Map: Tropical mosquito infestation spreads to 8 O.C. communities

Tropical mosquitoes which bite relentlessly and are capable of spreading painful diseases are now infesting more Orange County neighborhoods, and if they survive the winter, they could be here to stay.

Two tropical species – know commonly as Asian tiger and yellow fever – have been found in nine sites over eight communities, including two locations in Anaheim, one of which, at Katella Avenue and Haster Street, is a half-mile from Disneyland Resort.

The Disneyland site is particularly concerning, said Orange County Vector Control spokesman Jared Dever, because these mosquitoes spread diseases after biting a person who is sick – typically a traveler from a region where the diseases are prevalent, including Mexico and the Caribbean.

Disneyland operates its own vector control program, but a spokeswoman declined to provide specifics. “We have a very effective mosquito prevention and monitoring program in place and we work closely with Orange County Vector Control,” said spokeswoman Suzi Brown.

“We don’t do any work on Disneyland resort property,” said Dever.

Dever said officials are finding the mosquitoes – which can spread dengue and chikungunya viruses – at about 40 percent of the properties they inspect. He called the county’s level of infestation “disappointing.”

mosquito map

A warm, rainy winter ushered in by El Niño could favor the tropical mosquitoes, which might not survive freezing temperatures. They won’t likely be wiped out by torrents of rain, either. These species lay their eggs in containers, and the larvae dive to the bottom to avoid being flushed away.

“In the spring, the emergence of these mosquitoes will really be telling,” Dever said. “You could get to that threshold of entrenchment where the eggs are too abundant for an eradication program to be successful.”

The tropical mosquitoes are stealthy, aggressive and bold, usually biting legs, ankles and feet, where they cannot be heard buzzing. The insects will also bite during the daytime. These are habits different from the native mosquito, which spreads West Nile virus.

Experts are not sure why the tropical mosquitoes are coming to Orange County and California now. It doesn’t appear, however, that hot weather is a factor. They are in a dozen California counties, from Alameda to San Diego.

“These mosquitoes are very difficult to control – harder to control than (the mosquitoes that carry) West Nile virus,” said Vicki Kramer, head of the California Department of Public Health’s vector-borne disease division.

This year, West Nile virus has killed 32 California residents, the most since it was first detected in the state in 2003. Three of those deaths were in Orange County, which reported nine deaths in 2014.


“The higher fatality rate is not due, to the best of our knowledge, to any changes in the virus,” Kramer said. “It often has to do with the age and underlying medical conditions of people who get West Nile virus; we just might have had a more susceptible population.”

West Nile Virus was first found in Orange County in 2004. In 2014, it infected a record 280 Orange County residents. This year, 84 cases have been reported.

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