The two major forms of the infectious disease typhus are known as epidemic and endemic typhus respectively, both of which are caused by strains of the bacteria Rickettsia. Rickettsia-infected body lice and fleas transmit epidemic and endemic typhus, respectively. Outbreaks of these diseases are very much associated with people living in crowded, squalid conditions and frequently occur during times of war or famine, according to MedlinePlus.
Rickettsia Prowazekii
Human lice carry the bacteria Rickettsia prowazekii in their guts, which is transmitted when louse fecal matter is rubbed into the wound site, due to itching and scratching in response to louse bites. Once the bacteria enters the blood stream, an incubation period of one to two weeks follows, during which the bacteria multiplies prolifically leading to symptoms of fever, cough, rash, low blood pressure, stupor, light sensitivity and delirium. Fatalities in children under ten are rare, but mortality increases with age and may climb to 60 percent in untreated patients, according to the New World Encyclopedia.
Originally diagnosed as a virus due to its small size, but later reclassified, Rickettsia prowazekii is a rod-shaped bacteria with a highly porous membrane, and requires a host such as rat, human, louse or flee to exist in different stages of its lifecycle; therefore, it is classified as a parasite, according to Montana State University.
Rickettsia Typhi
Fleas carried on rats and other fury mammals, such as mice and cats are, hosts of the bacteria Rickettsia typhi, the causative agent of endemic typhus, which gains entry to the human blood stream in the same manner as the pathogen responsible for epidemic typhus. Symptoms of endemic typhus include headache, chills, fever, muscle pains, nausea, vomiting, and coughing. The majority of people who contract this form of typhus make a full recovery, although the elderly are particularly susceptible and death may occur in a small minority of cases, according to the Virginia Department of Health.
Rickettsia typhi is very similar to Rickettsia prowazekii both in terms of genetics and behavior, according to genome analysis published in the November 2004 issue of the "Journal of Bacteriology."
Trombiculid Mites
Trombiculid mites found in dense areas of vegetation transmit scrub typhus through a similar method to epidemic and endemic typhus leading to symptoms that considerably overlap with other forms of typhus. Without treatment, scrub typhus is fatal in up to 40 percent of cases, according to National Institutes for Health. Strictly speaking, this condition should not be classified as typhus as it is caused by a different type of bacteria, known as Orientia tsutsugamushi, according to Centers for Disease Control and Prevention.
Treatment
Treatment of patients with epidemic, endemic and scrub typhus with antibiotic such as doxycycline and chloramphenicol is frequently the best option, according to the British National Health Service
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References
- MedlinePlus: Typhus
- New World Encyclopedia: Typhus
- Virginia Department of Health: Endemic Typhus Fever (flea-borne)
- Montana State University: The Historical Impact of Epidemic Typhus
- "Journal of Bacteriology"; Complete Genome Sequence of Rickettsia typhi and Comparison with Sequences of Other Rickettsiae; M. McLeod et al; November 2004
