Sentinel Chicken Surveillance Programs: Pay Attention to Safety

The danger from West Nile virus is very real in Florida. There is great potential in Florida for a substantial number of human and horse cases. There will likely be a West Nile virus epidemic in Florida within the next five years. This epidemic could produce 1000-2000 human cases of West Nile in Florida.

The Florida Medical Entomology Laboratory (FMEL) has been a strong advocate for Florida's West Nile, eastern equine and St. Louis arbovirus sentinel surveillance programs. These programs can provide advance warning of mosquito transmission. Most importantly as pointed out repeatedly in Buzz Words, sentinel surveillance is a means to provide information for mosquito control to be more effective. We applaud the efforts of those Florida localities which had not previously had surveillance, that are now developing sentinel chicken surveillance programs.

It is essential that sentinel chicken surveillance programs be designed correctly to acquire the desired information. It is even more important that those responsible for operating surveillance have the appropriate training and experience to conduct the required operations in an absolutely safe manner. This is not a trivial concern. Everyone conducting sentinel chicken surveillance must be attentive to this issue. Surveillance personnel are likely to come into close contact with dangerous pathogens that are listed as biosafety level 2 or 3 pathogens. There is potential, of varying risk, that a surveillance worker could be infected as part of their work duties. Whenever such a situation is possible it is incumbent on the responsible organization to do the following:

  • Develop safe standard operating procedures (SOPs) designed to protect workers from infection.
  • Require appropriate safety training of all workers that clearly explain risks and the precautions instituted to prevent the risks.
  • Ensure that all workers are capable of following and adhering to SOPs.
  • Provide supervisory oversight by individuals considered expert in the methods and also with demonstrated proven ability to work safely in such a program.
  • Develop the appropriate program that ensures continual monitoring of worker activities to maintain high levels of safety.

Clearly West Nile virus poses new twists on surveillance operations. Langevin et al. (2001) ( showed the following:

  • Chickens develop a short and relatively low viremia, compared to many other birds, upon infection with West Nile virus.
  • Chickens may shed virus from the cloaca and virus may be found in feces.
  • Chickens have the capability of infecting cage mates through shed virus in the absence of mosquitoes.

The magnitude of these risks is certainly less in chickens compared to many other species of birds, yet the risk is real and there is potential. Accordingly the authors advise that animal care handlers should take personal protection precautions in handling and working with sentinel chickens. This advice is simply a standard precaution for these pathogens. These are dangerous pathogens and potentially infected animals should not be handled cavalierly or by inexperienced personnel. There are several possible routes for West Nile virus infection that should be considered for workers involved in a sentinel chicken surveillance program:

  • Infection via the bite of infected mosquitoes that are near or have fed on the sentinel birds.
  • Infection via contact with viremic chicken blood, through accidental autoinoculation, spilled blood and entry through abrasions, etc. The aerosol route for West Nile infection is less of a possibility, though not impossible, and should not be ruled out.
  • Infection through contact and exposure via infected tissues, feces, etc.

There are SOPs to protect workers from any risk from West Nile and other pathogens stemming from their job duties. Safety and training programs can be found in a variety of documents: CDC-NIH Guidelines: Biosafety in Microbiological and Biomedical Laboratories,; University of Florida Safety Manuals and Documentation ; Arthropod Containment Guidelines

It is unethical to place ill trained workers in situations where their chance of infection is higher due to inadequate safety, unsafe procedures, inadequate training and lack of appropriate supervision. This responsibility on the part of the supervisor or leader is absolutely required even if there is similar risk outside the work environment. A sentinel chicken surveillance program can be run and operated safely. It has been done so for many years in Florida through trained, experienced professionals who are specifically trained and dedicated to this important program. It requires planning, training and a commitment to protect workers from dangerous agents. My advice is to have well thought out SOPs in place to protect your employees.

Walter J. Tabachnick, Director
Florida Medical Entomology Laboratory