The Etiology of Potomac Horse Fever (Ehrlichia Risticii)

Potomac horse fever (PHF) was clinically characterized in 1979. It is fatal in approximately 30 percent of cases. The finding of antibodies to Ehrlichia sennetsu, causative agent of human sennetsu rickettsiosis, in the serum of horses recovering from PHF implicated a rickettsia as the potential causative agent of PHF. A rickettsial agent was subsequently isolated in cultured blood monocytes derived from a pony experimentally inoculated with blood from an acute case of PHF. This isolate was successfully adapted to continuous in vitro propagation in primary canine blood monocytes and the murine macrophage cell line P388D1. Two healthy ponies inoculated with organisms cultured in primary canine blood monocytes developed typical signs of PHF and the organism was reisolated in culture from the blood of both animals, thereby fulfilling Koch's postulates. Light and electron microscopy demonstrated that the morphology and ultrastructure of the organism was consistent with the genus Ehrlichia. The organisms were observed to be contained within a cytoplasmic vacuole and were intermediate in size between E. sennetsu and E. canis, ranging from 0.4 to 0.75 (mu)m in width and from 0.5 to 1.5 (mu)m in length. There was evidence that the organism divided by binary fission.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Veterinary Medical Science

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Holland, Cynthia Jane

• Biology, Veterinary Science

Identifier

(UMI)AAI8623323

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71335