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The Honolulu Advertiser
Posted on: Friday, September 7, 2007

Do your part to prevent mosquito-borne illnesses

By Jay Deputy

You may have noticed the heightened state of awareness from the state Department of Health concerning mosquito-borne diseases such as West Nile virus and dengue fever, not to mention yellow fever and Japanese encephalitis. Although none of these diseases have reached the Hawaiian Islands, two of the mosquito species that can carry the viruses causing them are here in full force.

I recently read a report on West Nile virus and was surprised to learn that it was first reported in New York City and a few other Northeastern states in 1999, and by 2005 had spread to all of the lower 48. Hawai'i and Alaska are the only two states the virus has not yet hit.

Like some of the other mosquito-borne diseases, West Nile virus infects different hosts. Birds are the most common host, and the disease is usually fatal to them. In fact, infected birds seem to be the most likely way that the virus is introduced into a new area. That's why the Department of Health asks that we call 211 to report any dead birds so they can run tests to confirm if West Nile is in Hawai'i.

The virus can spread rapidly when mosquitoes bite infected birds the newly infected mosquito bites and transmits the virus to other birds and animals, including humans. Horses are particularly susceptible. Based on the history of the virus on the Mainland, West Nile is practically impossible to eradicate once it is established.

Most healthy people infected with West Nile virus have no apparent long-term effects, but up to 20 percent of those infected suffer flu-like symptoms that may last three to 24 days; in some cases a general fatigue may last for months. About 1 percent of those infected suffer a swelling of the brain, resulting in vision loss, paralysis, coma and possibly death. Older people and those with weakened immune systems are at greatest risk. There is no human vaccine and antibiotics are ineffective.

Imagine the disastrous effects of a full-scale West Nile virus outbreak in Hawai'i. The Department of Health predicts a yearly total of 4,000 people would suffer symptoms, with 190 hospitalized, 133 with severe illness and eight to 10 deaths. Since 1999, when it was first reported in America, there have been 24,000 reported cases of the virus and 960 human deaths.

You can help avoid the crisis.

  • Eliminate standing water. Mosquitoes require standing water to reproduce. They deposit their eggs in water where the larval stage, commonly known as "wrigglers," develop into adult mosquitoes.

    Thoroughly inspect your home for breeding sites. Common sites are in water found in vine bowls, clogged roof gutters, cans, bottles, old tires, unused swimming pools, unused fish ponds, pineapple lilies, spider lilies, hollow bamboo stumps, uncapped hollow tile walls, uncapped fence pipes and overflow trays under house plants. At least once a week, tip over potted plants (especially bromeliads) to prevent water from accumulating. Alternatively, plants can be washed out, provided the water is dispersed and evaporates. Water should not be held in an uncovered container for more than three days. Old refuse, tires and unused pots and containers should be disposed of or kept in such a manner that water cannot accumulate in them.

    Use mosquito-eating fish, such as guppies, in fishponds, unused swimming pools or other large containers that cannot be removed or emptied. But don't release the fish into natural water sources such as streams or lakes, as they are not a native species.

  • Temporarily eliminate adult mosquitoes with aerosol insecticides. Use insecticides labeled for controlling mosquito larvae in breeding sites that cannot be emptied or removed. For personal protection, use approved insect repellents containing DEET at 30 percent to 33 percent for adults and 7.5 percent for children less than 12 years old. DEET should not be used on children less than 2 years old. Another material, picaridin at 7 percent, also is recommended by the U.S. Centers for Disease Control and Prevention.

  • Control mosquitoes through larvaciding. It is by far the best means of chemical mosquito control. These materials, when used correctly, keep mosquitoes from becoming adults and therefore keep the population down. The more modern types of larvacides are more environmentally friendly and are mainly biological controls. Biolarvacides are formulations of bacteria that eat, infect or cause the mosquitoes to die off before reproducing. They target actively feeding mosquito larvae and do not harm most other aquatic invertebrates.

    Bacillus thuringiensis var. israelensis (Bti)(trade names: Vectobac, Teknar and Bactimos to name a few), is best for clear water with lower organic content. Another bacterium, B. sphaericus (trade name Vectolex), works in turbid or heavily organic water. These biolarvacides are only effective against actively feeding larvae, and do not affect mosquito eggs, pupae or adults. These materials are available from pesticides distributors. Always follow the label exactly for correct use.

    Install or repair window screens and doors to keep out mosquitoes. Screens are your best protection against mosquito nuisance in your home.

    The Health Department is hard at work implementing programs to prevent the introduction of West Nile virus and similar diseases into our state. They stress that the only chance to control the virus is to have public support in finding it early, confine it to a small area and hit hard with rapid response. Current programs include bird quarantine and postal embargo; encouraging people to report dead birds; using insecticides to kill mosquito larvae, especially in ports of entry; expansion of state laboratory capacity; and media outreach and education. I hope in some small way this article can help increase awareness.

    Jay Deputy is an education specialist in landscape horticulture and turf at the University of Hawai'i-Manoa, Department of Tropical Plant and Soil Sciences, and Hawai'i state administrator for the Certified Landscape Technician Program sponsored by the Landscape Industry Council of Hawaii. Got a lawncare or turf question? Write to deputy@hawaii.edu.