Arboviruses are viruses spread by arthropods, which includes mosquitoes. Mosquito-borne viruses seen in Pinellas are West Nile virus, St. Louis encephalitis, and Eastern Equine Encephalitis.
Pinellas County monitors the mosquito population through traps located around the county. Mosquitoes are more prevalent in the hot, rainy months of the year but, even when general drought conditions exist in the county, mosquitoes can remain in swampy and tidal areas.
We also monitor viruses through “sentinel” chickens caged in eight target locations. Routine blood tests on these chickens detect virus antibodies—an early alert that a virus is present locally.
Chickens are effective sentinels because if bitten by a mosquito carrying a virus, they develop the antibodies much like we do for the common cold. The virus does not harm the chicken; however, because they have already developed antibodies, these chickens are no longer effective sentinels and cannot be used for further testing. Once a sentinel chicken tests positive, it is removed from the coop, as it will have those antibodies for the rest of its life.
Chickens are unique in that they do not pass on the virus. They can tell us it the virus is present without being part of the cycle.
Birds are usually the source of infection for mosquitoes, which can then spread the infection to other birds, horses, and people. The viruses normally cycle between birds and mosquitoes, with the virus reproducing and increasing in number within the host organism.
Different arboviruses are carried and transmitted by different kinds of mosquitoes. The presence of an arbovirus in a particular area depends on the availability of specific types of mosquitoes that can carry it and the number of birds in an area. Virus rates are often amplified during dry periods when the birds and mosquitoes are congregated in areas where water is available.
- Mosquito Control has 8 chicken coops in the county.
- Chickens are used as a screening mechanism to determine the presence or level of virus circulating in the mosquito-bird cycle.
- Mosquito Control staff take samples of the chickens’ blood each week; the Florida Department of Health Laboratory screens the samples for the presence of St. Louis encephalitis (SLE), Eastern equine encephalitis (EEE), and West Nile virus (WN).
- The Pinellas County Health Department alerts Mosquito Control when an imported case, contracted in another area or country, of malaria or dengue is diagnosed. Mosquito Control then does surveillance and treatment, if warranted, to prevent the disease from being transmitted here.
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