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In circumstances where uncontrolled movement of animals has occurred it may be
necessary to conduct serosurveillance before lifting movement restrictions.
Careful consideration must be given to the criteria for sampling, how and where
the samples are to be examined for antibody to FMD virus, and the actions which
will result when positive results are found.
Further details on serosurveillance are found in the 'Laboratory Diagnosis' module
but the following points must be considered:
• The objectives of surveillance must be clearly established before collection of samples begins and must be agreed between the Central Administration, the Veterinary Service in the field and the laboratory responsible for analysis of the samples. Possible objectives might be
• to confirm freedom from infection following stamping out
• to detect viral activity in a vaccinated population
• to establish the effectiveness of a vaccination campaign
Each objective will require a different sampling protocol
• The population to be sampled must be defined in terms of the
• unit of sampling (owner, herd, village, district)
• species of animals to be sampled
• age of animals to be sampled
• Sampling should be based on sound statistical principles by collecting sufficient samples to be able to detect a given prevalence of infection (as determined by the presence of specific antibody) at a given confidence level (e.g., 95% confidence of detecting a 5% prevalence)
• Consideration must be given BEFORE sampling starts as to the actions that will be taken in the event of positive results.
These could be
• If vaccination has been used, it is important to consider how this will influence results and how infected animals can be differentiated from those that have been merely vaccinated (see Prospects for Improved Surveillance)
• Agreement should be reached with the laboratory on the data to be collected for each sample.
Normally this falls into two categories:
• Unit data, i.e., village/owner, number of animals in
the population, epidemiological information relating to the unit such
as previous vaccination, infection etc. Where possible the geographical
coordinates should be supplied to allow analysis within a Geographical
Information System (GIS)
• Sample data, i.e., unit of origin, species, age, sex, vaccinal history
etc, for individual animals
• Full documentation is required if the results are to be used internationally to establish freedom from disease
• All animals sampled should be individually marked so that they can be identified and resampled if required
• Care must be taken in handling and shipping the collected sera to ensure
that they do not present a risk of transmission of infection.
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