Red clover is commonly infected with the fungus Rhizoctonia leguminicola causing 'black-patch' disease. The fungus produces a mycotoxin called slafaramine that induces profuse salivation in horses. Slaframine is very similar chemically to swainsonine the fungal toxin resposible for causing locoism.
Fungal infections of the clover (and other legumes)are usually associated with high rainfall and humidity.
Slaframine is an indolizidine alkaloid that is activated in the liver and acts as a parasympathomimetic to stimulate the salivary glands to secrete large volumes of saliva. This salivary response can be blocked by the administration of atropine.
A perennial or biennial legume with multilpe hairy, branching stems arising from a taproot. Leaves are made up of 3 leaflets on long stems, each leaflet having serrated edges and a 'V' whitish mark. The flower heads contain numerous individual pea-like flowers ranging from rosy-purple to creamy white.Seed pods are small, short, and contain kidney-shaped seeds varying in color from yellow to deep violet.
'Slobbers' is the common name given to the problem in horses that graze redclover infected with black-patch disease. Affected animals may become dehydrated if allowed to continue eating the diseased clover.
Removing the clover from the animal's diet usually results in rapid recovery.
Excessive salivation in horses or cattle grazing clover pastures is typically diagnostic
The fungus Rhizoctonia leguminicola also grows on other legumes such as alfalfa, alsike and white clover, lespedezia, soybeans and lupines.
1. Rainey DP, Smalley DB, Crump MH, et al: Isolation of salivation factor from Rhizoctonia leguminicola-infected red clover hay.Nature 205:203-204 1973.
2. Sockett DC, Baker JC, Stowe CM: Slaframine (Rhizoctonia leguminicola) intoxication in horses. J Am Vet Med Assoc 181: 606 (1982).
3. Croom WJ, Hagler WM, Froetschel MA,Johnson AD. The involvement of salframine and swainsonine in slobbers syndrome: a review. J Anim Sci 73:1499-1505, 1995.