West Nile still tops list of Solano’s mosquito-borne worries

Tuesday, April 17, 2018

Daily Republic, Todd R. Hansen

FAIRFIELD — Perhaps the last thing on anyone’s mind on a rainy Monday morning was the threat of mosquitoes.

However, according to the state Department of Public Health, “there has been a steep rise in detections of invasive mosquito populations in California . . . which increases the risk of local transmission of imported diseases.”

April 15-22 is Mosquito Awareness Week.

The end of the recent drought and the lifting of water restrictions also mean the return of water practices that create more mosquito habitat, the state agency reports.

“With millions of international travelers arriving or returning to California each year and the spread of these invasive mosquito species across California, the potential for local transmission of imported diseases is increasing,” David Heft, president of the Mosquito and Vector Control Association of California, said in a statement released Monday by the organization.

“All it will take is one invasive mosquito biting one infected traveler for these diseases to potentially spread to others here at home. While surveillance and mosquito control activities are critical to protecting public health, the public also needs to do everything in their power to get rid of sources in their own communities where mosquitoes develop,” he stated.

Two invasive mosquito species, Aedes aegypti – the yellow fever mosquito – and Aedes albopictus – the tiger or forest mosquito – have been found in nearly 200 cities in Southern and Central California, up from five years ago when only one or the other of those species were found in four cities.

“Both invasive species are capable of transmitting viruses that are dangerous to people such as chikungunya, dengue (fever) and Zika,” the organization reports.

None of the cities of Solano County are among the 200 cities, which are located in 12 counties, the closest being Merced County. One type of the species was detected in San Mateo County a couple of years ago, but that county is no longer part of the state location map.

Still, Solano County has its own concerns.

“A month back, we got a call about a man who had traveled to the Philippines and came back with dengue fever,” said Richard Snyder, district manager of the Solano County Mosquito Abatement District.

That particular mosquito type – or vector – does not exist in Solano County so the threat was nominal. Zika would have posed a greater threat, Snyder said.

Global travel is viewed as one of the most common reasons why the mosquito-borne diseases spread. An infected person is bit by a mosquito, which in turn bites someone else.

But Snyder said the West Nile virus is still the largest concern for Solano County.

There have been 16 reported human cases of West Nile virus in Solano County since 2007. Five cases were reported in 2014 and four in 2016. The other years saw between zero and two cases. No fatalities have been reported this year, according to the California Department of Public Health.

Between 2003 and 2017, the state has reported 6,582 human cases in California and 292 fatalities.

The only activity in 2018, according to the state, are a total of four dead birds found in San Mateo and Santa Clara counties.

Snyder said the primary habitats for the mosquitoes in Solano County are the marshes and some agricultural areas, but urban habitats are also commonplace.

“We’ve been doing a flyover of Solano County looking for green swimming pools and we will be doing that again next month,” Snyder said. “Last year, we had 600 pools identified and we ended up treating about 20 percent of them.”

That was an even bigger problem with the surge of home forfeitures after 2008 when people were walking away from properties that had pools.

Any standing, stagnant water, however, can be a concern so the district is trying to get the word out to residents to do their part. That effort includes advertisements on the back of area buses.

“All California residents play an important role in protecting public health and this is especially important as threats of mosquito-transmitted diseases continue to rise,” Assemblyman Bill Quirk, D-Hayward, said in the state mosquito association statement. “Mosquitoes can lay their eggs in sources of water as small as a bottle cap, so it is critical that Californians are cognizant of their water use and take steps to diminish mosquito breeding potential.”

Quirk authored the Assembly resolution recognizing Mosquito Awareness Week.