Introduction

Classification

Taxonomy

• Class:Arachnida; subclass:Acari
• Order:MetastigmataorIxodida
• Family:Ixodidae
• Genus:Dermacentor
• Species:D. variabilis

Active Forms

Resting Forms

Clinical Effects

Epidemiology

Habitat

• Preferred hosts for the adults are medium to large mammals, including wild and domestic carnivores (dogs, cats, wild canids, etc) and humans.
• Nymphs and larvae usually parasitize rodents and lagomorphs.
• Preferred habitats are grassland with tall grass and shrubs.
• Preferred environment is one of high humidity with mild winters.

Lifecycle

• Three host tick , ie each stage falls off the host into the environment after feeding, molts and finds another host for the next stage.
• Life cycle (egg to adult) can be completed in 3 months in optimum conditions but can take longer with overwintering of stages.

Pathological effects

• Pruritus in susceptible dogs, local hypersensitivity with tick-bite site ulceration and secondary pyoderma Skin: deep pyoderma.
• Tick paralysis if present in sufficient numbers.
• Vector ofRickettsia rickettsi(Rocky Mountain spotted fever) in dogs and humans.
• Vector of tularemia (Francisella tularensis), a human bacterial infection.

Control

Control via chemotherapies

• Amitraz Amitraz , Fipronil Fipronil , pyrethroids, pyriprole and isoxazolines are approved for treatment and prophylaxis in dogs.
• Flumethrin and fipronil approved for treatment and prophylaxis in cats.

Control via environment

Largely impractical except where infestation is confined to a limited space such as kennels.

• Outdoor premises control of ticks includes use of carbamates and synthetic pyrethroids. Older insecticides have efficacy but their use is controlled by regulatory approval.
• Synthetic pyrethroids for indoor control (and for use in cars, kennels and cages). Older drugs under regulatory control but may be used by commercial pest exterminators.
• Management of garden habitat, keeping grass short and shrubbery to a minimum.

Vaccination

• None available for tick control. See control of tick-borne diseases Tick control.

Other countermeasures

• Checking for ticks every 24 hours and removal with a tick hook using a 'twist and pull' action.
• Important to remove tick as soon as it is found to reduce risk of disease transmission.
• If the tick is removed but the mouthparts remain this will increase the risk of local soft tissue reaction and disease transmission.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Macaluso K R, Sonenshine D E, Ceraul S M et al (2002) Rickettsial infection in Dermacentor variabilis (Acari: Ixodidae) inhibits transovarial transmission of a second Rickettsia. J Med Entomol 39 (6), 809-813 PubMed.

Other sources of information

• Wall R & Shearer D S (Editors) (2008) Veterinary Ectoparasites: Biology, Pathology and Control, 2nd edn, Blackwell Science Ltd, London, pp 71-74.
• Baker A S (1990) Mite and ticks of domestic animals: An identification and information source. The Natural History Museum, The Stationery Office, London, pp 176-179.