Once infected the bacteria is rarely lost from the herd.
The bacteria localises in the tonsillar crypts and can then spread to the blood causing a fever. It can then localise in the brain and joints leading to the two most common findings, meningitis and arthritis. Spread to farms is predominantly through carrier pigs but fomites like clothing and boots may also introduce the disease. S.suis is a zoonosis and has been reported in veterinarians, farmers, abattoir workers and butchers.
How do you know if it’s on your farm?
S.suis typically affects pigs of three to 12 weeks of age but can affect any pigs including breeding stock. It is often seen post-mixing and in the moving of piglets, eg. fostering and weaning. The typical clinical picture is sudden death, fever, nervous signs like incoordination, tremors, paralysis and paddling. Arthritis is often seen in younger piglets and bronchopneumonia is not uncommon.
The incubation period is 24 hours to two weeks and often the first sign seen is death of pigs in good condition. Post mortem findings are fairly distinctive and diagnosis can be confirmed by bacterial culture.
How do you treat or prevent it?
S.suis is sensitive to a wide range of antimicrobials, although resistance has been reported. Strategic medication via injection, water or feed can be very effective. All-in all-out practices can have very positive effects by breaking the infection cycle. Proper washing and disinfection also controls the spread well. Clean dry pens, limited mixing/moving and low humidity have all been shown to control infection.
Eradication: Total depop-repop has been successful in eradicating S.suis from swine herds. Medicated early weaning may be effective, but obviously has a higher risk of not being successful. Treatment of herds, removal of carriers and internal isolation are not effective.
Pig Diseases – D.J.Taylor; Diseases of Swine – Straw, Zimmerman, D’Allaire, Taylor