Introduction

Classification

Taxonomy

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

Active Forms

Resting Forms

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 Skin: deep 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 Ehrlichiosis. Dogs may act as sub clinical carriers.
• Vector of Ehrlichia ewingii, a cause of polyarthritis in dogs Arthritis: rickettsial.
• 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 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

• 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

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.