“Haysickness” in Icelandic horses: Precipitin tests and other studies

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Abstract
Blood samples were taken from 18 healthy horses (Group A), 15 horses clinically diagnosed to have "haysickness" (farmer''s lung) (Group B), 10 closely related horses (group C) and 14 inbred horses (Group D). Precipitins in sera were measured by double gel diffusion test against Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, Alternaria, Penicillium and Rhizopus species. In Group A, all the horses were precipitin negative except one with a faint reaction to Rhizopus species. In Group B all had precipitin against M. faeni. One horse also had precipitins against Rhizopus species and another against Aspergillus fumigatus. In Group C, 7 of the 10 horses had precipitins against M. faeni. Of these, 5 had a history of respiratory signs, but 2 horses with a faint reaction had no such history. In Group D, 4 of 14 horses had positive precipitin tests against M. faeni. Of these 4 horses, 3 also had a faint reaction to A. fumigatus and 1 a faint reaction to Alternaria species. All were asymptomatic. Farmer''s lung in man and "haysickness" in horses are probably of the same origin. Further studies are necessary to substantiate the diagnostic or prognostic value of these precipitin tests in equine practice. The question of whether hereditary factors play a role in causing this disease also warrants further studies.