Objectives—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.
Sample Population—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.
Procedures—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 and Clinical Relevance—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. (Am J Vet Res 2005;66:2149–2153)