Study helps scientists understand scrub typhus

Scientists funded by the U.S. military and the U.K.-based Wellcome Trust recently conducted a study to better understand scrub typhus, a potential biological weapon that could be used by terrorists.

Scrub typhus is an endemic disease of the Asia-Pacific region caused by Orientia tsutsugamushi. The infectious disease spreads from field mice and rats to humans when mites that live on the animals bite humans. The scientists conducted the study to better understand the infection's initial host-pathogen interaction.

The researchers tested the early bacteria dissemination of three human pathogenic strains of O. tsutsugamushi using a CD-1 Swiss outbred mouse model following intradermal injection of the pathogen. By determining the early infection characteristics associated with the bacterial virulence of the pathogen, scientists may have the necessary information to create a suitable countermeasure.

The CD-1 mouse intradermal inoculation model exhibited features that are relevant to early scrub typhus infection in humans, including the development of distant organ dissemination, leukocyte activation and regional lymphadenopathy.

The researchers said that additional investigations into the host innate immune response at the inoculation site will need a more suitable animal model. The suitable animal model could help them determine how to create a protective immune response.

The study was funded by the U.S. Military Infectious Diseases Research Program and the Wellcome Trust. The study was published in the January 16 issue of PLoS ONE.

The O. tsutsugamushi pathogen can have a case fatality rate of 50 percent in untreated patients.