Can Lavender, Tea Tree Oils Treat Chewing Lice in Donkeys?

Can Lavender, Tea Tree Oils Treat Chewing Lice in Donkeys?

Lica can be found throughout the horse or donkey’s coat, where they feed on the sebum secretions at the base of the hair.

Photo: iStock

It seems that equine internal parasites aren’t the only ones becoming resistant to the products commonly used to treat them: The donkey chewing louse (Bovicola ocellatus) is developing resistance against pyrethroids, a common class of insecticide used against lice. The search for new lice treatments is on, and researchers from the United Kingdom believe that simple essential oil solutions could be one answer.

Bovicola equi, the species of chewing louse found on horses, is very similar in appearance and behavior to the donkey chewing louse, B. ocellatus; in fact, the donkey chewing louse has not been thoroughly characterized and may be the same species,” explained Lauren Ellse, BSc, PhD, a research assistant at the University of Bristol, in England.

Ellse said chewing lice measure less than 2 mm in length, have a rounded head, and are light brown. These parasites can be found throughout the horse or donkey’s coat, where they feed on the sebum secretions at the base of the hair, she said.

“Chewing lice in equines are found worldwide and are often found in much higher numbers than sucking lice, which feed on the host’s blood,” she said. “They are often found in high numbers in animals which are already suffering from other illnesses, and they significantly compromise animal welfare. Therefore, controlling them is very important. However, growing levels of insecticide resistance in ectoparasites has made many conventional insecticides ineffective, and so alternative control measures are required.”

Ellse and colleagues set out to evaluate whether lavender and tea tree essential oils might help control lice in naturally infested donkeys. The team evaluated 198 donkeys stabled at one of two donkey sanctuaries in England or Ireland during peak lice season. The team separated the donkeys into three groups at each location and used a different treatment method on each group. The team sprayed one of three solutions (a 5% lavender oil suspension, a 5% tea tree oil suspension, and a control excipient solution containing 99% water) on the donkeys before grooming it into the animals’ coats. The team treated each group twice, two weeks apart and conducted louse counts two weeks before and two weeks after each application. Each group of donkeys was housed separately during the study.

The team determined that tea tree and lavender essential oils appear to be valuable aids in managing equine lice infestations. Both groups treated with essential oils showed a significant decrease in louse numbers (with a mean of 78% fewer lice), while the control group’s lice count remained the same or increased. Lavender and tea tree solutions demonstrated similar rates of efficacy. The researchers did not observe any adverse reactions to the three solutions.

Additionally, Ellse noted that while donkeys with longer hair had greater lice populations, hair length did not play role in the solution’s efficacy.

“The formulation used in this study was very simple—just essential oils, water, and an emulsifier,” Ellse said. However, she added that there are likely better ways to apply the liquids to the affected equids’ skin. “Therefore, research into the effects of different carriers on coat penetration as well as the longevity of the essential oils would be beneficial.”

She also warned that not all essential oil products are the same for treating lice: “Because essential oils are natural extracts which have a strong odor, there are many products on the market that contain very low concentrations of essential oil or have the oil in an inappropriate formulation. These products are very unlikely to have any effect against ectoparasites and, therefore, it is important to be wary of these products when trying to find alternative parasite control measures.

“This is the first large-scale study to show the efficacy of lavender and tea tree oil in the control of equine lice in the field,” Ellse concluded. “The findings indicate that with further optimization, these essential oils could form the basis of equine lice management regimes.”

This study, “Essential oils in the management of the donkey louse, Bovicola ocellatus,” will appear in an upcoming issue of the Equine Veterinary Journal

About the Author

Natalie DeFee Mendik, MA

Freelance journalist Natalie DeFee Mendik is a multiple American Horse Publications editorial and graphics awards winner specializing in equestrian media. She holds an MA in English from Colorado State University and an International Federation of Journalists' International press card, and is a member of the International Alliance of Equestrian Journalists. With over three decades of horse experience, Natalie’s main equine interests are dressage and vaulting. Having lived and ridden in England, Switzerland, and various parts of the United States, Natalie currently resides in Colorado with her husband and two girls.

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