“Haysickness” in Icelandic horses: precipitin tests and other studies.

The research article investigates “haysickness” in Icelandic horses, looking at precipitin tests and other characteristics.

Research Methodology

• The researchers collected blood samples from several groups of horses. Group A had 18 healthy horses while Group B consisted of 15 horses diagnosed with “haysickness,” a disease similar to “farmer’s lung” in humans. Group C involved ten closely related horses, and Group D included 14 inbred horses.
• The team then measured precipitins, antibodies that cause precipitation when mixed with specific antigens, in the blood samples using a double gel diffusion test. They tested for reactions against several types of harmful microorganisms, including Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, Alternaria, Penicillium, and Rhizopus species.

Research Findings

• In Group A (healthy horses), all were precipitin-negative, except for one horse that showed faint reactivity towards the Rhizopus species.
• In Group B (horses with haysickness), all showed precipitins against M. Faeni, indicating a strong correlation between haysickness and this particular antigen. Two other horses also reacted to other antigens.
• In Group C (closely related horses), seven out of the ten horses were precipitin-positive against M. Faeni. Of the seven, five showed respiratory symptoms consistent with haysickness, but two did not, despite reacting to the antigen.
• In Group’s case D (inbred horses), four out of fourteen horses showed positive precipitin tests against M. Faeni. Among these, three also had a faint reaction to A. Fumigatus and one to Alternaria species. Notably, all these horses were asymptomatic.

Interpretation and Implication of Findings

• According to these findings, the researchers posit that “farmer’s lung” in humans and “haysickness” in horses are likely of the same origin, given the identical precipitin reactions in horses with haysickness.
• However, they also indicate that further research is necessary to establish the diagnostic or prognostic value of these precipitin tests in the equine medical practice. This is due to inconsistencies in symptoms observed versus testing results, suggesting not all reactions necessarily indicate disease states.
• Lastly, the researchers propose the potential for genetic factors in the disease’s development, evidenced in part by Group C’s (closely related horses) and the Group D (inbred horses) testing results. They emphasize that this role of hereditary factors also needs exploration in further studies.