The bacterium Borrelia burgdorferi causes Lyme disease, according to Mayo Clinic. Deer or black-legged ticks carry the bacterium, passing it to humans through bites. The bite allows the bacterium to make its way into the bloodstream, causing infection and Lyme disease. Usually, a carrier tick must attach itself to the human host for 36 to 48 hours in order to transmit the disease.
Deer or black-legged ticks are very small and hard to see, measuring only about the size of poppy seeds, reports Mayo Clinic. A swollen tick discovered on the body indicates extended attachment to the host and the possibility of transmission of the bacterium that causes Lyme disease.
After a tick bite or removal of a tick, a small red bump usually appears at the site, notes Mayo Clinic. This is normal and not an indicator of Lyme disease. Within a month, however, signs and symptoms of Lyme disease may occur, including a rash that develops from three to 30 days after the bite, forming in a bull's-eye pattern and expanding to spread more than 12 inches across. The rash may develop at more than one spot on the body. Chills, fatigue, fever, body aches and headache may also occur.
As Lyme disease advances and remains untreated, additional symptoms often crop up, reports Mayo Clinic. These include neurological problems, impaired muscle movement, joint pain and the development of meningitis.