HISTOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL INVESTIGATION OF NATURALLY-OCCURRING CHLAMYDIAL CONJUNCTIVITIS AND UROGENITAL INFLAMMATION IN KOALAS (PHASCOLARCTOS-CINEREUS)

Formalin-fixed conjunctival and urogenital (urinary bladder, urogenita l sinus and prostate or penis, or both) samples obtained from 29 free- living koalas were examined histopathologically and immunohistochemica lly for the presence and character of inflammation and for evidence of chlamydiae. Five koalas had no inflammation at any site examined and were chlamydiae-negative. Twenty-four koalas had inflammation al one o r more sites and 18 were positive for chlamydiae by serology or antige n detection tests, or both. Histopathological and immunohistochemical findings were consistent with those seen in chlamydial infections in o ther species. The inflammatory infiltrate was most dense in the lamina propria-submucosa and, in most tissues; predominantly consisted of ly mphocytes and plasma cells. Neutrophils and macrophages were variable in number. Lymphocytes in uninflamed and inflamed tissues consisted la rgely of T cells. B lymphocytes and plasma cells were mainly distribut ed immediately beneath the epithelium, but T cells were widely distrib uted. MHC II-positive lymphoid cells were present in variable numbers and, in some inflamed tissue samples, epithelial cell labelling was al so seen. Chlamydial inclusion bodies were uncommon in routinely staine d sections. Immunoperoxidase labelling for chlamydiae was positive in 16 of 52 inflamed tissues. The proportion of positive test results for chlamydial antigen by any method was directly related to the severity of inflammation. (C) 1997 W.B. Saunders Company Limited.