Out for Blood

They are arguably the most annoying creatures any of us encounters on a regular basis. We swat at them, try to avoid them and occasionally kill them. But according to Baylor biology professor Richard Duhrkopf, mosquitos actually make our lives better--in a way.

"They probably pollinate about 80 percent of our wildflowers," Duhrkopf said. "They pollinate more than bees do."

Duhrkopf has spent the past four decades studying the Spanish-named "little flies" that comprise the Culicidae family. His mosquito fascination dates back to fishing trips as a boy in northern Wisconsin. When his seventh-grade English teacher assigned a research paper, Duhrkopf chose mosquitos as the topic.

At Baylor, Duhrkopf's research centers around two species--the yellow fever and Asian tiger mosquitos, both members of the Aedes genus. The former has been in Texas for centuries, coming to North America from Africa via slave-trade ships. The latter arrived recently and competes with the yellow fever mosquito for territory.

"I'm intimately familiar with them," said Duhrkopf, who earned his BS, MS and PhD from The Ohio State University. When discussions of mosquito-transmitted viruses arise, his is a trusted voice. This year, Zika virus has been at the center of the conversation with its link to major birth defects and the Olympics taking place in Rio.

Zika virus derives its name from the Zika Forest in Uganda, where the virus was first discovered in 1947. While the virus is related to dengue, West Nile and yellow fever, it is less severe. In 2007, an outbreak in the Yap Islands east of the Philippines infected more than 70 percent of the islands' inhabitants.

"But right now, there is hardly any Zika virus on those islands," Duhrkopf said. "Our immune system is able to identify the virus, produce antibody and clear it. There are some lasting headache and neurological complications that can exist, but they seem to be very mild compared to West Nile virus."

Zika fever symptoms--headache, joint pain, muscle aches, rash, fever--can be so mild that a person may never know they are infected. Duhrkopf said 80 percent of infected people do not experience those symptoms.

"They may have a small little fever or a headache for a day, so they're definitely not going to go to the doctor," he said.

While Zika virus is not life threatening, it can cause other health issues. Venezuelan health services identified eight deaths in early March that were considered to be associated with Zika virus.

"If you're not healthy to begin with, you can die of dehydration as a result of the activity of the virus," Duhrkopf said. "But the virus itself didn't really cause the death."

Microcephaly, a medical condition that stunts brain development and results in smaller-than-normal head size, is much more concerning. Babies infected with microcephaly are on the rise in Brazil, where Zika virus is rampant.

"Initially, the Centers for Disease Control took it as a coincidence," Duhrkopf said. "But they decided it's not a coincidence, that it really is associated with the virus. Many of the children have problems with development of the retina and may face blindness, as well."

The CDC and the World Health Organization continue to monitor confirmed cases and to release updated information and warnings, including more links to birth defects.

In early April, the CDC reported more than 300 Zika travel-associated cases in the U.S. while the U.S. territories, including Puerto Rico, had more than 400 locally acquired cases. Texas reported 29 confirmed cases, with most of those in Harris County (or, the greater Houston area for those unfamiliar with Texas). Texas also reports one case that is considered sexually transmitted with the original infection occurring outside the U.S.

Duhrkopf said Brazil and other Latin America countries are prime breeding grounds for virus-carrying mosquitos due to both environmental and economic factors.

"These mosquitos breed in any place that holds a little bit of water, and there are a lot of those in Brazil," he said. "It's also intimately connected with poverty. In that kind of densely populated situation, there is a lot of trash around. Meanwhile, in upper-middle-class suburban areas, we have screens on our windows, we watch TV at night, we don't go out in the yard at night, and we're not being bitten as much."

While it is good to be aware of Zika, dengue is more likely to be locally contracted by those in the U.S. Duhrkopf, who noted that dengue is rampant in Mexico, said the same mosquitos that transmit Zika transmit dengue, but the latter produces broad-ranging and severe health risks for adults. Mosquitos are drawn to body heat; therefore, they are more attracted to some people than others.

"If you're infected by dengue, it's almost certain that you're going to get sick," Duhrkopf said, adding that about 10 percent of those infected have symptoms that last longer than two weeks. "You will get over it, but there are four different versions of the dengue virus, and the immune system reacts to them individually. You can get one version and recover from it, but you are still susceptible to the other versions."

Dengue is commonly known in many areas of the world as break-bone fever because of the severe bone and joint pains that give the sensation that every bone in the infected person's body is breaking. Duhrkopf said dengue has the ability to develop into an Ebola-like illness where blood vessels weaken and rupture.

"You have extensive hemorrhaging, lose tremendous amounts of blood and quite likely die from it," Duhrkopf said. "Dengue has a far greater potential for truly causing death than Zika."

According to Duhrkopf, there is a dengue outbreak along the Texas-Mexico border about every five or six years. Nonetheless, the nature of mosquito migration makes it unlikely cases of sizable outbreaks will find their way to other parts of the state anytime soon. There are more than 80 mosquito species in Texas, but most migrate locally.

"It's possible that some of those mosquitos could find their way onto a truck and make it to Austin or Waco or Dallas," Duhrkopf said. "But the mosquitos we're talking about tend to not be very good fliers. It's asking an awful lot of them to fly a block away from where they developed. I'm not going to get bitten by mosquitos that are developing in Crawford or McGregor. I'm getting bitten by mosquitos that are developed within 100 yards of where I am."

Duhrkopf's advice is to keep yards clear of standing water, which is prime breeding ground for mosquitos. Some mosquitos prefer dirty water; some prefer cleaner water.

"It depends on skin temperature and metabolism," Duhrkopf said. "High metabolism is bad; you're producing more heat, more carbon dioxide. When a mosquito lands on your arm, it's looking for things like lactic acid, which is a product of metabolism. The more active you are, the warmer you are, the more carbon dioxide is coming off your skin, the more lactic acid, and the more likely you are to be bitten."