The University of Georgia College of Veterinary Medicine

eorgia Veterinary Scholars Program

GVSP Summer 2007 Scholars

Georgia Veterinary Scholar	Faculty Mentor

Nori Acevedo Tuskegee University Class of 2009	Dr. Mark Jackwood

Experimental infection of domestic dogs with Ehrlichia ewingii

Nori Acevedo , Mark Jacwood , and Deborah A. Hilt

Nori D. Acevedo*, Mark W. Jackwood, Deborah A. Hilt
Department of Population Health, Poultry Diagnostic and Research Center
953 College Station Road,University of Georgia,Athens, GA 30602 USA

Infectious bronchitis virus (IBV) is the etiological agent of infectious bronchitis, a highly contagious upper respiratory tract disease of chickens. Egg adapted vaccines are currently used for control of the disease; however, they can revert to pathogenicity through back passage in chickens. To determine if the rate of viral replication plays a role in pathogenicity, we examined viral replication for pathogenic strains and egg adapted strains of IBV in specific pathogen free (SPF) embryonating eggs and in susceptible SPF chickens. A total of 140 ten-day old embryonating SPF eggs were separated into four groups and inoculated with the following viruses: Massachusetts 41 (Mass 41) vaccine (group 1), Mass 41 pathogenic strain (group 2), Arkansas DPI (Ark-DPI) vaccine (group 3), and Ark-DPI pathogenic strain (group 4). Chorioallantoic fluid from five eggs in each group was harvested at 0, 12, 24, 36, 48, 72, and 96 hours, post inoculation (pi), and viral RNA was extracted, purified, and quantified using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The Mass 41 vaccine virus had a significantly higher replication rate (p³ 0.1) when compared to the Mass 41 pathogenic strain at 24 hours pi. The Mass 41 vaccine, Ark DPI pathogenic strain, and Ark DPI vaccine reached maximum viral titer at 24 hours pi, whereas the Mass 41 pathogenic strain reached maximum viral titer at 36 hours pi. Viral replication rate in one-day old chicks was also studied. Chicks were separated into four groups and inoculated intranasally and intraocularly. Tracheal swabs were taken at 12, 24, 36, 48, 72, 96, and 120 hours pi. Viral RNA was extracted, purified and quantified by real time RT-PCR. The data will be compared to the viral growth rates observed in eggs and the results will be discussed with respect to viral replication rate and pathogenicity in chicks.