Turkey poults were inoculated at hatch with the "W" isolate of Bordetella avium. At 17 d of age, serum copper levels and ceruloplasmin activities were determined. The trachea and aorta were analyzed for collagen and elastin content in an attempt to relate these structural proteins to the clinical observations of tracheal ring distortion and cardiac dysfunction associated with bordetellosis. Serum copper levels and ceruloplasmin activity were elevated in the B. avium-infected poults and indicated enzyme activity sufficient for elastin and collagen cross-link formation. In the infected poults, crude elastin content was increased significantly (0.67% infected vs 0.59% control) in the trachea but not in the aorta (13.12% infected vs 12.68% control). However, collagen content in infected poults (69.7 hydroxyproline residues per 1,000 amino acid residues) was decreased in the trachea compared to the controls (97 hydroxyproline residues per 1,000 amino acid residues), whereas collagen and elastin cross-links (HLNL, hydroxy-lysinohydroxy-norleucine, moles per mole of collagen per 300 residues hydroxyproline) were increased in the trachea of infected poults (2.85 in infected vs 1.80 in control) and also increased (DHLNL, dihydroxy-lysinohydroxy-norleucine, moles/mole of collagen/300 residues hydroxyproline) in the aorta (0.49 in infected vs 0.39 in control) of infected poults. The differences in collagen and elastin content, in association with differences in the cross-linking, appeared to be the cause of tracheal collapse that is characteristic of B. avium infection and also may have an adverse influence on cardiovascular function.