Typhus

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

Primary Source Connection

BIBLIOGRAPHY

Introduction

Typhus is a group of diseases caused by bacteria belonging to the Rickettsiae genus. They are spread by ticks and small insects and are found in specific geographical locations around the world. Typhus has caused millions of deaths over the course of human history, being particularly common under conditions of war, famine, and mass migration.

There are four main types of typhus. Epidemic typhus is spread by lice and tends to occur in conditions of overcrowding and poor hygiene. The spotted fevers (sometimes also known as tick-borne typhus), like Rocky Mountain spotted fever, are a group of tick and miteborne rickettsial diseases found in parts of the United States, Africa, India, Australia, and parts of the Mediterranean. Endemic flea-borne typhus is spread by rats and occurs in rodent-infested environments such as garbage dumps and markets. Scrub typhus is spread by mites and is found in parts of South East Asia. Typhus is a potentially fatal disease, with prevention depending on control of its insect vectors (transmitters from one host to another).

Disease History, Characteristics, and Transmission

Typhus was confused with typhoid fever until the 1830s, when it was shown to be a separate disease, although the similarity between the two names persists. The Rickettsiae, which are the causative agents of the various forms of typhus, get their name from Howard Taylor Ricketts (1871–1910), the American pathologist who discovered them, and who also died from typhus. They are Gram-negative cocci or bacilli, having an oval shape or existing as chains. Gram-negative refers to the way in which the bacteria react with Gram's stain, which is used to prepare samples for microscopy.

The specific Rickettsiae associated with the different types of typhus have been identified. Therefore, R. prowazekii is the agent of epidemic louse-born typhus, and R. rickettsii, R. conorii, R. africae, R. japonica R. australis and several other species are involved in tick-borne typhus, each organism being found in a different geographical area. Endemic flea-borne typhus is associated with R. mooseri, and R. tsutugamusi is the agent of scrub typhus.

The incubation time of typhus is 12–15 days. The bacteria enter the bloodstream and can spread throughout the body. They invade the endothelial cells, which line the inner walls of the small veins, arteries and capillaries and make them swell up. This can cause thrombosis, or blood clotting, and in addition, small characteristic nodules made up of white blood cells and platelets may develop in the blood.

The early symptoms of all kinds of typhus are nonspecific and may range from mild to severe, consisting of fever, headache, an extensive rash, and perhaps mental confusion. Symptoms persist for about two weeks, but several months may pass before complete recovery occurs. A characteristic eschar, or thick blackened scab, is seen at the site of the vector bite in scrub typhus and some of the spotted fevers. It is not uncommon for typhus to be improperly diagnosed.

Epidemic typhus may cause a high fever, headache, chills, confusion, and limb pain, progressing to agitation, coma, and many other complications. Photophobia, which is an aversion to light, vomiting, and a rash that starts on the trunk can also occur. Epidemic typhus is a far more severe condition than endemic typhus, whose symptoms are milder, but similar.

Rocky Mountain spotted fever causes headache, fever, abdominal pain, and a rash that begins on the hands and feet and spreads to the rest of the body. The other spotted fevers cause similar symptoms, but with some regional variations. So, for example, African tickbite fever is not usually associated with a rash, and its symptoms are very similar to those of North Asian tick typhus. Scrub typhus causes breathing difficulties, cough, fever, headache, sweating, swollen glands, a swelling at the site of the bite, and a rash starting on the trunk.

WORDS TO KNOW

ARTHROPOD: A member of the largest single animal phylum, consisting of organisms with segmented bodies, jointed legs or wings, and exoskeletons.

ENDEMIC: Present in a particular area or among a particular group of people.

ESCHAR: Any scab or crust forming on the skin as a result of a burn or disease is an eschar. Scabs from cuts or scrapes are not eschars.

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.

MACULOPAPULAR: A macule is any discolored skin spot that is flush or level with the surrounding skin surface: a papule is a small, solid bump on the skin. A maculopapular skin disturbance is one that combines macules and papules.

PROPHYLAXIS: Treatment to prevent the onset or recurrence of disease.

RESERVOIR: The animal or organism in which the virus or parasite normally resides.

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.

Rickettsiae may damage blood vessels, causing clotting and even gangrene, the death of tissue at the extremities of the body because of oxygen deprivation. This can lead to the loss of limbs or digits (fingers and toes). The infection can also lead to organ failure. Other complications may occur, depending upon the type of typhus involved. For instance, tick-borne typhus may result in liver and kidney failure, while brain damage and coma can occur with scrub typhus.

