Feed-induced hypersalivation in horses from Austria, Germany and Switzerland.

Background: While previous reports come mostly from the southern Americas, several outbreaks of hypersalivation in horses were observed in Middle Europe from 2016 to 2018.

Objective: To describe feed-induced hypersalivation in European horses.

Study design: Analysis of feedstuffs.

Methods: Veterinarians and horse or stable owners were encouraged to submit feedstuffs from case outbreaks of hypersalivation in which, infectious diseases or other systemic causes of the syndrome were ruled out and intoxication was suspected. Feedstuff analysis was performed, including gross examination, microscopic analysis of fine particles, and for hay and forage mycological culturing and mycotoxin testing.

Results: Eleven case outbreaks were investigated. Typical clinical findings in the horses were either foamy saliva around the mouth or serous salivation with puddles forming on the ground. Some horses also showed lesions of the gingival mucosa and/or the tongue. Foamy hypersalivation, sometimes combined with lesions of tongue and/or gingiva, was associated with finding of ergot sclerotia and ergot alkaloids in hay or pasture plants (ergocornin and ergocorninin having the highest concentrations). Serous hypersalivation with massive loss of fluid was associated with the fungus Rhizoctonia spp. As indicated by the detection of traces of swainsonine, mycotoxin production on the forage was seen as likely cause. The cessation of clinical signs took days to weeks after diet change, probably depending on the duration, type and amount of toxin intake.

Main limitations: Small number of case outbreaks, records of clinical findings and horses' management were incomplete and were reported by horse owners.

Conclusion: Hypersalivation due to mycotoxins in the feed has become an emerging problem for horses in middle Europe.