Aedes mosquitoes have been first present in Ventura County


Tom Kisken
Ventura County Star

Published 19:28 EDT September 21, 2020

A potentially dangerous species of mosquito has emerged in the Simi Valley that was previously not found in Ventura County. More people report bites every day.

“We’re being flooded with calls,” said Ron Ventura, a supervisor for Ventura County’s Environmental Health Division. “We get at least a dozen calls a day.”

The little black mosquito with white stripes on its back and legs is called Aedes aegypti or yellow fever mosquito. The aggressive, biting insect was found in the Simi Valley on September 9 after a resident reported being bitten.

The mosquitoes are a cause for concern because they can carry potentially dangerous viruses such as zika, dengue fever, chikungunya and yellow fever.

Aedes mosquito affects officials

Although the invasive aedes have been found in increasing numbers across California, there are no known cases of mosquito transmission of Zika or other diseases, according to state health officials.

Officials fear the mosquitoes could become carriers by biting returning travelers infected in other parts of the world where the virus is more common, including Central America, Mexico and Asia.

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The first Aedes aegypti in the Simi Valley was found south of Sycamore Drive and Fitzgerald Road. The mosquitoes have also been spotted in eastern regions of the city.

By Monday morning, 15 of the insects had been caught, all in Simi.

Ventura urged residents to call the mosquito hotline at 805-658-4310 if they think they have been bitten.

“We want to identify as many parts of the city as possible in the Simi Valley to find out the extent of the infestation,” he said. The species is unusual because it often bites during the day.

“This is a very aggressive mosquito,” said Ventura. “A woman would bite and look for a blood meal about 30 times.”

Environmental health workers are inspecting nearby sites where the mosquitoes have been reported in a process complicated by COVID-19 that includes masks and social distancing.

Ventura emphasized that there are no known mosquito transmissions of Zika or other viruses associated with the invasive Aedes in California. Ventura said people should see their doctors if they get sick or experience side effects from bites.

You should also protect yourself by removing stagnant water that could act as a breeding ground. The mosquitoes lay their eggs directly above the water in containers such as dishes under pots, bird baths, hoops, ornamental fountains and children’s toys.

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What else you should know about the Aedes aegypti mosquito

The invasive aedes can breed in very small places such as water ingested by certain plants or in open lids and caps. Drain any water and remove the containers it was in, Ventura said.

The mosquitoes can also be found indoors.

“This mosquito has an affinity with people. They will settle in their homes and breed,” he said, emphasizing the importance of unwelcoming, tight-fitting screens and tight-fitting doors.

Removal of the water is a primary purpose of the on-site inspections. Sites can also be treated with pesticides, according to Ventura.

Another species of mosquito found in California that has been linked to Zika and other viruses is Aedes albopictus, known as the Asian tiger mosquito. This species has not yet been discovered in Ventura County, but in Los Angeles County.

“It is possible,” said Ventura of the species’ presence on site. “We always felt like the invasives were here in Ventura County.”

The insects that appear in Ventura County each year that can transmit the West Nile virus are several species of the Culex mosquito. Although the West Nile season often starts in September, there have been no confirmed reports of the virus in animals or humans in Ventura County.

To protect against all mosquitoes, people should remove standing water and protect their homes with screens. You should wear long-sleeved shirts, long pants, socks, and shoes.

Ventura said they should use an EPA-approved insect repellent as well.

Tom Kisken covers health care and other news for the Ventura County Star. Reach him at or 805-437-0255.

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