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| Murine typhus | |
|---|---|
| Other names | Endemic typhus |
 | |
| Chest Xray of a 40 yr old male in acute respiratory distress syndrome as a complication of murine typhus | |
| Specialty | Infectious disease |
Murine typhus, also known asendemic typhus orflea-borne typhus, is a form oftyphus caused byRickettsia typhi transmitted byfleas (Xenopsylla cheopis), usually onrats, in contrast toepidemic typhus which is usually transmitted bylice.[1][2][3] 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 byBritish POWs in Germany at the end ofWorld War I when they described conditions in Germany.[citation needed]
Murine typhus is also commonly known as endemic or flea-borne typhus, other names include shop, urban, Mexican, and rat typhus.[4]
Symptoms occur after 6–14 days with common symptoms beingpyrexia,dermatitis,prostration,delirium, and in severe casescoma. Untreated patients may be bedridden for 2–3 months and some are unable to work.[4]
Rickettsia typhi is the causative agent of murine typhus, the primary host species areRattus rattus andR. norvegicus with transmission occurring via the faeces of fleas (typicallyXenopsylla). 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 fromHoplopleura pacifica,Polyplax spinulosa,Laelaps echidnina,Ornithonyssus bacoti, andchiggers.[4]
R. typhi is not lethal to rats and simply causesrickettsaemia (rickettsiae in blood). Fleas feed on infected rats and become infected with the rickettsiae spreading to themidgutepthilelial cells and replicating there, infected cells move to thegut lumen and are excreted withfaeces. The most common flea vector isXenopsylla cheopis with other species beingX. astia,X. bantorum,X. brasiliensis,Ctenocephalides felis,Pulex irritans,Leptopsylla segnis, andNosopsyllus fasciatus.X. cheopis has been shown to transferR. typhi via bite in experimental settings and it has been theorised thataerosol transmission from faeces is possible as well. Some arthropods such as mites andchiggers can transferR. typhi to rats but do not transfer the bacteria to humans.[4]
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 inTexas, with homeless people inHouston having significantseropositivity.[4]
Diagnosis of murine typhus in humans is done via testing for antibodies toR. typhi or isolation ofR. typhi from a blood or tissue sample. Enzyme-linked immunosorbent assays andpolymerase chain reaction (PCR) tests can be used in the diagnosis of fleas and other animals.[4]
Different strains ofR. typhi have different virulence, withNew World strains having a fatality of around 2%, withOld World strains having fatality rates up to 70%. Despite this over 95% of untreated cases recover, although recovery can take 2–3 months.[4]
Antibiotics are used to treat murine typhus withdoxycycline andtetracycline being common.[4]