The western black-legged tick, one of two types of deer ticks in the U.S., is responsible for the spread of Lyme disease in California and other parts of the western U.S. Photo: Centers for Disease Control
The weather was warm when a friend and I went bowhunting for early-season deer. At day's end, we hadn't seen any whitetails, but when we arrived back at the truck, I did notice another creature. A tick was crawling up my hunting buddy's neck.
"There's nothing good about ticks," I said as I showed him the little blood-sucking parasite.
"Oh, yes, there is one good thing about them," he said.
"And what would that be?" I asked.
"They don't get as big as grizzly bears," he replied.
We are indeed fortunate that ticks are small because these arachnids are like little vampires. They bite unlucky humans who cross paths with them and then make a meal of their blood. A tick the size of Gentle Ben would certainly be frightening to encounter.
Fortunately, adult ticks aren't big, usually about the size of a lemon seed. And in most cases, a tick bite is nothing more than an inconvenience. The victim may not even realize a tick has drilled his epidermis until the bug has finished feeding, fallen off and left behind a swollen, itchy bite mark. After a few days, the bite usually disappears, and the victim is little worse for the wear.
This is not always the case, however. A number of infectious diseases are transmitted by ticks. And left untreated, some illnesses such as Rocky Mountain spotted fever, tularemia and Lyme disease can be dangerous or even deadly.
This chart shows the life stages of three types of common U.S. ticks, including the black-legged, or deer, tick. Black-legged tick nymphs are more likely to spread the Lyme disease bacterium than adults or larvae. Graphic: Centers for Disease Control
The fact that ticks are small acts against us in this case. If a tick remains undetected and attached to its victim several hours, the possibility of disease transmission greatly increases.
Several types of ticks are vectors of disease-causing bacteria, viruses and protozoans, including the American dog tick, brown dog tick, Lone Star tick and Rocky Mountain wood tick. It is the black-legged tick, however, (better known as the deer tick) that has garnered most of the bad press in recent years. That's because black-legged, or deer, ticks are more likely than other tick species to carry the bacterium Borrelia burgdorferi, which causes Lyme disease, the most common bug-borne illness in the United States. (Black-legged ticks also are vectors of the diseases babesiosus and anaplasmosis.)
Lyme disease was first recognized in the U.S. in 1975 after an unusual outbreak of arthritis near Lyme, Connecticut. Since then, reports of Lyme disease have increased dramatically, and the disease has become an important public health problem in some areas.
State health departments reported 28,921 confirmed cases and 6,277 probable cases of Lyme disease to the Centers for Disease Control in 2008, the most recent year for which statistics are available. This represented a five percent increase in confirmed cases compared to 2007.
The black-legged tick (Ixodes scapularis) spreads Lyme disease in the northeastern and north-central United States, and the western black-legged tick (Ixodes pacificus) spreads the disease on the Pacific Coast. Most cases of Lyme disease in the U.S. occur in these areas:
- Northeast, from Maryland to Maine
- North-central states, mostly in Wisconsin and Minnesota
- West Coast, particularly northern California
Black-legged ticks also occur throughout the southeastern U.S. and west to south-central Texas, Oklahoma, southern Missouri and eastern Kansas. However, few black-legged ticks in the Southeast have been found infected with Lyme disease bacterium. Therefore, the risk for Lyme disease from this tick in the southeastern part of the country is considered relatively low.
In general, ticks need to be attached for 36 to 48 hours before they can transmit the Lyme disease bacterium. Most humans are infected through bites of immature ticks called nymphs. Nymphs are smaller than a pinhead (less than 2 mm or .08 in.).
Adult ticks also can spread Lyme disease, but they are much larger (about the size of an apple seed) and more likely to be discovered and removed before they have time to transmit the bacteria.
Black-Legged Tick Life Cycle
Becoming familiar with the life cycle of black-legged ticks can help in understanding the risk of getting Lyme disease and how to prevent it.
Tick eggs are laid in spring and hatch as larvae in summer. Larvae feed on mice, birds and other small animals in summer and early fall. When a young tick feeds on an animal infected with Lyme disease bacteria, the tick ingests the bacteria along with the blood meal, and it remains infected for the rest of its life.
After this initial feeding, the larvae become inactive as they grow into nymphs. But the following spring, the nymphs reactivate and seek blood meals to fuel their growth into adults. When a nymph feeds, it can transmit the bacteria to its new host, usually another small rodent, but sometimes a human. Most cases of human illness occur in late spring and summer when the tiny nymphs are most active and human outdoor activity is greatest.
The nymphs molt into adult ticks in the fall. In fall and early spring, these adults feed and mate on large animals such as deer. Adult female ticks sometimes also feed on humans. In spring, adult female ticks lay their eggs on the ground, completing the two-year life cycle.
This photograph shows the "bull's-eye rash" that often manifests at the site of a tick bite when the Lyme disease bacterium is transmitted. Photo: Centers for Disease Control
How People Get Ticks
Black-legged ticks search for host animals from the leaf litter of the forest floor or from the tips of grasses and shrubs. Ticks crawl onto animals or people that brush against them; ticks cannot jump or fly. Ticks found on the scalp usually have crawled there from lower body parts.
