insecticide

Control of the chewing louse Bovicola (Werneckiella) ocellatus in donkeys, using essential oils

Citation

Lauren Ellse, Faith A. Burden, Richard Wall. December 2013. Control of the chewing louse Bovicola (Werneckiella) ocellatus in donkeys, using essential oils. Medical and Veterinary Entomology. 27:4. 408-413.

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Publication details
Publication date: 
1 December 2013
Volume: 
27
Issue: 
4
Page numbers: 
408-413
Abstract

Infestations by lice can be a significant clinical and welfare issue in the management of large animals. The limited range of commercial pediculicides available and the development of resistance have led to the need to explore alternative louse management approaches. The results of in vitro and in vivo trials undertaken to control populations of the donkey chewing louse, Bovicola ocellatus (Piaget) (Phthiraptera: Trichodectidae) using the essential oils of tea tree (Melaleuca alternifolia) and lavender (Lavandula angustifolia) are reported here. Results of contact and vapour bioassays showed that 5% (v/v) tea tree and lavender oils resulted in > 80% louse mortality after 2 h of exposure. On farms, separate groups of 10 donkeys sprayed with 5% (v/v) tea tree and lavender oil as part of their usual grooming regime showed significant reductions in louse numbers compared with a control group (0.2% polysorbate 80 in water). These findings indicate that tea tree and lavender essential oils can provide clinically useful levels of control of B. ocellatus when used as part of a grooming routine and suggest that with further development could form the basis of an easy to apply and valuable component of a louse management programme for donkeys.

Pyrethroid tolerance in the chewing louse bovicola (werneckiella)

Citation

Lauren Ellse, Faith A. Burden, Richard Wall. May 2012. Pyrethroid tolerance in the chewing louse bovicola (werneckiella). Veterinary Parasitology.

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Publication details
Publication date: 
1 May 2012
DOI number: 
doi:10.1016/j.vetpar.2012.03.018
Abstract

Equine pediculosis is a significant health and welfare issue, particularly in elderly and
chronically debilitated animals. Currently infestation is controlled predominantly using
topically applied pyrethroid insecticides, allowing limited scope for the rotation of drugs and increasing the risk of selection for resistance. Here the insecticidal efficacies of two pyrethroid-based products against the louse Bovicola (Werneckiella) ocellatus collected from donkeys were examined in vitro. The products were cypermethrin (DeosectTM, Pfizer Ltd., 5% (w/v) cypermethrin, cutaneous spray) and permethrin (SwitchTM, VetPlus Ltd., 4% (w/v) permethrin, pour-on). The pyrethroid efficacy was contrasted with that of the organophosphate diazinon, since the louse populations examined were unlikely to have had prior exposure to this compound. The efficacy of diluted pure permethrin, the excipient, butyl dioxitol and the synergist piperonyl butoxide in the presence of the pyrethroids, were also considered. At the concentrations recommended for animal application, neither 4% (w/v) permethrin, nor 0.1% (w/v) cypermethrin had any significant effect on the mortality of B. ocellatus and neither induced significantly more mortality than an acetone-only control. In contrast, 0.04% diazinon caused 70% mortality within 4 h and 100% mortality after 24 h
exposure. The addition of a potential pyrethroid synergist, piperonyl butoxide, in combinationwith cypermethrin and permethrin, resulted in no significant increase in mortality.

It is concluded that the population of lice tested display a high level of pyrethroid tolerance which is likely to reflect the development of resistance. Twenty-four hours after routine treatment of 10 donkeys with a pour-on permethrin product (SwitchTM, VetPlus Ltd., 4% (w/v) permethrin, pour-on) hair tufts taken from their flanks were not significantly insecticidal compared with hair from the midline application site, implying a low level of insecticide distribution. Such a distribution pattern is likely to create an insecticide concentration gradient over the body and further facilitate selection for resistance.

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