Efficacy of a federally approved flea bait, orally administered to white-footed mice (Peromyscus leucopus), against blood feeding Ixodes scapularis larvae under simulated field conditions

Abstract

A promising alternative approach to conventional vector control practices is the use of systemic insecticides/acaricides orally administered to relevant mammalian host species to control blood feeding disease vectors. In the United States, Lyme disease continues to be the most prevalent vector-borne disease with the Centers for Disease Control and Prevention estimating approximately 500,000 Lyme disease infections each year. Previous research has demonstrated the potential usefulness of a low dose fipronil bait in controlling Ixodes scapularis larvae feeding on white-footed mice. However, no such acaricide-only product is approved for use in treating white-footed mice to control I. scapularis. The purpose of the study was to evaluate the use of a federally approved fipronil flea control bait (Grain Bait) in controlling I. scapularis parasitizing white-footed mice (Peromyscus leucopus). A simulated field trial was conducted in which Grain Bait was presented to grouped white-footed mice alongside an alternative diet for 168 h. Mice were fitted with capsules and manually parasitized with I. scapularis larvae. Replete larvae detaching from each mouse were collected and monitored for molting to nymphs. The inside of each capsule was observed to evaluate tick attachment. Blood was collected from all Treatment group mice via cardiac puncture to determine the fipronil sulfone concentration in plasma (CP) for each animal. Results indicated that Grain Bait would be consumed in the presence of an alternative diet and that bait acceptance was greater for males, relative to females. Treatment with Grain Bait prevented 100% larvae from feeding to repletion at Day 7 post-exposure and prevented 80% of larvae from feeding to repletion and 84% from molting at Day 21 post-exposure, relative to Control groups. Molted nymphs were not recovered from mice that had CP detectable ≥18.4 ng/ml. The results suggest that this federally approved flea product could be utilized for tick control and that other medically important vector-host relationships should be considered.

Keywords: Acaricides; Borrelia burgdorferi sensu stricto; Fipronil bait; Ixodes scapularis; Peromyscus leucopus; Systemic insecticides; Vector control; White-footed mice.

Graphical abstract

Fig. 1

Capsule observations via microscopy. (A) Non-engorged (deceased) larvae, (B) engorging larvae, (C) fully engorged (replete) larvae nearing detachment.

Fig. 2

Representative images of Day 2 and Day 4 capsules observations. Non-engorging larvae attached to Treatment mouse at (A) Day 2 and (B) Day 4. Engorging larvae attached and actively feeding on Control mouse at (C) Day 2 and (D) Day 4. At Day 4, the majority of larvae fed to repletion and detached from the Control mice, while the majority died in situ on the Treatment mice. Green arrows indicate live larvae and red arrows indicate dead larvae. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)