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Title: Studies of the epidemiology, causation and transmission of Potomac Horse Fever
Author: Perry, Brian Derek
ISNI:       0000 0000 8316 385X
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1987
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A newly recognized disease of horses, called Potomac Horse Fever (PHF), emerged during the late 1970's in a region close to the Potomac River near Washington, D.C., United States of America. The studies which were carried out by a research group to define the epidemiology and establish the cause of the disease are described. Further studies examined the possible route of transmission of the causative organism, and the role of farm animals and wild rodents in the epidemiology of the disease. Results of a case-control study conducted in 1983 characterised the disease as a non-contagious, infectious seasonal disease of horses of all age, sex and horse-use categories. The study found a lack of association with most of the variables studied, and assisted in discounting some of the numerous aetiologies proposed at the time. The results showed positive associations with a few variables, which included the previous presence of the disease in a barn, the presence of other livestock and the presence of habitats favourable for arthropod breeding and development. The disease was established experimentally in ponies following blood transfusion from natural cases of PHF, an Ehrlichia was isolated from the white blood cells of the experimentally infected ponies and this organism subsequently reproduced the disease on inoculation into susceptible ponies. The experimental disease was consistent with that seen in field cases. Pathological studies on the disease were carried out, and the causative Ehrlichia was identified on the wall of the large intestine of affected animals. Experiments established that the intradermal route was effective in transmitting the disease to ponies. A serological survey of farm animals and wild rodents from affected farms showed no indication of previous exposure to the causative Ehrlichia in 98% of samples tested. None of the mammalian species studied appears to serve as a reservoir of the infection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.V.M.&S.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Horse disease epidemiology