Fipronil Susceptibility Evaluation for the Establishment of a Diagnostic Concentration for Rhipicephalus sanguineus sensu lato from Mexicali, Baja California, Mexico

Résumé fourni par la source

The brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.), is of medical and veterinary relevance and is primarily controlled with acaricides. Because acaricide resistance in this tick is a growing concern, evaluating effective acaricides is particularly important in Baja California, where tick-borne pathogens associated with R. sanguineus s.l. are endemic. This study aimed to estimate a candidate discriminating concentration (DC) for fipronil in R. sanguineus s.l. from the city of Mexicali and to assess fipronil susceptibility in three tick populations. Engorged female ticks were collected from naturally infested dogs in Valle de Puebla, Solidaridad Social, and El Encanto. After hatching, larvae were exposed to seven concentrations of a commercial fipronil formulation (0.0016%, 0.0032%, 0.0047%, 0.0062%, 0.0093%, 0.0125%, and 0.025%) using the larval packet test. Mortality at 24 h was analyzed by probit regression to estimate the median lethal concentration (LC50) and the lethal concentration for 99% mortality (LC99). The estimated LC50 and LC99 were 0.0031% (95% CI: 0.0022–0.0042%) and 0.025% (95% CI: 0.0178–0.0331%). A candidate DC of 0.05% was estimated for the Valle de Puebla population. Application of this concentration to the other populations showed 100% mortality when exposed to both 0.025% and 0.05% fipronil, indicating similar susceptibility across all evaluated populations. These findings provide preliminary susceptibility data for future monitoring of fipronil susceptibility in R. sanguineus s.l. populations from Mexicali and suggest that this acaricide may remain a useful option for urban tick control where local populations are susceptible.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.