It’s a common misconception that ticks cause Lyme disease. Ticks are vectors for the disease, meaning they carry it and transmit it, but they do not cause it. The disease is bacterial and can cause a range of symptoms. It was first seen in the United States in the 1970s, in the town of Lyme, Connecticut.

According to a public health fact sheet released by the Purdue University Extension, Lyme disease is carried by ticks, and affects people and pets alike. It is found across the United States, but 90 percent of all cases occur in the Mid-Atlantic states, and in Minnesota and Wisconsin.

“Lyme disease is caused by a bacterium with the scientific name Borrelia burgdorferi (the Lyme disease spirochete). Spirochetes are relatively large, spiral-shaped bacteria that are mobile and highly invasive. Following the bite of an infected tick, Lyme disease spirochetes initially multiply and disseminate in the skin surrounding the bite. If untreated, spirochetes can invade the blood stream, where they multiply and cause flu-like symptoms. Eventually, spirochetes may invade other parts of the body such as the nervous system, heart muscle and large joints, where they multiply and produce a variety of disease symptoms … ”

There are multiple species of ticks that carry the bacteria, and "do all ticks carry Lyme disease" is a common question. In fact, only a few species are known to pass it along to humans. Of the ticks that carry Lyme disease, the blacklegged tick, also called a deer tick or Lyme disease tick, is the worst offender. According to a Lyme disease fact sheet released by the Pennsylvania State University Extension, it is this type of tick, and two of its relatives, that are proven to be vectors for the disease’s transmission to humans.

“The larval and nymphal stages of the tick are no bigger than a pinhead (less than 2 mm). Adult ticks are only slightly larger. Research in the eastern United States has indicated that, generally, ticks transmit Lyme disease to humans during the nymphal stage, probably because nymphs are rarely noticed on a person’s body due to their small size. Thus, the nymphs typically have ample time to feed and transmit the infection (ticks need at least 24 to 36 hours to transmit the infection). Ticks search for host animals from the tips of grasses and shrubs and transfer to animals or persons who brush against vegetation. They usually attach themselves in areas that are more hidden or hairy, such as the groin, armpits, and scalp. However, ticks can attach under watch bands and waistbands, and in many other body locations. Ticks feed on blood by inserting their mouthparts into the skin of a host animal. They are slow feeders: a complete blood meal can take 3 to 5 days. Although in theory Lyme disease could spread through blood transfusions or other contact with infected blood or urine, no such transmission has been documented.”

Just because there are blacklegged ticks in an area does not mean that Lyme disease bacteria are also present. According to the Centers for Disease Control’s information sheet on ticks, there are several factors that must align for a blacklegged tick to transmit Lyme disease.

“This tick is widely distributed in the northeastern and upper midwestern United States. I. scapularis larvae and nymphs feed on small mammals and birds, while adults feed on larger mammals and will bite humans on occasion. It is important to note that the pathogen that causes Lyme disease is maintained by wild rodent and other small mammal reservoirs, and is not transmitted everywhere that the blacklegged tick lives. In some regions, particularly in the southern U.S., the tick has very different feeding habits that make it an unlikely vector in the spread of human disease.”

If you have been in an area where blacklegged ticks are present and you begin to feel ill, call a medical professional and ask about Lyme disease. Ticks are more active in summer months. If you are seeing ticks on family pets, it may be time to call a pest management professional to discuss your options.