Typhus is usually more severe in adults than in children. The introduction of antibiotics has reduced overall mortality (death) rates to between three to four percent. Untreated, the mortality rate of epidemic typhus, which is the most serious form of the disease, ranges from five to 40 percent; in healthy individuals, the mortality rate is around 20 percent, but can be as high as 60 percent in elderly, malnourished, or debilitated individuals. Mortality from treated murine typhus is about one to four percent, and is less than one percent for scrub typhus.

Those who survive endemic typhus generally have lifelong immunity to another attack, but may relapse many years later with a milder form called Brill-Zinsser disease. This occurs because the Rickettsiae may linger even after antibiotic treatment, especially if this has been incomplete or the person is malnourished. People surviving other forms of typhus generally have long-term or lifelong immunity from further attacks.

Transmission of typhus is from an animal or human host infected with Rickettsiae through an arthropod (flea, tick, mite) vector. In epidemic, louse-borne typhus, the bacteria pass—usually under crowded, unhygienic conditions—from one person to another via the body (clothing) louse, which thrives on worn, unwashed clothing. Head and pubic lice do not usually acts as vectors for Rickettsiae.

The Rickettsiae live in the digestive tract of the louse and are shed in its feces. Transmission usually occurs when the louse bites a human for a blood meal, defecating as it eats. The bite itches and scratching it crushes the louse and releases the bacteria from contaminated louse feces into the bloodstream. Rickettsia can survive for many months in dust containing dried louse feces and may be transmitted in this form through the eyes or mouth.

Endemic typhus, sometimes called murine typhus, is carried by the flea Xenopsylla cheopsis, with rats, mice, opossums, raccoons, and skunks acting as the animal reservoirs. In tick-borne typhus, including the spotted fevers, rodents, dogs, cats, opossums, and hares act as animal reservoirs in various locations, with the vectors usually being ticks. However, Rickettsiael pox, which occurs in Russia, South Africa, and Korea, is carried by mites and R. felis infection, which is similar to endemic typhus, is spread by cat and dog fleas in parts of Europe and South America. Finally, scrub typhus is spread by mite bites.

Scope and Distribution

Typhus is a disease that has killed millions over the course of human history and is particularly prevalent under conditions of war, famine, and natural disaster where hygiene is poor and overcrowding and malnutrition are common. First described in the fifteenth century, typhus has been known as famine fever, ship fever, camp fever, and gaol (jail) fever, names that reflect the conditions under which it is most commonly found. It arrived in Europe in 1489 with soldiers who had been fighting in Cyprus. An outbreak between 1557–1559 killed around ten percent of the English population.

In the nineteenth century, typhus ravaged Napoleon's troops on their Moscow campaign, typhus hit Ireland between 1816–1819, and again during the famine of the 1840s. London experienced a serious typhus epidemic in the 1840s during a time of railway construction and building trade strikes that led to dislocation and deprivation in the city, and the disease began to claim more lives than smallpox.

During World War I (1914–1918), typhus caused 150,000 deaths in Serbia in 1915, and this epidemic was eventually brought under control by a British sanitary team. In the four years from 1918, epidemic louse-borne typhus caused 30 million cases and three million deaths in Eastern Europe and Russia. This epidemic was triggered by war and revolution, food and fuel shortages, and economic collapse, and was spread by the railways that enabled mass movement of people.

A famous victim of typhus was the teenage diarist of the second World War (1939–1945), Anne Frank, who died of typhus in the Bergen-Belsen concentration camp in 1945. Frank was just one victim in an epidemic which had a mortality of around 50 percent, killing almost 35,000 of the inhabitants of the camp.

More recently, in 1997, the World Health Organization (WHO) reported an outbreak of nearly 24,000 cases of epidemic typhus in Burundi, the largest outbreak in 50 years. The epidemic began with 216 cases occurring in a prison in N'Gozi, ideal conditions for contracting the disease, and then spread to the malnourished residents of refugee camps in the central highlands. WHO joined local teams in investigating the focal points of the outbreak, handing out doses of antibiotics to get the epidemic under control.

Epidemic typhus now occurs mainly in northeastern and central Africa. It is rare in most developed countries and would generally only be seen in communities and populations where body louse infestations are common, such as in refugee and prisoner populations during wars or famine.

In the eastern and central United States, around 15 cases of epidemic typhus have been reported among people with no history of lice infestation, but all described contact with flying squirrels and their nests. Therefore, campers and wildlife workers could be at risk of typhus if they come into contact with the squirrels or their nests, which are typically made in houses or in tree holes. The insect vector in such cases is the flying squirrel louse or flea.

