AUTHOR AND EDITOR INFORMATION

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INTRODUCTION

Section 2 of 11  

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Background

Relapsing fever is an acute febrile illness caused by spirochetes of the genus Borrelia. The high fevers of presenting patients spontaneously abate and then recur. This characteristic pattern of remission and relapse not only gives relapsing fever its name but also allows it to be differentiated clinically from other febrile illnesses as it has since the 1840s.

Large outbreaks of louse-borne relapsing fever have occurred throughout the past century. These outbreaks usually occur following man-made breakdowns in public health, as typified by the epidemic following World War II that involved about 10 million people.

Pathophysiology

Relapsing fever is transmitted to humans by 2 vectors, ticks and lice. The human body louse, Pediculus humanus, is the specific vector (Pediculus pubis is not a vector). Louse-borne relapsing fever is more severe than the tick-borne variety.

Louse-borne relapsing fever is caused by Borrelia recurrentis. No animal reservoir exists. Lice that feed on infected humans acquire the Borrelia organisms that then multiply in the gut of the louse. When an infected louse feeds on an uninfected human, the organism gains access when the victim crushes the louse or scratches the area where the louse is feeding. B recurrentis infects the person via either abraded or intact skin (or mucous membranes) and then invades the bloodstream.

Soft ticks of the genus Ornithodoros spread the tick-borne variety. The responsible Borrelia species are identified closely with its tick vector and they share parallel nomenclature. (For example, Borrelia parkeri infects Ornithodoros parkeri; Borrelia hermsii is the agent transmitted by tick bite by Ornithodoros hermsii.) Soft ticks feed for short periods of time (an hour or so), and the Borrelia organisms are inoculated within minutes. This is an important distinction from other tick-borne diseases such as Lyme disease.

Regardless of the mode of transmission, a spirochetemia develops. Borrelia organisms then invade the endothelium. This can produce a low-grade disseminated intravascular coagulation and thrombocytopenia. The relapse phenomenon occurs because of genetically programmed shifting of outer surface proteins of the Borrelia that allows a new clone to avoid destruction by antibodies directed against the majority of the original infecting organisms. Thus, the person clinically improves until the new clone multiplies sufficiently to cause another relapse. Tick-borne disease tends to have more relapses (average of 3) compared with the louse-borne variety (often just 1).

The recent resurgence of interest in Borrelia because of Lyme disease and, especially the recent publication of the genomic sequence of B burgdorferi, has led to advances in the understanding of the host-parasite interactions of the relapsing fever Borrelia.

Frequency

United States

Louse-borne relapsing fever is not endemic in the United States, although an occasional traveler presents with an imported case.

Few cases of tick-borne relapsing fever are reported in the United States; however, sporadic cases continue to occur. It is highly focal, with 13 counties producing 50% of cases. Most of these are found in the late spring and summer in the western mountainous states, south into Texas, and northwest into Washington.

Undoubtedly, many cases occur that either are misdiagnosed or go unreported.

Clusters of cases are reported; often groups of campers share a rustic facility infested with rodents on which the ticks feed.

International

Endemic foci of louse-borne relapsing fever occur in much of the world where war, poverty, and overcrowding exist; all of which are conditions that favor louse infestation. Civil wars, which result in large refugee camps, are also fertile ground for lice and relapsing fever.

Mortality/Morbidity

• Mortality rates from 30-70% are reported in untreated patients during epidemics of the louse-borne variety; the mortality rate falls to about 5% with treatment. This striking figure probably reflects the underlying malnutrition and coexisting infections that exist in these situations.
• The mortality rate of patients with tick-borne relapsing fever who are treated is less than 1%.

Sex

A slight preponderance of female patients exists in louse-borne epidemics (60%); tick-borne relapsing fever occurs more often in males (60%) than in females. The latter figure probably reflects the greater likelihood of males being exposed to ticks through recreational and occupational activities.

Age

A trend toward pediatric cases of both forms of relapsing fever exists. In the case of the louse-borne variety, this may reflect the general state of health in populations where relapsing fever is endemic. Regarding the tick-borne disease, this may reflect activities that lead to tick exposure.

CLINICAL

Section 3 of 11  

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History

Relapsing fever develops abruptly 3-18 days (average, 7-8 d) after exposure to the spirochete.

As with all the tick-borne diseases, the season of onset and epidemiologic history suggesting possible tick exposure are important clues. Ornithodoros ticks often frequent caves and decaying woodpiles. Many patients report a history of having spent time in rustic cabins in which the ticks gain access by hitching a ride on a rodent.

