Relapsing fever is an acute infectious disease caused by various bacteria within the genus Borrelia. The disease is commonly recognized by repetitious bouts of fever. Relapsing fever is a zoonotic (acquired from animals) disease that is transmitted to humans primarily from parasitic insects called body lice (louse-borne relapsing fever), which enter the inside of the body, and by the bites of soft-bodied ticks (tick-borne relapsing fever), which occur on the outside of the body.
The louse-borne relapsing fever (LBRF) is transmitted to humans from lice (specifically, Pediculus humanus) that are infected with the bacterium Borrelia recurrentis. The lice enter the human body through mucous membranes and then invade the bloodstream. They eventually multiply inside the abdomen of the host.
The tick-borne relapsing fever (TBRF) is transmitted to humans from bites of ticks infected with Borrelia bacteria species such as Borrelia hermsii and Borrelia Parkeri. The ticks spread from hosts such as rodents and other animals. B. hermsii and B. recurrentis cause similar symptoms, but B. hermsii causes more relapses and is responsible for more deaths. B. recurrentis infection, on the other hand, results in longer periods with fever and without fever, and with more extended incubation periods.
WORDS TO KNOW
INCUBATION PERIOD: Incubation period refers to the time between exposure to disease causing virus or bacteria and the appearance of symptoms of the infection. Depending on the microorganism, the incubation time can range from a few hours (an example is food poisoning due to Salmonella) to a decade or more (an example is acquired immunodeficiency syndrome, or AIDS).
HOST: Organism that serves as the habitat for a parasite, or possibly for a symbiont. A host may provide nutrition to the parasite or symbiont, or simply a place in which to live.
VECTOR: Any agent, living or otherwise, that carries and transmits parasites and diseases. Also, an organism or chemical used to transport a gene into a new host cell.
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
For both forms of the disease, the first symptoms occur five to 15 days after the bite of an infected vector (an organism such as the tick or louse that transmits a diseasecausing organism). Symptoms include, initially, a high and sudden fever, followed by chills, shakes, neck stiffness, sweating, low body temperature, low blood pressure, nausea, vomiting, rash, headache, and muscle and/or joint pains.
When these symptoms become serious, many patients develop central nervous system (CNS) problems such as stupor, seizure, facial droop, weakness, and coma. Heart and liver tissues that are invaded by the bacteria often result in hepatitis (inflammation of the liver), meningitis (inflammation of the meninges), or myocarditis (inflammation of the heart muscle). Bleeding and pneumonia are other problems associated with the disease. Death occurs in up to 10% of untreated persons with these serious symptoms of relapsing fever.
In LBRF, the first round of symptoms lasts from three to six days and is followed by other milder rounds of symptoms, with each episode lasting up to three days. Fever may be absent for up to two weeks before another round occurs. Generally, the patient has symptoms when the organism is within the host's blood and, then, the symptoms disappear when the organism leaves the blood.
The effects of LBRF become critical to the patient when severe jaundice (yellowing of the skin and mucous membranes due to impaired liver function), changes in mental status, bleeding, and prolonged QT interval on an ECG (the measure on an electrocardiogram between the beginning of the Q wave and the end of the T wave within the heart's electrical cycle). According to the Centers for Disease Control and Prevention (CDC), LBRF has a mortality rate of 1% with treatment and between 30–70% without treatment.
IN CONTEXT: PERSONAL RESPONSIBILITY AND PROTECTION
- Avoid sleeping in rodent infested buildings.
- Limit tick bites by using insect repellent containing DEET (on skin or clothing) or permethrin (applied to clothing or equipment).
- Rodent-proof buildings in areas where the disease is known to occur.
- Identify and remove any rodent nesting material from walls, ceilings and floors.
- In combination with removing the rodent material, fumigate the building with preparations containing pyrethrins and permethrins. More than one treatment is often needed to effectively rid the building of the vectors, the soft-ticks. Always follow product instructions, and consider consulting a licensed pest control specialist.
SOURCE: Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Vector-Borne Infectious Diseases
LBRF occurs primarily in Ethiopia and Sudan in northern Africa. It is also found in Europe and India. The disease is often the cause of epidemics within areas of poor living conditions and regions where famine and war are prevalent. During World War I (1914–1918) and World War II (1939–1945), millions of people died from LBRF.
TBRF is found in Africa, Asia, Saudi Arabia, South America, Spain, and certain areas in the western section of the United States and Canada. In the United States, it usually occurs west of the Mississippi River, predominately in the mountains of the West and the high-elevation deserts and plains of the Southwest. There are now signs of TBRF infecting people in the southeastern parts of the United States. According to the CDC, there are about 25 cases in the U.S. annually.
According to the CDC, treatment of TBRF usually involves a one-week course of antibiotics. When treated properly, most people recover and death only rarely occurs. Tetracycline is often used as the antibiotic of choice; however, up to one-half of all persons with relapsing fever have negative reactions to tetracycline, including anxiety, fever, sweating, rapid heart rate, and low blood pressure. Chloramphenicol, doxycycline, erythromycin, and penicillin are also used to treat the disease.