Epidemic typhus today occurs sporadically outside the United States in cool mountainous regions of Africa, Asia, and Central and South America, especially during the colder months when louse-infested clothing may not be washed frequently. Travelers who do not come into contact with either lice or people with lice are not at risk in areas where epidemic typhus occurs. However, healthcare workers and military personnel who do have such contact may be at risk of contracting typhus.

Tick-borne typhus occurs in many places throughout the world, including the eastern United States, Brazil, the Mediterranean basin, the African veldt, India, and Australia. For instance, Rocky Mountain spotted fever occurs in Mexico, Central America, and South America, while tick-borne disease caused by R. slovaca is found in Europe. The spring and summer months are the peak times for transmission of tick-borne typhus. Travelers taking part in outdoor activities such as camping or hiking, could be at risk of acquiring tick-borne typhus if they do not take adequate precautions against tick bites.

Endemic flea-borne typhus causes sporadic cases in locations worldwide where humans and rodents live close together, such as in markets and garbage dumps. Flea infested rats are found all year round in humid tropical climates, and are more common in the warmer winter months in temperate regions. In the United States, cases have occurred in southern California and southern Texas, more commonly among adults. Travelers to places where there are rat-infested buildings and homes, especially by rivers and coastal port regions, could be at risk of contracting endemic typhus. Other animals, such as feral cats and opossums may carry the flea vectors of the disease, and contact with them should be avoided in endemic countries.

Scrub typhus is acquired from the bite of larval mites living on waist high Imperata grass that grows in previously cleared jungle around villages and in plantations. It occurs in South East Asia, the Indian subcontinent, Sri Lanka, and the other Indian Ocean islands, Papua New Guinea, and North Queensland in Australia. No cases have occurred in the United States except among travelers coming back from endemic areas. The incidence of scrub typhus worldwide is unknown, because its rather non-specific symptoms make it difficult to diagnose and there is a lack of diagnostic lab facilities in many parts of the world where it is endemic.

Treatment and Prevention

In 1948, the antibiotic chloramphenicol was introduced for the treatment of scrub typhus. Tetracycline became an alternative drug but, these days, doxycycline is the recommended treatment. Some antibiotic-resistant cases of scrub typhus have been reported. In areas where this is so, first-line treatment with rifampicin or ciprofloxacin might be recommended. The type of antibiotic treatment for all forms of typhus is similar.

Lab tests are important to determine the cause of the disease, but treatment is usually begun before the results of these are available to prevent complications. Treatment usually continues for up to three days after the fever has cleared.

There is no vaccine against typhus. Where there is epidemic typhus, mass prophylaxis with doxycycline is often necessary, as was accomplished in the Burundi outbreak. Long-term prevention efforts depend upon controlling the insect vector and the animal reservoirs of Rickettsia. Therefore, for louse-borne typhus, clean clothes, dusted with one percent malathion or one percent permethrin insecticide helps protect against the disease.

Prevention of endemic typhus depends upon controlling the local rodent population, while those at risk should use insect repellent to keep the fleas away. Tickborne typhus can be prevented by the use of DEET (diethyltoluamide) or permethrin. Finally, prevention of scrub typhus is aided by clearing jungle grass within or near affected villages. Travelers should protect themselves with jungle boots, long trousers, and impregnate their clothing with DEET or permethrin. Prophylactic doxycycline may also be useful for those who must travel through high-risk areas.

Travelers are generally not at high risk of developing typhus via exposure to an infected person, except in cases of epidemic typhus. However, people traveling to any of the many countries where typhus is endemic seek advice from their healthcare provider about precautions. In general, covering the body to avoid tick and fleabites, and frequent washing and changing of clothes will help prevent typhus. Insecticides also have an important role to play in keeping the vectors under control.

Impacts and Issues

Typhus has long been one of the great human killers. It remains a threat in many parts of the world where the relevant animal reservoirs and disease vectors are not adequately controlled, and where sanitation and the health infrastructure are poor. War, famine, and mass migration have created epidemics of typhus in the past and will continue to do so, especially in the absence of an effective vaccine against the disease.

The advent of antibiotic treatment has greatly reduced the death toll from typhus, where it is available. However, in Thailand there have been reports of strains of Rickettsiae that are becoming resistant to the drug of choice, doxycycline, Small clinical trials conducted in areas of drug resistance have suggested that rifampicin and azithromycin may be effective alternative treatments. But in case resistance against these drugs also emerges, researchers are focusing on developing a wider range of treatments for all types of typhus.

