Clinical and neurophysiological features of tick paralysis

Abstract

The clinical and neurophysiological findings in six Australian children with generalized tick paralysis are described. Paralysis is usually caused by the mature female of the species Ixodes holocyclus. It most frequently occurs in the spring and summer months but can be seen at any time of year. Children aged 1-5 years are most commonly affected. The tick is usually found in the scalp, often behind the ear. The typical presentation is a prodrome followed by the development of an unsteady gait, and then ascending, symmetrical, flaccid paralysis. Early cranial nerve involvement is a feature, particularly the presence of both internal and external ophthalmoplegia. In contrast to the experience with North American ticks, worsening of paralysis in the 24-48 h following tick removal is common and the child must be carefully observed over this period. Death from respiratory failure was relatively common in the first half of the century and tick paralysis remains a potentially fatal condition. Respiratory support may be required for > 1 week but full recovery occurs. This is slow with several weeks passing before the child can walk unaided. Anti-toxin has a role in the treatment of seriously ill children but there is a high incidence of acute allergy and serum sickness. Neurophysiological studies reveal low-amplitude compound muscle action potentials with normal motor conduction velocities, normal sensory studies and normal response to repetitive stimulation. The biochemical structure of the toxin of I. holocyclus has not been fully characterized but there are many clinical, neurophysiological and experimental similarities to botulinum toxin.

Tick Paralysis: A Treatable Disease Not to Be Missed

“…The current hypothesis is that sodium flux across axonal membranes at the node of Ranvier is blocked, whereas neuromuscular transmission is not impaired [5,6]. In contrast, the toxin from Ixodes holocyclus appears to block the release of acetylcholine at the level of the neuromuscular junction, similarly to the mechanism of action of botulinum toxin [7].…”

Review of public health advice about ticks

“…8,9 Tick paralysis is caused by neurotoxins contained in the saliva of engorging female adult ticks. Symptoms start several days after attachment of the tick, when the tick reaches a rapid feeding phase accompanied by intense salivation, which coincides with high production of toxins.…”

“…Symptoms start several days after attachment of the tick, when the tick reaches a rapid feeding phase accompanied by intense salivation, which coincides with high production of toxins. 8 Initial symptoms of tick paralysis include unsteady gait, weakness of limbs, and lethargy; an ascending, flaccid and symmetrical paralysis progresses over hours. In severe cases ventilatory failure may occur.…”

“…However, an important characteristic of paralysis caused by I. holocyclus is that the condition may continue to deteriorate even after the tick has been removed. 3,8,10 Recovery is often slow.…”

“…4 The introduction of residual insecticides and improved standards of domestic hygiene have significantly reduced the bedbug problem but a number of recent studies indicate a reappearance of bedbugs overseas and in Australia. [5][6][7][8] Increasing complaints of bedbugs by shortstay guests, including reports to the City of Sydney's Environmental Health Unit, the South Eastern Sydney Public Health Unit, and local doctors, prompted us to conduct a survey of the situation in short-stay lodges in Sydney.…”