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  • Author or Editor: Nora E. Wineland x
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Objective

To determine epidemiologic features associated with reported cases of scrapie in sheep in the United States.

Design

Retrospective study.

Sample Population

Records for scrapie-positive sheep flocks and sheep with clinical signs consistent with scrapie reported to the USDA from 1947 through 1992.

Procedure

Records from the USDA's scrapie control and eradication program were abstracted, entered into a computer database, and statistically analyzed.

Results

1,117 sheep from 657 flocks located in 39 states were scrapie positive during the study period. Seasonal or spatial trends were not evident. Mean yearly proportion of scrapie-positive flocks increased slightly from 1965 through 1992. One hundred sixty-eight rams and 949 ewes were reported to be scrapie positive during the study period, which was slightly more rams than expected if the disease was equally likely to affect rams and ewes. Suffolks (972/1,117; 87%) and Hampshires (68/1,117; 6%) were most commonly affected.

Clinical Implications

The prevalence of scrapie in sheep in the United States is unknown. Bias in this study may have resulted from inconsistencies in available information, misclassification of sheep with clinically suspicious signs of scrapie, and changes in the national scrapie control and eradication program that likely affected willingness of owners and veterinarians to report potentially infected sheep. (J Am Vet Med Assoc 1998; 212:713-718)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate herd-level risk factors for seropositive status of cattle to 1 or more bluetongue viruses.

Animals—110 herds of cattle in Nebraska, North Dakota, and South Dakota.

Procedure—Blood samples were collected before and after the vector season. Samples were tested for antibodies against bluetongue virus by use of a commercially available competitive ELISA. Factors evaluated included descriptors of geographic location and management practices. Trapping of insect vectors was conducted to evaluate vector status on a subset of 57 operations. A multivariable logistic regression model was constructed to evaluate associations.

Results—For the full data set, altitude and latitude were associated with risk of having seropositive cattle (an increase in altitude was associated with an increase in risk, and a more northerly location was associated with a decrease in risk of a premise having seropositive cattle). Import of cattle from selected states was associated with an increase in risk of having seropositive cattle. From the subset of herds with data on vector trapping, altitude and latitude were associated with risk of having seropositive cattle, similar to that for the full model. However, commingling with cattle from other herds was associated with a decrease in risk of seropositivity.

Conclusions and Clinical Relevance—Findings reported here may be useful in generating additional hypotheses regarding the ecologic characteristics of bluetongue viruses and other vector-borne diseases of livestock. Sentinel surveillance programs are useful for documenting regionalization zones for diseases, which can be beneficial when securing international markets for animals and animal products. (Am J Vet Res 2005;66:853–860)

Full access
in American Journal of Veterinary Research