Acute respiratory distress syndrome (ARDS) in lambs. Mycology and hypersensitivity

Grass samples from six aftermath pastures, where lambs were found to suffer from Acute Respiratory Distress Syndrome (ARDS), were examined for fungi. Only various common types of fungi were found, none in any dominating quantity. All six samples contained Fusarium spp, Alternaria spp and Cladosporium spp. In addition, five of the samples contained Torula spp, Helminthosporium spp and Trichothecium spp, while one sample contained Dreschslera spp and Septoria spp. All samples contained nematodes (eggs and larvae), additional unidentified hyphomycetes and smut spores. Antigens for intradermal testing were made from the six fungal species occurring in 5 or 6 samples, and intradermal tests were performed on 5 lambs three to six days after appearance of ARDS. Intradermal testing with the same antigens were also made on six healthy lambs kept indoors throughout summer, and two lambs which had been grazing farm leys. Four of the diseased lambs had a positive reaction to Fusarium spp and Trichothecium spp, and three of them had a positive reaction to Alternaria spp. All others were negative, except for one of the healthy lambs that showed a positive reaction to Fusarium spp after having been fed indoors throughout summer. Dermal toxicity studies made with extracts from Torula spp and Fusarium spp on rabbits, and oral dosing with Fusarium spp to healthy lambs, were negative. The results indicate that involvement of immunological factors cannot be excluded. However, it is pointed out that this hypersensitivity reaction will occur at a time with sudden ruminal histamine production, aggravating the symptoms as well as contributing to kidney damage.