An experimental model of human body louse infection with Rickettsia prowazekii

Rickettsia prowazekii is transmitted to humans by the body louse. A new experimental model of body louse infection with R. prowazekii is reported here. Eight hundred human lice were infected by feeding on a rabbit that was made bacteremic by injecting 2 × 10⁶ plaque-forming units of R. prowazekii. The bacterium invaded the stomach cells and was released in feces, in which it was detected 5 days after infection. At day 6 after infection, as a result of the cell burst and the spread of erythrocytes in the hemolymph, the louse became bright red and died within 4 h. The life span of infected lice was shortened by 20-23 days, compared with that of uninfected control lice. Infected lice did not transmit R. prowazekii to their progeny. Through cell culture, rickettsiae were cultivated from fecal samples up to 10 days after their emission. The administration of doxycycline to the rabbit during louse feeding did not cure lice from R. prowazekii infection.