Experts Say Zika Not A Big Risk In PA, Ticks Pose A Bigger Threat

Mar 29, 2016

  Post updated March 29 at 5 p.m. 

The aedes aegypti mosquito carries the Zika virus.
Credit Felipe Dana / AP

The aedes aegypti mosquito that carries the Zika virus is present in Pennsylvania, and there are now 11 confirmed cases of people who became infected with the virus while traveling abroad.

And Allegheny County officials announced Tuesday afternoon the first confirmed case of Zika locally, contracted by a man who had visited "an affected area." 

But public health officials keep saying the risk of contracting the disease is slim to none. Have you ever wondered why?

If the mosquito is here and the virus is here, why is it unlikely that anyone in Pennsylvania will become infected?

There are a couple of reasons.

First, life in southwestern Pennsylvania is very different than life in Brazil, and many other affected countries according to Bill Todaro, an entomologist for Allegheny County. People have screens on their windows. They also have air conditioning, and often keep their windows closed all summer long.

By contrast, developing countries affected by Zika are a relative paradise for mosquitoes.

"They have buckets laying there because they don’t have water service, they don’t have sewer service. They don’t have a lot of the amenities that we have, so this mosquito is breeding underneath the kitchen sink.”

Credit Centers for Disease for Control and Prevention

  There just aren’t as many mosquitoes here. The breeding season is shorter. There are fewer overall bites and fewer opportunities for disease transmission.

“People have open doors and windows," Todaro said. 

Second, the aedes aegytpi mosquitoes don’t bite birds. To understand why that’s significant, one can consider another mosquito-borne illness that is more common in southwestern Pennsylvania: West Nile Virus.

“The birds are a vector as well,” said Todaro. “They’re a host for the virus and they move into a new area every spring to have their babies, and they bring the virus in. They are the ones that infect the mosquitoes, and then the mosquitoes bite other birds and amplify the virus over the summer.”

Birds migrating from South and Central America to Pennsylvania for the spring and summer will not be infected with Zika. Zika’s only hosts are primates, said Kristen Mertz, medical epidemiologist with Allegheny County.

“And we don’t have monkeys and chimpanzees wandering around in this area,” she said.

Furthermore, monkeys and chimpanzees aren’t making the trek from South America to have their babies in Pennsylvania.

Deer ticks carry Lyme Disease. Lyme transmission has exploded in Pennsylvania over the last 15 years.
Credit Victoria Arocho / AP

The only primates making that journey are humans. And unlike a flock of birds, when a flight full of people arrives in the U.S. from Ecuador or Colombia, everyone goes back to their own states, cities and neighborhoods.

There is unlikely to be a critical mass of Zika-infected hosts—in this case, people—in one area.  

But there is another creepy crawly critter out there that poses far more of a threat than mosquitoes: ticks.

Bill Todaro said the mild temperatures over the past few months have made it easier for some species of mosquito to survive over winter, but that it’s the ticks that are really going to come out in full force.

“Anytime the temperature goes about 45 or 50 degrees, ticks become active,” Todaro said. “They come up out of the duft -- the dead leaf layer in the soil -- and they climb up little branches and shrubbery, and they’re questing for a host."

As the weather continues to warm, a new generation of ticks will hatch.

“This is the nymph stage and it’s a very tiny stage of the (deer) tick … it’s about the size of the period on the end of (a) sentence,” Todaro said. “These things crawl up your pant legs and get onto a spot on your body where you would never notice them and if they’re there for two or three days before you notice them, there’s a good chance you could pick up Lyme disease.”

So while your chances of getting Zika in Pennsylvania are almost nonexistent, the risk of contracting Lyme Disease from a tick is increasing every year.

Todaro said more than 40 percent of the ticks they’ve captured have tested positive for Lyme.

Incidences of Lyme Disease transmission have more than doubled nationwide over the last 20 years.
Credit Centers for Disease Control and Prevention

  In 2014, there were more than 800 documented cases of Lyme Disease in Allegheny County, but Kristen Mertz said that’s actually probably an underestimate.

“Our surveillance is mostly based on lab tests. We get positive lab tests reported by the laboratories, and so we follow up on those cases,” Mertz said. “However, a lot of providers will not do a test because a person has the classic rash. So we depend on them to report cases to us.  However providers are notoriously bad at reporting disease in, in some situations.”

The classic rash looks like a bullseye, and Mertz said about two-thirds of people infected with Lyme will develop it. Other signs of infection are fever, aches and flu-like symptoms. Left untreated, Lyme disease can lead to joint problems and neurologic and cardiac complications.

Just north and east of Allegheny County the risk of contracting Lyme jumps dramatically.

An 8-county region just north and east of Pittsburgh is a hot spot for Lyme Disease transmission.
Credit Pennsylvania Task Force on Lyme Disease and Related Tick-Borne Disease

Butler, Armstrong and Indiana counties are the southernmost in an eight-county region that is a hotspot for Lyme transmission. Those counties have a more than 1 percent incidence of Lyme per capita, the Centers for Disease Control and Prevention now lists them among the highest risk counties in the nation.

So what do you do? You can’t prevent tick breeding as easily as mosquito breeding, by clearing your gutters and dumping out standing water, but you can protect yourself.

Todaro said to spray designated outdoor shoes with a special tick neurotoxin made for clothing. Keep tick-carrying deer and mice away from your yard with repellents.

And after hiking or working in the garden, strip down in front of the mirror and check yourself for ticks, or have your partner check you, maybe with a magnifying glass.

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