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Determination of the Discriminating Concentration Towards Permethrin for Surveying Resistance in Amblyomma americanum
Z D Kaplan1, E A Richardson1,2, C E Taylor1
1Entomology and Nematology Department, University of Florida, Gainesville, FL, 32611, USA.
Abstract:
Amblyomma americanum Linnaeus (Ixodida: Ixodidae) is ubiquitously present throughout the southeastern United States and is capable of vectoring several pathogens. White-tailed deer are the main host for adult A. americanum. However, this tick species is a generalist that will feed on most vertebrates, including humans, deer, livestock, and pets. Management of this species can be challenging due to a lack of cost-effective strategies. Acaricides are often utilized, however, this may lead to pesticide resistance. The Food and Agriculture Organization of the United Nations (FAO) larval packet test (LPT) was performed on susceptible A. americanum to determine the lethal concentration (LC) and discriminating concentration (DC) values for permethrin. The FAO LPT was used at these pre-established values to compare levels of resistance in ticks collected from a captive deer farm and wild areas representing high and low permethrin exposure settings, respectively. Resistance ratios (RR) calculated from the LC values for the ticks collected from farmed and wild deer ranged between 1 and 2. A. americanum collected from farmed and wild deer were not found to be resistant, however, some samples had slightly elevated RRs as compared to the susceptible laboratory strain, which may suggest tolerance development. Although the A. americanum sampled in this study were not resistant to permethrin, the DC calculated in this study will allow for rapid evaluation of resistance in a permethrin resistance monitoring program such that alternate management strategies can be adopted if resistance is detected.
Insights
The lone star tick (Amblyomma americanum) showed no significant permethrin resistance in farmed or wild populations. However, monitoring is advised to detect early signs of tolerance, enabling timely adoption of alternative tick management strategies.
Area of Science:
- Veterinary Entomology
- Pest Management
- Toxicology
Background:
- Amblyomma americanum, a significant vector in the southeastern US, primarily infests white-tailed deer but also feeds on humans and livestock.
- Effective management of this tick species is hindered by the lack of cost-effective strategies, with acaricides often leading to pesticide resistance.
- Permethrin is a commonly used acaricide for tick control, necessitating an understanding of resistance levels in Amblyomma americanum populations.
Purpose of the Study:
- To determine the lethal concentration (LC) and discriminating concentration (DC) values for permethrin in susceptible Amblyomma americanum.
- To compare permethrin resistance levels in Amblyomma americanum populations from a captive deer farm and wild areas with varying historical permethrin exposure.
- To establish a baseline for a permethrin resistance monitoring program for Amblyomma americanum.
Main Methods:
- The Food and Agriculture Organization of the United Nations (FAO) larval packet test (LPT) was employed to assess permethrin susceptibility.
- LC and DC values were determined using a susceptible laboratory strain of Amblyomma americanum.
- Ticks collected from a deer farm and wild habitats were tested using the FAO LPT with established permethrin concentrations.
Main Results:
- Resistance ratios (RR) for ticks from farmed and wild deer ranged from 1 to 2, indicating no significant resistance.
- Amblyomma americanum populations sampled from both farmed and wild environments did not exhibit resistance to permethrin.
- Some tick samples displayed slightly elevated RRs compared to the susceptible strain, suggesting potential tolerance development.
Conclusions:
- The study established permethrin LC and DC values for Amblyomma americanum, crucial for future resistance monitoring.
- While no resistance was detected, the findings highlight the potential for tolerance development in Amblyomma americanum populations.
- The established DC values will facilitate rapid resistance evaluation, enabling the timely implementation of alternative management strategies if resistance emerges.
