JULY 18, 2024 – As a result of the COVID-19 pandemic, most people have a heightened awareness of how to avoid common infectious diseases, such as the flu and respiratory syncytial virus, or RSV, that are transmitted between humans.
Unlike these human-transmitted diseases, some diseases are transmitted by insects such as mosquitos, ticks, and flies. These bugs are known as “vectors” as they can carry and transmit viruses, bacteria, or parasites that cause vector-borne disease, or VBD.
“You don’t catch VBDs from a person, so a primary difference between preventing human- transmitted infectious disease and preventing VBDs is to avoid the biting nuisances that carry the disease-causing germs,” said U.S. Army Lt. Col. (Dr.) David H. Yun, a preventive medicine clinician and chief of disease epidemiology for Defense Health Agency-Public Health in Aberdeen, Maryland.
According to the Centers for Disease Control and Prevention, there are hundreds of VBDs worldwide, and new ones continue to be identified. While some VBDs are rare, others affect thousands of people every year. Although most VBDs cause mild or moderate illness, some cause severe symptoms or can result in long-term complications or even death.
The CDC warns of numerous VBDs present in North America, such as Lyme disease, dengue fever, West Nile virus, Rocky Mountain spotted fever, plague, rickettsiosis, and ehrlichiosis. Other VBDs like chikungunya, malaria, Rift Valley fever, and yellow fever viruses are not commonly found in the U.S. but can pose risks to travelers and deployed personnel.
Not every vector will carry a disease, but vectors found in some areas of the world are more likely to transmit a certain type of VBD. Because there are numerous types of VBD, it’s important to identify the VBD risks associated with an area before and after traveling there for leisure or military deployment.
How Does the Military Monitor VBDs?
“The military is concerned with all types of VBDs because we have troops all over the world,” said Yun. “Military health surveillance helps us identify priorities at different locations.”
Sometimes surveillance data requires interpretation by medical experts. For example, a recent report published on health.mil described the four most diagnosed VBDs in the military population over the past decade are Lyme disease, Rocky Mountain spotted fever, or RMSF, malaria and dengue fever.
While these four VBD are currently the most frequently identified in health surveillance, the locations where cases are being reported may vary from the locations where personnel are getting bitten.
“Though high numbers of malaria and dengue fever cases are reported in North America, the vast majority were acquired from mosquito bites that occurred during travel to regions outside of the U.S., especially warmer regions closer to the equator,” said Yun. “The numerous cases of Lyme diseases and RMSF reported in North America, on the other hand, were transmitted by certain ticks commonly found in parts of the U.S.”
While there’s been a decrease in military VBD rates between 2010 and 2022 due to reduced troop deployments, surveillance of VBDs has informed the military medical community of efforts to control VBDs affecting troops in deployed settings.
One prominent example was the notable increase in cases of leishmaniasis, a disease transmitted by the sand fly, seen during the early phase of the wars in Iraq and Afghanistan.
“At the start of the Iraq conflict in 2003, the military had limited enclosed structures to house troops in Iraq and Afghanistan, so exposure to the sand flies was especially high,” said Yun. “Improvements to tents and buildings such as air conditioning and sand fly-proof windows, and an emphasis of U.S. military troop training on personal protective measures to avoid sand fly bites, proved to be effective.”
The resulting military health surveillance data demonstrated how the increased protection measures had successfully reduced the leishmaniasis risk in that region .
What Can You Do to Lower your Risk of Contracting a VBD?
To reduce risk of becoming sick with a VBD, the best defense against is avoiding the bites of the vectors. To prevent bites, service members are encouraged to comply with the Department of Defense’s Insect repellant System, which includes wearing insect repellent on exposed skin and wearing uniforms treated with permethrin, an insecticide.
Importantly, there is also an additional form of protection to get before you travel.
“You need to know if there are preventive medications, known as prophylaxis, or vaccines that will keep you safe from VBDs that are common in the areas you will be in,” said Yun.
Yun suggests that talking with a travel medical clinic or health care provider trained in travel medicine is the best way to get proper advice.
Military providers and service members currently have DOD-authorized access to Shoreland’s Travax travel medicine system, which allows them to tailor medical recommendations based on travel plans.
Anyone can also proactively investigate what prophylaxis or vaccines are recommended for their area of travel by using the CDC’s Traveler’s Health guide.
The military specifies requirements for vaccines and prophylaxis medications based on worldwide regions of deployment.
Currently, the military only uses VBD vaccines for tick-borne encephalitis, Japanese encephalitis, and yellow fever for service members stationed or deployed to endemic areas. Other VBD vaccines may only be approved for children, such as malaria and dengue, or are still so new that policies on their use have not been incorporated into military requirements, such as for chikungunya.
Instead of vaccines, for most VBDs the military opts for prophylaxis medications, which are effective and used by civilians.
“One of the most known prophylaxis is for malaria,” said Yun. “While the military primarily uses a medication commercially known as Malarone, there are various other medications that work. But very importantly—most malaria prophylaxis require taking the medication daily for at least one to two days before travelling to an area of risk, every day while there, and then likely after you return for one to four weeks.”
“Failure to complete taking the prophylaxis medication after a person has returned is a common mistake that can lead to malaria,” said Yun.
Even if a person feels fine, at the time, malaria can take weeks or months up to a year to develop. Yun said completing the prophylaxis after returning is necessary to eliminate any potentially incubating parasites.
What Do You Do if You Feel Ill After Travelling?
“Symptoms for VBD are often nonspecific, such as fevers and flu-like symptoms,” said Yun. “Symptoms can also develop weeks, months or possibly years after you were exposed, so when you see a doctor for symptoms, be sure to explain your travel history.”
“Before travel, find out what vector-borne diseases are in areas you will be going,” said Yun. “Check with your travel health clinic for necessary preventive medicines or vaccines. After returning, complete all medications, and tell your provider your travel history if you develop illness.”
Courtesy Story
Defense Health Agency