ESSENTIALS OF DIAGNOSIS
Prodrome of headache, then chills and fever.
Severe, intractable headaches, prostration, persisting high fever.
Macular rash appearing on days 4–7 on the trunk and in the axillae, spreading to the rest of the body but sparing the face, palms, and soles.
Diagnosis confirmed by complement fixation, microagglutination, or immunofluorescence.
Epidemic louse-borne typhus is caused by Rickettsia prowazekii, an obligate parasite of the body louse Pediculus humanus (other lice were thought not to contribute although a 2018 report from Turkey suggests P humanus capitus may transmit R prowazekii) (Table 32–3). Transmission is favored by crowded, unsanitary living conditions, famine, war, or any circumstances that predispose to heavy infestation with lice. After biting a person infected with R prowazekii, the louse becomes infected by the organism, which persists in the louse gut and is excreted in its feces. When the same louse bites an uninfected individual, the feces enter the bloodstream when the person scratches the itching wound. Dry, infectious louse feces may also enter via the respiratory tract. Cases can be acquired by travel to pockets of infection (eg, central and northeastern Africa, Central and South America). Outbreaks have been reported from Peru, Burundi, Ethiopia, Turkey, and Russia and are associated with migration of peoples as well as with refugee camps where crowding and poor hygiene may occur. Because of aerosol transmissibility, R prowazekii is considered a possible bioterrorism agent. In the United States, cases occur among the homeless, refugees, and the unhygienic, most often in the winter.
Table 32–3.Rickettsial diseases. |Favorite Table|Download (.pdf) Table 32–3. Rickettsial diseases.
|Disease ||Rickettsial Pathogen ||Geographic Areas of Prevalence ||Insect Vector ||Mammalian Reservoir ||Travel Association |
|Typhus Group |
|Epidemic (louse-borne) typhus ||Rickettsia prowazekii ||South America, Northeastern and Central Africa ||Louse ||Humans, flying squirrels ||Rare |
|Endemic (murine) typhus ||Rickettsia typhi ||Worldwide; small foci (United States: southeastern Gulf Coast) ||Flea ||Rodents, opossums ||Often |
|Scrub Typhus Group |
|Scrub typhus ||Orientia tsutsugamushi ||Southeast Asia, Japan, Australia, Western Siberia ||Mite1 ||Rodents ||Often |
|Spotted Fever Group |
Rocky Mountain spotted fever
Brazilian spotted fever
|Rickettsia rickettsii || |
Western hemisphere; United States (especially mid-Atlantic coast region)
|Tick1 ||Rodents, dogs, porcupines, capybaras for Brazilian spotted fever ||Rare |
|California flea rickettsiosis ||Rickettsia felis ||Worldwide ||Flea ||Cats, opossums || |
|Mediterranean spotted fever, Boutonneuse fever, Kenya tick typhus, South African tick fever, Indian tick typhus ||Rickettsia conorii ||Africa, India, Mediterranean regions ||Tick1 ||Rodents, dogs ||Often |
|Queensland tick typhus ||Rickettsia australis ||Eastern Australia ||Tick1 ||Rodents, marsupials ||Rare |
|Siberian Asian tick typhus ||Rickettsia sibirica ||Siberia, Mongolia ||Tick1 ||Rodents ||Rare |
|African tick bite fever ||Rickettsia africae ||Rural sub-Saharan Africa, Eastern Caribbean ||Tick1 ||Cattle ||Often |
|Lymphangitis-associated rickettsiosis ||R sibirica mongolitimonae ||Europe, Africa, Mongolia ||Tick1 ||Unknown ||Unknown |
|Tick-borne lymphadenopathy/Dermacentor-borne necrosis erythema lymphadenopathy/scalp eschar neck lymphadenopathy ||R slovaca, R raoultii, Candidatus R rioja ||Europe ||Tick ||Unknown ||Occasional |
|Transitional Group |
|Rickettsialpox ||Rickettsia akari ||United States, ...|