[I] The pathology of experimental Corynebacterium ...

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Title [I] The pathology of experimental Corynebacterium equi infection in foals following intrabronchial challenge. [II] The pathology of experimental Corynebacterium equi infection in foals following intragastric challenge
Author(s) J. A. Johnson, J. F. Prescott, R. J. Frederick Markham
Journal Veterinary Pathology
Date 1983
Volume 20
Issue 4
Start page 440
End page 449, 450-459
Abstract Six foals were inoculated intrabronchially with a suspension of C. equi. Six weeks before this challenge, three foals were vaccinated with a C. equi bacterin. Three foals were unvaccinated controls. All foals developed a severe bronchopneumonia in the inoculated lung, indicating that vaccination was not protective. Three foals (two vaccinated, one control) were killed eight to nine days after infection. One control died on day 9 with lesions of disseminated intravascular coagulation. The remaining two foals (one vaccinated, one control) were killed on day 17. C. equi was cultured in large numbers from affected lung and bronchial lymph nodes, and in smaller numbers from unaffected lung, spleen, and liver in all foals. In the 8- to 9-day-old lung lesions, the alveoli were filled with macrophages, neutrophils, and multinucleate giant cells and most contained many C. equi. The few foci of alveolar necrosis were associated with groups of bacteria-laden degenerating macrophages. In the lesions of 17-day duration, there was extensive parenchymal destruction with little fibrous tissue reaction. Lesions common to both groups included hyperplastic bronchiolitis, pulmonary oedema, and perivascular lymphocytic cuffs and a pyogranulomatous lymhadenitis in bronchial nodes. One vaccinated foal had a microscopic pyogranulomatous colitis. The lesions in the experimentally infected foals are compared with those in naturally infected foals, and the likely pathogenic mechanisms involved in C. equi pneumonia in foals are discussed. The intragastric inoculation of a suspension of Corynebacterium equi on five consecutive days induced severe ulcerative colitis, typhilitis, and lymphadenitis of colonic and caecal nodes in two ponies killed three weeks after infection. No gross lesions were observed in two ponies killed ten days after infection. A single inoculum of equivalent size failed to induce gross lesions in four ponies killed at 10 or 20 days after infection. Microscopic lesions consistent with early C. equi infection of Peyer's patches were seen in two of the ponies killed ten days after infection. Only one small pulmonary abscess occurred in one foal, suggesting that intestinal lesions are not likely to be the usual precursor of pulmonary disease in naturally infected foals. The gross and microscopic lesions in the experimentally infected ponies were typical of the intestinal form of naturally occurring C. equi associated disease in foals..

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