title: Strain variation in Dermatophilus congolensis demonstrated by cross-protection studies.
abstract: Cross-protection studies were conducted with vaccines prepared from two isolates of Dermatophilus congolensis (designated strain 1 and strain 2). The vaccines were prepared as either heat-inactivated, washed, formalized filamentous phase bacterium, mixed with alum as an adjuvant, and inoculated intramuscularly (type A vaccine) or sedimented live filaments inoculated intradermally (type B vaccine). The vaccinated sheep were challenged with D. congolensis zoospores of one or other strain. Challenge sites were observed for the presence and severity of lesions. Serum antibody levels to D. congolensis were monitored after vaccination and challenge. Type A and B vaccines from both strains produced some reduction in the severity of lesions when sheep were challenged with strain 1 but not with strain 2. Unvaccinated control sheep developed more severe and persistent lesions when challenged with strain 2 than controls challenged with strain 1. Serum antibody levels to the type B vaccine prepared from strain 1 were significantly higher (P less than 0.05) than antibody levels to type B vaccine from strain 2. These findings showed there was significant variation in virulence and antigenicity between these two isolates of D. congolensis.
authors.affiliation: Animal Health Laboratories, Department of Agriculture, South Perth, Australia.
authors.forename: T M
authors.initials: TM
authors.lastname: Ellis
authors.forename: S S
authors.initials: SS
authors.lastname: Sutherland
authors.forename: G
authors.initials: G
authors.lastname: Davies
mesh_terms: D000192:Actinomycetales / Q000276:immunology* / Q000472:pathogenicity; D000193:Actinomycetales Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001428:Bacterial Vaccines / Q000276:immunology*; D003429:Cross Reactions; D005260:Female; D007156:Immunologic Memory; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000382:microbiology; D015164:Vaccines, Inactivated / Q000276:immunology; D014774:Virulence
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D015164:Vaccines, Inactivated