Tick paralysis

Background

• Non-infectious disease caused by saliva injected during tick bite

Epidemiology

• Most common in Pacific Northwest of the US and Canada, and in Australia
• In North America, most commonly caused by Dermacentor variabilis or Dermacentor andersoni from April to June
• In Australia, most commonly caused by Ixodes holocyclus (marsupial ixodid tick), and may be more severe

Pathophysiology

• Unclear mechanism for Dermacentor species ticks
• Ixodes holocyclus produces a botulinum-like neurotoxin

Clinical Manifestations

• Ascending neuromuscular paralysis with preserved sensation
• Can cause ataxia
• Often misdiagnosed as Guillain-Barré syndrome until an engorged tick is found, often hidden in hair

Differential Diagnosis

Feature	Tick Paralysis	Guillain-Barré syndrome	Cervical Spine Lesion	Poliomyelitis
Onset	acute and rapid, within 24 to 28 hours	slower, over days to weeks	abrupt or gradual	days to weeks
Ataxia	present	absent	absent	absent
DTRs	hypo- or areflexia	hypo- or areflexia	variable	hypo- to areflexia
Plantar reflex	downgoing	downgoing	upgoing	downgoing
Sensation	unaffected	mildly affected	affected	unaffected
Meningismus	no	rarely	no	yes
Fever	no	rarely	no	yes
CSF protein	normal	high	normal or high	high
CSF WBCs	normal	normal		elevated
CSF differential	normal	<10 mononuclear cells	variable	lymphocytosis
Time to recovery	rapid ≤24 hours after tick removal	weeks to months	variable	months to years
Permanent sequelae	none	possible	possible	possible

• Botulism causes descending paralysis

Management

• Removal of tick with forceps; recovery typically within 24 hours