• Onset of symptoms generally is abrupt.
• Pulse is rapid in proportion to the fever, a point of differential value with typhoid fever with which louse-borne relapsing fever can be confused.
• Headache is a very common symptom, occurring in nearly 95% of cases.
• Myalgias and chills also occur in approximately 90% of cases.
• Arthralgias
• Weakness
• Anorexia
• Weight loss
• Cough
• Systemic symptoms
• • Patients commonly complain of nausea, vomiting, and upper abdominal pain due to liver and spleen involvement.
  • Hepatic and splenic involvement is more common in louse-borne relapsing fever.
  • A dry cough frequently is observed, a feature that is in common with typhoid fever.
• Relapses
• • The primary febrile episode typically ends after 3-6 days by crisis that can culminate in fatal shock. About 7-10 days later, the first relapse occurs abruptly. Subsequent relapses tend to be less severe.
  • The primary febrile episode usually lasts an average of 3 days (Southern, 1969).
  • Louse-borne relapsing fever normally produces fewer relapses.
  • In tick-borne disease, relapses average 3, and there can be more than 10.

Physical

Physical findings are not diagnostic.

• Fever (most common finding)
• Tachypnea
• Tachycardia
• Hypotension
• Abdominal tenderness with hepatosplenomegaly
• Petechial or maculopapular rash
• Rales
• Rhonchi
• Nuchal rigidity
• Lymphadenopathy
• Jaundice
• Iritis and iridocyclitis
• Neurologic findings are more common in louse-borne disease and include coma, cranial neuropathy (especially Bell palsy), hemiplegia, meningitis, and seizures.

Causes

Relapsing fever is caused by infection with the causative Borrelia species.

DIFFERENTIALS

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Other Problems to be Considered

Typhoid
Typhus fever
Rat bite fever

WORKUP

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Lab Studies

• Hematologic studies occasionally reveal anemia and thrombocytopenia.
• • The white blood cell (WBC) count usually is normal.
  • The prothrombin time (PT) and partial thromboplastin time (PTT) frequently are elevated.
• The hepatic transaminases and serum bilirubin levels can be elevated.
• In louse-borne relapsing fever, azotemia can occur.
• Definitive diagnosis is established by visualizing spirochetes in smears of peripheral blood during a febrile episode.
• • Multiple smears (both thick and thin, using Wright and Giemsa stains) may need to be examined.
  • This is the best way to secure the diagnosis in the ED.
  • Organisms are not found between relapses.
• Injection of blood into laboratory animals followed by examination of their blood sometimes is useful.

Imaging Studies

• Imaging studies are not routinely useful, although chest radiography and hepatobiliary ultrasonography might be indicated in isolated cases in which pulmonary or hepatic manifestations predominate.
• CT scanning of the brain may be indicated in cases with predominant central nervous system (CNS) manifestations.

Other Tests

• The electrocardiogram (ECG) may show a prolonged QTc interval.
• Nonspecific antibody response to Proteus OXK antigens is elevated in about one third of tick-borne cases and most louse-borne cases.

TREATMENT

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Emergency Department Care

ED care of these patients focuses on the establishment of the diagnosis of relapsing fever and excluding other treatable infections with which it can be confused. As well, data from a randomized study published in 2006 shows that, for postexposure treatment, a 5-day course of doxycycline was effective at preventing tick-borne relapsing fever (Hasin, 2006).

Consultations

An infectious diseases consultation may be appropriate.

MEDICATION

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In the treatment of relapsing fever, antimicrobials are the drugs of choice. However, following the antimicrobial treatment, patients may develop a Jarisch-Herxheimer (JH) reaction, which can be severe, especially in louse-borne relapsing fever when patients' host defenses may be otherwise compromised. This reaction has been reported to occur in 50% of patients with tick-borne relapsing fever.

The JH reaction produces apprehension, diaphoresis, fever, tachycardia, and tachypnea with an initial pressor response followed rapidly by hypotension. The JH reaction can be fatal. Recent studies have shown that tumor necrosis factor-a (TNF-a) may be partly responsible for the reaction (Fekade, 1996). Preadministration of glucocorticoids does little to limit the JH reaction, but antibodies to TNF-a do help.

Note that the regimens listed below are for tick-borne disease. Adults with louse-borne relapsing fever can be treated with a single 500 mg dose PO/IV of tetracycline, chloramphenicol, or erythromycin or 100 mg of doxycycline. Penicillin also can be used for louse-borne disease.

Antipyretics are indicated to reduce fever.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Drug Category: Antipyretics

In treating relapsing fever, bed rest and mild analgesic-antipyretic therapy are often helpful in relieving the associated lethargy, malaise, and fever associated with the disease.

FOLLOW-UP

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Further Inpatient Care

• Many patients with louse-borne relapsing fever are malnourished and will require inpatient care to correct their hypovolemia, coagulation abnormalities, and nutritional status.
• Patients with abnormal mental status also require close observation with airway protection, as indicated.
• Those with prolonged QTc intervals are best monitored by telemetry.
• Be especially vigilant in monitoring for a JH reaction.

Further Outpatient Care

• Refer patients to follow up with their primary care physician to address complete recovery, any malnutrition issues, and any laboratory or ECG abnormalities.