Primary Source Connection

Ludwick Gross (1904–1999) was a physician and medical researcher who pioneered the study of viruses as a possible cause of human cancers. After earning his medical degree in 1929 in his native Poland, Gross began a long association with the Pasteur Institute in Paris, where he met Charles Nicolle (1866–1936), the scientists who unraveled the mystery of how epidemic typhus is transmitted. Gross recounts Nicolle and the significance of his typhus research in the following excerpted memoir.

How Charles Nicolle of the Pasteur Institute Discovered that Epidemic Typhus Is Transmitted by Lice: Reminiscences from My Years at the Pasteur Institute in Paris

Until the first decade of this century, our information about epidemic, i.e., exanthematic typhus was rather scarce. We knew only that there existed a very dangerous, easily communicable disease, which decimated populations during wars, hunger, or flood, spreading with great speed and affecting large numbers of people. After World War I, 20–30 million people died in Eastern Europe from this disease, and an additional several million died during and after World War II. Crowding, the scarcity of clean clothes, and dirt were the principal factors enabling the spread of typhus. The disease causes high fever and maculopapular [small, red, raised] eruptions of the skin. Typhus is similar to a disease that occurs in the Rocky Mountains in the United States and is transmitted by ticks.

The fact that epidemic typhus is transmitted by lice was discovered by Dr. Charles Nicolle; a discovery for which he received the Nobel Prize in 1928. I met Dr. Nicolle in 1934 at the Pasteur Institute in Paris during my years as a guest investigator. I spoke to him several times in the corridor adjoining my laboratory. At my invitation he came to visit. He was a tall man, distinguished looking, impeccably dressed, lean, and slightly stooped, with dry skin and sparkling eyes. He was 68 years old at that time. It was difficult to talk with him because he was hard of hearing. In spite of his listening device, with its batteries and wires, which he was carrying, one had to almost shout to be understood. He was, like many Frenchmen, very polite and attentive. He agreed, at my request, to spend some time in my laboratory at the Pasteur Institute, and talk about his discovery.

Before long, still a few years before World War II, he came to my laboratory. He arrived wearing a shirt with a starched collar and starched cuffs, and sat himself comfortably in a large chair. He told the following story.

“I was delegated, some 30 years ago,” recalled Dr. Nicolle, “to become director of the Pasteur Institute in Tunis, and decided to do something about typhus, which was decimating the local population. The first step was to try to transmit the disease to experimental animals. I injected guinea pigs with blood from patients with typhus and observed that, at least in some of these animals, the injection produced only high temperature. I realized, nevertheless, that even though some of them did not develop fever, they still carried the causative agent. This way we learned that typhus could exist, at least in some species, without any symptoms, except now and then, only fever. The most important point, however, was to discover how it was transmitted from man to man under natural life conditions. I learned this by accident. Tunis was full of typhus patients; the hospital was full and the number of new patients increased every day. Not only was every bed occupied and waiting rooms filled, but patients were waiting in front of the hospital, on the streets, to be admitted. At that point I made the crucial observation,” said Dr. Nicolle, “that patients infected others out on the street, and also that their clothing was infectious; service personnel at the hospital and also in the laundry room became infected. The moment the patients were admitted to the hospital, however, after they had a hot bath and were dressed in hospital clothing, they ceased to be infectious. There was no longer fear of disease transmission in a hospital room full of patients. This observation was so simple and uncomplicated that it could have been made not necessarily by a physician, but by an administrator without professional medical training. I determined that there must therefore exist a transmitting vector, in the clothing and underwear of the patients. I anticipated,” said Dr. Nicolle, “that most probably lice could be responsible for the transmission of typhus from man to man.”

Dr. Nicolle continued his story.

“At the end of June, 1909, I asked Dr. Emile Roux, who was at that time Director of the Pasteur Institute in Paris, for a few chimpanzees. My request was granted, and the chimpanzees arrived promptly. I injected one chimpanzee with blood from a patient suffering from typhus. After several days, I collected from the injected chimpanzee a few lice, and transferred them to another chimpanzee; before long, after about 10 days, this animal developed typhus. I repeated this experiment, with similar results. It was now obvious that typhus was transmitted by lice. That was in September 1909. The first step in the search for typhus control was accomplished. Lice were demonstrated to be the transmitting vectors. The Tunisian government now began intensive measures to limit the typhus epidemic with attempts to combat infestation by lice.

The initial step had been accomplished, but great difficulties were ahead. Typhus is very infectious and many laboratory workers engaged in research on the typhus epidemic became infected accidentally, in the course of their laboratory work, and some of them died of the disease.”

Ludwik Gross, M.D.

