Dynamics of Yersinia pestis and Its Antibody Response in Great Gerbils (Rhombomys opimus) by Subcutaneous Infection

BACKGROUND: Rhombomys opimus (great gerbil) is a reservoir of Yersinia pestis in the natural plague foci of Central Asia. Great gerbils are highly resistant to Y. pestis infection. The coevolution of great gerbils and Y. pestis is believed to play an important role in the plague epidemics in Central Asia plague foci. However, the dynamics of Y. pestis infection and the corresponding antibody response in great gerbils have not been evaluated. In this report, animal experiments were employed to investigate the bacterial load in both the liver and spleen of infected great gerbils. The dynamics of the antibody response to the F1 capsule antigen of Y. pestis was also determined. METHODOLOGY: Captured great gerbils that tested negative for both anti-F1 antibodies and bacterial isolation were infected subcutaneously with different doses (10(5) to 10(11) CFU) of a Y. pestis strain isolated from a live great gerbil during routine plague surveillance in the Junggar Basin, Xinjiang, China. The clinical manifestations, changes in body weight, anal temperature, and gross anatomy of the infected animals were observed. The blood cell count, bacterial load, and anti-F1 antibody titers were determined at different time points after infection using a blood analyzer, plate counts, and an indirect hemagglutination assay, respectively. CONCLUSIONS/SIGNIFICANCE: The dynamics of bacterial load and the anti-F1 antibody concentration in great gerbils are highly variable among individuals. The Y. pestis infection in great gerbils could persist as long as 15 days. They act as an appropriate reservoir for plague in the Junggar Basin, which is part of the natural plague foci in Central Asia. The dynamics of the Y. pestis susceptibility of great gerbil will improve the understanding of its variable resistance, which would facilitate the development of more effective countermeasures for controlling plague epidemics in this focus.