Lyme disease is caused by bacteria called Borrelia burgdorferi. This bacterium is carried by certain ticks, and spreads to the host when the tick bites. The bacterium is normally found in small animals such as mice, squirrels, chipmunks, shrews, etc.
Lyme disease in humans can have a range of effects from rashes and flu-like symptoms to more serious symptoms including arthritic, cardiac and neurological effects. It can often be effectively treated, especially if detected in the early stages.
Lyme disease is an occupational concern for people who work outdoors. Any person who spends time outdoors is also at risk.
In the United States, Lyme disease is the most common "vector borne" disease. (Vector is the term for any insect or arthropod that carries and transmits a disease pathogen (virus, bacteria, etc.)).
Ticks usually live in woods or tall grasslands in Canada, the United States, Europe and Asia. Ticks infected with Borrelia burgdorferi spread the disease when they feed on blood from the host. Ticks cannot fly - they hang onto small bushes or tall grasses and are usually found close to the ground. They wait for an animal or person to pass near them and when the animals or person make contact, the ticks attach themselves to the skin to feed.
In North America, Lyme disease is transmitted (spread) mainly by two species of ticks:
Tick bites are usually painless and most people do not know they have been bitten. Signs and symptoms of Lyme disease vary greatly from person to person.
In the first stage, one of the first signs of infection is a circular rash, often referred to as a "bull's eye" rash because it will have rings spreading from the bite site (known as erythema migrans). Other rashes may occur. Rashes do not appear in every case of Lyme disease infection. Reports of rashes appearing range from 70-80% of infected people to as low as 30-50% in adults and less than 10% children. The rash may appear three days to a month after infection. Images of rashes are available from the Centre for Disease Control and Prevention (CDC).
Additional symptoms include:
As the disease progresses, it can enter a "second stage" which can last several months. Symptoms at this stage include:
Stage three includes chronic arthritis and neurological symptoms including headaches, dizziness, numbness and paralysis. Deaths from Lyme disease are rare but may occur.
Lyme disease can be difficult to recognize, and it has been confused with other diseases. It is important for people to consult with their doctor if they feel it is possible that they have Lyme disease.
In most cases, most often people will experience 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 health problems.
Pregnant women should seek medical help immediately as Lyme disease can be a health risk to the baby including still births.
In most cases, yes. Antibiotics can effectively treat Lyme disease, especially when treatment begins early. Cases that reach the later stages of the disease, however, can be difficult to treat and may develop in to a chronic illness.
Many people who develop the disease do not remember seeing ticks or being bitten. Tick bites commonly occur from May to September in North America, 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 could be as big as a raisin or a small grape.
For more information about ticks (including photographs), please see the Ticks and Lyme Disease document on the Public Health Agency of Canada's.
Yes and no. There are areas in which the bacteria is endemic meaning the disease is established and present more or less continually in that community.
In Canada, these endemic areas include the north shore of Lake Erie including the Long Point area, Rondeau Provincial Park, and Turkey Point as well as the St. Lawrence Islands National Park area in Ontario. Other areas where there may be higher risk of infection include
However, it is important to note that ticks (including those that are infected with the Borrelia burgdorferi bacteria) can be spread by birds, in particular songbirds that feed off the forest floor. Because these birds are migratory, there is the potential for new populations of the bacteria to spread across the country. This fact means that you do not have to be in an endemic or high-risk area to be at risk of contacting ticks and the disease.
When a person becomes infected, the body creates antibodies to protect itself from the bacteria. Certain blood tests are available to measure these antibodies. However, sometimes a "false negative" test can result if there are not enough antibodies in the blood for the tests to detect accurately. A doctor should also do a complete medical examination and get information about your activities in order to make a clinical diagnosis for Lyme disease.
Many occupations may be at risk, including forestry, farming, veterinarians, construction, landscaping, ground keepers, park or wildlife management, and anyone who either works outside or has contact with animals that may carry the ticks (including domestic animals like dogs, cats, goats, cows, horses, etc.)
Similarly, any person who spends a lot time outdoors (hiking, camping, birding, etc.), especially in grassy or wooded areas may also be at risk.
In areas where ticks are found, people should know about the risk of Lyme disease and should take precautions to protect themselves. Be aware of the signs and symptoms of Lyme disease so it can be detected and treated promptly.
Document last updated on April 15, 2008