Influence of the Addition of Antibiotics on Survival of Herpesvirus of Turkeys

Abstract

To determine the influence of the antibiotics ceftiofur sodium from two different laboratories (A and B) and gentamycin sulfate on a Marek's disease commercial vaccine herpesvirus of turkey (HVT), samples were assayed by titration in chicken embryo fibroblasts (CEF). Viruses were tested in vitro to establish the average number of plaque-forming units before and after different periods of incubation with the addition of the antibiotic. These tests showed no effect of gentamycin or ceftiofur A or B on HVT titers when treatments were for 1 hr or less. However, ceftiofur B decreased the titer at 2 hr. The in vivo effects of the antibiotics were determined by vaccinating 15 one-day-old chickens with HVT plus gentamycin or ceftiofur A or B. Birds were considered viremic at 1 wk postvaccination when one or more plaques were detected in CEF 5 days after inoculation of peripheral blood lymphocytes. Viremia levels were similar between 1 and 16 wk after vaccination with HVT with ceftiofur A or B. The pH values (7.5) were the same in vaccines with and without antibiotics.