Earth & Sky

Our thanks to the following individuals and institutions who assisted in the preparation of this script:

Dr. Julie Rawlings
Epidemiologist
Texas Department of Health
Austin, TX

Suggested Further Reading and References:

American Lyme Disease Foundation, Inc.

National Institutes of Health – Lyme Disease and Other Tick-Borne Diseases

CDC Division of Vector-borne Diseases

Ticks and Tick-borne Diseases in Texas

More information on Lyme Disease
by Shireen Gonzaga

Since it was first diagnosed, there has been a dramatic increase in cases of Lyme
disease in North America. Perhaps that’s because more and more people are living closer to the woods, closer to wildlife that carry the disease. In some parts of North America, the increasing white-tailed deer population, a major reservoir for the Lyme disease bacteria, has been blamed. The increases could also be attributed to more awareness of, and correct diagnosis of the disease.

In the early 1970s, a mysterious illness was afflicting many children in the town of Lyme, Connecticut, as well as other nearby towns. At first, physicians diagnosed their illness as juvenile rheumatoid arthritis. But something about this outbreak did not fit the profile for juvenile rheumatoid arthritis; many children were falling ill, not just a few isolated cases. The disease did not occur randomly during the year, but mostly emerged during the summer months. Many of the sick children lived near wooded areas, and some parents reported that the arthritic symptoms had been preceded by tick bites that caused a rash at the site of the bite.

By the late 1970s, the culprit had been identified. It was a bacteria. Borrelia burgdorferi was found in the guts of many deer ticks, and was being transmitted to the children when the ticks bit into their skin.

The disease became known as Lyme disease, named after the town that was ground zero for the outbreaks in Connecticut. Little is known about the the origins of Lyme disease. A similar disease was known in Europe prior to the 1970s, and today, Lyme disease is found in many other countries around the world.

In the past 2 decades, there has been a dramatic increase in cases of Lyme disease in North America. More and more people are living closer to the woods, closer to wildlife that carry the disease. In some parts of North America, the increasing white-tailed deer population, a major reservoir for the Lyme disease bacteria, has been blamed for the increasing cases of Lyme disease. But perhaps, the increases could also be attributed to more awareness of, and correct diagnosis of the disease.

In the United States, most cases occur in the Northeast, mid-Atlantic states, upper Midwest, as well as northern California and the coast of Oregon. The density of infected ticks varies considerably, from state to state, county to county, and even within a county. In the eastern U.S., the bacteria is transmitted by deer ticks (Ixodes scapularis), in the west by the black-legged tick (Ixodes pacificus), and in the south and south-central U.S., by the Lonestar Tick (Amblyomma americanu) .

The main reservoir of Lyme disease is not the ticks themselves, but small wild mammals, primarily rodents, that carry the disease. In the northeast and north-central United States, for instance, the white-footed mouse is the main reservoir, followed by the white-tailed deer, as well as other mammals and birds.

The lifespan of a tick is about 2 years. Adults usually mate in the fall and early spring, while feeding and hitching a ride on their host animals. Females bearing eggs then drop off their hosts, and lay their eggs in the ground. The eggs hatch during the summer, and for the rest of the summer and into the fall, tick larvae feed on the blood of mice, other small mammals, and birds.

During the winter, the larvae become inactive, but revive in the spring to molt into tick nymphs. The pinhead-sized nymphs continue feeding on small rodents into late spring and summer, then molt into adults in the fall. The Lyme disease bacteria is often taken on by a tick during the nymphal stage, when the nymph feeds on small animals, particularly the white-footed mouse. Tick larvae can also become carriers of the bacteria if they happen to feed on an infected animal, but this is not a common occurrence. Once a larvae or nymph is infected, the bacteria will remain in the animal, even after it has molted from one life stage to another.

Perched on the tips of blades of grass or leaves, the tick will wait for a passing animal or person. Once they climb onto their prey, the ticks crawl around looking for a suitable site to feed on the blood of their host. Adult ticks and nymphs will generally attach anywhere on the exposed skin of a person, but prefer hidden or hairy areas, like the back of the knee, nape of the neck, armpit, groin, and scalp. The larvae, nymph, or adult tick sinks its mouth parts into the skin, and sucks its prey’s blood, gradually ballooning out as its body fills with blood. However, ticks are only able to transmit the bacteria after it has been feeding for 36 to 48 hours, so finding a tick within 24 hours of being bitten significantly reduces the chances of contracting Lyme disease.

