Although a number of small animals, and even birds, may be infected with the spirochete, only specific species of rodents seem to maintain spirochetes in their blood for prolonged periods to allow an opportunity for the ticks to feed on. The three stages of vector ticks larva, nymph, and adult each feeding once on a different host, transmit the organism to the hosts. The life cycle spans a 2-year period. Eggs are usually deposited in June and July, with the larvae emerging in late July or early August. Larvae attach themselves to small rodents and birds, feed during late summer, and molt before winter.
Females then seek large vertebrate hosts during early fall.
The onset of Lyme disease in human beings has been reported throughout the year, with peaks in June and July. All age groups are equally affected, although the disease is not that common in children less than 2 or 3 years of age. Peak incidence is reported in children between the ages of 5 and 9 years and in adults over 35 years, the least reported incidence is in the 20 to 25 age group. Males and females are affected in equal proportions, but some studies show a greater frequency in males, which is probably related to recreational activities and outdoor occupations favored by males. It is fastidious, slow growing, and difficult to culture.