Crew members in protective suits load their C-130 Hercules with the weapon it will need for a night mission near Charleston Air Force Base, South Carolina. The enemy has the numbers, but the 910th Airlift Wing will use less than an ounce of insecticide per acre to eliminate them from the “battlefield.”
Shortly after sunset, the C-130 commences its attack run at 300 feet, with its Modular Aerial Spray System (MASS) unloading a mist over 18,000 acres of marshy enemy-held territory adjacent to the base perimeter.
Sunrise reveals countless enemy dead. An entire mosquito horde — wiped out. Their mission to feast on the blood of Airmen — thwarted.
The 910th AW, based at Youngstown Air Reserve Station, Ohio, targeted the mosquitoes for spraying before they could potentially spread diseases to service members and their families. But the order of battle against these insects began to unfold long before this attack, with the Air Force’s four-component strategy of controlling and preventing mosquito-transmitted diseases, beginning with trapping and surveillance.
“When it comes to strategies… as far as protecting our Airmen from mosquito-borne illnesses, in the past most of our focus was on the deployed settings because in the United States we have not necessarily had a lot of mosquito-borne diseases of concern,” said Col. James A. Mullins, the associate corps chief for public health and the Air Force Surgeon General’s consultant for public health.
In the early 2000s, the West Nile virus swept across the continental United States, and in the past few years, outbreaks of the chikungunya virus hit the southernmost regions of the country.
Now, the Zika virus threatens the Western Hemisphere.
“We’re poised to respond in case locally acquired cases occur in the United States,” Mullins said. “That’s where much of our effort and focus on surveillance and protection have come most recently.”
Mosquito-borne diseases, such as dengue fever, malaria, and the West Nile and Zika viruses, affect more than 390 million people each year, or about 40 percent of the world’s population, according to the Centers for Disease Control and Prevention. The number of pregnant women with Zika in the United States has more than tripled from 48 to 157, according to a CDC report. It isn’t known whether the increase was due to a change in tracking or if there are actually that many more pregnant women with the disease.
According to the report, there are 122 pregnant women with Zika in the U.S. territories. The two vectors – or species that carry these diseases — Aedes aegypti and Aedes albopictus mosquitoes — flourish in many parts of the United States.
An important part of preventing mosquito-transmitted diseases is eradicating the insects that spread them, especially on Defense Department installations. That’s where the 910th AW comes into play. The wing has the DOD’s only large-area fixed-wing aerial spray capability for controlling disease-carrying insects. The wing’s C-130s, equipped with the palletized MASS, sprays areas larger than 5,000 acres from altitudes of 100 to 150 feet and conducts nighttime operations using night vision technology at 300 feet. Nighttime missions are important because mosquitoes are more active at dawn and dusk, said Air Force Reserve Maj. Steve Stroney, the wing’s chief of aerial spray.
“The main reason for our mission (in Charleston) is to do vector control for vector-borne illness caused by the mosquito,” Stroney said. “Any disease that mosquitoes transfer is one thing that we’re concerned about, and the ability for us to control disease by killing mosquitoes is beneficial. It provides us with training, as well, as an aircrew because we do have a wartime tasking for this mission.
“The biggest benefit that our unit provides in cases like this is the ability to do large areas in a single night,” he continued. “We could obviously load more to do a larger block (more than 18,000 acres).”
Public health staffs at many bases work closely with their civil engineers, who also spray to prevent mosquito larvae from developing, said Maj. Kristen Robertson, the 1st Special Operations Aerospace Medical Squadron public health flight commander.
Because of the large mosquito population in Florida, public health at Hurlburt Field operates mosquito surveillance routinely each year, although they began earlier this year in February because of the Zika virus threat. They routinely set up traps on the golf course, temporary lodging facilities, child care center, the outdoor recreation and family camping area, and any other sites mosquitoes begin to populate, Robertson said.
“Since, at Hurlburt Field, we have a very robust deployment mission here, obviously, our priority is going to be ensuring that our Airmen are safe,” Robertson said. “We are also concerned that our families are safe, as well. So as far as on base, we’re going to be concerned with the areas where they live.”
Base personnel also coordinate closely with local health departments to relay data on other mosquito control efforts to Airmen and their families, she added.
Once the mosquitoes are trapped and frozen, public health technicians look at the specimens under a microscope and discard the males since only the females feed on human blood. Female specimens are then sent to the U.S. Air Force School for Aerospace Medicine (USAFSAM), part of the 711th Human Performance Wing at Wright-Patterson AFB, Ohio.
The lab receives up to 20,000 samples a year from public health offices at installations worldwide, said Capt. Elizabeth Foley, the USAFSAM entomology chief.
“We’re doing surveillance to find a better way to track them and also a better way to detect diseases in the field,” Foley said. “Once we’re finished with that research, we can present it to DOD and maybe it will push funding for the development of a novel piece of equipment or put into place a standard use product.”
