Acaricides for eradication of the tick Amblyomma variegatum in the Caribbean.

The success of an eradication campaign against the tropical bont tick in the Caribbean imposes the use of active acaricide compounds, if possible with residual activity, easy to apply and requiring few or no accessible water supplies and expensive application equipment. Tests of in vitro susceptibility of tick strains from Puerto Rico and Guadeloupe as well as observations of the impact of the current tick control campaigns conducted in some Caribbean islands, seem to indicate that there is no problem of resistance to acaricides. Pyrethroid acaricides have an advantage since they are active at very low concentration levels and have a low toxicity for mammals and to the environment. Some of them are in a pour-on formulation which allows for rapid application and complete coverage of the whole body of the animal. A withdrawal period is not necessary. However, improvements must be found to facilitate the application onto the back of cattle that, for the majority in the Caribbean, are tethered and not perfectly restrained. A spot-on application method with a drench gun seems more adapted to tethered animals than the pour-on. For small ruminants and dogs but also for cattle, slow release devices impregnated with acaricides may be useful in reducing the frequency of animal treatments. However, experiments on goats with collars impregnated with flumethrin indicate an efficiency of less than 55 days, insufficient to justify their use on a large scale in an eradication program.