ISSN 2398-2950      

Neurology: tick paralysis

ffelis
Contributor(s):

Laurent Garosi


Introduction

  • Cause: paralysis in cats in Australia, produced by a neurotoxin mostly generated by the hard-bodied tick, Ixodes holocyclus.
  • 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).
  • Prognosis: usually favorable.

Pathogenesis

Etiology

  • Tick neurotoxin (holocyclotoxins).
  • Ixodes holocyclus is the most important species of ticks.
  • Other species that occasionally cause paralysis are:
    • Ixodes cornuatus.
    • Ixodes hirsti.
  • Several toxins have been isolated from the salivary glands of ixodes holocyclus. 
  • Attachment sites of the ticks are mostly inaccessible to scratching and grooming with the most commonly reported anatomical locations including the head, under the chin, the neck, between the shoulder blades, and caudal to the elbow.

Pathophysiology

  • Adult ticks, especially females, produce a salivary neurotoxin that circulates in the host animal and interferes with acetylcholine presynaptic release at the neuromuscular junction and/or impulse propagation along motor axon terminals. The toxin may also interfere with acetylcholine release from parasympathetic nerves, which may account for autonomic signs.
  • 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.  
  • Respiratory depression due to diaphragmatic and intercostal paralysis.
  • Pulmonary edema rather than inhalation pneumonia is more common in cats that died from tick toxicity.

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 is uncommon but can occur rapidly 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.
  • 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.
  • Schull D N, Litster A L, Atwell R B (2007) Tick toxicity in cats caused by Ixodes species in Australia: a review of published literature. J Feline Med Surg (6), 487-493 PubMed.
  • Schull D (2004) Tick paralysis in a cat with subclinical hypertrophic cardiomyopathy. Australian Veterinary Practitioner 34 (1), 32-36 ResearchGate.
  • Atwell R B & Campbell F E (2001) Reactions to tick antitoxin serum and the role of atropine in treatment of dogs and cats with tick paralysis caused byIxodes holocyclus: a pilot study. Aust Vet J  79 (6), 394-397 PubMed.
  • Collins G H & Ingwerson K (2000) Paralysis tick research. Aust Vet J 78 (5), 311 PubMed.

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