Most cases of Lyme disease are caused by nymphs because these pinhead-sized creatures are difficult to see. Undetected, they are able to feed for a long time, long enough to transmit the bacteria to its victim. Tick larvae, even smaller than nymphs, can also transmit the bacteria, but few carry it because they have not been exposed to as many infected mammals compared to the adult and nymph ticks. Adult ticks are big enough to see, and are usually caught within a few hours of climbing onto a person.

In most case of Lyme disease, a rash, called erythema migrans, appears at the site of the tick bite, usually about 1 to 2 weeks after a person is bitten, though it can appear as early as 3 days or as late as 30 days after a bite. The rash, usually between 2 to 6 inches in diameter, can appear as a circular or oval-shaped solid red blotch, or take on the shape of a bullseye. On dark-skinned people, the rash may appear as a dark bruise. Sometimes, after the main rash appears, several smaller rashes can appear on other parts of the body. This tell-tale symptom of Lyme disease can persist for about 5 to 6 weeks, and medical treatment should be sought immediately.

At about the same time as the onset of the rash, one or a combination of other symptoms begin to emerge as well: joint pain, muscle aches, chills, fever, fatigue, headaches, and stiff neck. These symptoms can easily be dismissed as the flu, especially if the rash does not appear or isn’t noticed. Left untreated, for weeks or months, more serious symptoms begin to appear: temporary paralysis of facial muscles, poor motor coordination, memory loss, and recurring attacks of painful and swollen joints. In a few cases, Lyme disease patients develop temporary heart problems, and very rarely, the disease can be fatal.

Diagnosing Lyme disease using blood tests during the first month of infection is generally not recommended because tests can be misleading. Doctors have to rely primarily on symptoms, correlating them with the prior activities of patients in tick-infested areas. When caught at the early stages, Lyme disease is treated with antibiotics and patients almost always make a full recovery. Later stages of the disease are harder to treat because people react differently to the disease and to treatment, but generally, a more vigorous regimen of antibiotics is used. In some cases, symptoms can linger for months or years after treatment, and in a few rare cases, permanent damage occurs.

A high risk area for ticks carrying Lyme disease could be your own backyard, if you live near the woods or areas of overgrown brush. A hike or camping trip in the woods can expose vacationers to the disease, and people who work in forestry and wildlife management are constantly at risk. Prevention is the best cure. When you enter a a tick-infested area, wear light-colored clothing with a tight weave so that ticks can easily be seen. Tuck your pant legs into your socks to keep ticks from crawling up your legs, and spray insect repellent containing DEET on your skin and clothes. Avoid sitting on the ground, and stay on well-travelled trails. Check yourself every few hours for ticks. And most important of all, at the end of the day, do a careful full-body examination for ticks.

Homeowners can reduce the tick population in their yards by taking a few simple precautions. Deer ticks like leaf litter, brush, wood piles, and tall grasses. Keep your lawns clear of leaves and brush regularly, keep woodpiles stored above the ground, and regularly mow the lawn. Areas under birdfeeders should be kept clean so as to not attract mice and other small mammals that scavenge uneaten seed. If there is a very bad tick infestation in your yard, have the area around your home sprayed with a pesticide by professional pest removal specialists, in late spring to kill nymphs, and in the fall to kill adult ticks.

If you live or work in a tick-infested area, you may want to consider the recently-available Lyme disease vaccine. Three shots are administered over the course of a year, and after the third shot, the risk of contracting Lyme disease is reduced by about 80%. However, the vaccine should not encourage complacency, there is always that 20% chance of infection that you should guard against!

If you find a tick attached to your skin, don’t immediately assume you have contracted Lyme disease. Not all ticks carry the bacteria that causes Lyme disease. Also, if you found the tick within 24 hours of when you think you were bitten, it is unlikely that the tick has had a chance to transmit the disease. To remove the tick, grasp the tick using a pair of fine-tipped tweezers, as close as possible to the skin, preferably at the head. With a firm and steady motion, pull it away, and immediately apply an antiseptic to the bite site. Never grab the body of the tick when removing it; that may rupture the body and since the Lyme disease bacteria lives in the tick’s gut, it may spill onto the bite site, causing an increased chance of infection. For the following month, monitor the site of the tick bite for the tell-tale rash, and for the onset of flu-like symptoms. If these symptoms appear, and you suspect you have contracted Lyme disease, immediately see a doctor.