The risk of exposure to ticks is greatest in the woods and in edge areas between lawns and woods. But ticks also are carried into lawns and gardens by animals and into houses by pets. Campers, hikers, outdoor workers and others may be exposed to infected ticks in wooded, brushy and grassy places. People living in houses built in heavily wooded areas where infected ticks are common also are at higher risk for exposure.
Lyme Disease Symptoms
If a tick harboring Lyme disease bacteria remains attached for three to four days, there is a good chance the victim will become infected. Different symptoms occur at different times. Not all patients with Lyme disease exhibit all symptoms, and many of the symptoms occur with other diseases as well. If you believe you may have Lyme disease, it is important to consult your health-care provider for proper diagnosis.
The first sign of infection is usually a circular rash that occurs in 70 to 80 percent of infected persons. This begins at the site of a tick bite after a delay of three to 30 days. A distinctive feature of the rash is that it gradually expands over a period of several days, reaching up to 12 inches across. The center of the rash may clear as it enlarges, resulting in a bull's-eye appearance. The rash may be warm but is seldom painful. Patients also may experience fatigue, chills, fever, headache, muscle and joint aches, and swollen lymph nodes.
Untreated, the infection may spread to other parts of the body within a few days to weeks, producing an array of discrete symptoms. These include loss of muscle tone on one or both sides of the face (called facial or Bell's palsy), severe headaches, neck stiffness, shooting pains, heart palpitations, dizziness and pain that moves from joint to joint. Many of these symptoms will resolve, even without treatment.
After several months, approximately 60 percent of untreated patients have intermittent bouts of arthritis, with severe joint pain and swelling. Large joints are most often affected, particularly the knees. In addition, up to five percent of untreated patients develop chronic neurological complaints months to years after infection. These include shooting pains, numbness or tingling in the hands or feet, and problems with concentration and short-term memory.
A tick that has embedded itself in the skin should be removed using tweezers or a tick extractor without squeezing or mashing the tick. Graphic: Centers for Disease Control
Most cases of Lyme disease can be cured with antibiotics, especially if treatment is begun early in the course of illness. However, a small percentage of patients have symptoms lasting months to years even after treatment with antibiotics. These symptoms can include muscle and joint pains, arthritis, cognitive defects, sleep disturbance and fatigue. The cause of these symptoms is not known.
Fortunately, there are several tactics you and your family can use to prevent tick bites and reduce the risk of tick-borne illnesses such as Lyme disease.
- Use a DEET or permethrin-based insect repellent when outdoors. Repellents containing DEET will repel ticks several hours and are safe for use on skin and clothing if you follow label directions and precautions. Permethrin products such as Permanone and Duranon will kill ticks on contact for several days when used to treat clothing, shoes, tents, sleeping bags and chairs, but these products never should be used on the skin. Once again, follow label directions.
- When in areas likely to harbor ticks, wear long pants with the cuffs tucked in your socks to prevent ticks from crawling up inside your pant legs. Where ticks are abundant, you might even want to wrap some duct tape around your ankles, over the top of your socks. Keep your shirt tucked into your waistband, too. And wear light-colored clothing that makes it easier to see ticks crawling on you.
- When possible, walk in the center of trails and avoid brushing against vegetation or traipsing through leaf litter.
- Inspect yourself and your children for ticks after trips outdoors, even in your own yard. Check your pets, too. Use a mirror to view all parts of your body and remove any tick you find. Pay special attention to the armpits, groin, waist, ears, belly button, backs of knees and hair on the scalp.
Should you find a tick that has embedded its mouthparts in the skin, remove it as soon as possible using these tips from the Centers for Disease Control:
- Use fine-tipped tweezers or a notched tick extractor, and protect your fingers with a tissue, paper towel or latex gloves. Avoid removing ticks with bare hands.
- Grasp the tick as close to the skin surface as possible and pull upward with steady, even pressure. Do not twist or jerk the tick; this may cause the mouthparts to break off and remain in the skin.
- After removing the tick, disinfect the bite site and wash your hands with soap and water.
- Do not squeeze, crush or puncture the tick's body because its fluids may contain infectious organisms. Skin accidentally exposed to tick fluids can be disinfected with iodine scrub, rubbing alcohol or water containing detergents.
- Save the tick for identification in case you become ill. This may help your doctor make an accurate diagnosis. Place the tick in a sealable plastic bag and put it in your freezer.
- Don't use petroleum jelly, hot matches or other folk remedies as these may cause a tick to release additional saliva or gut contents, increasing chances of infection.
While tick bites can cause problems, those problems are relatively rare. Don't stop enjoying nature, the great outdoors and your favorite warm-weather activities because you're fearful of tick bites. Just be sure to protect yourself first and do tick checks after being outdoors.
The American Mosquito Control Association (www.mosquito.org) offers these rules to follow when using insect repellents containing DEET:
- Use repellent sparingly; one application will last approximately 4 to 6 hours. Saturation does not increase efficacy.
- Keep repellents away from eyes, nostrils and lips; do not inhale or ingest repellents or get them into the eyes.
- Avoid applying high-concentration (>30% DEET) products to the skin, particularly of children.
- Avoid applying repellents to portions of children's hands that are likely to have contact with eyes or mouth.
- Pregnant and nursing women should minimize use of repellents.
- Never use repellents on wounds or irritated skin.
- Wash repellent-treated skin after coming indoors.
- If a suspected reaction to insect repellents occurs, wash treated skin, and call a physician. Take the repellent container to the physician.