Add Powassan Virus to Our Summer Tick Concerns
Darin Seehafer
Darin Seehafer
Sr. Director, Center for Vaccines and Emerging Infectious Diseases

According to the Centers for Disease Control, this could be one of the worst summers on record for ticks. While Lyme disease is the most commonly known tick-borne illness, ticks carry a number of pathogens that can cause other diseases, too, including the Powassan virus (POW).

While not a new virus, POW is a much more serious tick-borne disease and it is showing up more and more in the northeastern part of the U.S., primarily around the Great Lakes region. But it’s also slowly spreading to the New England area, as well. The virus has infected approximately 75 people in the past 10 years.

Myth: Ticks are insects.
Fact: They are a species of parasite called arachnids, and like their cousin spiders, they have eight legs and belong to the same family as mites.

Myth: Ticks jump and fly.
Fact: Ticks crawl.

Myth: The best way to remove a tick is with a lit match or “painting” the tick with nail polish or petroleum jelly.
Fact: The best way to remove a tick is to use fine-tipped tweezers to grasp the tick as close to the skin as possible and pull upward with steady, even pressure. After removing, cleanse the bite area and your hands with rubbing alcohol, iodine scrub, or soap and water.

The virus itself is an RNA virus related to West Nile, St. Louis encephalitis, and tick-borne encephalitis viruses. The POW virus is transmitted in a cycle between ticks and small to medium size rodents—primarily woodchucks, squirrels and mice. Patients with symptoms of encephalitis accompanied by a fever, and dizziness who live in tick infested areas should be tested for POW.

Are there any tick vaccines?

Currently there are no available tick vaccines in the US. Identifying a vaccine to lower tick-borne illness is challenging due to the fact that there are many tick species that live in a variety of areas. A Lyme disease vaccine, LYMErix, was introduced in the US in 1998 but the manufacturer discontinued production in 2002.

One of the challenges during the LYMErix trials was infections causes by ticks after vaccination. Many participants in the study were only concerned about Lyme disease and unfortunately, a significant number of vaccinated subjects inadvertently lapsed in their personal preventative measures and were subsequently bitten by a tick and infected with any number of other tick-borne diseases. Often these diseases were difficult to distinguish, so it called into question the efficacy of the vaccine. This opened the debate over the notion of vaccinating against only one of the almost 20 diseases ticks carry. Lastly, Lyme disease is/was considered to be a “regional” problem and therefore there was only limited uptake of the vaccine, a major contributing factor to LYMErix’s demise.

Over the past two decades the number of cases of Lyme disease have tripled in the U.S., with an estimated 300,000 Americans infected.

Despite the failure of LYMErix and other earlier tick-related vaccines, researchers continue their quest for a solution. In late 2016, a French biotech company was given permission by the Food and Drug Administration to start clinical trials for a new Lyme disease vaccine. The European Union’s Clinical Trial Application also gave similar approval.

ANTIDotE (The Anti-tick Vaccines to Prevent Tick-borne Diseases in Europe), a European consortium, has focused on creating a vaccine that eradicates the tick itself, rather than the illness it carries. ANTIDotE is in the process of identifying antigens that could provide an anti-tick vaccine that can protect against multiple tick-borne illnesses. ANTIDotE’s main goal is to create a vaccine for humans that protects against multiple human tick-borne diseases that can be incorporated into Europe’s health systems.

Powassan virus symptoms include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and seizures. Symptoms occur within one week to one month of the tick bite, though many infected people may not experience any symptoms at all. This virus is extremely dangerous, as it may cause encephalitis (inflammation of the brain) and meningitis (inflammation of the membranes that surround the brain and spinal cord). In extreme cases, Powassan virus can be fatal with 10% of diagnosed cases resulting in death.

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