Effects of inhalation of dust and endotoxin on respiratory tracts of pigs

Objective-To assess the effects of inhalation of feed flour dust and dustbo rne endotoxin on respiratory tracts of pigs. Animals-29 healthy Belgian Landrace pigs. Procedure-Pigs housed in an environmental chamber ber were exposed for 6 da ys to feed flour dust (1 to 15 mg/m(3)) and dustborne endotoxins (50 to 2,5 00 ng/m(3)). Effects were evaluated by measuring albumin concentration, lac tate dehydrogenase (LDH) activity. cell composition of nasal lavage (NL) an d bronchoalveolar lavage (BAL) fluids and blood, and percentages of CD4(+) and CD8(+) T lymphocytes in blood and lavage fluids. Dustborne endotoxin wa s obtained by mixing endotoxins from Escherichia coli (:serotype O127:B8) w ith feed flour before spraying the flour in the environmental chamber. Results-Exposure did not affect cell composition of NL fluid or blood. Tota l cell counts of BAL fluids were increased in all groups exposed to dust. M acrophage counts were increased in pigs exposed to inhalable dust concentra tions as low as 4.4 mg/m(3), and lymphocyte counts were increased in groups exposed to high dust concentrations. Percentages of CD4(+) and CD8(+) T ly mphocytes in blood and lavage fluids were unchanged. In all dust-exposed gr oups, albumin content of BAL fluid was increased, whereas LDH activity was unaffected. Macrophage and lymphocyte infiltration and edema in the bronchi were identified by light microscopy. Effects attributable to E coli endoto xin exposure were not identified. Conclusions-Inhalation of feed flour dust did not affect nasal mucosa but d id induce bronchial airway inflammation. Dustborne endotoxins did not have effects attributable to endotoxin alone.