Horses of all ages are susceptible, though strangles is most common in animals less than 5 years of age and especially in groups of weanling foals or yearlings. Foals under 4 months of age are usually protected by colostrum-derived passive immunity. (1) S. equi is main-tained in the horse population by carrier horses but does not survive for more than 6–8 weeks in the environment. Although the organism is not very robust, the infection is highly contagious. Transmission is either by direct or indirect contact of susceptible animals with a diseased horse. Direct contact includes contact with a horse that is incubating strangles or has just recovered from the infection, or with an apparently clinically unaffected long-term carrier. Indirect contact occurs when an animal comes in contact with a contaminated stable (buckets, feed, walls, doors) or pasture environment (grass, fences, but almost always the water troughs), or through flies. (2) Susceptible horses develop strangles within 3–14 days of exposure. (2) Animals show typical signs of a generalized infectious process (depression, inappetence, and fever of 39°C–39.5°C). More typically of strangles, horses develop a nasal discharge (initially mucoid, rapidly thickening and purulent), a soft cough and slight but painful swelling between the mandibles, with swelling of the submandibular lymph node. Horses are often seen positioning their heads low and extended, so as to relieve the throat and lymph node pain.
Posted on: Wed, 04 Sep 2013 01:17:59 +0000
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