The duration for antibiotic treatment of LBRF, according to the CDC's Division of Vector-Borne Infectious Diseases (DVBID), is one single dose of antibiotics. The death rate for untreated LBRF ranges from 10 to 70% and for TRBF the death rate is between 4 and 10%. With early treatment, death rates are reduced to between 2 to 5%. However, people with liver dysfunction, myocarditis, and pneumonia have a higher risk of death than others.
Both forms of relapsing fever can be prevented by wearing protective clothing and using insect repellent. Comprehensive lice and tick control should be used in areas hardest hit with the infections.
Relapsing fever was once a global concern. However, with antibiotic treatment, it is now restricted mostly to areas of the developing world. Circumstances such as increased worldwide travel by humans and wide movements by animals, however, and even the trend toward washing clothes in cold and warm water rather than hot water, are causing a re-emergence of relapsing fever.
In addition, according to the CDC, since the 1980s, increased numbers of Borrelia species have been discovered to be associated with relapsing fever.
The most recent cases of tick-borne relapsing fever have occurred in mountainous areas of the western United States, primarily among vacationers to forests or cabins in higher-elevations (above 8,000 feet, or 2,438 meters). Campers and other persons rarely realize that they are bitten by the soft ticks that carry TBRF, as the ticks feed for a few minutes, then fall off. When experiencing a fever after vacationing in the mountains, therefore, it is advisable to seek medical treatment. TBRF remains on the list of modifiable diseases for health officials in many western states, in order to track the prevalence of the disease and the ticks that cause it.
All of these situations demonstrate that the potential for relapsing fever, as it is with other re-emerging infectious diseases, is unpredictable. The potential for it to emerge in areas where not recognized earlier is great. People who are very young, old, pregnant, or have weakened physical conditions have increased risk of the affects and complications of relapsing fever.
Edlow, Jonathan A., ed. Tick-borne Diseases. Philadelphia, PA: W.B. Saunders Company, 2002.
Goodman, Jesse L., David T. Dennis, and Daniel E. Sonenshine. Tick-borne Diseases of Humans. Washington, DC: ASM Press, 2005.
Cutler, Sally J., Veterinary Laboratories Agency (Surrey, United Kingdom), U.S. Centers for Disease Control and Prevention. “Possibilities for Relapsing Fever Reemergence.” March 2006 <http://www.cdc.gov/ncidod/eid/vol12no03/05-0899.htm> (accessed April 27, 2007).
Centers for Disease Control and Prevention. “Relapsing Fever: Introduction.” November 10, 2004 <http://www.cdc.gov/ncidod/dvbid/RelapsingFever/index.htm> (accessed April 27, 2007).
Centers for Disease Control and Prevention. “Treatment of Tick-Borne Relapsing Fever.” November 10, 2004 <http://www.cdc.gov/ncidod/dvbid/RelapsingFever/RF_Treatment.htm> (accessed April 27, 2007).
Relapsing fever refers to two similar illnesses, both of which cause high fevers. The fevers resolve, only to recur again within about a week.
Relapsing fever is caused by spiral-shaped bacteria of the genus Borrelia. This bacterium lives in rodents and in insects, specifically ticks and body lice. The form of relapsing fever acquired from ticks is slightly different from that acquired from body lice.
In tick-borne relapsing fever (TBRF), rodents (rats, mice, chipmunks, and squirrels) which carry Borrelia are fed upon by ticks. The ticks then acquire the bacteria, and are able to pass it on to humans. TBRF is most common in sub-Saharan Africa, parts of the Mediterranean, areas in the Middle East, India, China, and the south of Russia. Also, Borrelia causing TBRF exist in the western regions of the United States, particularly in mountainous areas. The disease is said to be endemic to these areas, meaning that the causative agents occur naturally and consistently within these locations.
In louse-borne relapsing fever (LBRF), lice acquire Borrelia from humans who are already infected. These lice can then go on to infect other humans. LBRF is said to be epidemic, as opposed to endemic, meaning that it can occur suddenly in large numbers in specific communities of people. LBRF occurs in places where poverty and overcrowding predispose to human infestation with lice. LBRF has flared during wars, when conditions are crowded and good hygiene is next to impossible. At this time, LBRF is found in areas of east and central Africa, China, and in the Andes Mountains of Peru.
Causes and symptoms
In TBRF, humans contract Borrelia when they are fed upon by ticks. Ticks often feed on humans at night, so many people who have been bitten are unaware that they have been. The bacteria is passed on to humans through the infected body fluids of the tick.
In LBRF, a louse must be crushed or smashed in order for Borrelia to be released. The bacteria then enter the human body through areas where the person may have scratched him or herself.
