U.S. Malaria Cases Emphasize Need for Insect Protection

All it took was one mosquito bite to launch Bob Scott on a multi-week-long struggle against malaria.

Malaria hit the headlines in the United States this week following confirmation from the Centers for Disease Control and Prevention of cases in which malaria was contracted locally, as opposed to being contracted in another country and brought to the U.S. These are the first locally acquired cases in the U.S. since 2003. In the last two months, five cases were identified, four in Florida and one in Texas.

According to the CDC, malaria was considered eradicated from the U.S. by 1949, following an effort begun in 1947 that included spraying DDT inside homes and eliminating mosquito breeding sites. The National Malaria Eradication Program was a cooperative undertaking by state and local health agencies of 13 southeastern states and the Communicable Disease Center of the U. S. Public Health Service.

Emily McDermott, assistant professor in the department of entomology and plant pathology, says protecting yourself from mosquitoes is the first line of defense against diseases such as malaria, which are transmitted by mosquitoes. (UA System Division of Agriculture photo by Fred Miller)

Malaria is caused by any of five species of protozoan parasite of the genus Plasmodium. If left untreated, the disease can be fatal in humans. 

Scott, who heads the Cooperative Extension Service for the University of Arkansas System Division of Agriculture, was on a dove-hunting trip to Bolivia in the winter of 2015. He and the rest of the hunting party were well covered, protected from their surroundings.

“But I had some gloves that had a hole where your thumb is and it got me right there,” he said. About 24 hours later, he began to feel the first symptoms.

On the flight back, “I started feeling nauseous,” Scott said. “Then I started having fever, body aches, and chills. It was like having the flu without the congestion.”

His doctor gave him a malaria test, which came back negative. Because Scott had also suffered a tick bite, his doctor began treating him for a potential tick-borne virus. The treatment had him feeling better for about two weeks. When that course of medication ended, the malaria hit him hard.

“I kept going downhill. I lost 15 to 20 pounds,” Scott said. “I was on my way to the hospital when my doctor called, saying that ‘everything that I’m looking at says you have malaria except that test.’

The doctor started Scott on the antimalarial medicine mefloquine, and Scott said he felt better within 24 hours. The treatment left him anemic, which took another 10 days to two weeks to overcome.

Because locally acquired malaria is uncommon, “my worry here is that our healthcare system is not accustomed to dealing with it so it's something we have to look for,” he said.

Mosquito-specific disease

The CDC said that “Despite these cases, the risk of locally acquired malaria remains extremely low in the United States. However, Anopheles mosquito vectors, found throughout many regions of the country, are capable of transmitting malaria if they feed on a malaria-infected person.”

In the U.S., specifically the Southeast, the culprit is Anopheles quadrimaculatus — the common malaria mosquito, said Emily McDermott, an assistant professor of entomology for the University of Arkansas System Division of Agriculture. While more common in areas with large amounts of standing water, such as rice-growing regions, the malaria mosquito can also be found in northwest Arkansas.

Protecting oneself from mosquitoes is the best way to forestall malaria or any of the diseases mosquitoes can carry.

“Topical repellents are really great and the ones that are recommended by the CDC like DEET and picaridin are very effective,” McDermott said.

“If you don't like DEET we really recommend going with one of the other things that the CDC recommends like IR3535, oil of lemon-eucalyptus. These are all things that we have evidence that they are effective at preventing mosquitoes from biting,” she said. “A lot of people like botanicals, but we kind of like to steer people away from that because those products might not be as consistent or have the same kind of level of quality control.”

What makes you attractive to mosquitoes?

“The big attraction for any sort of blood-feeding insect is going to be your breath and particularly carbon dioxide,” McDermott said. “This is a universal attraction for blood-feeding insects because all mammals are going to be expelling carbon dioxide. It's a really strong cue that there's something alive to feed on.”

Beyond the carbon dioxide, the insects also picked up on scents produced by the body, she said. The scents produced by bacteria on the skin will vary by person. “We have slightly different scents that we give off. So, some individuals might be more attractive to mosquitoes and other blood feeders than others.”