title: Serologic and clinical responses of premunized, vaccinated, and previously infected cattle to challenge exposure by two different Anaplasma marginale isolates.
abstract: Two Anaplasma marginale isolates, one originating in Florida (FAM) and the other from Virginia (VAM), were compared immunologically by cross-challenge exposure of 14 Anaplasma carrier cattle, 8 previously infected cattle, and 6 splenectomized carrier calves. In addition, 28 cattle vaccinated with a commercially available adjuvant killed vaccine and 22 nonvaccinated cattle were challenge exposed with either FAM or VAM. A detectable clinical response was not produced by either FAM or VAM challenge exposure in carrier and previously infected cattle; however, evidence of A marginale growth as characterized by low percentages of parasitemia and increased serum complement-fixation titers was seen in carrier cattle given a heterologous challenge organism and in previously infected cattle inoculated with either homologous or heterologous organisms. Among splenectomized calves, there was virtually no cross protection to the heterologous challenge exposure, whereas a homologous challenge failed to elicit any detectable response. Vaccinated cattle were resistant to VAM exposure, but the clinical response to FAM exposure was severe with a 47% mortality. Most of these cattle displayed typical acute anaplasmosis that was only marginally less severe than that encountered in nonvaccinated cattle.
mesh_terms: D000709:Anaplasma / Q000276:immunology* / Q000472:pathogenicity; D000712:Anaplasmosis / Q000276:immunology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis; D000942:Antigens, Bacterial / Q000276:immunology*; D002353:Carrier State / Q000276:immunology / Q000662:veterinary; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology*; D003168:Complement Fixation Tests; D000939:Epitopes; D005260:Female; D005431:Florida; D008297:Male; D013156:Splenectomy / Q000662:veterinary; D014611:Vaccination / Q000662:veterinary; D014768:Virginia
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D000939:Epitopes