Deterrence/Prevention

• See Tick-borne Diseases, Introduction.
• In 2006, a study was published that studied postexposure prophylaxis with a 5-day course of doxycycline to prevent tick-borne relapsing fever. A 200-mg dose (day 1) followed by 100 mg daily for 4 more days had 100% efficacy (although the 95% confidence intervals were wide [46-100] because of small numbers of patients (Hasin, 2006).
• In many situations (eg, a refugee camp) maintenance of personal hygiene is difficult or impossible.
• • Chemical delousing may be required in epidemic situations.
  • For the louse-borne variety, maintaining personal hygiene to avoid lice prevents the disease.

Complications

• Bleeding is a common complication with both forms of the disease. Bleeding in the skin, nose, eyes, lungs, urinary tract, GI tract, and brain can occur. The latter two can be fatal.
• JH reaction

Prognosis

• In untreated epidemics of louse-borne disease, the mortality rate is 30-70%. This is lowered to less than 1% with appropriate antibiotic therapy.
• Poor prognostic signs include severe jaundice, severe change in mental status, severe bleeding, and prolonged QTc interval.

Patient Education

• Educate patients about the vectors and how they can be avoided.
• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Ticks.

MISCELLANEOUS

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Medical/Legal Pitfalls

• Because physicians, especially in developed countries, almost never see (or diagnose) relapsing fever, they tend not to include the diagnosis in the differential. In all patients with a febrile illness, an appropriate epidemiologic history must be taken, to include tick and other insect exposure, travel, and lifestyle. Simply asking these questions may suggest a diagnosis that might have been overlooked otherwise.
• Taking a detailed history of the pattern of fever may suggest this diagnosis. While physicians are more likely to consider malaria in the setting of intermittent, recurring fevers, a careful examination of a blood smear will be likely to diagnose both diseases.

Special Concerns

• The JH reaction can be severe. At a minimum, patients ought to be counseled that it might occur (so they do not mistake it for an allergic reaction). Patients who are ill should probably be observed for this reaction in a monitored setting.

MULTIMEDIA

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Media file 1:  Relapsing fever can be tick- or louse-borne. Soft-bodied ticks of the genus Ornithodoros transmit tick-borne cases. Below is an image of such a tick. Unlike the hard-bodied ticks, the Ornithodoros feed briefly and can transmit disease within minutes. Photo courtesy of Julie Rawlings, MPH, Texas Department of Health.
	View Full Size Image
Media type:  Photo

Media file 2:  Photomicrograph of a patient who presented to the ED with cyclical fevers and chills, which she developed while traveling in one of the recently formed Soviet Republics in 1990. A blood smear for malaria was obtained, and this is what the laboratory technician observed.
	View Full Size Image
Media type:  Photo

REFERENCES

Section 11 of 11

• Authors and Editors
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• Anda P, Sanchez-Yebra W, del Mar Vitutia M, et al. A new Borrelia species isolated from patients with relapsing fever in Spain. Lancet. Jul 20 1996;348(9021):162-5. [Medline].
• Cadavid D, Barbour AG. Neuroborreliosis during relapsing fever: review of the clinical manifestations, pathology, and treatment of infections in humans and experimental animals. Clin Infect Dis. Jan 1998;26(1):151-64. [Medline].
• Dworkin MS, Anderson DE Jr, Schwan TG, et al. Tick-borne relapsing fever in the northwestern United States and southwestern Canada. Clin Infect Dis. Jan 1998;26(1):122-31. [Medline].
• Dworkin MS, Schwan TG, Anderson DE Jr. Tick-borne relapsing fever in North America. Med Clin North Am. Mar 2002;86(2):417-33, viii-ix. [Medline].
• Fekade D, Knox K, Hussein K, et al. Prevention of Jarisch-Herxheimer reactions by treatment with antibodies against tumor necrosis factor alpha. N Engl J Med. Aug 1 1996;335(5):311-5. [Medline].
• Hasin T, Davidovitch N, Cohen R, et al. Postexposure treatment with doxycycline for the prevention of tick-borne relapsing fever. N Engl J Med. Jul 13 2006;355(2):148-55. [Medline].
• Horton JM, Blaser MJ. The spectrum of relapsing fever in the Rocky Mountains. Arch Intern Med. May 1985;145(5):871-5. [Medline].
• Nordstrand A, Barbour AG, Bergstrom S. Borrelia pathogenesis research in the post-genomic and post-vaccine era. Curr Opin Microbiol. Feb 2000;3(1):86-92. [Medline].
• Paul WS, Maupin G, Scott-Wright AO, et al. Outbreak of tick-borne relapsing fever at the north rim of the Grand Canyon: evidence for effectiveness of preventive measures. Am J Trop Med Hyg. Jan 2002;66(1):71-5. [Medline].
• Raoult D, Roux V. The body louse as a vector of reemerging human diseases. Clin Infect Dis. Oct 1999;29(4):888-911. [Medline].
• Southern PM, Sandford JP. Relapsing fever: a clinical and microbiological review. Med. 1969;48:129-43.

Article Last Updated: Jan 3, 2007