typhus

Typhus 

Definition

Several different illnesses are called "typhus," all of them caused by one of the bacteria in the family Rickettsiae. Each illness occurs when the bacteria is passed to a human through contact with an infected insect.

Description

The four main types of typhus are:

• epidemic typhus
• Brill-Zinsser disease
• endemic or murine typhus
• scrub typhus

These diseases are all somewhat similar, although they vary in terms of severity. The specific type of Rickettsia that causes the disease also varies, as does the specific insect that can pass the bacteria along.

Epidemic typhus, which is sometimes called jail fever or louse-borne typhus, is caused by Rickettsia prowazekii, which is carried by body lice. When the lice feed on a human, they may simultaneously defecate. When the person scratches the bite, the feces (which carrys the bacteria) are scratched into the wound. Body lice are common in areas in which people live in overcrowded, dirty conditions, with few opportunities to wash themselves or their clothing. Because of this fact, this form of typhus occurs simultaneously in large numbers of individuals living within the same community; that is, in epidemics. This type of typhus occurs when cold weather, poverty, war, and other disasters result in close living conditions that encourage the maintenance of a population of lice living among humans. Some medical historians think that the Great Plague of Athens in 430 B.C. may have been epidemic typhus. Epidemic typhus is now found in the mountainous regions of Africa, South America, and Asia.

Brill-Zinsser disease is a reactivation of an earlier infection with epidemic typhus. It affects people years after they have completely recovered from epidemic typhus. When something causes a weakening of their immune system (like aging, surgery, illness), the bacteria can gain hold again, causing illness. This illness tends to be extremely mild.

Endemic typhus is carried by fleas. When a flea lands on a human, it may defecate as it feeds. When the person scratches the itchy spot where the flea was feeding, the bacteria-laden feces are scratched into the skin, thus causing infection. The causative bacteria is called Rickettsia typhi. Endemic typhus occurs most commonly in warm, coastal regions. In the United States, southern Texas and southern California have the largest number of cases.

Scrub typhus is caused by Rickettsia tsutsugamushi. This bacteria is carried by mites or chiggers. As the mites feed on humans, they deposit the bacteria. Scrub typhus occurs commonly in the southwest Pacific, southeast Asia, and Japan. It is a very common cause of illness in people living in or visiting these areas. It occurs more commonly during the wet season.

Causes and symptoms

The four types of typhus cause similar types of illnesses, though varying in severity.

Epidemic typhus causes fever, headache, weakness, and muscle aches. It also causes a rash composed of both spots and bumps. The rash starts on the back, chest, and abdomen, then spreads to the arms and legs. The worst types of complications involve swelling in the heart muscle or brain (encephalitis). Without treatment, this type of typhus can be fatal.

Brill-Zinsser disease is quite mild, resulting in about a week-long fever, and a light rash similar to that of the original illness.

Endemic typhus causes about 12 days of high fever, with chills and headache. A light rash may occur.

Scrub typhus causes a wide variety of effects. The main symptoms include fever, headache, muscle aches and pains, cough, abdominal pain, nausea and vomiting, and diarrhea. Some patients experience only these symptoms. Some patients develop a rash, which can be flat or bumpy. The individual spots eventually develop crusty black scabs. Other patients go on to develop a more serious disease, in which encephalitis, pneumonia, and swelling of the liver and spleen (hepatosplenomegaly) occur.

Diagnosis

A number of tests exist that can determine the reactions of a patient's antibodies (immune cells in the blood) to the presence of certain viral and bacterial markers. When the antibodies react in a particular way, it suggests the presence of a rickettsial infection. Many tests require a fair amount of time for processing, so practitioners will frequently begin treatment without completing tests, simply on the basis of a patient's symptoms.

Treatment

The antibiotics tetracycline or chloramphenicol are used for treatment of each of the forms of typhus.

Prognosis

The prognosis depends on what types of complications an individual patient experiences. While children usually recover well from epidemic typhus, older adults may have as much as a 60% death rate without treatment. Brill-Zinsser, on the other hand, carries no threat of death. People usually recover uneventfully from endemic typhus, although the elderly, those with other medical problems, or people mistakenly treated with sulfa drugs may have a 1% death rate from the illness. Scrub typhus responds well to appropriate treatment, but untreated patients have a death rate of about 7%.

The relatively high death rate from untreated typhus is one reason why some researchers are concerned that its causative organisms might be used in the future as agents of bioterrorism.

Prevention

Prevention for each of these forms of typhus includes avoidance of the insects that carry the causative bacteria. Other preventive measures include good hygiene and the use of insect repellents.

Key terms

Antibody — Specialized cells of the immune system, which can recognize organisms that invade the body (such as bacteria, viruses, and fungi). The antibodies are then able to set off a complex chain of events designed to kill these foreign invaders.

