Efficacy of low-dose fipronil bait against blacklegged tick (Ixodes scapularis) larvae feeding on white-footed mice (Peromyscus leucopus) under simulated field conditions

David M Poché,Richard M Poché,Kelsey Dawson,Batchimeg Tseveenjav

doi:10.1186/s13071-021-04930-z

Abstract

BackgroundLyme disease, caused primarily by Borrelia burgdorferi sensu stricto, is the most prevalent vector-borne disease in the United States. Treatment of rodent pathogen reservoirs with an oral acaricide may suppress the production of infected host-seeking ticks posing a risk for human infection. A previous study showed that an oral fipronil bait effectively controlled larval Ixodes scapularis ticks on white-footed mice (Peromyscus leucopus) up to 15 days post-bait exposure. The present study expands upon this finding by exposing group-housed white-footed mice to fipronil bait under simulated field conditions prior to tick infestation.MethodsMice (n = 80) were housed in groups of 10 within large enclosures and offered a choice between fipronil bait within a commercial bait station and an alternative diet. The mice were assigned to two treatment groups and two control groups to undergo bait exposure durations of either 24 h (reduced) or 168 h (extended). Groups were further differentiated by the time point post-bait exposure when larval ticks were applied to mice within feeding capsules (reduced day 1, day 15; extended day 21, day 35). For 4 days post-tick introduction, attached larvae were observed by microscopy and replete larvae were recovered. Replete larvae were monitored for molting success. Plasma was collected from all treatment group mice to obtain fipronil plasma concentrations (CP).ResultsThe fipronil bait (0.005% fipronil) was palatable and controlled larval ticks on white-footed mice when presented under simulated field conditions. Efficacy in preventing attached larvae from feeding to repletion was 100% (day 1), 89.0% (day 15), 85.8% (day 21), and 75.2% (day 35). When also considering molting success, the fipronil bait prevented 100% (day 1), 91.1% (day 15), 91.7% (day 21), and 82.5% (day 35) of larvae attaching to mice from molting. The mean CP per mouse was 191.5 ng/ml (day 1), 29.4 ng/ml (day 15), 10.6 ng/ml (day 21), and 1.0 ng/ml (day 35).ConclusionsThe results suggest that fipronil bait will be consumed by white-footed mice in the presence of an alternative diet, and effectively control larval ticks on treated mice. A field trial is needed to confirm the results of this study. Low-dose fipronil bait may provide a cost-effective means of controlling blacklegged ticks to be integrated into tick management programs.Graphical

Highlights

Lyme disease, caused primarily by Borrelia burgdorferi sensu stricto, is the most prevalent vector-borne disease in the United States
A recent laboratory study indicated that a low-dose fipronil bait (0.005%) presented orally to whitefooted mice for 48 h could control 100% of blacklegged tick larvae blood-feeding at days 1, 9 and 15 post-exposure [17]. These results provided early evidence suggesting a fipronil-based oral acaricide bait could be a useful addition to integrated tick management programs
The primary objective of the current study was to investigate the efficacy of a low-dose fipronil bait, presented to white-footed mice, in controlling blood-feeding blacklegged tick larvae under simulated field conditions conducted in the laboratory

Summary

Introduction

Lyme disease, caused primarily by Borrelia burgdorferi sensu stricto, is the most prevalent vector-borne disease in the United States. A previous study showed that an oral fipronil bait effectively controlled larval Ixodes scapularis ticks on white-footed mice (Peromyscus leucopus) up to 15 days post-bait exposure. The present study expands upon this finding by exposing group-housed white-footed mice to fipronil bait under simulated field conditions prior to tick infestation. The blacklegged tick (Ixodes scapularis) is the primary vector of B. burgdorferi s.s. in the Midwest and Northeast [6] and its range in the eastern USA is expanding [3]. The blacklegged tick has been documented in at least 45.7% of the continental USA and blacklegged ticks and the western blacklegged tick (Ixodes pacificus) are present in at least 49.2% of the counties in the continental United States, marking a 44.7% expansion in range since 1998 [3]

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