Countermeasures for vector-borne diseases are often offered in the military when a service member is deployed to certain parts of the world. These types of countermeasures were developed to protect from infections spread by insects, rodents, and other animals. Insect-borne diseases, such as yellow fever, tick-borne encephalitis, Japanese encephalitis, and others infect millions of people each year.

The Military Health System has a long history of providing medical countermeasures for insect-borne diseases. We spoke to two experts in the MHS to learn about the various diseases and what the MHS has done to combat them.

Dr. Cecilia Mikita is medical director of the Defense Health Agency Immunization Health Care Division, North Atlantic Region, at Walter Reed National Military Medical Center. Dr. Margaret Ryan is the medical director of the DHA Immunization Health Care Division, Pacific Region, at the Naval Medical Center in San Diego, California.

MHS Communications: What is tick-borne encephalitis?

Mikita: Tick-borne encephalitis is a potentially serious viral disease associated with bites from infected ticks. TBE virus is not found in the United States; it is isolated to specific geographic regions extending from western and northern Europe through eastern and northern Asia. The virus is primarily transmitted to humans by infected ticks, with the highest risk between April and November. TBE-infected ticks are found in woodland habitats, and persons undertaking recreational outdoor activities, including hiking and camping, or who may be occupationally exposed, are at highest risk.

MHS Communications: What are the symptoms of tick-borne encephalitis?

Mikita: TBE is a potentially chronic and fatal neurologic disease. Most people infected with TBE virus have flu-like symptoms of fevers, fatigue, headaches, joint and muscle aches, and nausea which resolve in one to eight days. Approximately one-third of patients may progress to a second phase of neurologic symptoms including meningitis, encephalitis, myelitis, and paralysis.

MHS Communications: How does this illness affect service members?

Mikita: In the past 20 years, there have been 20 cases of TBE diagnosed in Department of Defense beneficiaries who traveled to parts of Europe, China, or Russia. The U.S. military has excellent programs, including disease tracking by the Armed Forces Health Surveillance Division and Integrated Pest Management, to prevent exposure to ticks carrying the virus in at-risk areas of the world.

MHS Communications: Is there a vaccine against tick-borne encephalitis?

Mikita: TBE vaccines have been available in Europe since the 1970s. The currently available TBE vaccine was licensed by the Food and Drug Administration in the U.S. in 2021. TBE vaccine is not a Force Health Protection requirement, but it is highly recommended for military service members and family members who will be traveling and living in at-risk areas of Europe and Asia and undertaking at-risk activities.

MHS Communications: Who is the vaccine approved for?

Mikita: The vaccine is approved for people aged 1 and older who are at risk of TBE exposure. The primary vaccine series is three doses, and one booster dose administered at least three years after the primary series if there is ongoing risk of exposure. It is a highly effective vaccine, creating an excellent immune response in 99% of vaccine recipients.

MHS Communications: How can you protect against TBE?

Mikita: Tick precautions are a very effective prevention strategy. The military’s Integrated Pest Management Program plays a crucial role in preventing TBE. Precautions include the use of DEET or picaridin, wearing long pants and sleeves, and treating clothing and gear with permethrin. Tick checks should be performed on your body after being outdoors. Programs than combine mosquito control with individual vaccination are highly effective at preventing TBE.

MHS Communications: What is yellow fever?

Mikita: Yellow fever is a mosquito-borne virus found in tropical and subtropical areas in South America and Africa. It is transmitted from one host to another via the bite of an infected mosquito.

MHS Communications: What are the symptoms of yellow fever?

Mikita: Symptoms can vary widely from a mild febrile illness to severe infection. The incubation period is typically three to six days. If symptomatic, individuals present with sudden onset of fever, chills, headache, back pain, muscle aches, fatigue, weakness, nausea, and vomiting. Approximately 15% of individuals progress to a more serious or toxic form of the disease after a brief remission. Symptoms include high fevers, jaundice, bleeding, shock, and multisystem organ failure. Twenty to 50% of severe cases with liver or kidney involvement may die from YF.

MHS Communications: Is there a vaccine against yellow fever?

Mikita: The first YF vaccine was developed in 1938. The currently available vaccine is approved for individuals nine months of age and older. YF vaccine is required for military and civilian/DOD personnel deploying to or traveling to YF-endemic areas, including South America and Africa. Vaccination may be required for entry into certain countries. Most travelers require a single, lifetime dose of YF vaccine. YF vaccine is highly effective, with 99% of people developing immunity within 30 days after vaccination.

MHS Communications: How can you protect against yellow fever?

Mikita: Mosquito control is an essential part of YF disease prevention. The Integrated Pest Management Program, including the use of insect repellent and insecticides, is imperative to preventing YF and other mosquito-borne infections. Programs than combine mosquito control with individual vaccination are highly effective at preventing YF.

MHS Communications: What is Japanese Encephalitis?

Ryan: Japanese Encephalitis virus is a mosquito-borne virus found in Asia and many areas of the Western Pacific. JE virus is closely related to West Nile virus. The virus can infect birds, certain farm animals, and humans; infected animals and persons are sometimes called “hosts.” Mosquitos transmit the virus between hosts; mosquitoes are called “vectors.”

MHS Communications: What are the symptoms of this illness?

Ryan: Although most people infected with JE virus have only mild fever or body aches, approximately one in every 250 people with JE infection will develop encephalitis within one to two weeks after becoming infected. Encephalitis means “inflammation or the brain.” Encephalitis from JE infection is characterized by high fever, severe headache, stiff neck, confusion, seizures, and/or paralysis. JE infection is fatal in approximately one-third of those who develop encephalitis. Among people who survive encephalitis after JE infection, approximately half will have lifelong disability.

MHS Communications: Is there a vaccine against Japanese Encephalitis?

Ryan: Yes, there is a highly effective vaccine available to prevent JE in humans. The vaccination is part of the routine childhood immunization schedule for children in Japan. It is required for military service members who travel to, or live in, JE-risk areas. JE vaccination is strongly recommended for military family members and others who travel to, or live in, JE-risk areas.

JE vaccine is recommended for all people ages two months and older who are at risk of JE exposure. The primary vaccine series is two doses, given at least one month apart. For persons who remain in, or return to, a JE-risk area after their primary vaccine series, a third dose can be given one year later.

MHS Communications: When was the vaccine developed?

Ryan: JE vaccines have been available in the United States since 1992. The current vaccine, which is abbreviated as JE-VC was FDA-licensed in 2009.

MHS Communications: How can you protect against JE?

Ryan: The military’s Integrated pest management program, which include appropriate use of insecticide and insect repellent, is critical in preventing JE as well as other mosquito-borne infections. Programs than combine mosquito control with individual vaccination are highly effective at preventing JE.