Diseases caused by insects more prevalent

ATLANTA — Diseases caused by insects are booming.

Earlier this month, the federal Centers for Disease Control and Prevention reported illness spread by ticks, mosquitoes and fleas had tripled since 2004.

Between 2004 and 2016, there were more than 640,000 reported cases of insect-borne diseases, according to the agency, and the numbers are growing.

So why are insects making people sick more often?

In an interview with The Atlanta Journal-Constitution, Dr. Lyle Petersen, director of the center’s Division of Vector-Borne Diseases, explained the separate trends that are combining to promote the spread of these illnesses.

The first of these trends is the expansion of global trade and global travel.

Each year in the 1950s about 50 million people crossed an international border, Peterson said. Today, more than a billion people cross an international border every year. Crossing with them are new diseases that are then propagated in new territories.

Among the new mosquitoborne diseases that have entered the U. S. are West Nile, which arrived in 1999, chikungunya (from 2014) and Zika (from 2015).

One of the most significant of these is still the West Nile virus. Each year, between 700 and 3,000 Americans who contract the virus develop severe neurological symptoms.

“Most of those people do not recover fully, and about 10 percent will die,” Petersen said. “It doesn’t make the news, so much. People have gotten used to it,” he said, “but it’s still a very deadly disease and the fact is, you could die from one mosquito bite.”

Far more widespread is a milder version called West Nile fever, which affects 30 to 50 times as many people as its neurological cousin. These victims do not suffer paralysis or meningitis or encephalitis, but they develop a body-wracking fever that lasts weeks.

“While it won’t kill you, it will definitely ruin your summer,” Petersen said.

Another trend is raising the incidence of tick-borne disease. Deer ticks are moving into new territory due in part to warming temperatures, an expansion that is steadily increasing the incidence of Lyme disease. Petersen said up to 350,000 people a year contract Lyme disease.

“It doesn’t kill many people, but if left untreated, they can develop heart problems, they can develop neurological problems, they can develop severe arthritis.”

Another trend is making the matter worse: Fewer predators and bigger suburban forests have led to a boom in the deer population. “There are more deer, and more deer ticks, and the diseases they spread.”

Dealing with these diseases is complex. There are 1,900 separate “vector control” organizations, including public health departments, mosquito-control districts and other local agencies.

Coordinating the efforts of all these groups is difficult, Petersen said. Control organizations need to do better surveillance of mosquito and tick populations and collect better data on the effectiveness of insecticides.

Backyard fogging companies may have success in preventing nuisance mosquitoes, but there’s no data on whether they are reducing disease, he said. They also may be aggravating the problems by producing more mosquitoes that are resistant to insecticide.

In the meantime, said Petersen, people can help prevent disease by using insect repellent, wearing long sleeves and long pants, using clothes and gear (like backpacks and tents) impregnated with permethrin, and keeping ticks off household pets.

And, taking a page from Brad Paisley, Petersen also recommends checking for ticks as soon as you come inside. To develop Lyme disease, for example, requires a few days’ contact with a tick. If it’s removed quickly, it won’t have time to infect a person, Petersen said.