Both types of relapsing fever occur some days after having acquired the bacteria. About a week after becoming infected, symptoms begin. The patient spikes a very high fever, with chills, sweating, terrible headache, nausea, vomiting, severe pain in the muscles and joints, and extreme weakness. The patient may become dizzy and confused. The eyes may be bloodshot and very sensitive to light. A cough may develop. The heart rate is greatly increased, and the liver and spleen may be swollen. Because the substances responsible for blood clotting may be disturbed during the illness, tiny purple marks may appear on the skin, which are evidence of minor bleeding occurring under the skin. The patient may suffer from a nosebleed, or may cough up bloody sputum. All of these symptoms last for about three days in TBRF, and about five days in LBRF.
With or without treatment, a crisis may occur as the bacteria are cleared from the blood. This crisis, called a Jarisch-Herxheimer reaction, results in a new spike in fever, chills, and an initial rise in blood pressure. The blood pressure then falls drastically, which may deprive tissues and organs of appropriate blood flow (shock ). This reaction usually lasts for about a day.
Recurrent episodes of fever with less severe symptoms occur after about a week. In untreated infections, fevers recur about three times in TBRF, and only once or twice in LBRF.
Diagnosis of relapsing fever is relatively easy, because the causative bacteria can be found by examining a sample of blood under the microscope. The characteristically spiral-shaped bacteria are easily identifiable. The blood is best drawn during the period of high fever, because the bacteria are present in the blood in great numbers at that time.
Either tetracycline or erythromycin is effective against both forms of relapsing fever. The medications are given for about a week for cases of TBRF; LBRF requires only a single dose. Children and pregnant women should receive either erythromycin or penicillin. Because of the risk of the Jarish-Herxheimer reaction, patients must be very carefully monitored during the initial administration of antibiotic medications. Solutions containing salts must be given through a needle in the vein (intravenously) to keep the blood pressure from dropping too drastically. Patients with extreme reactions may need medications to improve blood circulation until the reaction resolves.
In epidemics of LBRF, death rates among untreated victims have run as high as 30%. With treatment, and careful monitoring for the development of the Jarish-Herxheimer reaction, prognosis is good for both LBRF and TBRF.
Prevention of TBRF requires rodent control, especially in and near homes. Careful use of insecticides on skin and clothing is important for people who may be enjoying outdoor recreation in areas known to harbor the disease-carrying ticks.
Prevention of LBRF is possible, but probably more difficult. Good hygiene and decent living conditions would prevent the spread of LBRF, but these may be difficult for those people most at risk for the disease.
Endemic— Refers to a particular organism which consistently exists in a particular location under normal conditions.
Epidemic— Refers to a condition suddenly acquired by a large number of people within a specific community, and which spreads rapidly throughout that community.
Shock— A state in which the blood pressure is so low that organs and tissues are not receiving an appropriate flow of blood.
Relapsing fever is an acute relapsing systemic illness caused by infection with spirochetal bacteria in the genus Borrelia. Louse-borne (epidemic) relapsing fever (LBRF) is caused by Borrelia recurrentis, and tick-borne (endemic) relapsing fever (TBRF) by several closely related species of Borrelia. Louse-borne relapsing fever is transmitted by the human body louse, Pediculus humanus ; TBRF is transmitted by the bite of various soft-bodied ticks of the genus Ornithodorus. LBRF has, for the past several decades, been reported only in Ethiopia and several surrounding countries. It especially affects populations that are crowded, impoverished, and displaced by war or famine—all factors associated with poor hygiene and lice infestation. TBRF occurs in scattered temperate and tropical areas worldwide; in the United States it occurs almost exclusively in the western states, especially in forested, mountainous areas. TBRF typically occurs in small, often familial, clusters, and it is associated with sleeping in rodent- and tick-infested homes or cabins.
Following a usual incubation period of four to seven days, illness begins with the abrupt onset of fever, aches and pains in muscles and joints, headache, shaking chills, sweats, loss of appetite, weakness, and prostration. Periods of fever usually last for several days, typically ending with a crisis characterized by rigors and rising temperature, followed by an abrupt fall in temperature, profuse sweating, and hypotension. Untreated, relapses may recur after intervals of several days to a week or more. An average of three, and as many as ten, relapses may occur in TBRF, while only one to three relapses occur in LBRF. Relapses are associated with antigenic changes in bacterial outer-surface proteins.
The diagnosis of borrelial fevers is made by eliciting a history of possible infective exposure, by the typical relapsing character of the illness, and by identifying borreliae in the patient's blood. Relapsing fever is readily cured with any of several antibiotics—tetracyclines, erythromycin, and chloramphenicol are recommended choices. Control and prevention of LBRF relies on basic sanitation and hygiene to prevent or rid clothing and bedclothes of body lice, early case detection, and treatment. TBRF is prevented by removing rodent nests from buildings, rodent-proofing homes and cabins, and treating suspected tick harborage with chemical acaricides.
David T. Dennis
(see also: Communicable Disease Control; Environmental Determinants of Health; Vector-Borne Diseases )
Anonymous (2000). "Relapsing Fever." In Control of Communicable Diseases Manual, 17th edition, ed. I. Chin. Washington, DC: American Public Health Association.