Feeding of Hard Ticks In Vitro: New Perspectives for Rearing and for the Identification of Systemic Acaricides

Abstract

Experiments on in vitro feeding of the hard ticks Ixodes ricinus, Boophilus microplus, Amblyomma variegatum and Amblyomma hebraeum are described. An in vitro test for systemic acaricides is presented. Work started with a feeding chamber continuously supplied with new blood. It proved too susceptible to fungal contamination and not efficient enough. Simple feeding units made of honey jars with an inner glass tube were far more practical. Reinforced silicone membranes or baudruche membranes impregnated with glue were stretched across the bottom end of the tube. Weekly open-collected bovine blood from the slaughter house, where it is considered as discard, served as nutrient and was changed 1-3 times a day. The feeding jars were held in a waterbath (38° C). The blood contained microbicides. Attachment of ticks on the membranes was induced with combinations of host hair, conspecific tick faeces, bovine hair extract and synthetic aggregation attachment pheromone mixtures (Amblyomma). Larvae of the one-host cattle tick B. microplus were bred in vitro through the nymphal to the unfed adult stage. Females gained half of the natural body mass and laid eggs. The life-cycle of A. hebraeum was completed in vitro by consecutive feeding of all life-stages (larvae, nymphs, adults) on silicone membranes. In adult B. microplus, A. variegatum and A. hebraeum the reproductive capacity was strongly impaired, possibly in consequence of the low quality of the blood. A sub-optimal in vitro nutrition was more fatal for the fertility than for the moult of ticks, as demonstrated by the good results for larvae and nymphs, particularly those of A. hebraeum. The toxicity of the systemic acaricide Ivermectin® for nymphs of A. hebraeum was confirmed using the in vitro feeding method. This method offers new in vitro possibilities for tick rearing as well as for tests with systemic acaricides, anti-feedants and repellents. It allows experiments on transmission of pathogens and with radioactive markers.