Repellency to ticks (Acari: Ixodidae) of extracts of Nigella sativa (Ranunculaceae) and the anti-inflammatory DogsBestFriend™.

Motivated by observations that the canine anti-inflammatory cream DogsBestFriend™ (DBF) appeared to deter flies, mosquitoes, and ticks from treated animals, repellent efficacy bioassays using four species of ticks were conducted with three extracts of Nigella sativa L. (Ranunculaceae), a constituent of DBF. The DBF cream was tested against nymphs of lone star tick, Amblyomma americanum (L.). In vertical filter paper assays, the three extracts applied at 0.413 mg extract/cm(2) filter paper repelled 96.7-100 % of brown dog tick, Rhipicephalus sanguineus (Latreille) nymphs, whereas, at the same rate, only one extract repelled >90 % A. americanum nymphs. Adult (mixed sexes) American dog ticks, Dermacentor variabilis (Say), required a higher concentration to be repelled effectively; two extracts, applied at 0.827 mg extract/cm(2) filter paper, repelled ≥90 % of the D. variabilis. In contrast, all extracts applied at much lower concentration (0.206 mg extract/cm(2) filter paper) repelled 100 % adult blacklegged ticks, Ixodes scapularis Say (only females tested). Of the two more repellent extracts, one lost most of its activity against A. americanum nymphs in <4 h when applied at 0.827 mg extract/cm(2) filter paper, whereas the other repelled 66.7 % of the nymphs at 192 h after application. At 0.206 mg extract/cm(2) filter paper, one extract was as repellent as deet against A. americanum nymphs. In a vertical bioassay in which nylon organdy was substituted for filter paper, DBF, at the rates of 1.67 and 0.835 mg cream/cm(2), repelled 76.7 and 30.0 % A. americanum nymphs, respectively. These findings indicate that when applied appropriately DBF should afford some protection to canines against tick bites.