Relationships between prevalence of Leptospira interrogans in cattle, and regional, climatic, and seasonal factors

David A. Miller From the National Veterinary Services Laboratories, Science and Technology, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, IA 50010 (Miller, Wilson), and the Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011 (Beran).

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Mark A. Wilson From the National Veterinary Services Laboratories, Science and Technology, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, IA 50010 (Miller, Wilson), and the Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011 (Beran).

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George W. Beran From the National Veterinary Services Laboratories, Science and Technology, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, IA 50010 (Miller, Wilson), and the Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011 (Beran).

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SUMMARY

On the basis of serologic test results and isolation of leptospires from mature cattle, distribution and prevalence of Leptospira interrogans serovars and genotypes were compared by state and region of the United States. Relationships between isolation rate and month of sample collection, mean regional temperature, and mean regional precipitation were examined. Isolation rate and seroprevalence were significantly (P < 0.001) higher for southeastern, south central, and Pacific coastal regions than for other regions of the United States. Isolates of genotypes hardjo-bovis A and kennewicki A and B, and of serovar grippotyphosa appeared to be randomly distributed. Genotype hardjo-bovis B isolates came from a southern area of the country that extends from Georgia to New Mexico. To the authors’ knowledge, this is the first recorded isolation of serovar hardjo from Hawaii. Although significant relationship was not documented between isolation rate and month or season of the year, seroprevalence for summer, fall, and winter was significantly (P < 0.001) higher than that for spring. Regional isolation rate was related more to mean temperature (r = 0.83; P < 0.05) than to mean precipitation amount (r = 0.34; P > 0.50).

SUMMARY

On the basis of serologic test results and isolation of leptospires from mature cattle, distribution and prevalence of Leptospira interrogans serovars and genotypes were compared by state and region of the United States. Relationships between isolation rate and month of sample collection, mean regional temperature, and mean regional precipitation were examined. Isolation rate and seroprevalence were significantly (P < 0.001) higher for southeastern, south central, and Pacific coastal regions than for other regions of the United States. Isolates of genotypes hardjo-bovis A and kennewicki A and B, and of serovar grippotyphosa appeared to be randomly distributed. Genotype hardjo-bovis B isolates came from a southern area of the country that extends from Georgia to New Mexico. To the authors’ knowledge, this is the first recorded isolation of serovar hardjo from Hawaii. Although significant relationship was not documented between isolation rate and month or season of the year, seroprevalence for summer, fall, and winter was significantly (P < 0.001) higher than that for spring. Regional isolation rate was related more to mean temperature (r = 0.83; P < 0.05) than to mean precipitation amount (r = 0.34; P > 0.50).

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