Mosquitos — And Their Diseases — Skyrocket In CA As Recent Rain And Heat Make Matters Worse

LOS ALAMITOS, CA — September has brought a slew of dramatic behavior from Mother Nature — coastal flooding, downpours, scorching temperatures, and a thick blanket of humidity. That means a thick blanket of mosquitos is likely next/

The elements are creating a banner year not just for heat records but for mosquitos and the diseases they spread.

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As of Friday, there were 126 human cases of West Nile Virus in California - about tripple the state's five-year average. Six cases were fatal this year. Vector control and health officials are expecting one of the worst years on record for the spread of the disease based on thousands of mosquito samples that have recently tested positive for the disease in nearly every county.

At the same time, the Golden State has confirmed nearly 20 cases of locally transmitted dengue fever since the Aedes aegypti — better known as the ankle biter mosquito — first appeared in California more than a decade ago. Climate change is quickly turning the Golden State into a more hospital environment for dengue to become endemic just like West Nile Virus, which was first confirmed in California in 2003.

Conditions such as the humid heat that has plagued California this month make the Golden State more hospitable for the blood-sucking ankle biter.

Lisa I. Couper, a postdoctoral scholar in environmental health sciences at UC Berkeley is the primary author of a new study warning of the spread of the mosquito-borne disease in California amid rising temperatures.

"It's just a horrible disease," Couper, told UC Berkeley. "Even mild cases are described as having a really high fever, joint pain, muscle pain and intense fatigue. More severe cases can involve vomiting, bleeding and being out of commission for weeks, and can be fatal....California is on the edge of temperature suitability for dengue.

"The optimal temperature for the virus to reproduce is around 29 degrees Celsius (or 84 degrees Fahrenheit)," she told UC Berkeley News. For a lot of the year, and for most places, California is below that optimum temperature. But as the climate warms in California, we're getting closer to it."

Mosquito and vector control officials said that this may be the worst year the county has seen for West Nile, sparking a worrying trend across the region.

"We're looking at upwards of 6,000 mosquitos testing positive for West Nile that we've collected in our traps," Orange County Mosquito and Vector Control District spokesperson Brian Bannon told Patch.

According to state health officials, at least 123 human cases of West Nile have been reported so far this year, and that number may not reflect all infections diagnosed since Hurricane Marie brought heat and humidity to California.

"Mosquitos are cold blooded, so the warmer it is, the more active they are," Bannon said. "We had a decent amount of rain, which could be a good thing — a torrential rain would wash the mosquitos breeding in storm drains into the ocean."

However, Bannon said that the recent showers were likely not heavy enough to flush out storm drains.

"It is not a good year," Bannon said. "Well, I guess it is a good year for mosquitos. Just not a good year for us, who don't really like them."

Bannon said California residents can try to mitigate the pests by walking their properties weekly in search of standing water.

"It's important that people are taking a good look around their homes — inside and out, because the ankle biters can actually breed inside of your home," he said. "But the thing is with the ankle biters, they only need a bottle cap full of water to breed — it could be a really small source."

Bannon said that anything from flower pot saucers to yard drains can serve as fruitful breeding grounds for mosquitos.

Vector control officials have a myriad of approaches to curbing the explosion of mosquito populations from breeding of mosquito fish in Sacramento to a pilot program in Los Angeles and Orange counties to release sterilized non-biting males to mate with females and suppress reproduction rates.

The Sterile Insect Technique, climbed to notoriety for its success in whittling down harmful populations of agriculturally-devastating bugs — including the Mediterranean Fruit Fly, Bannon said. Recently, it's been deployed in Sacramento, Contra Costa County, the Inland Empire, Orange County and the the San Gabriel, Antelope and Coachella valleys.

According to Bannon, the process rears male mosquitos and exposes them to x-rays to sterilize them before releasing them into the project area.

Batches of the irradiated male mosquitoes are released to mate with as many females as possible, so they can't lay fertilized eggs, reducing the mosquito population over time.

The technique is currently being implemented in with Aedes aegypti, due to the pest's growing prevalence.

For the present time, however, many community's greatest weapon has been the use of EPA-approved insecticides.

"Right now, we're going where it's the worst and taking care of it," Bannon said.

According to Bannon, the district has found success in focusing applications of DeltaGard insecticide on areas with high populations of mosquitos testing positive for West Nile or other diseases.

"Either Ultra-Low Volume (ULV) adulticide treatments or Wide Area Larvicide Spraying (WALS) treatments will be conducted in concentrated areas most at risk for disease occurrence, or where travel-related mosquito-borne disease cases have been identified," an OC Mosquito and Vector Control District advisory read.

Beyond that, residents can request Vector Control staff to come and do a free house canvassing to see what can be done to minimize mosquitoes on the property.

Such services are offered in Orange, Riverside, San Diego and Los Angeles counties. Bannon urged all residents to take advantage of these resources before peak mosquito season hits in the summer.

Here are some tips and tricks to dealing with mosquitoes in September, per OC Vector:

Preventing mosquito bites

• Apply mosquito repellents to exposed skin before going outdoors and reapply if needed.
• Wear repellent containing DEET, Picaridin, IR3535 or lemon eucalyptus oil.
• Close all unscreened doors and windows to prevent mosquitoes from entering your home.
• Wear long-sleeved shirts and long pants as well as lighter-colored clothing.

How to get rid of mosquito breeding sources from your property

• Dump and drain any contained that fill with water at least once a week.
• Clean and scrub bird baths and pet water bowls weekly.
• Dump water from potted plant saucers.
• Don't move or share plant stems rooted in water.
• Drill a hole or puncture containers to eliminate standing water.