Call for Super Chicken
By John Albright, Shasta Mosquito and Vector Control District
One of the important functions we perform at the Shasta Mosquito and Vector Control District is to control the spread of mosquito-borne disease in within the district. I have no idea how difficult this may sound to you, but trust me -- it is beyond the abilities of mere mortals. No amount of squinting through a microscope can tell you which mosquitoes are carrying some sort of disease. I think most of us can agree that it would be preferable to know when mosquitoes are spreading diseases in our area prior to anyone actually becoming ill. So we seem to be stuck between the district biologist's lack of psychic abilities and the public's need to know... or are we? As is often the case when our human senses fall short we turn to other allies within the animal kingdom. Narcotic agents have their drug sniffing dogs, and we in the mosquito business have our "sentinel chickens".
By
day, these protectors of the public good look like your ordinary barnyard fowl
scratching and pecking haphazardly in their rustic little wire-clad domiciles
("chicken pens" is the technical term.) By night, however, when
they are roosting, they become feather-festooned mosquito magnets. In
particular, the chickens look like a late night snack to Culex tarsalis,
a mosquito which transmits several types of equine encephalitis.
Allow me to digress for a while and explain about mosquito-borne equine encephalitis. Since you are probably not a horse, you may wonder what equine encephalitis has to do with you. Well, let me muddy the water further by explaining that equine encephalitis is a bird disease which is sometimes caught by humans. It also causes extremely severe disease in horses, which explains the name equine encephalitis. Encephalitis means swelling of the brain, which is the symptom of the disease in humans and horses which causes us so much concern. Although many human cases probably go undetected, causing mild flu-like symptoms at most, severe cases may lead to hospitalization, coma, brain damage or death. Since horses often die in excruciating agony from equine encephalitis they are probably not the ideal animal to use for routine testing for the transmission of this disease.
Although the virus is most commonly found in the bird population it does not cause disease symptoms in birds. They simply make antibodies to the disease within their bodies and continue their little bird lives. The virus moves from one host to another when Culex tarsalis mosquitoes feed on an infected bird and carry the encephalitis virus to another bird, horse, or human.
The Shasta Mosquito and Vector Control District has located our chicken flocks in areas that are known to be favorite migration routes for the birds and mosquitoes which transport the virus within the state. Blood samples are taken from the chickens by district personnel every two weeks and sent to the state Viral and Rickettsial Disease Laboratory to test for the presence of antibodies to encephalitis virus. This has proved to be a much better use of chickens than examining their entrails to predict the future. In fact chickens tested positive throughout the state for about two months before the first case of transmission to a horse was detected.
In 1997 Chickens tested from Shasta Mosquito and Vector Control District flocks have tested positive for the antibodies to western equine encephalitis (WEE). It is important to understand that chickens which have had WEE or other types of mosquito-borne encephalitis do not pose a health threat to humans or horses. These diseases are only transmitted between animals in the saliva of mosquitoes which have fed on infected animals. As a result the Shasta Mosquito and Vector Control District has stepped up adult mosquito control within the district to prevent the spread of WEE to humans and horses by the Culex tarsalis mosquito. As always we appreciate information from residents of the district about areas where mosquitoes are creating a nuisance.
For More Information:
(530) 365-3768