Other
Tick-Borne Illnesses
While Lyme Disease is the most publicized illness
related to tick bites, it is not the only cause for concern. If
you suspect you have been infected by a tick seek medical attention
immediately.
Tick-Borne Illnesses include:
Babesiosis
Babesia are parasitic organisms that infect red blood
cells. They are transmitted by the same ticks that transmit Lyme
disease. Infections with these organisms may mimic malaria as they
look similar on microscopic examination of blood smears. A travel
history is crucial in distinguishing the two diseases as malaria
is only rarely acquired within the United States. Many infected
persons are asymptomatic. Hence, the incidence of babesiosis is
unknown.
Most cases of babesiosis occur in the northeastern
United States during the summer months. The highest incidence of
babesiosis occurs in the islands off the coast of Massachusetts
(Nantucket and Martha’s Vineyard), eastern and south-central
Long Island (Shelter and Fire Islands), areas of Westchester, New
York and Eastern Connecticut. Ticks infected with Babesia have also
been found in New Jersey. Atlantic, Camden, Burlington, Ocean, Monmouth,
Mercer, Somerset and Hunterdon are the 8 New Jersey counties in
which reported cases of babesiosis were acquired from 1993-2001.
Risk factors for symptomatic babesiosis include advanced
age, asplenia (lack of a functioning spleen), and immunodeficiency.
Patients without these risk factors are more likely to have asymptomatic
infection. In one study of 136 patients with babesiosis in New York
State, 23% were also infected with Lyme disease.
The incubation period for babesiosis is 1-4 weeks
following the tick bite. Nonspecific symptoms include fatigue, loss
of appetite, muscle aches, nausea, headache, sweating, chills, abdominal
pain, mood swings, depression and dark urine. Patients may have
fever and a mildly enlarged liver. Blood tests may show anemia,
low platelets and elevated liver enzymes.
The diagnosis is usually made by examining a blood
smear for the Babesia parasites. Antibody tests may be helpful.
It is important to note that the antibody tests may remain positive
for weeks to months after successful treatment. Therefore a positive
antibody test does not necessarily equate to active disease. A molecular
biological test called PCR (polymerase chain reaction) may also
be useful if the disease is suspected in patients with negative
blood smears. Patients should assure that their doctors send their
blood tests to a laboratory that has been accredited by the College
of American Pathologists. Patients may check their laboratory’s
accreditation status by pointing their browser to http://cap.org
and clicking on the section for laboratory accreditation. (It is
important to note that PCR blood tests are not useful for the diagnosis
of Lyme disease.)
Most patients have a mild illness and recover without
specific treatment. If treatment is needed, a combination of azithromycin
(Zithromax) and atovaquone (Mepron) is usually prescribed for 7
days. In severe cases, patients may require hospitalization and
exchange blood transfusions in addition to the antibiotics.
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Ehrlichiosis
Ehrlichiae are bacteria that live in certain animals
and are spread to other animals and humans through tick bites. In
the United States there are two main types of Ehrlichia infections.
Ehrlichia chaffeensis causes Human Monocytic Ehrlichiosis (HME)
while Anaplasma phagocytophila causes Human Granulocytic Ehrlichiosis
(HGE). HGE is now referred to as anaplasmosis or HGA (Human Granulocytic
Anaplasmosis).
Unlike Lyme disease, ehrlichiosis is considered to
be an acute infection without long-term consequences. Many people
who are exposed to the disease remain asymptomatic, while others
suffer mild symptoms that resolve without treatment. In a minority
of patients, Ehrlichia infection produces severe symptoms requiring
immediate antibiotic treatment. These cases may be life-threatening
and even fatal for elderly patients and for patients with compromised
immune systems.
Like Lyme disease, transmission of the ehrlichiosis
bacterium is delayed for an average of 36 hours or more after an
infected tick begins to feed. The HME bacterium, E. chaffeensis,
is primarily transmitted by the lone star tick. Ticks infected with
E. chaffeensis occur mostly south of the line connecting southern
New Jersey and western Texas, and throughout the high plains states
north of Texas to the Canadian border.
A. americanum (Lone Star Tick)
Approximate Distribution of the Lone Star Tick
The HGA bacterium is transmitted by the deer tick
(Ixodes scapularis). This is the same tick that transmits Lyme disease
and babesiosis. A single tick bite may transmit 1, 2 or all 3 of
the infections. Ixodes scapularis is found mostly in the upper Midwest
and along the eastern seaboard from New Jersey to Massachusetts.
From left to right: The deer tick Approximate
Distribution of Ixodes
(Ixodes scapularis) adult female,
scapularis adult male, nymph,
and larva on a centimeter scale.
HME and HGA are not clinically distinguishable as
they present with similar symptoms. The onset of either infection
generally begins within one week of a tick bite. Fever, severe headache,
malaise, muscle pains and chills are common. Nausea, vomiting, confusion
and joint pains are less common manifestations of Ehrlichia/Anaplasma
infections. Laboratory abnormalities frequently include a low white
blood cell count, a low platelet count and elevated liver enzyme
tests. The diagnosis is suspected based on the symptoms, laboratory
abnormalities, and the time of year as well as the patient spending
time in an area in which the ticks are present. Laboratory confirmation
may be achieved by finding a positive PCR blood test within the
first 10 days of infection and by an antibody test after 21 days
of infection. It is important to note that the antibody tests may
remain positive for weeks to months after successful treatment.
Therefore a positive antibody test does not necessarily equate to
an active infection and may not require treatment. Occasionally
a blood smear may show the organisms. Patients should assure that
their doctors send their blood tests to a laboratory that has been
accredited by the College of American Pathologists. Patients may
check their laboratory’s accreditation status by pointing
their browser to http://cap.org and clicking on the section for
laboratory accreditation. (It is important to note that PCR blood
tests are not useful for the diagnosis of Lyme disease.)
Empiric therapy for suspected Ehrlichia/Anaplasma
infections is essential prior to laboratory confirmation. Doxycycline
is the drug of choice and is prescribed for 7-10 days. Ehrlichiosis/Anaplasmosis
symptoms usually subside within 24-48 hours of treatment. Doxycycline
will also treat Lyme disease but will have no effect on babesiosis.
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