A comparison of the occurrence of borreliae in nymphal and adult Ixodes ricinus ticks.

The prevalence of borreliae in 209 nymphal and 251 adult Ixodes ricinus was investigated in two areas of southern Moravia, Czechoslovakia, using the dark-field and the Giemsa stained-smear techniques. The proportions of infected ticks were 3.8% in nymphs and 10.6% in adults of area A, while they were 29.1% in nymphs and 35.9% in adults of area B. The mean number of borreliae per tick was about 3 to 10 times greater in adult than in nymphal I. ricinus. The results indicate a significant role of nymphal I. ricinus in the ecology of Borrelia burgdorferi and in the epidemiology and epizootiology of Lyme borreliosis.