Detection of ivermectin and fipronil resistance in Rhipicephalus sanguineus sensu lato in Maha Sarakham, Thailand

Research (Published online: 19-08-2023)

11. Detection of ivermectin and fipronil resistance in Rhipicephalus sanguineus sensu lato in Maha Sarakham, Thailand

Bunnada Siriporn, Amornrat Juasook, Nattarika Neelapaijit, Piyatida Kaewta, and Zhiliang Wu

Veterinary World, 16(8): 1661-1666

Bunnada Siriporn: Veterinary Infectious Disease Research Unit, Faculty of Veterinary Sciences, Mahasarakham University, Maha Sarakham, Thailand.

Amornrat Juasook: Bioveterinary Research Unit, Faculty of Veterinary Sciences, Mahasarakham University, Maha Sarakham, Thailand.

Nattarika Neelapaijit: Bunsiri Animal Hospital, Samut Prakan, Thailand.

Piyatida Kaewta: Faculty of Veterinary Sciences, Mahasarakham University, Maha Sarakham, Thailand.

Zhiliang Wu: Department of Parasitology and Infectious Disease, Graduate School of Medicine, Gifu University, Gifu, Japan.

doi: 10.14202/vetworld.2023.1661-1666

Article history: Received: 31-03-2023, Accepted: 17-07-2023, Published online: 19-08-2023

Corresponding author: Amornrat Juasook

E-mail: amornrat.j@msu.ac.th

Citation: Siriporn B, Juasook A, Neelapaijit N, Kaewta P, and Wu Z (2023) Detection of ivermectin and fipronil resistance in Rhipicephalus sanguineus sensu lato in Maha Sarakham, Thailand, Veterinary World, 16(8): 1661-1666.

Abstract

Background and Aim: Administration is the main strategy for controlling ectoparasites in dogs. Ivermectin and fipronil are most extensively used to prevent and treat Rhipicephalus sanguineus sensu lato infestation in dogs in Thailand. Several researchers have reported resistance to acaricides in R. sanguineus s.l. globally, but documentation of acaricide resistance in the tick population in Thailand is lacking. In this study, we investigated the status of resistance to commonly used acaricides in Thailand in R. sanguineus s.l.

Materials and Methods: Engorged brown dog tick females (10 tick populations) were field-collected directly from parasitized dogs in Maha Sarakham, Thailand, for toxicological bioassays with ivermectin and fipronil. Bioassays were performed in three replicates at 25°C-27°C and 80%-85% relative humidity under a 12-h/12-h photoperiod. The 50% of lethal concentration and its confidence intervals and the slope were estimated for each tick population using probit analysis. Resistance ratios (RRs) of field ticks were characterized based on the relative susceptible population of each acaricide.

Results: Six tick populations (P1-6) were tested for resistance to ivermectin, three of which (P2-4) exhibited low-level resistance to ivermectin (RR = 2.115-2.176). Of four tick populations (P7-10) treated with fipronil, two exhibited moderate-to-severe resistance (P7 and P9, RR = 21.684 and 4.387, respectively). All tick populations deemed resistant to acaricides had a history of exposure.

Conclusion: Based on RR values, four R. sanguineus s.l. tick populations from Maha Sarakham province were resistant to ivermectin and fipronil. To the best of our knowledge, this represents the first documentation of acaricide-resistant populations of R. sanguineus s.l. in Thailand, and recommendations on tick control programs must be formulated with veterinarians and pet owners to prevent the development of further resistance.

Keywords: bioassay, dog, fipronil, ivermectin, resistance, Rhipicephalus sanguineus sensu lato, Thailand.