MediRabbit

Ticks in rabbits

Esther van Praag Ph.D.

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Ticks plague all members of the lagomorph family, including wild and domestic rabbits, living indoors. Intermediate stage ticks are indeed light and easily carried by wind. They can enter a home through windows left open, or ventilators placed in front of an open window. Ticks can be categorized in two types:

• Ixotid ticks are protected by a hard shield and their mouthpieces can clearly be seen. They include commonly found ticks all over the world, like Ixodes sp., Amblyomma sp., Boophilus sp., Rhipicephalus sp., and Haemophysalis sp. All can affect rabbits.

• Argasid ticks are soft ticks whose mouthparts and “false head” (capitulum) cannot be seen when viewed from the dorsal side. They live essentially in arid regions on the American continent, Africa and India. Members of the Otobius sp., and Ornithodoros sp. can plague rabbits.

Haemophysalis leporis-palustris

Ticks are small (less than 5 mm in length) and have a reddish or brownish color. Their life cycle is complex. Wild rabbits, cottontails and hares are commonly plagued by Haemophysalys leporis palustris. This tick has typically three developmental phases, which occur on three different hosts. After feeding blood or serum from its host, the tick larva will fall to the ground, in order to molt. The next stage larva or nymph will find a new host to feed on. Once adult, the tick will hide in the vegetation. When it detects the presence of a host thanks to organs sensing its release of CO₂ release and body temperature, it will crawl onto its fur and start engorging with blood. During the feeding, the tick will release saliva and enzymes into its host, to keep the bite open. During this phase, tick-borne diseases can be transmitted.

Soft ticks also affect lagomorphs. The commonly found one is the red tick Otobius lagophilus. All the larval and nymphal intermediates are found on rabbits, where they feed on lymph secretions. Soft ticks can be vector for various diseases affecting rabbits.

A. van Praag

Non-engorged tick found crawling on the fur of the hind limb of a rabbit.

Ticks are implicated in the transmission of viral, bacterial and protozoan diseases that affect rabbits. These pathogens depend on the regions of the world where the rabbit lives and the local wildlife. Viral diseases include myxomatosis, rabbit hemorrhagic disease 1 and 2 (VHD/RHD), the Shope papilloma virus, or new emerging diseases such as the West Nile Virus. Pathogen bacteria include those causing tularemia (rabbit fever), Lyme disease or Rocky Mountain spotted fever.

In regions where myxomatosis and VHD1 or VHD2 are endemic, vaccination of domestic rabbits is highly recommended. Several vaccines are available. Nobiviac Myxo-RHD will protect against RHD1 only and myxomatosis. It will not protect against RHD2. The Filavac and Eravac vaccines will protect against RHD2. Nobiviac Myxo-RHD PLUS offers protection against RHD1, RHD2 as well as myxomatosis. The availability of these vaccines depends on the sanitary politics of each country.

Clinical signs

Ticks are usually found while inspecting the fur of a rabbit. Preferred locations are the ears, the area between the ears, the neck and the dewlap of female rabbits.

Severe infestation can lead to macrocytic (enlarged red blood cells) normochromic (referring to a red blood cell of normal color, usually because it contains the right amount of hemoglobin) anemia.

daveynin, https://www.flickr.com/photos/daveynin/2755939908/

Cottontail infested with replete (fully engorged with blood) ticks. Once feeding on blood is finished, the tick will detach itself from its host and fall to the ground.

Treatment

As many ticks as possible should be carefully removed with forceps and killed rapidly by immersion in an acaricide solution, alcohol, or chloroform solution. This avoids eventual contamination or spreading diseases carried by the tick host.

If the presence of further ticks is noticed, or if the infestation is severe, administration of ivermectin (0.400 mg/kg, SC, once) is will successfully get rid of the ticks.

Although successfully killing ticks, the use of insecticide products containing pyrethrin, permethrin, amitraz must be avoided, due to their secondary toxic effects in rabbits. Fipronil is forbidden for use in rabbits.

Severe tick infestation can lead to anemia and death. When observed in a rabbit, blood transfusion from a healthy rabbit can be attempted.

For detailed information on ticks in rabbits,

“Skin Diseases of Rabbits”

by E. van Praag, A. Maurer and T. Saarony,

408 pages, 2010.

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Acknowledgements

Thanks are due to David Fulmer for the permission to use the picture of an infested cottontail and to Iris Klimczuk (USA) for her suggestion.