Some communities in southeast Texas are fighting back against a massive influx of mosquitoes that some describe as the worst in years.

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• Mosquito Control: Treatment Locations | Activity Map | Harris County Mosquito Control

Floodwater mosquitoes hatched about a week after the Oct. 9 rains and are to blame for the recent surge in bites across the city, officials said.

The Fort Bend County Mosquito Control District said it's the worst infestation in years.

"Normally, we have maybe 100 to 200 in a trap, but today, there's more like 5,000-10,000, maybe even 15,000, per trap," said Weldon Sheard with Fort Bend County Mosquito Control.

Fort Bend County has been spraying to control the outbreak.

"We're spraying everywhere trying to get the whole county covered," Sheard said.

An entomologist at Texas AgriLife Extension Service said floodwater mosquitoes tend to be larger, have a more noticeable bite, and may bite through light clothing. The pests are the worst at dawn and dusk.

Officials said the floodwater mosquitoes do not carry diseases. However, that means the Harris County Mosquito Control District will not spray for them, only for bugs that could carry diseases such as West Nile virus.

"We don't spray for pest mosquitoes unless there's a specific emergency," said Dr. Rudy Bueno, the director of the Harris County Mosquito Control District.

Harris County will be spraying a north central neighborhood after a positive West Nile virus sample was found Tuesday.

Pasadena and Montgomery County also do not have plans to do any extra spraying to get rid of the pests.

However, other places, including Sugar Land, Missouri City, West University Place, Galveston County and Brazoria County, plan to step up their mosquito-spraying efforts.

Galveston County will use seven trucks to spray the West End, the Bolivar Peninsula and Santa Fe Tuesday night.

Brazoria County will spray in Alvin and Angleton. Officials said they have 10 trucks and one plane going out.

Pet owners are worried about the pests because experts said that floodwater mosquitoes can transmit heartworms in animals.

"It's going to affect the dog in the long-term because literally, when you see a heart with heartworms, it's literally hundreds of these heartworms stuck in the valves of the vessels," said Chava Septein, who works at the Washington Heights Animal Clinic. "The mosquito, once it bites an animal infected with heartworm -- cat or dog -- the larva goes into the blood stream of the pet. So the mosquito sucks the blood, the larva goes into the mosquito and stays in the mosquito until it bites another pet."

Septein predicts that the number of positive heartworm cases in the area will go up in a few months.

"Probably within six months, we're going to have a population of dogs testing positive for heartworms because of this bout of mosquitoes," Septein said.

Veterinarians said as long as pets are taking a heartworm-prevention medication, they should be protected.

The Health Department has been inundated with phone calls from residents trying to avoid getting bitten. Experts suggest wearing long-sleeve shirts outside, empty any containers with standing water such as small swimming pools and bird baths, and wear mosquito repellent while outdoors.

Officials said a cool front could bring relief later this week.