Murine Typhus

Murine typhus, also known as "endemic typhus," "Mexican typhus," and "flea-borne typhus," is a flea-borne infection of humans worldwide. Symptoms are similar to those of epidemic typhus fever (transmitted by the human body louse), but typically much less severe. If untreated, patients with murine typhus can require hospitalization, but the case fatality rate is only about 2% in the U.S. However, travelers to Asia and African should note that the case fatality rate is thought to approach 70% in certain areas in which murine typhus occurs.

In the U.S., 20-80 cases of murine typhus are reported each year, but many more cases go undiagnosed. The vast majority of cases occur in Texas, but several are reported each year in California and Hawaii. The causative agent is a bacterium that exists primarily in rodents in urban areas. However, murine typhus also exists in rural areas in a transmission cycle that involves opossums, feral cats, feral dogs, and the cat flea Ctenocephalides felis.

Causative agent

• A bacterium with the scientific name Rickettsia typhi (R. mooseri in older literature).
• It is an intracellular parasite that infects cells lining the walls of small blood vessels.

Geographical distribution of cases

• Worldwide.
• In the U.S.: nearly all cases reported from southern Texas, southern California, and Hawaii.

Symptoms of infection

• Headache, backache, joint pains, and nausea.
• Spotted rash appearing initially on the body, which subsequently may develop on arms and legs.

Reservoir hosts of Rickettsia typhi in the U.S.

• In urban areas: several species of rodents including mice and rats (especially the Norway rat).
• In rural areas: opossums and feral cats.
• NOTE: Reservoir hosts of Rickettsia typhi typically show no signs of the infection.

Vectors of Rickettsia typhi in the U.S.

• In urban areas: the Oriental rat flea, Xenopsylla cheopis.
• In rural areas: the cat flea, Ctenocephalides felis.

Modes of Transmission

• Primarily via infected flea feces scratched into skin or rubbed into an eye.
• NOTE: Transovariole transmission has been documented in female Oriental rat fleas.
• NOTE: Laboratory research suggests that transmission is possible via bites of the cat flea.

Diagnosis of infection

• Difficult because initial symptoms are similar to several other diseases, including epidemic typhus fever.
• Serological tests are needed to confirm a diagnosis.

Treatment of infection

• A physician prescribed antibiotic.

Prevention of infection

• There is no vaccine available in the U.S.
• Do not provide foods that attract reservoir animals such as rodents, opossums, and feral cats.
• Do not provide places for reservoir animals to hide or live.

Control of vectors

• Consult with a veterinarian regarding flea control on pets.