The month of May is “Lyme Disease Awareness Month.” In honor of Lyme Disease Awareness Month for 2011, Pain.com is publishing a series of four articles about lyme disease. This article describes what lyme disease is, how lyme disease is spread and who gets lyme disease. Future articles will discuss the signs and symptoms of lyme disease and how lyme disease is diagnosed, treatment of lyme disease and prevention of lyme disease.
Lyme disease is ultimately caused by a species of spirochete bacterium called Borrelia burgdorferi, but lyme disease requires a vector for transmission. That is, developing a case of lyme disease requires two things to happen.
First, a tick has to pick up the Borrelia bacterium from the blood of an animal. Animals that commonly harbor this bacterium include several different species of wild rodents, like squirrels and mice. Second, a human has to be bitten by this infected tick. When the tick bites a person, the bacterium can get into the person’s body through the wound and cause an infection.
Multiple strains exist of the spiral-shaped Borrelia bacterium, and there may be as many as 100 distinct strains of Borrelia burgdorferi in the United States alone.
However, there are only two species of ticks that are associated with lyme disease in America: the black-legged tick and the western black-legged tick. These ticks are two different species of the genus Ixodes, and their common name is “deer tick.” They do indeed bite deer, but they feed upon many other types of animals as well, including rodents.
Rodents are more likely to harbor the Borrelia bacterium than deer, but deer can carry ticks around that have already been infected with Borrelia. Other types of ticks in the United States are not thought to spread lyme disease, but some of them can harbor and transmit other vector-borne diseases, such as tularemia and Rocky Mountain spotted fever.
Lyme disease is not known to be transmitted to humans through any method except via tick bites, although it is theoretically possible to get lyme disease from a blood transfusion if the donor was infected with Borrelia bacteria. Lyme disease is not transmitted through sexual contact, airborne transmission, water, food or from the bites of other disease vectors, like mosquitos.
Mammalian pets, like cats and dogs, can get lyme disease; however, it has not been shown that a pet can directly transmit the disease to humans or other pets. It does not appear that lyme disease can be transmitted to a fetus when a woman is pregnant; however, it is possible that lyme disease can have a negative impact on the pregnancy if untreated.
For example, the infection can affect the placenta, which increases the risk of having a miscarriage. It is also unlikely that the bacterium can be transmitted to an infant through breast milk.
In certain parts of the country, ticks are able to bite nearly year-round; however, most cases of lyme disease develop during the spring or summer months, when people are more likely to be outside walking in the woods or in tall grass. Lyme disease affects people of all ages more or less equally and men and women are basically equally affected.
Lyme disease is one of the most common vector-borne illnesses in the United States.
The next article in the Lyme Disease Awareness Month series will describe the clinical signs and symptoms of lyme disease and discuss how lyme disease is diagnosed.
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