A Common Fungal Disease:
Saliva syndrome is actually a fungal disease. Doubtlessly, you have encountered a horse that looks perfectly healthy with not problems in walking, a shiny coat, and a good disposition only to notice an excessive flow of saliva from the mouth that seems to be almost endless. It is not uncommon to see affected horses actually have pools of slobber in front of them.
The fungus at the root of this problem is rhizoctonia leguminicola, which infects legume forages, specifically clover. When contaminated clover or feed is introduced to the horse’s digestive system, the fungus releases an alkaloid referred to as slaframine which causes to the salivary glands to overproduce saliva, which is then excreted from the mouth.
Other effects of the alkaloid are an overproduction of tears, a sudden difficulty with breathing, a marked increase in urination and sometimes also diarrhea, and if the horse is especially uncomfortable it will also refuse feed entirely. In the most extreme cases it is possible for a broodmare to abort a foal. Keep in mind that not only horses but also other grazing animals, such as sheep, goats and cattle may be infected. Death of adult animals is exceedingly rare.
If you are looking at your pasture, you will want to keep an eye on the red clover, which is a common host for this fungus. White clover - and other types of clover - as well as alfalfa are oftentimes infected. Look for small black patches on the leaves – you may need a microscope to diagnose this condition for sure. This fungus will experience the most growth during very humid weather. Yet it is not just the pasture that you will need to be concerned about. If hay is baled from pastures that host this fungus, then the alkaloid will proceed into the bales.
It is very disconcerting that the toxic effects of the fungus will linger for as much as several years. When speaking to your veterinarian about the symptoms you observe, she or he may refer to them as SLUD, which is an acronym of salivation, lacrimation, urination, and defecation.
You will be able to see the first symptoms within one hour after ingesting the infected legume, and the length of the symptoms may be as long-lasting as three days. To counteract the effects of the fungus, it is best to curtail the feeding of hay and remove the animals from the affected pasture immediately. While treatment is not usually needed, an extended display of symptoms might warrant a call to the veterinarian. Treating your pasture is more difficult. Fungicides only yield limited success, and it is best to discuss this issue with an expert in the field who will be able to make sound recommendations for your particular case.
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