Acknowledgments
This work was funded by the Consejo Nacional de Ciencia y Tecnología,
México, through an Institutional Links grant: FONCICYT 277863; and the
Birtish Council, through Institutional Links Newton Grant 276305277.
The authors wish to thank colleagues at INIFAP, Queretaro for the
excellent care and upkeep of the animals used in this experiment and all
their help with the collection and processing of samples. The authors
also wish to thank Mr Alejandro Nava and Ms Itzel Jiménez for their help
in the handling of the animals at the time of inoculation.