Bacteriologic, ecologic, serologic, and immunogenetic studies of Corynebacterium pseudotuberculosis-induced caseous lymphadenitis in small ruminants

Abstract

Corynebacterium pseudotuberculosis-induced caseous lymphadenitis (CLA) is an economically important chronic disease of small ruminants characterized by abscessation of either or both lymph nodes or visceral organs. The concentration of C pseudotuberculosis in purulent exudate and the survival of the microorganism in this exudate was determined. Subcutaneous challenge exposure of goats to 10('7) colony forming units of C pseudotuberculosis resulted in infection. The microflora of the experimentally induced chronic abscesses was evaluated 24 weeks later and the concentration of C pseudotuberculosis was determined. The concentration of the agent in axenic lesions ranged from 2.2 x 10('5) to 2.6 x 10('8) CFU/ml with an average of 2.9 x 10('7) CFU/ml, while in lesions with mixed microflora, it varied from 2.1 x 10('6) to 4.0 x 10('8) CFU/ml with an average of 7.0 x 10('7) CFU/ml. The survival of C pseudotuberculosis on or in a number of different fomites including inanimate surfaces (plastic, wood, and steel), particulate fomites (wood shavings, hay, straw, feces, and soil), and water was determined at 37, 22, and 4 C. The organism generally remained viable for longer time periods when CLA abscess contents were mixed with particulate fomites then when spread on surfaces. Incubation at lower temperatures generally, but not always, extended the survival period for the organism outside the host. Depending upon the source of water C pseudotuberculosis was able to remain viable for up to three days. The survival of C pseudotuberculosis in soil-purulent exudate mixtures was studied in both sterilized and unsterilized soil samples. The organism persisted in most sterilized soil samples for 6 months or more and in an unsterilized sandy loam soil for 3 to 7 weeks. A bacterial agglutination test using a petroleum ether extracted sonicated cell wall antigen was developed for detecting antibodies against C pseudotuberculosis. In conjunction with bacteriologic and pathologic studies this serologic test was used to study prevalence of CLA in a population of mature culled sheep. Data from this study suggested that the bacterial agglutination serodiagnostic test may be useful as an in vitro immunodiagnostic test for ovine CLA. The relationship between ovine lymphocyte antigen (OLA) alleles and predisposition to C pseudotuberculosis-induced ovine CLA was investigated. These disease association studies revealed a relationship between certain OLA alleles and predisposition to either or both superficial and visceral forms of the disease. One OLA allele (214) was significantly associated with predisposition to all forms of CLA.