DESCRIPTION

Tick paralysis involves progressive weakness leading to generalized paralysis.

• Ticks in the United States that cause tick paralysis include:
  • Pacific Northwest. Dermacentor andersoni (wood tick).
  • Southeast. D. variabilis (dog tick), Amblyomma americanum (lone star tick), A. maculatum (Gulf Coast tick), and Ixodes scapularis (black-legged deer tick).
• Outside the United States, ticks causing paralysis may be found in:
  • Crete. Hyalomma truncata and I. ricinus.
  • Australia. I. cornatus, I. holocyclus, and I. hirsti.
  • South Africa. Rhinicephalus simus and R. evertsi.

PATHOPHYSIOLOGY

• Adult female ticks bite painlessly to feed on blood.
• A neurotoxin is secreted from an attached and engorging pregnant female tick's salivary glands.
• The mechanism of neurotoxin effect is unclear; the toxin may interfere with the release of acetylcholine at the neuromuscular junction and slow motor conduction.

TOXIC DOSE

One tick is sufficient to produce toxicity; however, it must remain attached and feed for several days before symptoms develop.

EPIDEMIOLOGY

• Poisoning is rare.
• Toxic effects following exposure are typically mild to moderate, with death occurring rarely.
• Most cases in the United States occur in the Northwest and Southeast during the spring and summer months.

CAUSES

Poisoning usually occurs via an accidental environmental encounter.

Section Outline:

• DESCRIPTION
• PATHOPHYSIOLOGY
• TOXIC DOSE
• EPIDEMIOLOGY
• CAUSES

DIFFERENTIAL DIAGNOSIS

• Toxic causes of progressive weakness and paralysis include diphtheria, tetanus, botulism, arsenic, thallium, and selenium, among others.
• Nontoxic causes include periodic paralysis, Guillain-Barré syndrome, transverse myelitis, myasthenia gravis, and Eaton-Lambert syndrome, among others.

SIGNS AND SYMPTOMS

• Ticks typically attach in relatively concealed areas of the body, including the scalp, axilla, ear, groin, or popliteal areas.
• Tick paralysis usually presents as an ascending flaccid paralysis that develops several days following tick attachment. Sensory function is typically preserved.

Vital Signs

Fever (tick-induced fever) is a separate condition that has rarely been associated with motor dysfunction.

HEENT

• Ticks are commonly found in the scalp concealed by hair.
• Diplopia and dysarthria may be early signs of bulbar weakness.
• Nystagmus has been reported.
• Bulbar paralysis and upper airway obstruction or aspiration can result in death if not recognized.

Dermatologic

• Local reaction to a tick bite often produces a pruritic papule.
• Bacterial superinfection is common, with excoriation due to pruritus.

Pulmonary

• Dyspnea may be an early sign of respiratory muscle weakness.
• Respiratory paralysis can result in death if it is not recognized.

Gastrointestinal

• Dysphagia may be an early sign of bulbar involvement.
• Nausea, vomiting, and diarrhea can be associated with tick-induced fever.

Neurologic

• Muscle weakness usually starts in the distal muscles of the lower extremities and ascends over 24 to 48 hours to involve the proximal lower extremities, the trunk, the upper extremities, and the head.
• Muscle weakness originating in proximal muscles has occurred rarely.
• Decreased deep tendon reflexes usually develop after the onset of muscle weakness and may progress to areflexia over 24 to 48 hours.
• Sensation usually remains intact, although paresthesia has been reported.
• Ataxia may be an early sign of muscle weakness.

PROCEDURES AND LABORATORY TESTS

Essential Tests

No tests may be needed in a minimally symptomatic patient on whom the tick has been discovered and removed.

