Murine typhus, also known as endemic typhus or flea-borne typhus, is a form of

typhus Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...

transmitted by

flea Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, ...

s (''

Xenopsylla cheopis The Oriental rat flea (''Xenopsylla cheopis''), also known as the tropical rat flea or the rat flea, is a parasite of rodents, primarily of the genus ''Rattus'', and is a primary vector for bubonic plague and murine typhus. This occurs when a fl ...

''), usually on rats, in contrast to epidemic typhus which is usually transmitted by

lice Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a resul ...

. Murine typhus is an under-recognized entity, as it is often confused with viral illnesses. Most people who are infected do not realize that they have been bitten by fleas. Historically the term "hunger-typhus" was used in accounts by British POWs in Germany at the end of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

when they described conditions in Germany.

Signs and symptoms

Symptoms of endemic typhus include headache, fever,

muscle pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another like ...

joint pain Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...

and

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenter ...

. 40–50% of patients will develop a discrete rash six days after the onset of signs. Up to 45% will develop neurological signs such as confusion, stupor, seizures or imbalance. Symptoms may resemble those of

measles Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...

rubella Rubella, also known as German measles or three-day measles, is an infection caused by the rubella virus. This disease is often mild, with half of people not realizing that they are infected. A rash may start around two weeks after exposure and ...

, or possibly

Rocky Mountain spotted fever Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally made up of small spots of bleedin ...

. These symptoms are likely caused by a

vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused ...

caused by the rickettsia.

Causes

It is caused by the bacterium '' Rickettsia typhi'', and is transmitted by the

s that infest rats. While rat fleas are the most common vectors, cat fleas and mouse fleas are less common modes of transmission. These fleas are not affected by the infection. Human infection occurs because of flea-fecal contamination of the bites on human skin. Rats, cats, and opossums maintain the rickettsia colonization by providing it with a host for its entire life cycle. Rats can develop the infection, and help spread the infection to other fleas that bite them, and help multiply the number of infected fleas that can then infect humans. Less often, endemic typhus is caused by '' Rickettsia felis'' and transmitted by fleas carried by cats or

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered No ...

s. In the United States of America, murine typhus is found most commonly in southern California, Texas and Hawaii. In some studies, up to 13% of children were found to have serological evidence of infection.

Diagnosis

, early diagnosis continued to be based on clinical suspicion, and treatment of the disease is indicated even before laboratory results confirm its presence. Because of the lag between the onset of infection and the appearance of antibodies in a blood test, serologic tests are merely confirmatory and retrospective. Weil-Felix agglutination reactions are not sensitive to the disease. Indirect fluorescence antibody

assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of ...

s that are specific to ''R. typhi'' antigens are the recommended route for detection and diagnosis: diagnostic

titer Titer (American English) or titre (British English) is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positiv ...

s are present in half of all cases within the first week of infection and in nearly all cases by day-15. The sharing of antigens by rickettsiae means routine serologic evaluation will not distinguish between murine typhus and epidemic typhus. Bacterial cultures are rarely performed because although they are highly accurate for diagnosis, the biohazard risk of generating them is often considered too high.

Treatment

The disease can be fatal if left untreated, but endemic typhus is highly treatable with antibiotics. Most people recover fully, but death may occur in the elderly, severely disabled or patients with a depressed immune system. The most effective antibiotics include

tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. Common side effects in ...

and

chloramphenicol Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. This includes use as an eye ointment to treat conjunctivitis. By mouth or by injection into a vein, it is used to treat meningitis, plague, chole ...

. In the United States, the CDC recommends solely

doxycycline Doxycycline is a broad-spectrum tetracycline class antibiotic used in the treatment of infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, Lyme disease, cholera, typhus ...

References

External links