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It’s always a muggy Washington summer inside the U.S. Army’s insectary, the nursery where researchers grow mosquitoes from eggs into adults. The temperature is kept at a toasty 82 degrees, with a humidity level that borders on the swampy.
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About 10,000 mosquitoes a week are reared at the Walter Reed Army Institute of Research, at the edge of a light industrial park in Silver Spring. I started feeling itchy a few minutes after I entered the insectary, a room about the size of my dining room. I hadn’t been bitten, but I had trouble convincing my brain of that.
The rmy cares about mosquitoes because every soldier stricken with a bug-borne illness — malaria, Zika, viral encephalitis — is a soldier who can’t enter battle. The work done at WRAIR has helped develop insect repellents and vaccines.
“We call it maintaining the fighting force,” said Lt. Col. Elizabeth Wanja, director of WRAIR’s entomology branch.
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To learn how mosquitoes spread disease — and to develop and test vaccines against those diseases — you need a reliable supply of mosquitoes. WRAIR currently rears six species, including Aedes aegypti, Aedes albopictus, three types of Anopheles and Culex.
Along one wall in the brightly lit insectary are shelves holding large shallow pans, each with a few inches of water. Tiny mosquito eggs — they reminded me of ground black pepper — are added to the water. The eggs hatch and grow into larvae. The larvae are fed with fish food, then fished out and put into white plastic buckets on shelves on the opposite wall. There — under fine-meshed screen — they grow into pupae, which is sort of the tadpole stage of the mosquito.
When I moved my hand above one bucket, the hundreds of tiny black commas floating inside rippled as one, like a murmuration of starlings.
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“We call those tumblers,” Wanja said of the tumbling pupae that had been startled by my shadow. It was one of the creepiest things I’ve ever seen.
It takes about a week to go from egg to adult.
If you’re studying mosquito-transmitted disease, all you want are female mosquitoes, the ones that need a blood meal to lay eggs. Females are more attracted to heat — the better to find a living animal to bite — so to sort the sexes, an insectary worker holds a heat source against the bucket.
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And to feed them? Donated human blood is put in a small glass cup sealed with a membrane. Pushing the membrane against the mesh screen is like ringing the dinner bell. The mosquitoes rise up and start drinking.
When you buy eggs at the grocery store, you get a dozen per carton. When you get mosquitoes from the insectary, you get 250 per bucket. Feeding them blood that’s been infected with malaria allows researchers to test vaccines on volunteers.
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How does one enter the world of mosquitoes in the first place? Tobin Rowland is the insectary’s chief. His first duty assignment after enlisting in the Army in 2003 as a medical laboratory technician was inside WRAIR’s insectary.
“I just fell in love with it,” said Rowland, now a civilian.
Wanja grew up in Kenya, where she was fascinated by insects as a girl. She was earning her PhD in entomology in 1998 when terrorists blew up the U.S. Embassy in Nairobi. Some of her relatives were among those killed. Wanja wondered how she could employ her skills against the terrorists. Fighting mosquitoes was the answer.
“It was one of the ways I could come in and actually work to support the military to be able to get rid of these guys,” she said.
In 2007 and 2008, Wanja spent 15 months in Iraq studying insects and how to combat them.
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How do people react when Wanja and Rowland explain their jobs?
“I think the most common response is: ‘You play with bugs for a living? That’s not work,’” said Rowland. “Most people don’t really understand the threat that’s associated with insects.”
And not just from mosquitoes. The insectary also raises sand flies, which have a bite even worse than the mosquito’s. Sand flies are “pool” feeders. Rather than pierce the skin with a hypodermic-needle-like proboscis, they use their mouthparts to cut into the tissue, feeding on the blood that bubbles up to the surface. In the process, they can pass along leishmaniasis and sand fly fever.
Global warming seems to be expanding the territory of tropical diseases. And a new threat is on the horizon.
“Ticks are starting to become the main problem,” said Wanja. “We’re finding pathogens we did not know about in ticks.”
That means WRAIR will need to study them. Soon, the pitter-patter of tiny tick feet will be coming to the insectary.
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John Kelly’s Washington
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