Canis ISSN: 2398-2942

Neurology: tick paralysis

Contributor(s): Kyle Braund, Laurent Garosi, Peter Irwin

Introduction

  • Cause: paralysis in dogs (and cats in Australia) produced by a neurotoxin generated by some strains of certain species of ticks.
  • Signs: flaccid, afebrile ascending motor paralysis, progressive respiratory failure.
  • Diagnosis: clinical signs, presence of ticks.
  • Treatment: tick removal, topical/systemic insecticides, (neutralization of circulating toxins and supportive therapy in Australia).
  • Prognosis: usually favorable; guarded in Australia.

Pathogenesis

Etiology

  • Tick neurotoxin.
  • In North America, most common species are the Rocky Mountain wood tick (Dermacentor variabilis,the American dog tick (Dermacentor variabilis), the Lone Star tick(Amblyomma americanum) and the Gulf coast tick (Amblyomma maculatum).
  • In Australia (especially along the East coast) Ixodes holocyclus is the most important species.
  • Other species that occasionally cause paralysis are:
    • Ixodes cornuatus.
    • Ixodes hirsti.
    • Ixodes scapularis.
  • Several toxins have been isolated from the salivary glands of Ixodes holocyclus.

Pathophysiology

  • Adult ticks, especially females, produce a salivary neurotoxin that circulates in the host animal and interferes with acetylcholine liberation at the neuromuscular junction and/or impulse propagation along motor axon terminals.
  • Effects on neuromuscular transmission shown to be temperature dependent in vitro. The clinical value of this is currently unclear but a cool environment may benefit the outcome.
  • In Australia, heavy infestations with nymphs or larvae may result in paralysis.
  • Respiratory depression due to diaphragmatic and intercostal paralysis.
  • Cardiovascular depression in paralyzed dogs associated with primary diastolic dysfunction Murmur: overview and reduced LV fractional shortening (impaired myocardial relaxation).
  • Pulmonary edema Lung: pulmonary edema of cardiogenic origin occurs and is a major cause of death.

Timecourse

  • Onset of clinical signs gradual with dogs becoming recumbent in 24-72 hours, 5-14 days after attachment of the tick(s).
  • Death from respiratory failure occurs 18-32 hours later if the ticks remain attached and no treatment is provided.
  • Clinical signs can continue to progress for up to 48 hours after tick removal if tick antitoxin serum is not administered.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Eppleston K R, Kelman M, Ward M P (2013) Distribution, seasonality and risk factors for tick paralysis in Australian dogs and cats. Vet Parasitol 196 (3-4), 460-468 PubMed.
  • Webster R A, Mills P C, Morton J M (2013) Indications, durations and outcomes of mechanical ventilation in dogs and cats with tick paralysis caused by Ixodes holocyclus: 61 cases (2008-2011). Aust Vet J 91 (6), 233-239 PubMed.
  • Webster R A, Mackie J T, Haskins S C (2013) Histopathological changes in the lungs from dogs with tick paralysis: 25 cases (2010-2012). Aust Vet J 91 (8), 306-311 PubMed.
  • Holland C T (2008) Asymmetrical focal neurological deficits in dogs and cats with naturally occurring tick paralysis (ixodes holocyclus): 27 cases (1999-2006). Aust Vet J 86 (10), 377-384 PubMed.
  • Adamantos S, Boag A, Church D (2005) Australian tick paralysis in a dog imported into the UK. Aust Vet J 83 (6), 352 PubMed.
  • Atwell R B and Campbell F E (2001) Reactions to tick antitoxin serum and the role of atropine in treatment of dogs and cats with tick paralysis caused by Ixodes holocyclus: a pilot study. Aust Vet J 79 (6), 394-397 PubMed.
  • Collins G H & Ingwersen K (2000) Paralysis tick research. Aust Vet J 78 (5), 311 PubMed.
  • Atwell R B and Fitgerald M (1994) Unsolved issues in tick paralysis. Aust Vet Practit 24 (3), 156-161 VetMedResource.
  • Malik R & Farrow B R (1991) Tick paralysis in North America and Australia. Vet Clin North Am Small Anim Pract 21 (1), 157-171 PubMed.
  • Malik R et al (1988) Megaoesophagus associated with tick paralysis in three dogs. Aus Vet Pract 18 (4), 156-159 VetMedResource.
  • Ilkiw J E et al (1987) Infestation in the dog by the paralysis tick, Ixodes holocyclus. 1. Clinical and histological findings. Aust Vet J 64 (5), 137-139 PubMed.

Other sources of information

  • Braund K G (2002) Neurotoxic Disorders. In: Clinical Neurology in Small Animals - Localization, Diagnosis and Treatment. Ed K G Braund. Ithaca: International Veterinary Information Service (www.ivis.org), 2002; document no. B0223.0901.
  • Merial, National Tick Paralysis Forum.Tick poisoning in dogs and cats. Bulletin 1.
  • Merial, National Tick Paralysis Forum.Tick poisoning in dogs. Bulletin 2 (July 2000).


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