The two mosquito species that transmit the Zika virus and dengue fever could become established in the Sacramento region and open a new chapter in local mosquito control efforts, says the lab director of the Sacramento-Yolo Mosquito & Vector Control District.
Lab director Paula Macedo said the Aedes aegypti and Aedes albopictus mosquitoes are due to appear in the region, which has so far been focused on controlling the common culex mosquito that transmits West Nile virus.
“The two species are on the move and they’re on the move northward,” Macedo said. “It’s only a matter of time before we find these mosquitoes here.”
So far, neither mosquito has been seen in Sacramento or Yolo counties, after making an appearance in Los Angeles in 2011. However, the mosquitoes have been found as far north as San Mateo and Fresno counties in 2013. Last year, the Alameda County Mosquito Abatement District found the Aedes aegypti mosquito in an industrial area of Hayward.
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Macedo contends the mosquitoes’ arrival would usher in a new set of challenges for mosquito control officials. “They’re going to be game changers,” she said.
The Aedes aegypti mosquito is the main vector for the spread of Zika virus, which made its first appearance in Brazil last year and has been implicated in a 20-fold increase in the birth defect microcephaly. It is also a vector in the transmission of dengue fever and chikungunya – viruses that cause fever and joint pain.
UC Davis mosquito researcher Chris Barker took a more guarded view about the appearance of the mosquitoes in the Sacramento region. “I’m not sure that Aedes aegypti would eclipse West Nile virus as a concern if it arrives here,” he said. “But it requires completely different surveillance and control methods that would require additional staff.”
Barker said the species’ movement from city to city is largely a result of human activity, with the adult mosquitoes known to fly into passenger vehicles that then carry them to other regions. Barker said he doesn’t believe the Aedes aegypti is making a gradual northward advance yet. Even if the insect should arrive, outbreaks may be small, he said.
The Zika virus can also be transmitted sexually, said Vicki Kramer, chief of vector-borne disease at the California Department of Public Health.
Twenty-one cases of Zika have been identified in California since 2013 as of March 18, all of them travel-related cases, according to the department.
This month’s storms, which doubled the normal rainfall totals for March, have so far not resulted in larger mosquito populations, said Luz Robles, spokeswoman for the Sacramento-Yolo vector district.
Macedo said the Aedes aegypti mosquito would present a challenge for local vector control districts because its eggs can survive in extremely dry conditions and remain viable for months on dry surfaces.
“Whenever humidity hits, or if it gets flooded, the eggs will hatch,” Macedo said.
The Aedes aegypti mosquitoes thrive in containers and other confined spaces. Finding and eradicating them can prove labor intensive. “In countries that have them, they’ve had to put thousands of people to hunt for it – door to door,” Macedo said.