Broadly, rickettsial infections are caused by a wide range of bacterial species. These genera include Rickettsia, Neorickettsia, and Orientia. Additionally, bacteria in the Anaplasma, Ehrlichia, and Neoehrlichia also are technically rickettsial species, but are frequently considered as separate, causing Anaplasmosis and Ehrlichosis.
The bacteria in the Rickettsia genus are divided into two subgroups based on the symptoms they produce. These groups are the spotted fever and the Typhus Fever groups. In the United States, the most prevelant species include Rickettsia rickettsia and Rickettsia typhi with others such as Rickettsia akari, Rickettsia parkeri, Rickettsia prowazekii, and Rickettsia felis being less common. Rickettsia typhi and Rickettsia prowazekii are the two species that belong to the Typhus Fever group, while all other Rickettsia species belong to the spotted fever group.
The rickettsial diseases most commonly contracted outside of the United States include: African tick-bite fever (R. africae found in Southern Africa), Mediterranean spotted fever (R. conorii found in Europe, Africa, India, and Middle East), Rocky Mountain Spotted fever or Brazilian spotted fever (R. rickettsia found in Western Hemisphere), and murine or flea born typhus (R. typhi found in tropics/subtropics). Scrub typhus is caused by another species called Orientia tsutsugamushi, while not a Rickettsia species it exhibits a similar illness that may be contracted outside of the United States.
African tick-bite fever
Queensland tick typhus
Mediterranean spotted fever
Cat flea rickettsiosis
Far Eastern spotted fever
Flinders Island spotted fever
Japanese spotted fever
Mediterranean spotted fever-like disease
Mediterranean spotted fever-like illness
Rocky Mountain spotted fever
North Asian tick typhus
The transmission of these diseases usually occurs through a bite from an ectoparasite arthropod or insect such as a flea, tick, lice or mite. In areas where rickettsial diseases are common the use of insect repellent, avoidance of areas with these insects, and dressing with long pants and sleeves may reduce exposure risk. In addition to insect bites the exposure to infectious feces or fluids from the parasites into the skin or inhalation may also cause disease.
Serology testing is the most common methods for the detection and monitoring Rickettsiosis. DNA detection-based methods such as PCR or DNA sequencing can assist in the detection and speciation of Rickettsia species. Fry Laboratories, LLC offers both DNA sequencing and serology testing to aid in the detection of Rickettsia.