Evaluation of surveillance and sample collection methods to document freedom from infectious bovine rhinotracheitis in cattle populations.
OBJECTIVE
To assess the sensitivity of the current surveillance program used in Denmark for detecting outbreaks of infectious bovine rhinotracheitis (IBR) at the herd level and to evaluate the impact of alternative sample collection strategies on the sensitivity of the system in an acceptable time frame.


METHODS
Data from the Danish Central Husbandry Register on cattle of 24,355 and 25,233 beef herds and on 13,034 and 12,003 dairy herds in the years 2000 and 2001, respectively.


METHODS
Surveillance programs were evaluated under current sample collection conditions and under 3 alternative scenarios by use of simulation modeling. Data from the current detection component of the surveillance system were used as input, taking into consideration the sensitivity and specificity of bulktank milk and serologic testing.


RESULTS
The current system identifies infected dairy herds within a 3-month period with desired accuracy largely because of the test characteristics and number of bulk-tank milk samples. The system is less likely to detect infected beef herds in a timely manner because surveillance in beef herds depends solely on serologic testing at the time of slaughter. The efficiency of surveillance in dairy cattle herds was not decreased substantially when the slaughter-surveillance component was omitted.


CONCLUSIONS
Geographically targeted sample collection during the high-risk season (winter) was predicted to increase the probability of rapid detection of IBR infection in cattle. This approach can be used for assessing other surveillance systems to determine the best strategies for detection of infected herds.
Chriel
Mariann
M
Danish Dairy Board, Frederiks Alle 22, DK-8000 Aarhus C, Denmark.
Salman
M D
MD
Wagner
Bruce A
BA
D000818:Animals; D002417:Cattle; D003612:Dairying / Q000379:methods; D016208:Databases, Factual; D003718:Denmark / Q000453:epidemiology; D005069:Evaluation Studies as Topic; D005260:Female; D007241:Infectious Bovine Rhinotracheitis / Q000453:epidemiology*; D008297:Male; D008892:Milk / Q000382:microbiology*; D012680:Sensitivity and Specificity; D018571:Sentinel Surveillance / Q000662:veterinary*; D012698:Serologic Tests / Q000662:veterinary; D013048:Specimen Handling / Q000379:methods / Q000662:veterinary; D013997:Time Factors