An official website of the United States government.
<OL> <LI> Create a veterinary practitioner network dedicated to the surveillance of foreign animal diseases. The working hypothesis for this research objective is that private veterinary practitioners are the first line of defense to prevent the incursion of an FAD from becoming an uncontrolled epidemic. The skills and expertise of practicing veterinarians are not being exploited for active surveillance of FADs. A skilled network of practicing veterinarians will improve our ability to detect FADs and protect U.S. agriculture. <LI> Determine the effectiveness of three active surveillance techniques for detection of foreign animal diseases by using currently endemic cattle pathogens that mimic the epidemiology, pathogenicity, and virulence of FADs. The working hypothesis for this research objective is that active surveillance strategies using specimens that are currently collected for other disease programs are an equally sensitive method for detecting low prevalence, low morbidity diseases as more comprehensive, and expensive, survey methods. It is hypothesized that current brucellosis surveillance programs could be modified to include testing for select agents determined to be of high consequence to U.S. agriculture and public health. It is further hypothesized that active surveillance of clinically ill cattle (targeted) is necessary for the rapid detection of diseases that are more virulent with higher morbidity proportions. Using endemic cattle diseases that mimic FADs is necessary for the development of future FAD surveillance programs in the absence of actual outbreaks. <LI> Develop a decision support system for the initiation of a foreign animal disease (FAD) investigation based on spatiotemporal clustering of results from an imperfect screening test. The working hypothesis for this research objective is that intensive surveillance programs for FADs using tests with imperfect diagnostic specificity will lead to the unnecessary investigation of false-positive test results unless the appropriate decision tools are developed. It is hypothesized that all screening tests will have some proportion of false-positive results and mechanisms can be developed to account for background levels of spatiotemporal clustering of these results to prevent unnecessary and costly FAD investigations including quarantines and hold orders. Developing these mechanisms is necessary for the design and implementation of future surveillance systems.
NON-TECHNICAL SUMMARY: The intentional or accidental introduction of a foreign animal disease poses a great risk to the animal agriculture industry of the United States. The purpose of this project is to determine the most effective surveillance system for foreign animal diseases of cattle by creating a network of veterinary practitioners and its comparison to other survey techniques.
<P>
APPROACH: A practitioner network has been formed based on the American Veterinary Medicine Association (AVMA) member directory. A brief mailing was performed describing the objectives of the current proposal and included a postcard for the veterinarian to return stating his or her interest level in participating in this type of study. Educational materials will be developed concerning foreign animal disease diagnosis and surveillance and distributed to the veterinarians participating in this network in addition to currently available materials such as the CD version of the Grey Book available from the United States Animal Health Association (USAHA). A monthly newsletter will be created including a disease of the month feature spotlighting pertinent pathological and epidemiological characteristics of different foreign animal diseases. The newsletter will also contain updates concerning the research activities including the number of samples submitted and disease prevalences. Practitioners enrolled as part of the surveillance network will be requested to submit serum samples from cattle with illnesses that cannot be definitively diagnosed based exclusively on physical exam findings. Practitioners will be asked to submit serum and data from 2 cattle per month over a 2-year sample collection period. A random sample of serum specimens submitted to the State-Federal Laboratory in Austin, Texas will be selected for inclusion in the research project. A non-probability sample of Texas cattle will also be evaluated as part of this research project to compare to the other methods of active surveillance. These cattle were sampled in a manner proportional to the overall cattle distribution throughout Texas. The total number of serum samples tested over the 2-year period will be 1000 for each surveillance system. Submitted samples will be tested for select infectious agents including Paratuberculosis, Bovine Leukemia Virus, Bovine Virus Diarrhea, and West Nile Virus. The owner may also choose not to view the results in which case only the researchers directly involved with the study will ever know the disease status of the sampled animals. Statistical simulation models will be developed and used as a decision support system to identify disease clusters caused by the introduction of a foreign animal disease. Spatiotemporal scan statistical methods are often used for these types of problems. These models can also be adjusted for covariates to account for a non-random distribution of cases through time and space (non-uniform baseline risks). The surveillance for FADs will necessitate modeling the baseline risk of a false-positive test result, rather than the baseline level of disease. Statistically significant clusters found after adjusting for the covariate-adjusted risk of false-positives will be identified as clusters. Covariates that may be important for modeling false-positive reactions include cattle type (beef versus diary) and ecological factors such as climate, which may be associated with presence of cross-reacting organisms.
