Mosquitoes, Fogging and Chikungunya

The Aedes aegypti mosquito

From the Center for Disease Control, San Juan:

The Aedes aegypti mosquito can transmit the viruses that cause dengue fever and chikungunya. The female mosquito lays eggs in containers with water and plants near the home. It bites people and animals. This species can survive year round in tropical and subtropical climates.

General Information
Aedes aegypti is a small, dark mosquito with white lyre shaped markings and banded legs. They prefer to bite indoors and primarily bite humans. These mosquitoes can use natural locations or habitats (for example tree holes and plant axils) and artificial containers with water to lay their eggs. They lay eggs during the day in water containing organic material (e.g., decaying leaves, algae, etc.) in containers with wide openings and prefer dark-colored containers located in the shade. About three days after feeding on blood, the mosquito lays her eggs inside a container just above the water line. Eggs are laid over a period of several days, are resistant to desiccation and can survive for periods of six or more months. When rain floods the eggs with water, the larvae hatch. Generally larvae feed upon small aquatic organisms, algae and particles of plant and animal material in water-filled containers. The entire immature or aquatic cycle (i.e., from egg to adult) can occur in as little as 7-8 days. The life span for adult mosquitoes is around three weeks. Egg production sites are within or in close proximity to households

Aedes aegypti historically is considered to be a primary vector of viral diseases such as dengue fever, chikungunya and yellow fever.

Aedes aegypti is extremely common in areas lacking piped water systems, and depend greatly on water storage containers to lay their eggs. Male and female adults feed on nectar of plants; however, female mosquitoes need blood in order to produce eggs, and are active in the daytime. Eggs have the ability to survive drying for long periods of time, allowing eggs to be easily spread to new locations. Artificial or natural water containers (water storage containers, flower pots, discarded tires, plates under potted plants, cemetery vases, flower pots, buckets, tin cans, clogged rain gutters, ornamental fountains, drums, water bowls for pets, birdbaths, etc.) that are within or close to places where humans live are ideally larval habitats for this mosquito. This species has also been found in underground collections of water such as open or unsealed septic tanks, storm drains, wells, and water meters.

Biting Behavior
Aedes aegypti bites primarily during the day. This species is most active for approximately two hours after sunrise and several hours before sunset, but it can bite at night in well-lit areas. This mosquito can bite people without being noticed because it approaches from behind and bites on the ankles and elbows. Aedes aegypti prefers biting people but it also bites dogs and other domestic animals, mostly mammals. Only females bite to obtain blood in order to lay eggs

Mosquito Control

Check your yard weekly for water-filled containers.

Throw away or recycle water-holding containers that are not needed.

If empty containers or large objects, such as boats or old appliances must be stored, they should be covered, turned over or placed under a roof that does not allow them to fill with water.

Clean and scrub birdbaths and pet-watering dishes weekly and dump the water from overflow dishes under potted plants and flowerpots. Check that gutters are not holding water and cover rain barrels with tight screening so that mosquitoes cannot enter.

Fill tree holes and other cavities in plants with sand or soil.

Check for hidden bodies of water such as wells, septic tanks, manholes, clogged drains, etc.

Call the health authorities when you detect unusual numbers of mosquitoes. Avoid mosquito bites Use personal protection to avoid mosquito bites.

Wear long sleeve shirts, long pants, socks and shoes when mosquitoes are most active.

Apply repellents such as DEET, picaridin, oil of lemon eucalyptus or IR3535 only to exposed skin and/or clothing (as directed on the product label). Do not use repellents under clothing. In addition to wearing repellent, you can protect yourself and your family by taking these precautions:

Use mosquito netting over infant carriers, cribs and strollers.

Install or repair window and door screens to keep out mosquitoes.

Dengue Branch, San Juan, PR:
For more information please contact Centers for Disease Control and Prevention
1324 Cañada Street, San Juan, Puerto Rico 00920
Telephone: 787-706-2399

 About Fogging

Virgin Islands Daily News

In recent weeks, the public in the U.S. Virgin Islands has criticized the territory’s Health Department for not turning to a method of prevention known as truck-mounted fogging, during which trucks travel to specific areas where mosquitoes are known to be and emit a chemical fog that kills the adult mosquito population.

However, the Health Department refuses to use that the strategy for a number of reasons.

Studies in other areas have shown that truck-mounted fogging is ineffective in killing Aedes aegypti mosquitoes, the mosquitoes which are responsible for spreading chikungunya and dengue, another mosquito-borne virus common in the territory.

The Aedes aegypti mosquito is known to remain indoors, which means it is difficult to reach via fogging.

“These mosquitoes are in our closets and under our beds. When we’re spraying from our trucks, it’s just not getting to them,” said Dr. Brett Ellis, an entomologist with the Health Department.

These mosquitoes also are known to bite more aggressively during the daytime, though fogging is more often conducted during the evening, he said.

“I’m not saying chemicals don’t work on mosquitoes, they just don’t work on these mosquitoes,” Brett Ellis said.

The fogging has been used in the past, but, additionally, scientists have discovered that the chemical, permanone 30-30, is unstable in water and the Environmental Protection Agency has raised concerns that is could contaminate rain and cistern or well water, according to Health officials.

A recommendation from Fran Jacobson, C.N.M – Cruz Bay Family Practice

Fran reports good results from a product called My Mosquito Deleter. I will be ordering one and testing it. Stay tuned…

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