Caseous lymphadenitis in goats: The pathogenesis, incubation period and serological response after experimental infection

Twenty goats, in two groups of 10, were injected intradermally with Coryneb acterium pseudotuberculosis. The doses of infection were 1 x 10(5) and 5 x 10(4) colony-forming units (cfu) for groups 1 and 2, respectively. Thereaft er, a goat from each group was killed every 2-3 days and examined for gross and microscopic caseous lesions in the draining lymph nodes. Bands or zone s of macrophages and polymorphonuclear granulocytes were observed microscop ically on the second day of infection in both groups. Gross caseous lesions were observed from days 8 and 9 of infection, respectively. Positive bacte rial agglutination test and haemolysis inhibition test titres were detected after 15-17 days and 20-25 days of infection, respectively. These results indicated that caseous lymphadenitis is a subacute disease with an incubati on period of 8-9 days, but that it is not detectable serologically until af ter 15 days of infection.