Lethal effects of a silica gel + pyrethrins (Drione) on Amblyomma americanum (L.) (Ixodida: Ixodidae) larvae and nymphs

Authors: Showler, Allan; GARCIA, ABIGAIL - SCHREINER UNIVERSITY; CAESAR, RYAN - SCHREINER UNIVERSITY

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2020
Publication Date: 6/22/2020
Citation: Showler, A., Garcia, A.R., Caesar, R.M. 2020. Lethal effects of a silica gel + pyrethrins (Drione) on Amblyomma americanum (L.) (Ixodida: Ixodidae) larvae and nymphs. Veterinary Parasitology. https://doi.org/10.1093/jme/tjaa119.
DOI: https://doi.org/10.1093/jme/tjaa119

Interpretive Summary: Hard ticks ingest blood from host animals, transmitting pathogenic organisms that cause diseases in humans and animals. As resistance to synthetic conventional acaricides becomes more common, alternative tactics are being investigated. Efficacy of CimeXa, a commercially available silica gel desiccant dust, and Drione, a commercially available product containing silica gel + pyrethrins, were assessed for activities against lone star tick larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and Drione caused total larval mortality within 1 h when they were briefly immersed in the dusts and when they crawled across dust-treated substrate. Nymphs were completely killed by Drione within 4 h. Mortality of lone star tick larvae and nymphs occurred after the pests crawled across dried aqueous suspensions of the products but this was not as efficient and fast-acting as when immature life stages were exposed to dry dusts, and dried aqueous suspensions of Drione were not substantially more efficient than dried aqueous suspensions of CimeXa. CimeXa and Drione will provide prophylactic protection of cattle because silica gel can remain on the host until physically removed, and Drione effectively kills ixodids in the process of feeding as well. Both of the dust-based products will likely be effective against other ixodid species, such as the southern cattle fever tick.

Technical Abstract: Ixodids ingest blood from host animals, vectoring and transmitting pathogenic organisms that induce medical and veterinary diseases. As resistance to synthetic conventional acaricides becomes more common, alternative tactics are coming under heightened scrutiny. Laboratory bioassays were used to assess the efficacy of CimeXa, a commercially available silica gel desiccant dust, and Drione, a commercially available product containing silica gel + pyrethrins, against lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and Drione caused total larval mortality within 1 h when they were briefly immersed in the dusts and when they crawled across dust-treated substrate; nymphs were completely killed by 4 h. Mortality of A. americanum larvae and nymphs occurred after the pests crawled across dried aqueous suspensions of the products but this was not as efficient and fast-acting as when the immature life stages were exposed to substrate treated with dry dusts, and dried aqueous suspensions of Drione were not substantially more efficient than dried aqueous suspensions of CimeXa. CimeXa and Drione will provide prophylactic protection of cattle because silica gel can remain on the host until physically removed, and Drione effectively kills ixodids in the process of feeding as well. Both of the dust-based products will likely be effective against other ixodid species, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), a one-host tick that searches for hosts only in the most vulnerable larval stage.