2. A Case Study!
• September 7th, 2006: 51-year-old man cleans room associated with a 100-
year-old solar telescope at Mt. Wilson Observatory, located at 1,737 m (5,700
feet) elevation in San Gabriel mountains. Floor was littered with rodent feces,
acorn husks, and other debris suggesting years of rodent occupation.
• September 9th, 2006: Carried old boxes with rodent nests. Some material
transferred to clothing. Noticed 2 “insect bites” on each leg just above sock line.
• September 17th, 2006: Experienced sudden onset of weakness, fever, shaking
chills, muscle and joint pain.
• September 18th, 2006: Nausea and vomiting developed.
• September 20th, 2006: Sought help at a clinic, prescribed antiemetics. No
improvement.
• September 21st, 2006: Presented at hospital emergency department. Physical
indicated fever and dehydration. CBC showed mild thrombocytopenia and
increased granulocyte count. Treated with ketorolac, metoclopramide, and
intravenous saline for possible viral illness and was released. Improved over
the next several days.
3. Case study cont.
• September 27th, 2006: Relapsed with increased weakness, arthralgia,
and myalgias, fever, shaking chills and nausea and vomiting.
• September 28th, 2006: Illness peaked.
• September 29th, 2006: Illness improved.
• October 1st, 2006: Relapsed. Returned to emergency room and was
hospitalized. High fever, and treated with intravenous fluids, antiemetics,
and piperacillin/tazobactam. CBC showed leukocytosis, left shift and
thrombocytopenia. Routine blood cultures (which do not support Borrelia
growth) were negative. Improved after a few hours of receiving
antimicrobial drug treatment and was mildly hypotensive for a day.
• October 3rd, 2006: Drug treatment discontinued. Patient was released.
Night sweats continued for 2 days after discharge and felt generalized
weakness for the next several days.
• October 16th, 2006: Patient returned to full time work.
4. Disease Presentation
• Tick-borne relapsing fever (TBRF) is characterized by
recurring febrile episodes. Each febrile episode ends with
a sequence of symptoms collectively known as a "crisis”.
• This phase is followed by the "flush phase", characterized
by drenching sweats and a rapid decrease in body
temperature. Patients may become transiently
hypotensive.
• Patients who are not treated will experience 1 to 4
episodes of fever before illness resolves.
5. Identifying Characteristics
• Typical laboratory results of TBRF patients include:
1. Normal to increased white blood cell
count with a left shift towards immature cells
2. Mildly increased serum bilirubin level
3. Mild to moderate thrombocytopenia
4. Elevated erthrocyte sedimentation rate
5. lightly prolonged prothrombin time (PT) and
partial thromboplastin time (PTT)
• Patients typically appear moderately ill and may be
dehydrated. Occasionally a macular rash or
scattered petechiae may be present on the trunk
and extremities.
6. Diversity and Distribution
• First observed in California, USA, in 1921 when
2 persons were infected in a cabin in Nevada County,
north of Lake Tahoe.
• Most persons who became ill had exposures at high
elevations in various mountain locations.
• Later found to be endemic near Big Bear Lake in the San
Bernardino Mountains, San Bernardino County, in
southern California.
• The primary cause of tick-borne
relapsing fever in western North
America and responsible for
most cases in the United States
is Borrelia hermsii.
8. Transmission: The vector
• Borrelia bacteria that cause TBRF are transmitted to humans through the bite of
infected "soft ticks" of the genus Ornithodoros.
• Humans come into contact with soft ticks by sleeping in rodent-infested cabins.
The ticks emerge at night and feed briefly on humans while they sleep. Bites are
painless, most people unaware. Humans are “accidental” alternative host.
• There are several Borrelia species that cause TBRF, and these are usually
associated with specific species of ticks.
• Ornithodoros hermsi tends to be found at higher altitudes (1500 to 8000 feet)
where it is associated primarily with ground or tree squirrels and chipmunks.
• Soft ticks can live up to 10 years; in certain parts of the Russia the same tick has
been found to live almost 20 years!
9. Transmission: The organism
Borreliae is able to
undergo multiple cyclic
antigenic variations,
which results in the
relapses of the patients
0.2 to 0.5 μm by 4 to 18 μm
Seven to twenty periplasmic
flagella originate at each end
and overlap at the center of
the cell.
10. Isolation Methods
• Blood samples obtained before antibiotic
treatment can be cultured using:
1. BSK (Barbour Stoner Kelly) medium
2. By inoculating immature mice
• B. hermsii requires higher amount of
serum in the media.
• Microaerophillic
• Microscopy is the test of choice for
diagnosis of relapsing fever
11. Laboratory Diagnosis
• Diagnosis made by detecting spirochetes in a thin
and thick smear of peripheral blood prepared with
Wright’s or Giemsa stain or by culture isolation.
• Best visualized by dark field microscopy, but the
organisms can also be detected using Wright-
Giemsa or acridine orange stains.
• They do not Gram stain well.
• Organism is best detected from blood cultures
when the patient is febrile.
• Serology not useful for immediate diagnosis and
may have cross reactions with B. burdorgferi.
14. Treatment and Sequelae
• TBRF spirochetes are susceptible to penicillin and
other beta-lactam antimicrobials, as well as
tetracyclines, macrolides, and potentially
fluoroquinolones. CDC has not developed specific
treatment guidelines for TBRF.
• With appropriate treatment, most patients recover
within a few days. Long-term sequelae rare but
include iritis, uveitis, cranial nerve and other
neuropathies.
• TBRF contracted during pregnancy can cause
spontaneous abortion, premature birth, and neonatal
death.
• The maternal-fetal transmission of Borrelia is thought
to occur either transplacentally or while traversing
the birth canal.
15. Please, laugh a little…
Disease caused by
Borrelia hermsii although
few, but the impact of the
infections can be long and
mortality is estimated
around 5-10% if untreated.
Prevention includes:
1. Avoid sleeping in rodent
infested buildings
2. Rodent proof structures
to prevent colonization
of rodents and their soft
ticks.
