Epidemic typhus A75.9

Very rare rickettsiosis (Rickettsia typhi) transmitted from rats to humans by the rat flea, the clinical symptoms of which resemble those of classical epidemic typhus. However, the symptoms are less pronounced and the course is rather benign.

The reservoir for the pathogen Rickettsia typhi are mainly rats, from which the bacteria are transmitted to humans through the faeces of fleas.

The disease prefers warm zones or seasons and, unlike classical typhus, occurs singly or in small group cases. The diagnosis is confirmed by a blood test.

Epidemic typhus and endemic (murine) typhus are clinically, pathologically and serologically similar. Human epidemic typhus was probably a human-louse-man chain of infection without an animal reservoir. This concept is now being challenged. Antibodies to R. prowazeki have been detected in farm animals in Africa, in rats in Manila, and in flying squirrels and humans in the United States. R. prowazeki has been recovered from blood samples of goats, sheep, from ixodid ticks, lice, and flea ectoparasites of flying squirrels, and from tissues of flying squirrels. More than 20 cases of acute epidemic typhus from flying squirrels have been reported in the United States. R. prowazeki has not been detected in human cases. Chemical studies of R. prowazeki and R. typhi show genetic similarities, but differences in genome size and degree of hybridization suggest that conversions between the two pathogens do not occur rapidly in nature.