Avoiding tick bites is best defense against contracting Powassan virus (PV)

Q: I read that someone in Maine died of Powassan virus after getting it from a tick. Is this a new disease or a type of Lyme?

A: There are man pathogens that can be transmitted by a tick bite and cause infections. For most, the tick acquires the pathogen by biting an animal containing it. The infectious agent then multiplies inside the tick, and is "spit" onto a human when it feeds on them. Tickborne conditions include:

• Bacterial illnesses, such as various conditions due to Borrelia species including Lyme disease, tickborne relapsing fever and possibly southern tick-associated rash illness (STARI); ehrlichiosis; various Rickettsial diseases, including rickettsiosis, anaplasmosis, Rocky Mountain spotted fever and other conditions; and tularemia.

• Viral illnesses, such as Colorado tick fever, Heartland virus, Powassan virus (PV) and tickborne encephalitis.

• Parasitic illnesses, such as babesiosis.

• Non-infectious conditions, such as tick paralysis (due to a neurotoxin from the tick) or an acquired meat allergy.

So PV (due to a virus) is not the same as Lyme disease (due to a bacterium). Although PV is extremely rare (only two to three dozen or so cases reported in the U.S. annually during the last 5 to 10 years), it was first described in Powassan, Ontario, in 1958. So it's not new.

Although there are antibiotic treatments that are often effective for most of the bacterial diseases noted above (although some may still lead to chronic conditions, such as Lyme disease), there are no specific treatments available for the viral diseases (including no treatment available for PV). There are vaccines for some of these conditions (including one for people at high risk for tickborne encephalitis), but they do not exist for most of them (and none for PV).

So the best way to prevent these conditions is to avoid tick bites. Here's how:

• Avoid high-risk areas when possible. Stay to the center of trails when you walk through the woods.

• Wear long sleeves, pants (tucked into your socks) and a hat whenever you will be somewhere that a tick bite is possible.

• Wear light-colored clothes, so you can see a crawling tick before it makes it to your skin.

• Use insect repellent; the Centers for Disease Control recommend ones containing DEET, picaridin, IR3535 or the oil of lemon eucalyptus.

• Perform frequent tick checks on yourself and your pets.

• Make areas of your property less likely to have ticks by using wood chips or gravel to create a dry boundary (ticks like moisture) to diminish tick migration to your lawn, and by keeping your lawn mowed and without brush/leaf buildup. Consider pesticide treatments (discuss the pluses and minuses of this option with your pest control expert).

If you are bitten by a tick, don't panic; most tick bites do not transmit a disease. When a disease is transmitted, ticks may be responsible for transmitting different infectious agents (hence, some diseases are more likely to be found in different areas of the country), although certain diseases can be transmitted by multiple types of ticks (for example, even though deer ticks are often blamed for transmitting Lyme disease, many kinds of ticks have been implicated). Even after a tickborne infection is transmitted, many patients do not develop disease.

If you find a tick, it should be removed immediately by grasping it as close to the skin as possible (do not squish it), and gently but firmly pulling it away off (forceps or blunt tweezers may be useful). In most cases, early tick removal is beneficial by preventing or decreasing the amount of infectious agent transmitted; some infectious agents are rapidly transmitted, so prompt removal can be of limited benefit.

Prophylaxis after a tick bite depends on the circumstances and the risk, including what tickborne illnesses are endemic to that area. For example, if a tick has been on for 24 to 72 hours in an area where Lyme disease is endemic, then one dose of appropriate antibiotic is usually indicated.

When a specific disease is contracted from a tick bite, symptoms typically begin days to weeks later. In many cases, symptoms are mild and "flu-like" (for example fever, headache, malaise and/or body aches), and are self-limited; in these cases, the patient may not be diagnosed with an illness.

When symptoms are characteristic of a specific illness,) the specific disease may be diagnosed. Severe illnesses from tickborne diseases include encephalitis (PV may cause encephalitis) and/or other neurological conditions, muscular-skeletal issues (for example, joint problems), heart conditions or other organ system problems. Although not common, tickborne infections can be fatal.

For severe symptoms where a tickborne disease is possible, specific blood (or sometimes cerebral spinal fluid) tests may be indicated. However, in some cases the initial test may be negative, only yielding positive results later (after the body’s immune system has mounted an adequate response).

Do what you can to avoid tick bites, and see your clinician if you develop symptoms suggestive of a tickborne illness.

Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.

This article originally appeared on MetroWest Daily News: Tick bites can lead to many infections, including Powassan virus