Behavior of Dipetalonema viteae (Filarioidea) during escape from the vector tick, Ornithodoros tartakowskyi (Argasidae).

ABSTRACT

To determine the behavior of Dipetalonema viteae in its tick vector, Ornithodoros tartakowskyi, the ticks were fed on jirds at successive intervals of 30 to 35 days after a single infective blood meal, and the number of larvae passing from the tick during each bite was determined by recovery of 1) adult worms from the jirds' tissues; 2) larvae from skin snips taken at the feeding site immediately after the bite; and 3) larvae from serum and tissue after artificial feeding through a skin-membrane. All methods gave similar results. Ticks harboring few larvae released most of them (82%) during the first bite, and required only 2 bites to transmit all. Ticks with moderate or heavy infections required 3 or 4 bites to transfer all larvae. Factors which may explain this are 1) relatively short duration of the bite of heavily infected ticks due to irritation and damage to the muscles of mouthparts and pharynx by the larvae; 2) resistance of the anterior alimentary tract to penetration by the larvae; and 3) retarding effects of crowding on development and migration of larvae. Aging of infection in the tick apparently did not influence the rate of transfer of larvae. Infection adversely affected the feeding and retarded the molting of young nymphs, but with the loss of larvae in successive bites the ability to suck blood was regained.