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 exposu ...

caused by ''

Rickettsia typhi ''Rickettsia typhi'' is a small, Aerobic organism, aerobic, obligate intracellular, rod shaped Gram-negative bacteria, gram negative bacterium. It belongs to the typhus group of the ''Rickettsia'' genus, along with Rickettsia prowazekii, ''R. prowa ...

'' transmitted by

flea Flea, the common name for the order (biology), order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by hematophagy, ingesting the blood of their hosts. Adult f ...

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 (epidemiology), vector for bubonic plague, plague and murine ...

''), usually on

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...

s, in contrast to

epidemic typhus Epidemic typhus, also known as louse-borne typhus, is a form of typhus so named because the disease often causes epidemics following wars and natural disasters where civil life is disrupted. Epidemic typhus is spread to people through contact wit ...

which is usually transmitted by

lice Louse (: lice) is the common name for any member of the infraorder Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera was previously recognized as an order, until a 2021 genetic study determined th ...

. 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 or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

when they described conditions in Germany.

Names

Murine typhus is also commonly known as endemic or flea-borne typhus, other names include shop, urban, Mexican, and rat typhus.

Signs and symptoms

Symptoms occur after 6–14 days with common symptoms being

pyrexia Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with body temperature exceeding the normal range caused by an increase in the body's temperature set point in the hypothalamus. There is no single agre ...

dermatitis Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened ...

prostration Prostration is the gesture of placing one's body in a reverentially or submissively prone position. Typically prostration is distinguished from the lesser acts of bowing or kneeling by involving a part of the body above the knee, especially t ...

delirium Delirium (formerly acute confusional state, an ambiguous term that is now discouraged) is a specific state of acute confusion attributable to the direct physiological consequence of a medical condition, effects of a psychoactive substance, or ...

, and in severe cases

comatose A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. The person may ...

. Untreated patients may be bedridden for 2–3 months and some are unable to work.

Transmission

'' is the causative agent of murine typhus, the primary host species are ''

Rattus rattus The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is ...

'' and '' R. norvegicus'' with transmission occurring via the faeces of fleas (typically ''

Xenopsylla ''Xenopsylla'' is a flea genus in the family Pulicidae. References External links Siphonaptera genera Pulicidae {{flea-stub ...

''). The bacteria is excreted in the faeces of fleas and when a flea bite is scratched or picked at the bacteria enters the skin and commences infection. Other peridomestic rats and rodents are capable of being infected. Rats can also be infected from '' Hoplopleura pacifica'', '' Polyplax spinulosa'', '' Laelaps echidnina'', '' Ornithonyssus bacoti'', and

chigger ''Trombicula'', known as chiggers, red bugs, scrub-itch mites, or berry bugs, are small arachnids (eight-legged arthropods) in the Trombiculidae family. In their larval stage, they attach to various animals and humans, then feed on skin, often ...

s. ''R. typhi'' is not lethal to rats and simply causes rickettsaemia ( rickettsiae in blood). Fleas feed on infected rats and become infected with the rickettsiae spreading to the

midgut The midgut is the portion of the human embryo from which almost all of the small intestine and approximately half of the large intestine develop. After it bends around the superior mesenteric artery, it is called the "midgut loop". It comprises ...

epthilelial cells and replicating there, infected cells move to the gut lumen and are excreted with

faeces Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the ...

. The most common flea vector is ''

'' with other species being '' X. astia'', '' X. bantorum'', '' X. brasiliensis'', ''

Ctenocephalides felis The cat flea (scientific name ''Ctenocephalides felis'') is an extremely common parasitic insect whose principal host is the domestic cat, although a high proportion of the fleas found on dogs also belong to this species. This is despite the wide ...

'', '' Pulex irritans'', '' Leptopsylla segnis'', and '' Nosopsyllus fasciatus''. ''X. cheopis'' has been shown to transfer ''R. typhi'' via bite in experimental settings and it has been theorised that

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be generated from natural or Human impact on the environment, human causes. The term ''aerosol'' co ...

transmission from faeces is possible as well. Some arthropods such as mites and

chiggers ''Trombicula'', known as chiggers, red bugs, scrub-itch mites, or berry bugs, are small arachnids (eight-legged arthropods) in the Trombiculidae family. In their larval stage, they attach to various animals and humans, then feed on skin, often ...

can transfer ''R. typhi'' to rats but do not transfer the bacteria to humans.

Epidemiology

Murine typhus is a global disease found on all continents bar Antarctica. Significant volumes of cases occur Indonesia, China, North Africa, Central America, and Thailand. In the United States most cases occur in

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, with homeless people in

Houston Houston ( ) is the List of cities in Texas by population, most populous city in the U.S. state of Texas and in the Southern United States. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the county seat, seat of ...

having significant seropositivity.

Diagnosis

Diagnosis of murine typhus in humans is done via testing for antibodies to ''R. typhi'' or isolation of ''R. typhi'' from a blood or tissue sample. Enzyme-linked immunosorbent assays and

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

(PCR) tests can be used in the diagnosis of fleas and other animals.

Prognosis

Different strains of ''R. typhi'' have different virulence, with

New World The term "New World" is used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...

strains having a fatality of around 2%, with

Old World The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...

strains having fatality rates up to 70%. Despite this over 95% of untreated cases recover, although recovery can take 2–3 months.

Treatment

Antibiotics are used to treat murine typhus with

doxycycline Doxycycline is a Broad-spectrum antibiotic, broad-spectrum antibiotic of the Tetracycline antibiotics, tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat pneumonia, bacterial p ...

and

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

being common.

References

External links

{{Bacterial cutaneous infections Bacterium-related cutaneous conditions Typhus