The epidemiology and clinical manifestations of murine typhus
- Daniel J Sexton, MD
Daniel J Sexton, MD
- Editor-in-Chief — Infectious Diseases
- Section Editor — Bacterial Infections
- Professor of Medicine
- Duke University Medical Center
Murine (endemic) typhus is an uncommon flea-borne infectious disease caused by Rickettsia typhi. The illness is less commonly diagnosed in the United States than in the developing world because of improvements in hygiene and rat control efforts. The actual incidence of murine typhus is difficult to establish since infection can be mild and self-limited, and difficult to distinguish from other causes of rash and fever.
This topic will review the epidemiology and clinical manifestation of murine typhus. A discussion on diagnosis and treatment is found elsewhere. (See "Diagnosis and treatment of murine typhus".)
Rickettsia typhi is a member of the typhus group of rickettsiae that also includes the agent of epidemic typhus, R. prowazekii. These organisms are obligate intracellular, gram-negative bacteria that can only be grown in tissue culture, the cells of experimental animals, or chick embryos. (See "Biology of Rickettsia rickettsii infection".)
Murine typhus is primarily transmitted by the rat flea, Xenopsylla cheopis. Additional vectors include the cat flea, Ctenocephalides felis, and the mouse flea, Leptopsyllia segnis. Fleas remain permanently infected with Rickettsia typhi, but their lifespan is not shortened by the presence of rickettsiae. Humans are infected by inoculation of infective flea feces in bite wounds .
The majority of cases of murine typhus are associated with sites in which rats accumulate in large numbers. However, in suburban locations in the United States, domestic cats, cat fleas, and opossums may maintain a cycle of both R. typhi and Rickettsia felis (a spotted fever group rickettsia that is flea-borne and produces an illness that is clinically indistinguishable from murine typhus) . House mice, cats, and shrews may occasionally serve as hosts to infected fleas. In addition, domestic cats can show serological evidence of infection with R. typhi in both endemic and nonendemic regions. In one study, cats were also shown to have detectable R. typhi DNA in their blood using molecular methods . (See "Other spotted fever group rickettsial infections".)
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