GROSS, LUDWICK. “HOW CHARLES NICOLLE OF THE PASTEUR INSTITUTE DISCOVERED THAT EPIDEMIC TYPHUS IS TRANSMITTED BY LICE: REMINISCENCES FROM MY YEARS AT THE PASTEUR INSTITUTE IN PARIS.” PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. (OCTOBER 1996): VOL. 93, 10539–10540.

See AlsoArthropod-borne Disease; Lice Infestation (Pediculosis); Rickettsial Disease; Rocky Mountain Spotted Fever.

BIBLIOGRAPHY

Books

Pelis, Kim. Charles Nicolle, Pasteur's Imperial Missionary: Typhus and Tunisia. Rochester: University of Rochester, 2006.

Periodicals

Cowan, George. “Rickettsial Diseases: the Typhus Group of Fevers a Review.” Postgraduate Medical Journal. 76 (2000): 269–272.

Web Sites

Centers for Disease Control and Prevention (CDC). “Traveler's Health: Rickettsial Infections.” 2005–2006 <http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=disobj=rickettsial.htm> (accessed May 5, 2007).

Susan Aldridge

Typhus

Characteristics of typhus

Epidemic typhus

Endemic typhus

Scrub typhus

Prevention of typhus

Resources

Typhus is a disease caused by a group of bacteria called Rickettsia. Three forms of typhus are recognized: epidemic typhus, a serious disease that is fatal if not treated promptly; rat-flea or endemic typhus, a milder form of the disease; and scrub typhus, another fatal form. The Rickettsia species of bacteria that cause all three forms of typhus are transmitted by insects. The bacteria that cause epidemic typhus, for instance, are transmitted by the human body louse; the bacteria that cause endemic typhus are transmitted by the Oriental rat flea; and bacteria causing scrub typhus are transmitted by harvest mites (commonly called chiggers).

Characteristics of typhus

Typhus takes its name from the Greek word “typhos,” meaning smoke, which accurately describes the mental state of infected persons. Typhus is marked by a severe headache, chills, and fever, and if untreated, eventually stupor and delirium. A rash appears within four to seven days after the onset of the disease. The rash starts on the trunk and spreads to the extremities. In milder forms of typhus, such as endemic typhus, the disease symptoms are not severe. In epidemic and scrub typhus, however, the symptoms are extreme, and death can result from complications such as stroke, renal failure, and circulatory disturbances. Fatality can be avoided in these forms of typhus with the prompt administration of antibiotics.

Epidemic typhus

Epidemic typhus is a disease that has played an important role in history. Because typhus is transmitted by the human body louse, epidemics of this disease break out when humans are in close contact with each other under conditions in which the same clothing is worn for long periods of time. Cold climates also favor typhus epidemics, as people will be more likely to wear heavy clothing in colder conditions. Typhus seems to be a disease of war, poverty, and famine. In fact, according to some researchers, the retreat of French leader Napoleon Bonaparte (1769–1821) and his troops from Russia in the early nineteenth century was caused in part by typhus. During and shortly after World War I (1914–18), more than three million Russians died of typhus.

Epidemic typhus is caused by Rickettsia prowazekii. Humans play a role in the life cycle of the bacteria. Lice become infected with the bacteria by biting an infected human; these infected lice then bite other humans. A distinguishing feature of typhus disease transmission is that the louse bite itself does not transmit the bacteria. The feces of the lice are infected with bacteria. Thus, when a person scratches a louse bite, the lice feces that have been deposited on the skin are introduced into the bloodstream.

If not treated promptly, typhus is fatal. In addition, a person who has had epidemic typhus can experience a relapse of the disease years after he or she has been cured of the infection. Called Brill-Zinsser disease, after the researchers who discovered it, the relapse is usually a milder form of typhus, which is treated with antibiotics. However, a person with BrillZinsser disease can infect lice, which can in turn infect other humans. Controlling Brill-Zinsser relapses is important in stopping epidemics of typhus before they start, especially in areas where lice infestation is prominent.

Endemic typhus

Endemic typhus is caused by Rickettsia typhi. These bacteria are transmitted by the Oriental rat flea, an insect that lives on small rodents. Endemic typhus (sometimes called murine typhus or rat-flea typhus) is found worldwide. The symptoms of endemic typhus are mild compared to those of epidemic typhus. In fact, many people do not seek treatment for their symptoms, as the rash that accompanies the disease may be short-lived. Deaths from endemic typhus have been documented, however; these deaths usually occur in the elderly and in people who are already weakened by other diseases.

Scrub typhus

Scrub typhus is caused by Rickettsia tsutsugamushi, which is transmitted by chiggers. The term “scrub typhus” comes from the observation that the disease is found in habitats with scrub vegetation, but

KEY TERMS

Brill-Zinsser disease —A relapse of typhus symptoms experienced by persons who have had epidemic typhus. Symptoms are usually milder than those experienced with the first bout of typhus.

