Lyme disease was first recognized in North America in 1975 when doctors discovered an unusual number of people with arthritis in the town of Lyme, Connecticut, U.S.A.

The disease is caused by bacteria called Borrelia burgdorferi. Most often these bacteria cause a mild illness that is sometimes accompanied by a peculiar skin rash. In some cases, however, the bacteria can spread to the joints, heart, and brain and cause serious problems. It can also cross from mother to an unborn child and, in rare cases, cause birth defects.

Lyme disease is an occupational concern for people who work outdoors in certain areas infested with ticks. It affects people differently most often going unnoticed but sometimes it causes serious problems. If left untreated, it can cause disability.

Being aware of the signs and symptoms of Lyme disease is important so it can be detected and treated promptly. It is also important to follow simple precautions to reduce the risk of getting Lyme disease.

The bacteria that cause Lyme disease come from small, insect-like creatures called ticks. Ticks range in size from 1 to 4 millimeters (not much larger than a small ant). However, unlike insects, ticks have eight legs instead of six.

Ticks usually live in woods or tall grasslands in various regions of the country. Lacking wings, they hang onto small bushes or tall grass usually close to the ground, and wait for an animal or person to pass near them. They brush onto passing animals or people, and attach themselves to the skin to suck a small amount of blood. Sometimes people can feel ticks move around on the body but tick bites are usually painless and often occur unnoticed.

Lyme disease is spread mainly by two species of ticks in North America. One is the deer tick, Ixodes dammini, found mainly in the eastern regions of the continent. The other is the California black-legged tick, Ixodes pacificus in the western pacific regions. The wood tick, Dermacentor variabilis, sometimes carries the Lyme disease bacteria but it does not appear to spread the disease.

The Ixodes ticks prefer to feed on wild animals. Immature ticks normally feed on the white-footed mouse and adult ticks feed on white-tailed deer. Because of this habit, the number of mice and deer in a region influences the number of ticks found there.

Presently, the actual black-legged tick is common; however, Lyme disease does not seem to be prevalent in Canada. Between 1984 and the end of 1995, there was a total of 228 reported cases for all of Ontario. In the same period, 14 cases were reported in the Thunder Bay district: nine of these people had no history of travel outside the area. The disease is often concentrated in specific regions that have large populations of deer or other wildlife. In some areas where Lyme disease is common, blood tests in people show that up to 24 percent of the general population have been exposed to the infection. Long Point, Ontario appears to be the only region known to have a concentration of infected ticks and wild animals. Scattered cases of Lyme disease in other regions of the country suggest that pockets may exist.

In comparison, the United States had a total of 16,461 cases reported in 1996. This represents a 41% increase from the 11,700 reported cases in 1995, and a 26% increase from the 13,043 cases in 1994.

Ticks infected with the bacteria that cause Lyme disease spread the disease when they suck blood from people. They can spread the disease throughout their life cycle. Immature ticks seem more likely to bite people, and being smaller than adult ticks, are harder to notice. A recent study showed that ticks must feed for at least several hours before they can infect a person (or animal) with the bacteria causing Lyme disease.

Lyme disease does not spread from person to person. However, people who have had Lyme disease can get it a second time from ticks. People do not seem to develop a long-term immunity from the disease.

Studies estimate that about 25 percent of Lyme disease victims in the United States became infected at their work. It is an occupational hazard for people who work outdoors in regions that have large numbers of infected ticks. Studies from these regions show that more people who work outdoors have had Lyme disease than people who work indoors.

Lyme disease is sometimes difficult to recognize, and it has occasionally been confused with other diseases. It is important for people to consult with their doctors if they feel it is possible that they have Lyme disease.

The disease has three major features: a history of tick bites, a slowly expanding rash, and complications from nerve disease, heart disease, or arthritis.

