Horse News & Views - August 2004

Ministry of Agriculture, Food and Rural Affairs

Ontario Association of Equine Practitioners

• In the late spring, and more recently in July, veterinarians reported horses salivating profusely, with saliva hanging from the mouth and pooling on the floor. Affected horses commonly show no abnormal clinical signs except the profuse frothy salivation. Slaframine poisoning should be considered, especially in a cooler and wetter spring or fall when the clovers proliferate in pastures. The cooler wet conditions are also ideal for the growth of the fungus Rhizoctonia leguminicola (black patch). The fungus infects red clover (Trifolium pratense), white clover (Trifolium repens), alsike clover (Trifolium hybridum) and alfalfa. The name ‘black patch' is derived from the bronze to black spots or rings observed on the leaves and stems (1). The fungus produces the mycotoxin slaframine or slobber factor. It can be present on both pasture and in stored dry hay. The fungus persists on infected fields from year to year. Slaframine can be active in stored hay for 10 months or more; however, its biological activity does decrease. The analysis for slaframine is not readily available. ((1) Burrows GE, Tyril RJ. Toxic Plants in North America. Ames: Iowa State Press, 2001: 625-626.)
• Eastern equine encephalitis (EEE) is a mosquito-borne disease that can cause inflammation of the brain (encephalitis). The virus causing EEE belongs to the family Togaviridae, which includes Eastern, Western and Venezuelan equine encephalitis viruses. Periodically, EEE has been identified in horses that reside in the province of Ontario or have become infected while traveling through other areas of North America. Other diseases/conditions that can cause similar clinical signs include rabies, West Nile virus (WNV) infection, the neurological form of equine herpesvirus (EHV), equine protozoal myeloencephalitis (EPM) and botulism.

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