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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » LAPRU » Research » Publications at this Location » Publication #334398
Title: First documentation of ivermectin resistance in Rhipicephalus sanguineus sensu lato (Acari: Ixodidae)

Author
item RODRIGUEZ-VIVAS, ROGER - Autonomous University Of Yucatan
item OJEDA-CHI, MELINA - Autonomous University Of Yucatan
item TRINIDAD-MARTINEZ, IRIS - Autonomous University Of Yucatan
item Perez De Leon, Adalberto - Beto

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2016
Publication Date: 1/15/2017
Citation: Rodriguez-Vivas, R.I., Ojeda-Chi, M., Trinidad-Martinez, I., Perez De Leon, A.A. 2017. First documentation of ivermectin resistance in Rhipicephalus sanguineus sensu lato (Acari: Ixodidae). Veterinary Parasitology. 233:9-13.

Interpretive Summary: The scientific name Rhipicephalus sanguineus of what we commonly know as the brown dog tick was established in 1806. The brown dog tick is a cosmopolitan ectoparasite that bites and transmits disease-causing agents to animals and humans. The indiscriminate use of chemicals for tick control exerts a strong selective pressure for brown dog ticks to become resistant to them. Here, we investigated claims from the field regarding treatment failure associated with the use of veterinary products containing ivermectin (IVM) to control brown dog ticks infesting dogs in Yucatan state, Mexico. Dogs in six state municipalities were inspected to sample 15 brown dog tick populations. Interviews were conducted with dog owners and point of care veterinarians to gather information on the history of dog treatment with conventional acaricides and IVM. The larval immersion test was used on the progeny of adult female ticks infesting dogs to test for susceptibility to IVM. Experimental results were subjected to statistical analysis. Ten tick populations (66.7%) were classified as resistant compared with the lowest susceptible tick population. A high inter-population variation in the level of IVM resistance was evident. Tick populations classified as resistant were collected from dogs known to have been treated with IVM. To our knowledge, this is the first report of IVM resistance in the brown dog tick worldwide. Veterinary and pet owner education on integrated tick management practices is required to avoid widespread resistance and increased treatment failure with products containing IVM and other macrocyclic lactones used to control internal and external parasites affecting dogs. Integrated tick management will also help mitigate the burden of brown dog tick-borne diseases on human and animal populations.

Technical Abstract: The brown dog tick, Rhipicephalus sanguineus sensu lato (Latreille, 1806), is an ectoparasite and disease vector of significant veterinary and public health importance that is distributed widely around the world. The indiscriminate use of chemicals for tick control exerts a strong selective pressure for brown dog ticks to become resistant to them. Here, we investigated claims from the field regarding treatment failure associated with the use of veterinary products containing ivermectin (IVM) to control brown dog ticks infesting dogs in Yucatan state, Mexico. Dogs in six state municipalities were inspected to sample 15 R. sanguineus s.l. populations. Interviews were conducted with dog owners and point of care veterinarians to gather information on the history of dog treatment with conventional acaricides and IVM. The larval immersion test was used on the progeny of adult female ticks infesting dogs to test for susceptibility to IVM. Dose-mortality regressions, lethal concentrations (LC), their confidence intervals, and slope were estimated by probit analysis. Ten tick populations (66.7%) were classified as resistant compared with the lowest susceptible tick population. A high inter-population variation in the phenotypic level of IVM resistance was evident (resistance ratio at LC50% and LC99% ranged from 1.0 to 30.5, and from 1.0 to 458.8, respectively). Tick populations classified as resistant were collected from dogs known to have been treated with IVM. These brown dog ticks showed substantial interpopulation variation in the phenotypic level of IVM resistance. To our knowledge, this is the first report of IVM resistance in R. sanguineus s.l. worldwide. Veterinary and pet owner education on integrated tick management practices is required to avoid widespread resistance and increased treatment failure with products containing IVM and other macrocyclic lactones used to control endo- and ectoparasites affecting dogs. Integrated tick management will also help mitigate the burden of brown dog tick-borne diseases on human and animal populations.