<P>
PROGRESS: 2005/09 TO 2009/08 <BR>
OUTPUTS: Two thousand adult lactating dairy cattle from 76 herds in Puerto Rico were tested for encephalomyocarditis using a virus neutralization assay. Farm polygons were created as squares with an area equal to the farm size and centered at the coordinates of the milking parlor where the cattle were sampled. Land use and environmental factors of Puerto Rico were extracted and descriptive statistics for each variable within the farm polygons were summarized. Land use and environmental factors were then evaluated for associations with encephalomyocarditis in addition to anaplasma and babesia that were previously evaluated for these cattle. Encephalomyocarditis was chosen as a picornavirus that could serve as a model for foot-and-mouth disease virus. Accuracy of tests for anaplasmosis were estimated to determine the most sensitive test for screening and surveillance in lactating dairy cattle. A surveillance network consisting of 58 private veterinary practitioners was developed in Texas. These veterinarians submitted blood samples for serologic evaluation of Bovine Viral Diarrhea Virus (BVDV), Bovine Leukosis Virus (BLV), Johne's disease (JD), and West Nile Virus (WNV) in cattle with illnesses of unknown etiology. Purposive herd sampling (1084 cattle) and market cattle (1200 cattle) testing were also performed. Results from these three surveillance methods were evaluated by comparing prevalence and producing risk maps for each disease. New methods to evaluate spatial predictors of disease seropositivity were developed and results have been submitted for publication. Foreign animal disease (FAD) specific posters and newsletters were created to keep this network informed concerning progress of the research as well as providing information for highlighted FADs. Eight quarterly reports comprised of FAD posters and research-specific newsletters were sent to these practitioners. The FAD topics for the 8 newsletter/poster combinations were rinderpest, avian influenza, classical swine fever, heartwater, screwworm myiasis, contagious equine metritis, and peste des petits ruminants, and foot-and-mouth disease. <BR> PARTICIPANTS: Geoffrey T. Fosgate - PI Linda Highfield - Post-doctoral researcher. Coordinated testing for encephalomyocarditis, managed spatial data, and performed advanced spatial analytical techniques for the fulfillment of study objectives. <BR> <BR>
IMPACT: 2005/09 TO 2009/08<BR>
The overall prevalences of the 4 diseases were 1.3% (30/2362), 13% (317/2362), 2.3% (55/2362), and 0.2% (8/2362) for BVDV, BLV, JD, and WNV respectively. Herd testing has revealed prevalences of these diseases of 0.4% (4/1084), 2.8% (30/1084), 2.6% (28/1084), and 0% (0/1084). Market cattle testing has shown 1.9% (23/1200), 22% (258/1200), 1.6% (19/1200), and 0.4% (5/1200). Veterinarian submitted sample results were 3.8% (3/78), 37% (29/78), 10% (8/78), and 3.8% (3/78). These findings supported our hypothesis that different methods of sample collection affect the observed prevalence of disease. Targeted surveillance of clinically ill cattle was the most sensitive technique for all evaluated pathogens even though these conditions were not clinically evident upon physical examination. Existing surveillance methods for regulated disease, for example brucellosis, might be effective to routinely screen for select FADs depending upon the known epidemiology. The intentional or accidental introduction of a foreign animal disease (FAD) poses a great risk to animal agriculture of the United States. The purpose of this project is to determine the most effective surveillance system for FADs of cattle by creating a network of veterinary practitioners and its comparison to other possible sampling techniques. Development and maintenance of this surveillance network will improve practitioner awareness of FAD conditions and reporting procedures. Dissemination of educational materials related to select FADs will also improve the preparedness of practitioners to recognize and respond to potential outbreaks of these devastating diseases. Targeted sampling of clinically ill cattle through the recruitment of private veterinary practitioners provided a highly sensitive surveillance system for detection of evaluated diseases. Diagnostic laboratory submissions from clinically ill cattle could also be used as an efficient method for documenting disease freedom from FADs based on the principles of risk-based surveillance. Statistical tools are being developed that will optimize decision rules for the initiation of FAD outbreak investigations based on results from an imperfect screening test using the expected spatial clustering of false-positive results. The statistical techniques employed in these analyses have not been previously applied towards the development and evaluation of veterinary surveillance systems.