Disease-carrying Aedes aegypti mosquitoes confirmed in Jackson County, first of species found in Oregon

PORTLAND, Ore. (KTVZ) – The Oregon Health Authority, Jackson County Vector Control and Jackson County Public Health Division have confirmed the identification of Aedes aegypti (Ae. Aegypti) mosquitoes in the county – the first time the disease-carrying mosquito species has been found in Oregon.

Jackson County Vector Control identified the Ae. aegypti mosquito as part of its routine mosquito surveillance, which monitors different mosquito populations in the county and tests for diseases such as West Nile virus and Western equine encephalitis that are common to the Culex mosquito genus.

Mosquito surveillance provides Jackson County Vector Control the ability to determine human risk and implement strategies to control these insects and prevent disease spread.

Adult Ae. aegypti mosquitoes are relatively small and have a black-and-white pattern due to the presence of white/silver scale patches against a black background on the legs and other parts of the body.

Ae. aegypti mosquitoes most likely originated in Africa. Since then, the species has been transported globally throughout tropical and subtropical regions, and parts of the temperate world, through global trade and shipping activities.

 Ae. aegypti cannot fly far, only about 500 feet. These mosquitoes prefer warm and wet weather, and to live in or near homes or in neighboring woods. Changes in climate are allowing Ae. aegypti mosquitoes to expand their range to the western United States. 

“Aedes aegypti mosquitoes are a concern in the United States because they can carry and transmit various diseases that can have serious health consequences such as Zika virus, chikungunya, dengue and yellow fever,” said Emilio DeBess, D.V.M., state public health veterinarian based at OHA’s Public Health Division.

These viruses spread to humans through the bite of an infected Ae. aegypti mosquito. The mosquitoes become infected when they bite and feed on someone who is infected with the virus. These mosquitos primarily feed in the daytime and prefer to feed on humans.

“The risk of these infections to local residents is low and depends on the presence or arrival of someone who is currently infected with one of these diseases after infection outside the U.S.,” DeBess said. He added there have been no reports of anyone having acquired viruses from Ae. aegypti mosquitoes within Oregon.

John Mahan, M.D., chief medical officer of Jackson County Health & Human Services, said, “Jackson County Vector Control and Jackson County Public Health are working closely with OHA and vector-borne disease specialists regarding control of these mosquitoes and risk-reduction approaches.”

Invasive Ae. aegypti mosquitoes need only a quarter inch of water to complete their life cycle. The key to preventing these mosquitoes from becoming an established vector in Jackson County will be to eliminate standing water, even small amounts, and moisture from yards and gardens. Common mosquito breeding sources include flowerpot saucers, tires, kiddie pools, rooted plants in water, containers/buckets, and pet water bowls.

“Many prevention methods that work for other types of mosquitoes apply to Aedes aegypti,” said Geoff Taylor, manager of Jackson County Vector Control.

Those methods include:

• Dumping or draining any standing water around the home.
• Removing containers or objects that can hold water from your yard, such as water saucers from under plants, old tires, tarps, buckets, containers, toys, and other equipment.
• Repairing leaky outdoor faucets.
• Keeping rain gutters cleared.
• Covering, screening, or removing rain barrels, trashcans, bins, buckets, or tubs.
• Wearing mosquito repellent outside. Repellents containing DEET, picaridin, IR3535, some lemon eucalyptus, and para-menthane-diol products are most effective at preventing mosquito bites.
• Sleeping under a mosquito net when outside or in a room without screens.

“Discovery of Aedes aegypti underscores the importance of our mosquito trapping system," DeBess said. “Tracking and monitoring the types of mosquitoes that exist in Oregon communities is critical. This, in turn, helps us identify potential public health implications and implement measures to reduce risk.”

For more information:

• Aedes aegypti, Centers for Disease Control and Prevention (CDC): https://www.cdc.gov/mosquitoes/about/life-cycle-of-aedes-mosquitoes.html
• Potential range of Aedes mosquitoes, CDC: https://www.cdc.gov/mosquitoes/php/toolkit/potential-range-of-aedes.html
• Aedes aegypti in California: https://www.cdph.ca.gov/Programs/CID/DCDC/pages/Aedes-aegypti-and-Aedes-albopictus-mosquitoes.aspx
• Jackson County Vector Control District: https://jcvcd.org/
• JCVCD’s Aedes aegypti page: https://jcvcd.org/mosquito/aedes-aegypti/