EXPERIMENTAL STUDIES ON THE PATHOGENESIS OF CORYNEBACTERIUM-EQUI INFECTION IN FOALS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 44  (3) , 280-288
Abstract
Four month old foals were infected orally with 75 ml of a suspension of 5.0 .times. 108 C. equi [Rhodococcus equi]/ml. Two foals were killed after 10 days and had a scanty number of C. equi in the ceco-colic lymph nodes. No C. equi were recovered from the other 2 foals killed 20 days after infection. No gross pathological change was detected in these 4 foals although mild microscopic lesions were seen in the ileum of 1 foal. Results of lymphocyte blastogenesis using peripheral blood lymphocytes and C. equi antigens showed that lymphocytes became sensitized to C. equi following this challenge. In a 2nd experiment 4 mo. old foals were given orally the same dose of organisms but on 5 consecutive days. Two foals were killed 10 days after infection and showed mild histological changes in the large bowel mucosa and C. equi could be recovered from all intestinal lymph nodes cultured. In 1 of these foals moderate numbers of C. equi were present in the bronchial lymph node. Of the other 2 foals, 1 died after 22 days with severe ulcerative enterocolitis and intestinal lymphadenitis. Only 1 small pulmonary abscess was detected despite large numbers of C. equi in the lungs. The other foal developed similar intestinal changes and was euthanized 25 days after infection. No C. equi were detected in the lungs or bronchial lymph node. Lymphocyte blastogenesis in these animals showed a rapid rise in response to C. equi antigens. R. equi pneumonia in foals does not always arise from an intestinal infection. Minor intestinal infection causes a cellular immune response. Massive exposure of the bowel over a sustained period is necessary to induce intestinal lesions.