Recommended Tests

• Serum electrolytes, glucose, BUN, creatinine, magnesium, calcium, and phosphate levels are used to evaluate metabolic causes of weakness, such as hypokalemia.
• Arterial blood gases, pulse oximetry, and serial vital capacity measurements are used to assess respiratory function and the need for intubation.
• Lumbar puncture is used to detect elevated cerebrospinal fluid protein without cells, which is common with Guillain-Barré or lymphocytosis (e.g., viral-induced transverse myelitis).
• Heavy metal screening is used to evaluate patients with suspected exposure.
• A chest radiograph may be useful in ruling out Eaton-Lambert syndrome, which is often associated with underlying neoplasms.
• Motor nerve conduction studies will usually show normal to slightly slowed conduction velocities with normal distal latencies.
• Sensory nerve conduction is usually normal.
• Electromyographic studies will usually show that compound muscle action potentials are abnormally low.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • Vital Signs
  • HEENT
  • Dermatologic
  • Pulmonary
  • Gastrointestinal
  • Neurologic
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests

• Treatment should focus on removing the tick and supporting respiratory function.
• Supportive care with appropriate airway management is vital, with specific treatment initiated while supportive care continues.

DIRECTING PATIENT COURSE

The health-care provider should call the poison control center when:

• Diplopia, dysphagia, muscle weakness, or other severe effects are present.
• Symptoms and signs are not consistent with tick paralysis.
• Underlying disease presents an unusual problem.

The patient should be referred to a health-care facility when:

• Patient or caregiver seems unreliable.
• Any toxic effects are noted.
• Underlying disease presents an unusual problem.

Admission Considerations

Inpatient management is warranted for patients with neurologic effects.

DECONTAMINATION

• The area is washed with soap and water.
• The tick is then removed.
  • Using a magnifying glass, the tick is grasped as close to the skin surface as possible with fine forceps, blunt forceps, or gloved fingers.
  • A gentle steady traction is applied, being careful not to squeeze, crush, or puncture the body of the tick.
  • Grasping the tick by the side of the mouth may facilitate removal.
  • Application of oil or solvent is rarely helpful and may make grasping the tick more difficult.
  • Retained mouth parts must be removed and sometimes require excision under local anesthesia.
• The area must be reexamined with a magnification system to make sure the entire tick has been fully removed.
• The area is rewashed with soap and water.

ANTIDOTES

There is no specific antidote for tick paralysis.

ADJUNCTIVE TREATMENT

• Incomplete removal of a tick can produce a pruritic nodule (granuloma) that may require surgical excision.
• Endotracheal intubation and mechanical ventilation may be needed in severe cases.

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
• ANTIDOTES
• ADJUNCTIVE TREATMENT

PATIENT MONITORING

• Airway patency and respiratory function must be monitored continuously.
• Pulmonary function tests, specifically the negative inspiratory force, is a useful serial indicator of respiratory muscle strength.

EXPECTED COURSE AND PROGNOSIS

• Gradual improvement of motor function should begin within a few hours of tick removal.
• Complete recovery usually occurs within 48 hours but may take up to a week. One case reported weakness lasting months.
• Respiratory compromise can lead to hypoxic injury.

DISCHARGE CRITERIA/INSTRUCTIONS

Asymptomatic patients may be discharged from the emergency department or hospital after tick removal has been accomplished.

PATIENT EDUCATION

• Patients should wear long sleeves and long pants when travelling outdoors in tick-endemic areas.
• Chemical tick repellents are recommended.

Section Outline:

• PATIENT MONITORING
• EXPECTED COURSE AND PROGNOSIS
• DISCHARGE CRITERIA/INSTRUCTIONS
• PATIENT EDUCATION

DIAGNOSIS

• More than one tick may be involved and must be removed.
• Ticks also may be vectors for infectious diseases, including Rocky Mountain spotted fever, Q fever, tularemia, relapsing fever, borreliosis, babesiosis, Colorado tick fever, Boutoneneuse fever, ehrlichiosis, encephalitis, and Lyme disease.

TREATMENT

• The health-care professional must ensure that tetanus immunization status is up to date.
• Using a hot instrument is not recommended due to the risk of inflicting thermal injury.

FOLLOW-UP

The patient should not be discharged immediately after tick removal because muscle weakness may continue to progress after the removal of the tick due to further absorption of venom, failure to identify other ticks, or absorption of venom from retained mouth parts.

Section Outline:

• DIAGNOSIS
• TREATMENT
• FOLLOW-UP

Toxic effect of other substances, chiefly nonmedicinal as to source: venom.

RECOMMENDED READING

Doan-Wiggins L. Tick-borne diseases. Emerg Med Clin North Am 1991;9:303-324.

Author: Edwin K. Kuffner

Reviewer: Richard C. Dart