Characterization of an outbreak of anthrax in animals in North Dakota

243 cases (2005)

Abstract

The objective of this study was to characterize an outbreak of anthrax among animals in North Dakota in 2005, and determine characteristics and clinical signs associated with the disease. A total of 243 animals (183 cattle, 32 bison, 11 horses, 11 elk, five sheep and one deer) were diagnosed with anthrax at the Veterinary Diagnostic Laboratory at North Dakota State University, Fargo. Anthrax cases were defined as animals with typical clinical signs and positive results of laboratory culture and polymerase chain reaction (PCR) methods. Data for the study were obtained from veterinary laboratory records and questionnaires mailed to producers of affected animals. Anthrax occurred from July 1 to October 12 of 2005. The cases were located in 16 of 53 counties, specifically in eastern North Dakota, with Ransom, Lamoure and Barnes counties reporting most (71%) of the cases. The number of animals affected per premise varied from one to 40. The first cases were reported in bison. Males from all species infected had a higher attack rate (18/1000) than females (3/1000) with a gender ratio of 6:1, respectively. The predominant clinical signs in all cases were sudden death (38%) and bleeding from orifices (17%). Only 11 producers reported having vaccinated animals before the outbreak. Penicillin and tetracycline antibiotics were administered to animals during the outbreak. Forty producers (37%) burned and buried carcasses using commercial disposal services. Sixty-eight producers (63%) disposed of carcasses themselves by either burial only (11%), burned only (4.6%), or burned and buried (84.4%). Animals affected, clinical signs and final outcome were consistent with a natural anthrax outbreak.