Felis ISSN 2398-2950

Dermacentor variabilis

Synonym(s): American dog tick

Contributor(s): Centers for Disease Control, Maggie Fisher, Susan E Shaw, Ian Wright

Introduction

Classification

Taxonomy

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

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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.
  • Tick paralysis if present in sufficient numbers.
  • Vector of Rickettsia rickettsi (Rocky Mountain spotted fever) in dogs and humans.
  • Vector of tularemia (Francisella tularensis), a human bacterial infection.

Control

Control via chemotherapies

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

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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.

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