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Disease Surveillance Part 1

Role of Disease Surveillance and Reporting

The threat of diseases is a daily reality for all chicken farmers. It is important for farmers to be aware and prepared for any introduction of both new and old diseases. Biosecurity remains a very important aspect of disease control and management. Of equal importance, is the awareness of the disease status of the farm, status of the new birds on the farm and also the disease status of the personnel with particular reference to zoonotic diseases. Continued surveillance of the farm is very important to create an awareness of the current status as well as picking up any new disease introductions. This enables the farmers and veterinarians to control the diseases before they can spread widely throughout the farm as well as nationally.

The agency is in the process of investigating disease reporting systems that will be used by the veterinarian to continuously update the disease status of the national flock. The veterinarian will require the participation of the farmers to create a relevant system. In the long run, the industry should be able to introduce tools to fight existing diseases and prevent the spread of new diseases.

This series of articles aims to provide the farmers with the relevant facts around disease surveillance and reporting.

What is disease surveillance?

Disease surveillance is an information-based activity involving the collection, analysis and interpretation of large volumes of data originating from a variety of sources.

The information collated is then used in a number of ways to
• Evaluate the effectiveness of control and preventative health measures
• Monitor changes in infectious agents e.g. trends in development of antimicrobial resistance
• Support animal health planning and the allocation of appropriate resources within the system.
• Identify high risk populations or areas to target interventions
• Provide a valuable archive of disease activity for future reference.

To be effective, the collection of surveillance data must be standardized on a national basis and be made available at local, regional and national level.

Types of surveillance

Passive surveillance
Passive surveillance often gathers disease data from all potential reporting animal health. The data is reported on an on-going basis without any active solicitation by authorities.

Passive surveillance is the most common type of surveillance in humanitarian emergencies. Most surveillance for communicable diseases is passive. The surveillance coordinator may provide training to health workers in how to complete the surveillance forms, and may even send someone to periodically collect forms from health facilities. But little attention is given to individual health workers who report the information.

The data requested of each health worker is minimal. Nonetheless, passive surveillance is often incomplete because there are few incentives for health workers to report.

Active surveillance
An active surveillance system provides stimulus to health care workers in the form of individual feedback or other incentives. Often reporting frequency by individual health workers is monitored; health workers who consistently fail to report or complete the forms incorrectly are provided specific feedback to improve their performance. There may also be incentives provided for complete reporting.

Active surveillance requires substantially more time and resources and is therefore less commonly used in emergencies. But it is often more complete than passive surveillance. It is often used if an outbreak has begun or is suspected to keep close track of the number of cases. Community health workers may be asked to do active case finding in the community in order to detect those patients who may not come to health facilities for treatment.

Sentinel surveillance
Instead of attempting to gather surveillance data from all health care workers, a sentinel surveillance system selects, either randomly or intentionally, a small group of health workers from whom to gather data. These health workers then receive greater attention from health authorities than would be possible with universal surveillance.

Sentinel surveillance also requires more time and resources, but can often produce more detailed data on cases of illness because the health care workers have agreed to participate and may receive incentives. It may be the best type of surveillance if more intensive investigation of each case is necessary to collect the necessary data. For example, sentinel influenza surveillance in the United States collects nasopharyngeal swabs from each patient at selected sites to identify the type of influenza virus.

Continued in Part 2

This article is an adaptation of information from Health Protection Surveillance Centre Ie and London School of Hygiene and Tropical Medicine.