Anaplasmataceae pathogens : transmission, pathogenesis, and control

The family Anaplasmataceae is comprised of several genera of obligate intracellular, Gram-negative bacteria. Within these families can be found the genera Ehrlichia and Anaplasma to which belong the bacterial pathogens Ehrlichia ruminantium, Anaplasma phagocytophilum, and Anaplasma marginale. These three pathogens are considered to be of high agricultural, economic, as well as medical importance in the case of the zoonotic A. phagocytophilum. The focus of the studies here enclosed are: 1st to define the transmission and pathogenesis of E. ruminantium by a potential North American native tick vector Amblyomma maculatum; 2nd to advance the study of a modified live vaccine candidate for A. marginale in the context of tick transmission of the wild-type challenge; 3rd to develop and evaluate a modified live vaccine candidate for A. phagocytophilum; and 4th to establish methods for viable storage of vaccine candidate strains suitable for distribution. We found that: 1st while E. ruminantium can be maintained and transmitted by A. maculatum ticks, that the infection of sheep with this pathogen was unable to cause acute or severe disease; 2nd the modified live vaccine candidate stimulated protective immunity against tick transmission challenge with wild-type A. marginale; 3rd we developed a modified live vaccine candidate A. phagocytophilum that stimulated protective immunity against subsequent wild-type challenge; and 4th found that host-cell-free bacterial stocks maintain viability at -80 degreesC and also when lyophilized. These studies significantly advance the field in regards to vaccine development and storage.