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often than women, probably because they participate in activities that bring them
into contact with ticks more frequently.
Tick paralysis is thought to be caused by unidentified venom secreted by the tick
salivary glands during a blood meal. The disorder first appears five to six days
after attachment of the tick. The earliest symptoms are restlessness, irritability,
and paresthesias in the hands and feet. Twenty-four to forty-eight hours later, an
ascending, symmetric, flaccid paralysis with loss of deep tendon reflexes appears.
Weakness typically is initially worse in the lower extremities
Within one to two days severe generalized weakness develops. Cerebellar
dysfunction with ataxia and loss of coordination may appear. Dysfunction may
progress to bulbar and respiratory paralysis. Isolated facial paralysis may occur in
individuals with ticks imbedded behind the ear.
The paralysis resolves after removal of the tick, which establishes the diagnosis.
In North America recovery is usually rapid. It starts within hours and is complete
within days. Other than removing the tick, no therapy other than supportive care
is needed or available. However, undiagnosed tick paralysis can be lethal.
J. Relapsing Fever: Relapsing fever is the only major tick infection in the United
States transmitted by soft ticks, Argasidae, which are rarely seen, resemble
raisins, and may not be recognized as ticks. Unlike Ixodes ticks, the soft
Ornithodoros ticks rarely remain attached for more than thirty minutes, and the
tick bite is often unrecognized.
Hosts for these ticks are wild rodents, and the ticks live in the host's nests or
burrows, particularly cracks and crevices in the walls of cabins, and behave like
bedbugs. In the United States infections occur primarily in Oregon, Washington,
and northern California, although occasional infections occur in other western
states. Relapsing fever has a worldwide distribution.
Relapsing fever is caused by Borrelia spirochetes, and is characterized by bouts
of fever that alternate with afebrile periods. The onset is usually sudden and is
characterized by fever that commonly is higher than 39ºC. Often shaking chills,
severe headache, myalgias, arthralgias, nausea and vomiting, muscular weakness,
and lethargy accompany the fever and may be associated with sweats and intense
thirst. A transitory petechial rash is common during the initial attack. In some
cases, meningeal inflammation and peripheral facial palsy have occurred.
An average of six to seven days later, but with a considerable range, the fever
reappears. Three relapses is the average, but as many as ten or more can occur.
The relapses tend to be progressively less severe. The relapsing nature of this
illness appears to be related to antigenic variation. As an immune response
develops to the predominant spirochetal antigenic strain, variant strains multiply
and cause a recrudescent infection.
The diagnosis is established by identification of the organism in blood smears.
Tetracycline and erythromycin are effective antibiotics. To prevent infection,
rodent-infested cabins should be avoided.
