The Canadian Animal Health Surveillance System has reported a horse has tested positive for strangles in New Brunswick.
A veterinarian from the Provincial Veterinary Service who practices in the western half of the province of New Brunswick was called on November 5 to see a horse off feed and swelling of the right parotid area. The horse was cultured positive for Strept. equi equi four days later. This horse was euthanized for other health reasons.
The premise was put under quarantine on November 5 as strangles was suspected with the clinical signs. Three other horses on the farm were exposed to the positive case. One horse (a pony) showed clinical signs eight days later and was cultured positive. The two remaining horses on the farm were also sampled and one out of the two horses also cultured positive but both showed no clinical signs.
Currently the two horses have not shown clinical signs and the pony has made a full recovery. The farm continues to be under quarantine and serial nasal swabs are planned before the quarantine is lifted.
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 two 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 OMAFRA disease factsheet. Strangles is a good opportunity to remind your clients that the best disease control is disease prevention.
(with files from EDCC)