Comparing Control Strategies against Foot-and-mouth Disease: Will Vaccination be Cost-effective in Denmark?20 August 2013
Depopulation in zones is the measure most likely to control an outbreak of foot-and-mouth disease (FMD) in Denmark, according to a new study there although suppressive vaccination scenarios would be a cheaper option under some circumstances. Most of the costs would be attributable to the loss of exports.
Recent FMD outbreaks in Europe have highlighted the need for assessment of control strategies to optimise control of the spread of the disease, according to A. Boklund and colleagues at the Technical University of Copenhagen.
The objectives of their study - published in the journal, Preventive Veterinary Medicine - were to assess the epidemiological and financial impact of simulated FMD outbreaks in Denmark and the effect of using ring depopulation or emergency vaccination to control these outbreaks. Two stochastic simulation models (InterSpreadPlus (ISP) and the modified Davis Animal Disease Simulation model (DTU-DADS)) were used to simulate the spread of FMD in Denmark using different control strategies.
Each epidemic was initiated in one herd (index herd), and a total of 5,000 index herds were used. Four types of control measures were investigated:
- a basic scenario including depopulation of detected herds, 3-km protection and 10-km surveillance zones, movement tracing and a three-day national standstill
- the basic scenario plus depopulation in ring zones around detected herds ("depop")
- the basic scenario plus protective vaccination within ring zones around detected herds, and
- the basic scenario plus protective vaccination within ring zones around detected herds.
Disease spread was simulated through direct animal movements, medium-risk contacts (veterinarians, artificial inseminators or milk controllers), low-risk contacts (animal feed and rendering trucks, technicians or visitors), market contacts, abattoir trucks, milk tanks, or local spread.
The two simulation models showed different results in terms of the estimated numbers. However, the tendencies in terms of recommendations of strategies were similar for both models. Comparison of the different control strategies showed that, from an epidemiological point of view, protective vaccination would be preferable if the epidemic started in a cattle herd in an area with a high density of cattle, whereas if the epidemic started in an area with a low density of cattle or in other species, protective vaccination or depopulation would have almost the same preventive effect.
Implementing additional control measures either 14 days after detection of the first infected herd or when 10 herds have been diagnosed would be more efficient than implementing additional control measures when more herds have been diagnosed.
Protective vaccination scenarios would never be cost-effective, whereas depopulation or suppressive vaccination scenarios would most often be recommended.
Looking at the median estimates of the cost-benefit analysis, depopulation in zones would most often be recommended, according to Boklund and colleagues although, in extreme epidemics, suppressive vaccination scenarios could be less expensive.
They added that the vast majority of the costs and losses associated with a Danish epidemic could be attributed to export losses.
Boklund A., T. Halasa, L.E. Christiansen and C. Enøe. 2013. Comparing control strategies against foot-and-mouth disease: Will vaccination be cost-effective in Denmark? Preventive Veterinary Medicine. 111 3–4):206–219.
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