Posts Tagged ‘encephalitis’

Pesky mosquitoes, they can can bite you, causing considerable itching, and annoy you, buzzing around your ears and coming out of hiding when it’s finally cool enough to enjoy being outside. Mosquitoes can carry disease, which makes mosquito control a priority and a huge drain to budgets in the 61 areas of Florida with mosquito control departments.

Mosquito research has revealed that the antennae of mosquitoes are able to distinguish about fifty different smells, but how to use this information for effective mosquito control is mostly unclear. One exception is a mosquito trap is being developed by Tanzanian scientists at the Ifakara Health Institute, to lure and kill malaria-causing mosquitoes that are attracted to the smell of human feet. This product is expected to be on the market within two years, at an estimated cost of between $4 to $27 per trap.

In Florida, the spread of malaria by mosquitoes was eradicated in the 1940’s. The most common serious illness spread by arthropods (mosquitoes AND ticks) we experience in Florida, today, is encephalities caused by arboviruses. The arboviruses include St. Louis encephalitis virus (SLEV), West Nile virus (WNV), Eastern equine encephalitis virus (EEEV), Western equine encephalitis virus (WEEV), Venezuelan equine encephalitis virus (VEEV), Everglades encephalitis virus (EVEV), and California La Crosse encephalitis virus. People and animals infected with arboviruses are “dead-end hosts,” which means they do not further spread the disease.

Sentinel (warning) chickens are tested for the presence of mosquito borne illnesses. A positive test is a ‘warning’ that mosquitoes carrying disease are present in the area. Testing is also performed on mosquito pools, and people, animals or birds suspected of being infected. Nearby counties have had 9 positive test results this summer for SLEV and 1 positive result for WNV.

One actual case of Dengue Fever, “break-bone fever,” has been reported this summer in Marion County. This is a different virus which is also spread by mosquitoes. Symptoms include bone and muscle ache, pain behind the eye area, abnormal blood clotting and vascular permeability. It is rarely fatal unless the disease progresses to shock or encephalitis. Up to 50% of people infected with dengue do not display symptoms, but can still transmit the virus to mosquitoes.

Most cases of arboviral encephalitis occur from June through September, when mosquitoes are most active, but during a mild winter, mosquitoes can remain active during the winter months. Many people infected with an arbovirus have no symptoms at all. Many show only mild flu-like symptoms such as fever, headache, achiness, and fatigue. Only in rare cases does an arbovirus become neuroinvasive, causing encephalitis and threatening life. The use of antibiotics and antiviral agents has not been shown effective in treating arboviral encephalitis, so treatment focuses on reducing serious complications such as swelling of the brain and respiratory distress.

Currently, their is no commercially available vaccine for humans against arboviruses, but some are in development for humans against WNV. There is a vaccine for horses against WNV and one available for horses, ostriches and emus against EEEV, WEEV and VEEV.

THE FIVE D’s of MOSQUITO PREVENTION are DAWN, DUSK, DRESS, DEET and DRAIN. The prevention of mosquito-borne disease relies on reducing the number of mosquitoes and avoiding mosquito bites. (1) During DAWN and (2) DUSK, avoid being outdoors because this is the time mosquitoes are most actively seeking blood. (3) DRESS in light-colored clothing that covers most of your skin. (4) DEET – Use insect repellents containing DEET and picaridin (most effective) or oil of lemon eucalyptus (less effective and cannot be used on children under the age of three). Permethrin can be applied to clothing and gear (but should not be applied to skin). Read the label to know how a repellent should be applied, how often to reapply it, and if it can be used on a child. No repellent should be used on an infant under the age of two months. Repellents should never be applied near a child’s eyes, ears or mouth or on a child’s hands. A repellent should never be sprayed ON a child; it should be applied to an adult’s hand, then rubbed onto a child’s skin. (5) DRAIN – Check around your property and get rid of common breeding grounds for mosquitoes, such as gutters, pet water dishes, and containers that can hold standing water, such as flower pots, buckets, bottles, pots and pans, coolers, and tires. Discard or store such containers upside-down or tightly closed, and change your pets’ water frequently. Old tires and appliances, other common breeding grounds for mosquitoes, should be hauled away. Pools and spas should have continuous circulation and/or appropriate chlorination.

Phone numbers of area mosquito control agencies: Levy County Mosquito Control (352) 486-5127, Citrus County Mosquito Control District (352) 527-7478, and City of Gainesville Mosquito Control (352) 393-8287.

(Sources: Florida Department of Health Mosquito Guide for 2011 and Live Science July 13, 2011.)

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