01 April 2011 Veterinary Update, Animal Health and Welfare Branch, Ontario Ministry of Agriculture, Food and Rural Affairs
The Ontario Ministry of Agriculture Food and Rural Affairs has recently been made aware of a number of premises in the Greater Sudbury area and Manitoulin Island affected by Strangles. Strangles is a highly contagious bacterial disease of horses characterized by abscesses in the lymphoid tissue of the upper respiratory tract. The causative organism, Streptococcus equi subspecies equi, is highly host-adapted and generally produces clinical disease only in horses, donkeys, and mules.
Strangles is an endemic disease in horses and circulates relatively commonly in the horse population. A significant number of affected premises in a relatively confined geographical area is a good reminder to horse owners and veterinarians to practise appropriate biosecurity procedures for horses and equipment coming on and off the farm AND infection control within the barn.
Transmission occurs via fomites and direct contact with infectious exudates. Sharing of halters and brushes that may contact the fluid from draining abscesses can spread the disease. The source of Strangles on any of these premises could have been the entry of a new horse, contact with a carrier somewhere off the farm (e.g. at a show) or on the clothing, hands or equipment of a visitor (such as a feed supplier, farrier or veterinarian who had recent contact with an infected horse). Survival of the organism in the environment is dependent on temperature and humidity. Under ideal environmental circumstances, the organism can survive 7-9 weeks outside the host. Paddocks and barn facilities used by infected horses should be regarded as contaminated for about 2 months after resolution of an outbreak.
Carrier animals are important for maintenance of the bacteria between epizootics and initiation of outbreaks on premises previously free of disease. Horse owners need to be aware that clinically recovered animals should have three negative nasopharyngeal swabs to be determined “Strangles-free”.
Recommendations regarding vaccination can be found in the disease factsheets from the sources listed below. These sources also contain excellent information on basic biosecurity practices and infection control.
Strangles is a good opportunity to remind your clients that the best disease control is disease prevention.
AMERICAN ASSOCIATION OF EQUINE PRACTITIONERS
The Horsemen's Benevolent and Protective Association of Ontario