Infectious Disease Compendium

Rickettsia

Microbiology

Pleomorphic coccobacillus; obligate, intracellular parasites. Includes R. aeschlimannii, R. akari, R. africae, R. australius, R. conorii, R. felis, R. helvetica, Rickettsia monacensis, R. parkeri; R. prowazekii, R. rickettsii, R. slovaca, R. typhii. Rickettsia sp. XY99 in China. And Candidatus R tarasevichiae.

Epidemiologic Risks

All are spread to humans by arthropods from various hosts. They often occur in spring summer when the vector is feeding.

Candidatus R tarasevichiae (in China and Russia)(PubMed).

Rickettsia 364D: Eschar-associated illness in California (PubMed).

Rickettsia sp. XY99. A spotted fever in China, it resembles fever with thrombocytopenia syndrome (Pubmed).

R. aeschlimanni: tick, found in S. Europe and N. Africa (PubMed).

R. akari: in mice to mites to humans. Found in United States, Turkey, Croatia, and Ukraine, Mexico.

R. africae: Sub-Saharan and S. Africa. Also reported in Oceania and New Caledonia; often multiple tick bites with regional lymphadenopathy.

R. australius: ticks in Australia, found in rodents.

R. conorii: tick bite in the US SE, 30% of ticks are PCR positive (PubMed).

R. felis (PubMed): where there are domestic cats, spread by flea. Is found in Africa.  There is the suggestion that humans are a natural host and the organism is a symbiont (PubMed).  Look what symbionts did to Peter Parker.  Gives one pause.  I may be spread by mosquitos (PubMed) " R. felis was detected in mosquito feces up to day 14."  I imagine someone following a mosquito in a park with a teeny-tiny plastic bag,

R. helvetica: n 1.9%–12.5% of the population in Lao People’s Democratic Republic, France, Italy, Denmark, and Sweden are seropositive.

R. monacensis: N. Spain.

R. parkeri: ticks in Alabama, Florida, Georgia, Mississippi, and Texas and up and down the Atlantic Coast (PubMed) And now cases in Arizona (Pubmed). Also cases in Argentina.

R. prowazekii: body louse; world wide including Mexico and South Texas.

R. raoultii: Causes “SENLAT” --scalp eschar and neck lymph- adenopathy after tick bite (PubMed). Was made into a Pixar movie.

R. rickettsii: ticks in the Western hemisphere (US south, Arizona, and Central America), found in dogs and rodents.And in Sonora and Baja California Mexico (PubMed).

R. slovaca: Europe (France, Spain, Portugal, Hungary, Slovakia, Bulgaria, Italy, and Germany), tick bites esp to the head. Causes “SENLAT” --scalp eschar and neck lymph- adenopathy after tick bite (PubMed).

R. tsutsugamushi: see Orientia tsutsugamushi.

R. typhii: flea, worldwide, found in rodents. In US it is found in suburban California and Texas (Austin, Galveston) and associated with cats and opossums (PubMed).

Sennetsu neorickettsiosis: Eating fish in Laos.

Syndromes

Fevers, headache and, depending on species, a rash. Cytopenia and hepatitis are common. Think of Rickettsia when you have a patient that is very ill systemically and no focal infection. What makes these patients sick, and helps to understand the clinical manifestations, is that they infect endothelial cells. Serology to make the diagnosis.

Candidatus R tarasevichiae: fever with thrombocytopenia (usually viral in Asia. (PubMed).

Rickettsia 364D: Eschar-associated illness in California (PubMed).

R. aeschlimanni: fever, rash, eschar at bite.

R. akari: Rickettsialpox. It has a vesicular rash on trunk, extremities, face. Often an eschar at bite.

R. africae: fevers, regional adenopathy and multiple tache noir.

R. australius: Queensland tick typhus. It has a vesicular rash on trunk, extremities, face. Often an eschar at bite.

R. conorii: Boutonneuse Fever. It has a vesicular rash on trunk, extremities, face. Often an eschar at bite. R. parkeri: spotted fever with an eschar (often multiple), leukopenia and thrombocytopenia. It is a milder form of RMSF (PubMed).

R. felis: high fever, headache, myalgia; other manifestations occur, such as abdominal pain, nausea, vomiting, cough, eschar, photophobia, and hearing loss. No skin rash.

R. helvetica: fever, meningitis.

R. parkerii: like a mild RMSF with less severe neurologic disease and most patients have one or more eschar(s). Patients who have RMSF rarely have eschars.

R. prowazekii: Typhus. Rash is truck to extremities. No eschar.

R. monacensis: spotted fever.

R. raoultii: Causes “SENLAT” --scalp eschar and neck lymph- adenopathy after tick bite (PubMed).

R. rickettsii: Rocky Mountain spotted fever. Extremities to trunk No eschar. The rash may not appear until day 5, starts around wrist and ankles and take time to develop petechiae. Every day in delay of therapy increases mortality.

R. typhii: Murine typhus. Rash is truck to extremities. No eschar. It is common in Texas (PubMed).

R. slovaca: spotless fever with painful head and neck lymphadenopathy. “SENLAT” --scalp eschar and neck lymph- adenopathy after tick bite (PubMed). Occurs in the winter, has neither a rash nor a fever.

R. felis: fever, rash, meningitis, myalgias.

Sennetsu neorickettsiosis: fever.

Treatment

Tetracycline / doxycycline (preferred) OR chloramphenicol. Quinolones maybe, but stick with a tetracycline. Doxycycline for 7 days or azithromycin for three days are equally effective (PubMed) for scrub typhus.

And if you think about RMSF, either from the clinical picture or you are in an endemic area, start therapy as the sooner the better for mortality (PubMed).

Notes

G6PD deficiency leads to a more severe course of RMSF.