In the United States, slaughter surveillance combined with other measures has effectively maintained a very low prevalence of bovine tuberculosis (bTB). However, bTB continues to be sporadically detected, causing substantial economic burden to the government and cattle producers. To detect the infection earlier and reduce sudden economic losses, additional risk-based surveillance of live animals might be more cost-effective than slaughter surveillance alone to detect and prevent bTB infection. The objective of this study was to evaluate alternative risk-based surveillance strategies targeting high-risk herds to complement slaughter surveillance in a region with very low bTB prevalence. We developed an integrated within- and between-herd bTB transmission model with simulated premises-level cattle movements among beef and dairy herds in Minnesota for 10 years. We constructed ten risk-based surveillance strategies for beef herds and dairy herds, and predicted the epidemiological outcomes and costs for each strategy in combination with slaughter surveillance. Our models showed that slaughter surveillance alone resulted in low risk of between-herd transmission with typically small outbreak sizes, and also cost less compared to alternative risk-based surveillance measures. However, risk-based surveillance strategies could reduce the time to detect infection and the time to reach disease freedom by up to 9 months. At a higher initial prevalence, alternative risk-based surveillance could reduce the number of infected herds and shorten the time to disease freedom by almost 3 years (34–35 months). Our findings suggest that risk-based surveillance could detect infection more quickly and allow affected regions to reach disease freedom faster. If the bTB status of the affected regions changes after an outbreak happens, the reduced time to disease freedom could reduce the economic impact on the affected region.
Bibliographical noteFunding Information:
Bovine TB outbreaks pose a substantial economic burden to both cattle producers and government agencies at state and federal levels due to the costs of testing, indemnification, and movement restrictions. When an infected herd is detected, the producers are encouraged to depopulate or required to remain under quarantine for an extended period until its bTB-free status can be confirmed through repeated negative skin-test results. The skin tests in use in the US include the caudal fold tuberculin (CFT) test, followed by comparative cervical tuberculin (CCT) test (and sometimes other tests) among cattle with positive CFT test results ( USDA-APHIS, 2004 ). The financial burden of depopulation to the infected herd is partially mitigated by federal indemnity funding through the Commodity Credit Corporation or through contingency funds from USDA Animal and Plant Health Inspection Service ( United States Animal Health Association ), which shifts costs to the federal government. State and federal governments bear other outbreak costs, including the cost of the epidemiologic investigation to identify potential sources of infection and potential exposures to other herds. If more than one herd is confirmed bTB-positive within an affected region (e.g., a geographic zone, often a state, designated by animal health agencies for disease eradication purposes), the region may lose its bTB-free status, resulting in movement restrictions on other herds in the vicinity, increasing regulatory costs and reducing revenue. The 2005–2009 bTB outbreak in Minnesota, which involved 12 infected herds, was estimated to cost approximately $60 million for epidemiological investigation, depopulation, and decontamination of infected herds ( Buhr et al., 2009 ). This estimate did not include the cost of ongoing heightened surveillance efforts in the region, nor the economic impact of the outbreak on the broader Minnesota cattle industry.
This research was supported by the USDA-NIFA AFRI Foundational Program [grant #2013-01130 ]. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author and do not necessarily reflect the view of the U.S. Department of Agriculture.
We thank the USDA-APHIS-VS-STAS for providing the data on 1000 simulated county-level cattle movement networks (USAMM) and for input from Drs. Beth Thompson, Linda Glaser, and Stacey Schwabenlander of the Minnesota Board of Animal Health. This work was supported by the USDA-NIFA AFRI Foundational Program, grant #2013-01130.
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- Bovine tuberculosis
- Cattle movements
- Cost-effectiveness analysis
- Disease spread
- Mycobacterium bovis
- Targeted surveillance
PubMed: MeSH publication types
- Journal Article