Determination of vitellogenin titer in the hemolymph of Dermacentor variabilis (Acarina: Ixodidae) using an indirect enzyme-linked immunosorbent assay.

Using polyclonal antibodies against Dermacentor variabilis (Say) egg vitellin, we developed an indirect, competitive enzyme-linked immunosorbent assay (ELISA). Vitellogenin in the hemolymph of females was quantitatively monitored through feeding (slow feeding and rapid engorgement feeding periods) and postfeeding (preoviposition and oviposition) until death. Vitellogenin concentrations in hemolymph ranged from 1 microgram/ml on the first day of feeding to a maximum of 430 micrograms/ml on the third day of oviposition. The temporal pattern of vitellogenin production in this tick shows a gradual increase in the hemolymph vitellogenin titer throughout the slow feeding period followed by a rapid and substantial rise during the rapid engorgement feeding period and a continuation of this rise in titer through the most productive egg laying part of oviposition. The vitellogenin titer rapidly falls toward the end of oviposition as the tick nears death. There was a 170-fold increase in vitellogenin concentration as measured from the onset of rapid engorgement to the maximum vitellogenin titer. The rapid engorgement feeding period signaled a sharp increase in vitellogenin production.