Histamine and endotoxin contamination of hay and respirable hay dust.
An analysis of the histamine (51456) and endotoxin content of hay and respirable hay dust was conducted. Samples of three different hays were collected in a barn in which dairy-cows had exhibited asthma like symptoms. The samples were analyzed for their histamine and endotoxin content. Dusts were generated from the samples using a Pitt 3 dust generator and were analyzed for endotoxin and histamine. Blood samples were collected from the farmer who owned the barn and a nonsensitized person (comparison). An enriched basophil preparation was obtained from the samples and incubated with hay extracts to determine the extent of histamine release. Serum samples from the two subjects were analyzed for specific immunoglobulin-E (IgE) antibodies directed toward hay antigens. The endotoxin concentration in bulk hay samples ranged from 93.0 to 6138.3 endotoxin units/milligram (EU/mg). Endotoxin concentrations in total and respirable hay dust samples ranged from 603.9 to 1284.6 and 474.6 to 1473.6EU/mg, respectively. Histamine was not detected in one dust sample. Histamine concentrations in the two other samples were 0.500 and 0.175 nanograms/milligram (ng/mg). Histamine concentrations in the total dust samples were 7.0 and 2.8ng/mg. The histamine concentration in the respirable dust fraction of one sample was 3.48ng/mg. Basophils from the farmer released 12.5 and 25.8% of their histamine content to two hay extracts. Basophils from the comparison released less than 10% of the histamine content. Specific IgE hay antibodies were not detected in sera from either subject. The authors conclude that since the hays contain appreciable concentrations of fungi and bacteria which are currently being characterized, histamine and endotoxin contamination of the hays may not be fully responsible for the cows' respiratory symptoms.