History of Tick Bites

Most victims of Lyme disease were in situations where being bitten by a tick could be expected. Many people who develop the disease, however, do not remember seeing ticks or being bitten. Tick bites may cause small red irritations, but they often go unnoticed, especially those from small, immature ticks.

Tick bites commonly occur from May to September, although this varies from year to year and from region to region. Ticks sometimes move around on the body but they usually attach themselves to the skin and stay in one place. Before feeding, ticks look like small, brown scabs or freckles. After feeding, ticks may swell considerably, and, according to some people, look like a raisin or blood blister with legs. Soon after receiving a tick bite, some victims of Lyme disease experience a brief flu-like illness.

Slowly Expanding Rash

In about 75 percent of reported cases of Lyme disease, the victims develop a rash around or near the tick bite usually within one week. In some cases, a peculiar, bright red, circular rash develops. It soon expands to form a ring-shaped "bull's-eye" that can grow to the size of a dinner plate. Often, however, a more mild, general rash appears anywhere on the body. The rashes fade after several weeks. Some victims, however, never develop a rash, yet experience more advanced symptoms of the disease.

Nerve Disease, Heart Disease, Arthritis

About 15 percent of untreated victims develop temporary nerve problems from a few weeks to several months after a tick bite. The most common problem is meningitis (inflammation of the covering of the brain) with fever, headache and stiff neck. Some victims experience neuritis (nerve inflammation) with pain and other disturbances such as deafness. These nerve problems are usually temporary and disappear with proper treatment.

Heart disease occurs in about 5 percent of untreated victims often with no symptoms of infection. The most common problem is a heart block that affects the rhythm of the heartbeat. This problem is also temporary and disappears permanently with proper treatment.

Lyme disease causes arthritis in about 25 percent of studied cases and occurs several months to two years after receiving a tick bite. This arthritis most often affects the knees, although it also occurs in the shoulders, wrists, elbows, hips, and ankles. Prompt treatment usually solves this problem. Without treatment, however, this arthritis can lead to permanent disability.

In rare cases, people who have the disease for several months or years, and do not receive treatment, develop serious changes in the nervous system. These changes result in loss of feeling in the limbs, loss of memory, and extreme tiredness.

Blood tests can detect antibodies that the body produces to protect itself against the bacteria that cause Lyme disease. These tests help to prove that exposure has occurred, but they do not show people have active cases of the disease. A physician must do a medical examination and get a work history about job activities to diagnose Lyme disease.

Although Lyme disease can sometimes cause serious problems, several antibiotics are available to treat it at all stages effectively. Prompt treatment with drugs, such as tetracycline, can quickly clear up the early symptoms and prevent serious complications. Even in the late stages, penicillin and other drugs are still effective in most cases.

In areas where ticks are found, outdoor workers should know about the risk of Lyme disease and should take precautions to protect themselves.

• Find out from your local public health office if there are ticks in your area, especially Ixodes ticks. Now, Long Point, Ontario, is the only clearly defined risk area in Canada.
• Wear protective clothing to prevent ticks from getting access to your skin. This includes long sleeve shirts that fit tightly around the wrist, and long-legged pants tucked into stockings or boots.
• Use insect repellants that effectively repel ticks (such as those containing DEET). Apply the repellent to pant legs, socks, shoes, and the skin.
• Check for ticks on and under clothing after working in tick-infested areas. A daily total-body skin inspection greatly reduces the risk of infection since ticks may take several hours to two days to attach to the skin and feed.
• Carefully remove ticks found attached to the skin. Gently use tweezers to grasp head and mouth parts of the tick close to the skin as possible. Pull slowly to remove the whole tick. Try not to squash or crush them since this can help bacteria to get into the body.
• Wash affected area with soap and water or disinfect (with alcohol or household disinfectant) after removing ticks.
• Contact a doctor immediately if you have an illness that resembles Lyme disease, especially when you have been in an area where there are ticks.

As of February 25, 2002 the manufacturer of the LYMErix Lyme disease vaccine announced that it would no longer be commercially available.