Ask the Doctors

Dear Doctor: I've been reading a lot of warnings about the recent wet weather causing an abundance of ticks and their potential to cause disease. I knew about Lyme disease, but now Powassan virus? What's that? And just how dangerous are ticks?

Dear Reader: Ticks are external parasites that, because they feed on blood, are quite efficient at transmitting disease. In each of the three life stages that a tick goes through after hatching, it needs blood to survive. Depending on the species, ticks will feed on mammals (that's us), birds, reptiles and amphibians.

A variety of ticks throughout the United States can transmit more than a dozen dangerous and sometimes deadly diseases. These include Lyme disease, Rocky Mountain spotted fever, tularemia, and Colorado tick fever, to name a few of the most commonly known. The tick picks up the disease while feeding on an infected host, and then can transmit it through its saliva during future feedings.

One of the lesser-known diseases is Powassan virus, a flulike illness that can cause inflammation in the brain. It is spread by several types of ticks found in the northeastern states and in the Great Lakes region. The disease is fatal in up to 15 percent of individuals who show symptoms. About half of those who survive face ongoing neurological difficulties.

Powassan virus was once rare, with about two reported cases per year between 1950 and the early 2000s. That number has risen to 75 reported cases in the last decade, or close to eight per year. Some experts believe this may be due to increased awareness in diagnosing the disease.

However, Lyme disease, with close to 30,000 confirmed cases each year, remains the most common tick-borne illness in the U.S. According to the Centers for Disease Control and Prevention, the total may actually be as high as 300,000 infected individuals per year, when unconfirmed cases are factored in.

While there are some species of ticks that don't carry disease, without specialized knowledge it's almost impossible to tell them apart from those that do. As a result, the best advice is to protect yourself, your family and your pets against all tick bites.

Ticks prefer areas that are moist and humid, and concentrate in wooded and grassy areas. They can't jump or fly, so they perch at the tips of grasses and shrubs, where they can easily attach to a host as it brushes by.

To avoid tick bites:

-- When in grassy or brushy areas, wear long sleeves, long pants and close-toed shoes. Tuck pants into socks. Light-colored clothing makes spotting ticks easier.

-- Insect repellents that contain 20 percent DEET may be helpful. Some experts say picaridin is even better. Reapply according to manufacturer instructions.

-- Treat clothing, boots and tents with products containing 0.5 percent permethrin, which stays effective through several washings. Pre-treated clothing and gear is also available and may offer longer protection.

-- After spending time outdoors, be sure to do a tick check. Visually scan all areas of your body, including your scalp and hair.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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