Felis ISSN 2398-2950

Amblyomma americanum

Synonym(s): Lone star tick

Contributor(s): Ian Wright

Introduction

Classification

Taxonomy

  • Class: Arachnida; subclass: Acari
  • Order: Metastigmata or Ixodida
  • Family: Ixodidae
  • Genus: Amblyomma
  • Species: Amblyomma americanum

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Clinical Effects

Epidemiology

Habitat

  • Preferred hosts for the adults are large herbivores such as deer, horses, cattle and sheep but dogs, cats and people may also be infested.
  • Nymphs and larvae usually parasitize small rodents, lagomorphs and ground inhabiting birds. 
  • Preferred habitats are woodland or pasture bordering woodland.

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 usually taks 3 years with one generation per year but stages may overwinter.

Pathological effects

  • Pruritus, local hypersensitivity with tick-bite site ulceration and secondary pyoderma.
  • Adults can engorge with 0.5-2 ml blood so potential for anemia if present in large numbers.
  • Vector of Ehrlichia chaffeensi, cause of human monocytic ehrlichiosis. Dogs may act as sub clinical carriers.
  • Vector of Ehrlichia ewingii, a cause of polyarthritis in dogs. 
  • Vector of Rickettsia amblyommii, a cause of granulocytic ehrlichiosis in humans and dogs.
  • Vector of Cytauxzoon felis, cause of fatal Cytauxzoonosis in cats. Bobcats act as a wildlife reservoir, prognosis is very poor in infected cats.
  • Vector of southern tick-associated rash illness (STARI, possibly caused by the spirochete Borrelia lonestari). Causes a rash similar to Lyme disease in humans but other signs not as severe.
  • Vector of Rickettsia rickettsi (Rocky Mountain spotted fever) in dogs and humans.
  • Vector of tularemia (Francisella tularensis), a human bacterial infection.
  • Very painful bite.

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

  • Avoidance of woodland and pasture bordering woodland.
  • If walking through woodlands, keep to the center of paths rather than walking close to trees and shrubs at edge of path.
  • Management of garden habitat, avoiding significant garden plant cover in rural areas.

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.
  • Barbour A G, Maupin G O, Tetlow G J et al (1995) Identification of an uncultivable Borrelia species in the hard tick Amblyomma americanum: possible agent of a Lyme disease-like illness. J Infect Dis​ 173 (2), 403-409 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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