Endemic typhus —A relatively mild form of typhus that is transmitted by the Oriental rat flea.

Epidemic typhus —A form of typhus that is transmitted by the human body louse and can be fatal if not promptly treated.

Scrub typhus —A form of typhus that is transmitted by chiggers and can be fatal if not promptly treated.

the name is somewhat of a misnomer. Scrub typhus is found in beach areas, savannas, tropical rain forests, and deserts—in short, anywhere chiggers live. Scientists studying scrub typhus label a habitat that contains all the elements that might prompt an outbreak of the disease a “scrub typhus island.” A scrub typhus island contains chiggers, rats, vegetation that will sustain the chiggers, and, of course, a reservoir of R. tsutsugamushi. Scrub typhus islands are common in the geographic area that includes Australia, Japan, Korea, India, and Vietnam.

The rash that occurs in scrub typhus sometimes includes a lesion called an eschar. An eschar is a sore that develops around the chigger bite. Scrub typhus symptoms of fever, rash, and chills may evolve into stupor, pneumonia, and circulatory failure if antibiotic treatment is not administered. Scrub typhus, like epidemic typhus, is fatal if not treated.

Prevention of typhus

Prevention of typhus outbreaks takes a two-pronged approach. Eliminating the carriers and reservoirs of Rickettsia is an important step in prevention. Spraying with insecticides, rodent control measures, and treating soil with insect-repellent chemicals have all been used successfully to prevent typhus outbreaks. In scrub typhus islands, cutting down vegetation has been shown to lessen the incidence of scrub typhus. The second preventative prong is protecting the body from insect bites. Wearing heavy clothing when venturing into potentially insect-laden areas is one way to protect against insect bites; applying insect repellent to the skin is another. Proper personal hygiene, such as frequent bathing and changing of clothes, will eliminate human body lice and thus prevent epidemic typhus. A typhus vaccine is also available. However, this vaccine usually only lessens the severity and shortens the course of the disease, and is no longer manufactured in the United States.

Resources

BOOKS

Cormican, M. G., and M. A. Pfaller. “Molecular Pathology of Infectious Diseases,” in Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

PERIODICALS

Boostrom, A., M. S. Beier, and J. A. Macaluso. “Geographic Association of Rickettsia Felis-Infected Opossums with Human Murine Typhus, Texas.” Emerging Infectious Diseases 8, no. 6 (June 2002): 549–54.

Watt, G., and P. Parola. “Scrub Typhus and Tropical Rickettsioses.” Curr Opin Infect Dis 16, no. 5 (October 2003): 429–36.

OTHER

“Rickettsial Infections.” Centers for Disease Control and Prevention. < http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=rickettsial.htm > (accessed November 26, 2006).

Kathleen Scogna

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〉.

Typhus

Typhus is a disease caused by a group of bacteria called Rickettsia. Three forms of typhus are recognized: epidemic typhus, a serious disease that is fatal if not treated promptly; rat-flea or endemic typhus, a milder form of the disease; and scrub typhus, another fatal form. The Rickettsia species of bacteria that cause all three forms of typhus are transmitted by insects . The bacteria that cause epidemic typhus, for instance, are transmitted by the human body louse; the bacteria that cause endemic typhus are transmitted by the Oriental rat flea; and bacteria causing scrub typhus are transmitted by chiggers.

Characteristics of typhus

Typhus takes its name from the Greek word "typhos," meaning smoke, which accurately describes the mental state of infected persons. Typhus is marked by a severe stupor and delirium, as well as headache, chills, and fever. A rash appears within four to seven days after the onset of the disease. The rash starts on the trunk and spreads to the extremities. In milder forms of typhus, such as endemic typhus, the disease symptoms are not severe. In epidemic and scrub typhus, however, the symptoms are extreme, and death can result from complications such as stroke , renal failure, and circulatory disturbances. Fatality can be avoided in these forms of typhus with the prompt administration of antibiotics .

Epidemic typhus

Epidemic typhus is a disease that has played an important role in history. Because typhus is transmitted by the human body louse, epidemics of this disease break out when humans are in close contact with each other under conditions in which the same clothing is worn for long periods of time. Cold climates also favor typhus epidemics, as people will be more likely to wear heavy clothing in colder conditions. Typhus seems to be a disease of war, poverty, and famine. In fact, according to one researcher, Napoleon's retreat from Moscow in the early nineteenth century was caused by a louse. During World War I, more than three million Russians died of typhus, and during the Vietnam war, sporadic epidemics killed many American soldiers.

