25.2 Bacterial infections of the circulatory and lymphatic systems  (Page 15/24)

Epidemic typhus has played an important role in human history, causing large outbreaks with high mortality rates during times of war or adversity. During World War I , epidemic typhus killed more than 3 million people on the Eastern front. Drali, R., Brouqui, P. and Raoult, D. “Typhus in World War I.” Microbiology Today 41 (2014) 2:58–61. With the advent of effective insecticides and improved personal hygiene, epidemic typhus is now quite rare in the US. In the developing world, however, epidemics can lead to mortality rates of up to 40% in the absence of treatment. Centers for Disease Control and Prevention. CDC Health Information for International Travel 2014: The Yellow Book . Oxford University Press, 2013. http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-diseases-related-to-travel/rickettsial-spotted-typhus-fevers-related-infections-anaplasmosis-ehrlichiosis. Accessed July 26, 2016. In recent years, most outbreaks have taken place in Burundi, Ethiopia, and Rwanda. For example, an outbreak in Burundi refugee camps in 1997 resulted in 45,000 illnesses in a population of about 760,000 people. World Health Organization. “Typhus.” 1997. http://www.who.int/mediacentre/factsheets/fs162/en/. Accessed July 26, 2016.

A rapid diagnosis is difficult because of the similarity of the primary symptoms with those of many other diseases. Molecular and immunohistochemical diagnostic tests are the most useful methods for establishing a diagnosis during the acute stage of illness when therapeutic decisions are critical. PCR to detect distinctive genes from R. prowazekii can be used to confirm the diagnosis of epidemic typhus, along with immunofluorescent staining of tissue biopsy specimens. Serology is usually used to identify rickettsial infections. However, adequate antibody titers take up to 10 days to develop. Antibiotic therapy is typically begun before the diagnosis is complete. The most common drugs used to treat patients with epidemic typhus are doxycycline or chloramphenicol .

Murine (endemic) typhus

Murine typhus (also known as endemic typhus) is caused by Rickettsia typhi and is transmitted by the bite of the rat flea, Xenopsylla cheopis , with infected rats as the main reservoir. Clinical signs and symptoms of murine typhus include a rash and chills accompanied by headache and fever that last about 12 days. Some patients also exhibit a cough and pneumonia-like symptoms. Severe illness can develop in immunocompromised patients, with seizures, coma, and renal and respiratory failure.

Clinical diagnosis of murine typhus can be confirmed from a biopsy specimen from the rash. Diagnostic tests include indirect immunofluorescent antibody (IFA) staining, PCR for R. typhi , and acute and convalescent serologic testing. Primary treatment is doxycycline , with chloramphenicol as the second choice.

Rocky mountain spotted fever

The disease Rocky Mountain spotted fever (RMSF) is caused by Rickettsia rickettsii and is transmitted by the bite of a hard-bodied tick such as the American dog tick ( Dermacentor variabilis ), Rocky Mountain wood tick ( D. andersoni ), or brown dog tick ( Rhipicephalus sanguineus ).