Lyme disease is transmitted to humans and pets by a bite of the tiny deer tick. Deer ticks become infected during the larva and nymph phases by feeding on small mammals and birds which harbor the Lyme bacterium.
Later in their development, the infected nymphs and adults transfer the Lyme bacteria to animals during feeding. The rising number of deer and other small wildlife in suburban areas is linked to increasing numbers of ticks and Lyme disease cases.
In the United States, Lyme disease is mostly localized to states in the northeastern, mid-Atlantic, and upper north-central regions, and to several counties in California.
In 2002, 23,763 cases of Lyme disease were reported to the Centers for Disease Control and Prevention. Ninety-five percent of these cases were from the states of Connecticut, Delaware, Rhode Island, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New Hampshire, New York, Pennsylvania, and Wisconsin. Astonishingly, the CDC estimates that only 10-20% of cases are reported.
Most cases of Lyme disease occur in late spring and early summer when the nymphal state of the tick is active. The highest incidence of the disease in Connecticut is seen in young children as their play activities often place them at risk.
Most people develop a red rash, called erythema migrans (EM), within 3-21 days of a tick bite. The painless rash gradually expands often reaching 5 centimeters or more in diameter and disappears without treatment. The presence of an EM rash larger than a quarter in diameter usually confirms a diagnosis of Lyme disease.
Other common symptoms are flu-like, including fatigue, muscle and joint pain, fever, headache, chills and stiff neck. Fever is usually low-grade. Co-infection should be considered if one's temperature remains high.