To help improve surveillance methods on the mosquitoes that cause diseases such as chikungunya, dengue fever and the Zika virus, USAFSAM also has Biogen Sentinel 2 mosquito traps set up at an Air National Guard base in Puerto Rico and a cooperative security locationon the island of Curacao. In addition to the Biogen trap, the school uses ovitraps and lethal ovitraps. The ovitrap doesn’t actually trap mosquitoes, but provides a count of the mosquito population. The lethal ovitrap uses pesticide that kills mosquitoes shortly after they’re caught.
With the threat of Zika virus, especially with the link shown between the virus during pregnancy and the development of the birth defect called microcephaly, there is a greater emphasis on finding mosquitoes that could transmit the disease.
“One of the difficulties historically with this virus and with the vector is it’s very hard to detect within the vector,” Foley said. “So you will see it in human populations much faster than you will detect it within the vector. There have been cases where there were more than 3,000 mosquitoes tested in an endemic area where the disease is occurring, but only a small percentage was found positive.
“It’s not known yet why it’s difficult to find them in the mosquito, but so far we’ve tested a couple of dozen samples here at the lab, we’ve had samples sent in from Curacao, Puerto Rico, and some other areas, and we haven’t found any Zika positive mosquitoes yet. But we’re still looking,” she added.
The school’s Epidemiology Surveillance Laboratory also conducts laboratory testing on human specimens for medical treatment facilities throughout the DOD. The “reference laboratory for the Air Force” receives between 5,000 to 6,000 specimens each day, said Dr. Elizabeth Macias, lab director.
Macias said the lab stands ready to handle a surge of Zika specimens, similar to what it experienced during the influenza pandemic in 2009.
“There are a lot of projections and maps of where the mosquitoes are, but the mosquitoes can come up as far as Ohio, and I’ve seen maps that show them coming all the way up the East Coast,” Macias said. “So that’s why we’re gearing up to be able to handle a large number of specimens. Right now, it’s pretty easy because you’ve had to have traveled to the endemic areas — the Caribbean, South America or Central America. But once it’s CONUS, it’s going to be really hard to keep it under check.”
The DOD is also providing $1.76 million in extra funding to military laboratories to expand Zika virus surveillance worldwide and assess the virus’s impact on deployed service members’ health and readiness. The enhanced Zika virus surveillance will involve 10 projects in 18 countries and territories by four lab partners based in the United States and five located overseas.
Education and individual protection
To address education and personal protective measures, the second and third components of the service’s strategy for fighting mosquito-transmitted illnesses, Airmen are given information about health risks before deploying to a risk area, as well as guidance that can help families prevent mosquito bites in the first place, Mullins said.
The most important steps involve removing any containers around the home that could have standing water like birdbaths, buckets and pet food bowls, a prime target for mosquitoes to breed. Also, they should wear long sleeves and pants to limit exposed skin and wear insect repellent such as DEET, Mullins said.
Another way information about reducing the risks is disseminated is through travel medicine programs, which are open to active-duty members, retirees, and dependents, Robertson said. She recommends visiting public health anytime members and their families plan a trip outside of the U.S.
“We will provide them with vaccine recommendations and education on preventive health measures,” Robertson said. “We include actions to take when they return home, incorporating Zika-specific education, such as continuing to wear mosquito repellent for at least three weeks, avoiding unprotected sex for a designated period of time (eight weeks for males having shown no symptoms and six months for males who developed symptoms during travel), and additional precautions for pregnant women or those considering becoming pregnant.”
As with education, the fourth component also varies, depending on the disease. Medications and vaccines are another part of the strategy that the Air Force uses to keep its people healthy, especially when they deploy to at-risk locations around the world.
“Malaria is a great example,” Mullins said. “Whenever anyone is traveling in a malarious area, we’re going to write a prescription for them for an anti-malarial that they can take either once a week or daily, depending on what the drug is, and that will help keep them from becoming ill with malaria. Certainly for diseases such as yellow fever, we are fortunate that we have a very good vaccine for that, and we can immunize individuals before heading into an area where yellow fever is and keep them healthy.
A combination of education, personal protective measures and vaccines is the best deterrent against mosquito-transmitted diseases, Mullins said.
Even though emphasis on the Air Force’s stateside strategy has increased, the greater risk remains for Airmen deployed in austere environments where mosquito-borne diseases are a bigger threat.
“When it comes to the susceptibility of our Airmen to mosquito diseases, either overseas or in the continental U.S., the risk is going to vary, depending on where they are traveling,” Mullins said.
The threat remains greatest for Airmen when they deploy, he said. By using protective measures, vaccines and information given before they leave for a deployment in an austere environment, they can remain healthy and continue to support the mission, Mullins said.
So the war wages on, with the enemy mosquitoes continuing to bring in a seemingly endless supply of reserves to replenish the ranks decimated by the spray from the C-130 in the nighttime South Carolina sky.