Bioterrorism — The use of disease microorganisms to intimidate or terrorize a civilian population.

Endemic — Occurring naturally and consistently in a particular area.

Epidemic — A large cluster of cases all occurring at about the same time within a specific community or region.

Resources

Books

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Epidemic Tyhpus." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Periodicals

Cunha, B. A. "The Cause of the Plague of Athens: Plague, Typhoid, Typhus, Smallpox, or Measles?" Infectious Diseases Clinics of North America 18 (March 2004): 29-43.

Ge, H., Y. Y. Chuang, S. Zhao, et al. "Comparative Genomics of Rickettsia prowazekii Madrid E and Breinl Strains." Journal of Bacteriology 186 (January 2004): 556-565.

Raoult, D., T. Woodward, and J. S. Dumler. "The History of Epidemic Typhus." Infectious Diseases Clinics of North America 18 (March 2004): 127-140.

Organizations

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

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typhus /ty·phus/ (ti´fus) a group of closely related, acute, arthropod-borne rickettsial diseases that differ in the intensity of certain signs and symptoms, severity, and fatality rate; all are characterized by headache, chills, fever, stupor, and a macular, maculopapular, petechial, or papulovesicular eruption. Often used alone in English-speaking countries to refer to epidemic typhus, and in several European languages to refer to typhoid fever.ty´phous

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endemic typhus  murine t.

epidemic typhus  the classic form, due to Rickettsia prowazekii and transmitted between humans by body lice.

flying squirrel typhus  an acute infectious disease similar to epidemic typhus, occurring in the southeastern United States; it is caused by Rickettsia prowazekii and is transmitted by the fleas and lice of the flying squirrel.

Kenya tick typhus  boutonneuse fever.

murine typhus  an infectious disease, clinically similar to epidemic typhus but milder, due to Rickettsia typhi, transmitted from rat to human by the rat flea and rat louse.

recrudescent typhus  Brill's disease.

scrub typhus  an acute, typhus-like infectious disease caused by Rickettsia tsutsugamushi and transmitted by chiggers, characterized by a primary skin lesion at the site of inoculation and development of a rash, regional lymphadenopathy, and fever.

tropical typhus  scrub t.

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ty·phus (tfs)

n.

Any of several forms of infectious disease caused by Rickettsia, especially those transmitted by fleas, lice, or mites, and characterized generally by severe headache, sustained high fever, depression, delirium, and the eruption of red rashes on the skin. Also called camp fever, prison fever.

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typhous (-fs) adj.

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typhus

[tī′fəs]

Etymology: Gk, typhos, fever

any of a group of acute infectious diseases caused by various species of Rickettsia and usually transmitted from infected rodents to humans by the bites of lice, fleas, mites, or ticks. These diseases are all characterized by headache, chills, fever, malaise, and a maculopapular rash. Kinds of typhus are epidemic typhus, murine typhus, and scrub typhus. See also Brill-Zinsser disease, Rocky Mountain spotted fever.

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typhus (tīˑ·fs),

n an acute infectious disease caused by
Rickettsia species; characterized by chills, headache, fever, and maculopapular rash. The infection spreads from infected rodents to humans via bites from fleas, lice, ticks, or mites.

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typhus (tī´fs),

n a group of acute infectious diseases caused by various species of
Rickettsia and usually transmitted from infected rodents to humans by the bites of lice, fleas, mites, or ticks.

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typhus

acute infectious diseases caused by Rickettsia which are usually transmitted from infected rats and other rodents to humans by lice, fleas, ticks and mites.

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Abyssinian tick typhus

see boutonneuse fever.

canine typhus, canine tick typhus

see canine ehrlichiosis.

epidemic typhus

see rickettsiaprowazeki.

Kenya typhus

see boutonneuse fever.

murine typhus

a disease of humans caused by Rickettsia typhae; rats and cats are the mammalian reservoir.

Queensland tick typhus

caused by Rickettsia australis. See queensland tick typhus.

Sao Paulo typhus

see rocky mountain spotted fever.

scrub typhus

caused by Orientia tsutsugamushi. Wild rodents and occasionally dogs may be hosts.

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typhus

Brill-Zinsser disease; epidemic typhus; murine typhus, typhus fever Infectious disease A rickettsiosis transmitted by a louse or a flea Clinical Fever, a transient rash, and hypotension caused by either R prowazekii–epidemic typhus, Brill disease–rare in US or R typhi–murine typhus, a mild summer-fall infection most common in southeastern and southern US; < 2% mortality. See Epidemic typhus, Queensland tick typhus, Rickettsia São Paulo typhus, Scrub typhus.