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Published on: December 1, 2023
An experimental model of human body louse infection with Rickettsia prowazekii
Linda Houhamdi1, Pierre-Edouard Fournier, Rong Fang
1Unité des Rickettsies, Institut Fédératif de Recheche 48, Centre National de la Recherche Scientifique, Université de la Méditerranée, Marseille, France.
Abstract:
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 2x106 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.
Insights
A new experimental model shows body lice infected with Rickettsia prowazekii die rapidly due to bacterial invasion. Infected lice did not transmit the bacteria to offspring, and doxycycline treatment was ineffective.
Area of Science:
- Vector-borne diseases
- Microbiology
- Parasitology
Background:
- Rickettsia prowazekii is the causative agent of epidemic typhus.
- Human body lice (Pediculus humanus humanus) are vectors for R. prowazekii transmission.
- Existing models for studying louse-borne Rickettsia infections are limited.
Purpose of the Study:
- To establish and characterize a novel experimental model of R. prowazekii infection in body lice.
- To investigate the pathogenesis and transmission dynamics of R. prowazekii within the body louse.
- To evaluate the efficacy of doxycycline in treating R. prowazekii-infected lice.
Main Methods:
- Infection of 800 human body lice by feeding on a bacteremic rabbit inoculated with R. prowazekii.
- Monitoring of R. prowazekii presence in louse feces via culture.
- Observation of louse mortality, lifespan, and pathological changes.
- Assessment of transovarial transmission of R. prowazekii to progeny.
- Administration of doxycycline to the host rabbit during louse feeding.
Main Results:
- R. prowazekii successfully infected body lice, invading stomach cells and being excreted in feces starting at day 5 post-infection.
- Infected lice exhibited pathological signs, including erythrocyte spread in hemolymph, leading to death within 4 hours by day 6.
- The lifespan of infected lice was reduced by 20-23 days compared to controls.
- R. prowazekii was not transmitted to the progeny of infected lice.
- Rickettsiae were culturable from fecal samples up to 10 days after excretion.
- Doxycycline treatment of the host rabbit did not eliminate R. prowazekii infection in the lice.
Conclusions:
- The developed experimental model effectively replicates R. prowazekii infection in body lice, demonstrating rapid mortality and significant pathological changes.
- R. prowazekii infection in body lice is lethal and does not appear to be transovarially transmitted under these experimental conditions.
- Doxycycline administered to the host is not effective in curing lice of R. prowazekii infection, highlighting potential challenges in vector control strategies.