Epidemic typhus is caused by Rickettsia prowazekii. Humans play a role in the life cycle of the bacteria. Lice become infected with the bacteria by biting an infected human; these infected lice then bite other humans. A distinguishing feature of typhus disease transmission is that the louse bite itself does not transmit the bacteria. The feces of the lice are infected with bacteria; when a person scratches a louse bite, the lice feces that have been deposited on the skin are introduced into the bloodstream.

If not treated promptly, typhus is fatal. Interestingly, a person who has had epidemic typhus can experience a relapse of the disease years after they have been cured of their infection . Called Brill-Zinsser disease, after the researchers who discovered it, the relapse is usually a milder form of typhus, which is treated with antibiotics. However, a person with Brill-Zinsser disease can infect lice, which can in turn infect other humans. Controlling Brill-Zinsser relapses is important in stopping epidemics of typhus before they start, especially in areas where lice infestation is prominent.

Endemic typhus

Endemic typhus is caused by R. typhi. These bacteria are transmitted by the Oriental rat flea, an insect that lives on small rodents . Endemic typhus (sometimes called murine typhus or rat-flea typhus) is found worldwide. The symptoms of endemic typhus are mild compared to those of epidemic typhus. In fact, many people do not seek treatment for their symptoms, as the rash that accompanies the disease may be short-lived. Deaths from endemic typhus have been documented, however; these deaths usually occur in the elderly and in people who are already sick with other diseases.

Scrub typhus

Scrub typhus is caused by R. tsutsugamushi, which is transmitted by chiggers. The term "scrub typhus" comes from the observation that the disease is found in habitats with scrub vegetation, but the name is somewhat of a misnomer. Scrub typhus is found in beach areas, savannas, tropical rainsforests, and deserts—in short, anywhere chiggers live. Scientists studying scrub typhus label a habitat that contains all the elements that might prompt an outbreak of the disease a "scrub typhus island." A scrub typhus island contains chiggers, rats , vegetation that will sustain the chiggers, and, of course, a reservoir of R. tsutsugamushi. Scrub typhus islands are common in the geographic area that includes Australia , Japan, Korea, India, and Vietnam.

The rash that occurs in scrub typhus sometimes includes a lesion called an eschar. An eschar is a sore that develops around the chigger bite. Scrub typhus symptoms of fever, rash, and chills may evolve into stupor, pneumonia , and circulatory failure if antibiotic treatment is not administered. Scrub typhus, like epidemic typhus, is fatal if not treated.

Prevention of typhus

Prevention of typhus outbreaks takes a two-pronged approach. Eliminating the carriers and reservoirs of Rickettsia is an important step in prevention. Spraying with insecticides , rodent control measures, and treating soil with insect-repellent chemicals have all been used successfully to prevent typhus outbreaks. In scrub typhus islands, cutting down vegetation has been shown to lessen the incidence of scrub typhus. The second preventative prong is protecting the body from insect bites. Wearing heavy clothing when venturing into potentially insect-laden areas is one way to protect against insect bites; applying insect repellent to the skin is another. Proper personal hygiene, such as frequent bathing and changing of clothes, will eliminate human body lice and thus prevent epidemic typhus. A typhus vaccine is also available; however, this vaccine only lessens the severity and shortens the course of the disease, and does not protect against infection.

Resources

books

Cormican, M. G., and M. A. Pfaller. "Molecular Pathology of Infectious Diseases." In Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Hardy, Anne. The Epidemic Streets: Infectious Diseases and the Rise of Preventive Medicine, 1956-1900. New York: Oxford University Press, 1993.

Joklik, Wolfgang, et al. Zinsser Microbiology. 20th ed. Norwalk, CT: Appleton and Lange, 1992.

periodicals

Dumler, Stephen J., et al. "Clinical and Laboratory Features of Murine Typhus in South Texas, 1980 through 1987." The Journal of the American Medical Association 266 (September 11, 1991): 1365-70.

Green, Cornelia R., and Ira Gleiberman. "Brill-Zinsser: Still With Us." The Journal of the American Medical Association 264 (October 10, 1990): 1811-12.

Kathleen Scogna

KEY TERMS

Brill-Zinsser disease

—A relapse of typhus symptoms experienced by persons who have had epidemic typhus. Symptoms are usually milder than those experienced with the first bout of typhus.

Endemic typhus

—A relatively mild form of typhus that is transmitted by the Oriental rat flea.

Epidemic typhus

—A form of typhus that is transmitted by the human body louse and can be fatal if not promptly treated.

