Anti-Feeding Effect of a 9% Amitraz Collar Under Severe Experimental and Natural Rhipicephalus Sanguineus Infestations
Rhipicephalus sanguineus, the brown dog tick or kennel tick is an important pest of domestic carnivores in the Mediterranean region as well as in other parts of the World, where it has been introduced. Because it acts as an important vector of some prominent human and animal diseases, its control is a serious need wherever dogs are housed. In the first part of this study, a comparative analysis of ixodicide efficacy of some commercial compounds has been done under laboratory conditions, looking for the fastest activity against engorging females of R. sanguineus. In the second part, the best performing product was assayed in a kennel deeply infested with a natural population of R. sanguineus, looking for the efficacy of the compound against the already established tick population and the long lasting effect against reinfestations.
The compounds tested in the first experience were Preventic (Amitraz), Frontline (Fipronil) and Excalibor (Deltamethrin). Four groups of 10 dogs each were homogeneously prepared, according to animal size and sex. On day minus 1 (D-1) dogs were infected with 100 adult flat female ticks, and the same amount of males. Treatments were performed on D0, the fourth group receiving a placebo. Efficacy was assessed by counts of engorging ticks every day after treatment and until D+10. In the kennel, preliminary screening of the dogs revealed tick counts of more than 2,000 per animal. Therefore, Amitraz collars were selected to be used against the brown dog tick in a kennel highly infested by that tick. In the kennel, dogs were allocated to homogeneous groups, according to sex and weight: 16 animals were fitted with the Amitraz collar and 14 other dogs were fitted with a placebo collar. Dogs with the Amitraz collar and half of the dogs in the placebo group were housed in the same premises with no physical separation. The remaining dogs in the placebo group were housed separately. Three groups of dogs were therefore considered: treated dogs, untreated dogs living together with treated ones and distant untreated control dogs. Engorging female counts were performed every 10 days and until 3 months after the beginning of the study.
Twenty-four hours after the treatment onset (D+1), Amitraz collar provides a control of some 92% as compared with placebo dogs. This results means that the number of feeding ticks on Amitraz treated dogs was reduced more than 10 times in only 24 hours. Frontline provided a control of 51% and Excalibor of 63%. On D+10 the efficacy of Amitraz was 99%, while Frontline exhibited 86% and Excalibor 90%. These figures refer to the number of females killed before the onset of blood intake, as the better indicator of killing activity in the selected chemicals. A reduction in the number of ticks was recorded on every examination time points: the number of engorging females was reduced by 48% on the treated animals (as compared with untreated control dogs) on day 10, and by 97% three months later. Amitraz collar must be considered as one of the most thorough treatments for the control of the kennel tick in cases of high infestations, common in the Mediterranean region, because of its quick efficacy and long lasting formulation.
Amitraz 9% works better than other chemicals in the control of severe infestations of the brown dog tick (Rhipicephalus sanguineus) under experimental and natural conditions.