Molecular Epidemiologic and Geographic Information System Analyses of Mycobacterium bovis Isolates from North America

Abstract

Mycobacterium bovis, the etiological agent of bovine tuberculosis has been reported in a wide variety of domestic animals and wildlife. In the United States, the bovine tuberculosis eradication program was launched in 1917 during a period when the prevalence of disease was estimated to be 5% in cattle and 15% in swine. By 1991, 41 states plus the Virgin Islands were accredited tuberculosis free. During the past ten years bovine tuberculosis in the state of Texas has been on the rise and Texas now harbors more than 50% of M. bovis infected U.S. cattle. Epidemiological causes of disease are presumed to include importation of infected animals, incomplete depopulation of infected herds, movement of tuberculosis exposed animals between herds and transmission from unidentified wild life reservoirs. Identification and differentiation of various strains using recently developed DNA marker techniques would provide a better understanding of the epidemiology of M. bovis infections and effective control of the disease. In the present study, M. bovis isolates originating from North American cattle, deer and other were fingerprinted using IS6110 and DR probes. The isolates were categorized into 85 distinct RFLP types based on a combination of individual fingerprint patterns. This method revealed that bovine tuberculosis cases in North America are caused by strains exhibiting different RFLP types. A significant proportion of bovine isolates harbored multiple IS6110 copies which is a characteristic feature of isolates originating from animals other than cattle.