Scrub typhus

—A form of typhus that is transmitted by chiggers and can be fatal if not promptly treated.

Typhus

War, Famine, and Typhus

What Is Typhus?

Who Gets Typhus?

What Happens When People Have Typhus?

Resource

Typhus (TI-fus) is a group of infections caused by bacteria called rickettsiae that are spread by parasites such as lice that live on people or on other warm-blooded animals such as rats and mice.

KEYWORDS

for searching the Internet and other reference sources

Endemic typhus

Lice

Murine typhus

Scrub typhus

Rickettsial diseases

Typhus Epidemics

It is likely that typhus existed in ancient history, although the first clear historical description of typhus comes from the eleventh century, when an outbreak took place in a monastery in Sicily. Typhus reached epidemic proportions in 1489, during a siege in Granada. Typhus then spread throughout Europe.

Typhus also was present in the Americas, although there is some controversy as to whether Spanish explorers brought the disease in the sixteenth century, or whether the disease already was present in Aztec and other pre-Columbian societies.

In the early nineteenth century, typhus increased dramatically in Europe. In the twentieth century, typhus spread through Europe, North Africa, and the Pacific Islands, killing thousands of prisoners in German concentration camps.

War, Famine, and Typhus

Throughout history, war and famine have brought outbreaks of typhus, a group of infections spread by parasites that live on people or animals such as rats and mice. During World War II, typhus spread through Europe, North Africa, and the Pacific Islands, and it killed thousands of prisoners in German concentration camps. Epidemic typhus still can be a serious threat in parts of the world where a breakdown in society or a natural calamity such as an earthquake leads to unhealthy living conditions.

What Is Typhus?

Typhus is a group of infections caused by rickettsiae, a group of unusual bacteria. Rickettsiae are like other bacteria in that they can be killed by antibiotics. They are also like viruses, however, in that they must invade living cells in order to grow. There are three main types of typhus: epidemic, murine, and scrub.

• Epidemic typhus, caused by Rickettsia prowazekii, is a severe form of the disease spread by human body lice. In the United States, this type of typhus also occasionally is spread by lice and fleas on flying squirrels. Sometimes the symptoms of people with typhus become active again years after the original attack; this is called Brill-Zinsser disease. Brill-Zinsser disease is milder than epidemic typhus.
• Murine typhus, caused by Rickettsia typhi, is a milder form of the disease and is spread by fleas on rats, mice, and other rodents.
• Scrub typhus, caused by Rickettsia tsutsugamushi, is a form of the disease found in the Asian-Pacific area bounded by Japan, Australia, and the Indian subcontinent. It is spread by mites on rats, field mice, and other rodents.

Who Gets Typhus?

Both epidemic and murine typhus are found around the world. However, epidemic typhus is most common in situations where poor hygiene and crowded living conditions exist. Epidemic typhus is rare in the United States. Murine typhus is most common in rat-infested areas. It is the only type of typhus that occurs regularly in the United States, but fewer than 100 cases a year are reported, mainly in Texas and California.

What Happens When People Have Typhus?

Symptoms

The symptoms of typhus include fever, headache, chills, and general aches that are followed by a rash. The rash spreads to most of the body but usually does not affect the face, palms of the hands, or soles of the feet. In murine typhus, the symptoms are similar but milder. In epidemic and scrub typhus, the fever may rise as high as 104 to 105 degrees Fahrenheit and stay high for about two weeks. The headache is intense.

In severe cases of typhus, blood pressure may drop dangerously. Severe illness also may lead to confusion, seizures, coma, or even death. This accounts for the disease’s name, which comes from the Greek word “typhös,” meaning smoke, a cloud, or a stupor arising from a fever.

Diagnosis and Treatment

Blood tests are used to show if people are infected with typhus rickettsiae. People with typhus who are treated with antibiotics generally recover. If treatment is begun early, they usually get better quickly. If treatment is delayed, however, the improvement usually is slower, and the fever lasts longer. If left untreated, typhus can damage organs, lead to coma, and even to death.

Prevention

Prevention of typhus is based on avoiding the unsanitary conditions in which it spreads. It is always wise to steer clear of animals such as rats and mice that may carry disease. Travelers to areas where typhus is common should be especially cautious. To prevent the spread of typhus, body lice must be destroyed by removing them from people with the disease and by boiling or steaming their clothes.

See also

Bacterial Infections

Lice

Rocky Mountain Spotted Fever

Resource

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road N.E., Atlanta, GA 30333. The website for this government agency has information about typhus and other rickettsial infections. Telephone 800-311-3435 http://www.cdc.gov