Showing papers by "Michael L. Perdue published in 1991"

Measurement of avian embryo movement in intact eggs

Abstract: The present invention provides measurement of avian embryo movement in intact eggs by: directing light into and through at least one intact avian egg, with light of sufficient intensity and duration to stimulate embryo movement, whereby portions of the light exit the at least one intact avian egg; sensing instantaneous intensities of the portions of the light exiting each of the eggs, and; determining a ratio of, range of sensed light intensities (I R ) to average sensed light intensities (I A ), for each of the eggs. The ratio of I R :I A is a measure of avian embryo movement.

Emergence of highly pathogenic virus during selective chicken passage of the prototype mildly pathogenic chicken/Pennsylvania/83 (H5N2) influenza virus.

Abstract: The prototype mildly pathogenic A/chicken/Pennsylvania/21525/83 (H5N2) avian influenza virus, which was isolated more than 5 months before the emergence of highly pathogenic virus in the major 1983 Pennsylvania outbreak, was examined for the presence of minority subpopulations of highly pathogenic virus. Selective serial passage of the parental mildly pathogenic virus in leghorn hens did not lead to recovery of highly pathogenic virus. However, several highly pathogenic reisolates were recovered from hens inoculated with either of two mildly pathogenic virus clones selected for their ability to efficiently produce plaques in trypsin-free chicken embryo fibroblasts. Unlike the parental virus, these reisolates caused high mortality in chickens and produced postmortem lesions typical of highly pathogenic avian influenza. Electrophoretic mobilities of the hemagglutinin glycoproteins of the highly pathogenic derivatives resembled those of the prototype highly pathogenic A/chicken/Pennsylvania/1370/83 (H5N2) virus isolated in October 1983. These results suggest that unrecognized subpopulations of highly pathogenic virus may have infected Pennsylvania chickens for several months before emerging as the clinically manifest component of the virus population.

Amantadine resistance among hemagglutinin subtype 5 strains of avian influenza virus.

Abstract: Several avian influenza virus strains of hemagglutinin subtype 5 were assayed for sensitivity to the antiviral drug amantadine. Most strains exhibited little sensitivity to the drug as measured by plaque reduction. The A/Chicken/Scotland/59 (CS59), however, was highly sensitive, making it easily distinguishable from the other H5 strains. Drug sensitivity of the viruses was also assayed in chicken embryos. The in ovo patterns of amantadine sensitivity differed from those detected in cell culture. The CS59 isolate could not be distinguished from all the other strains on the basis of its response to amantadine in ovo. Although amantadine protected chickens inoculated with CS59 from morbidity and mortality, drug-resistant viruses were readily isolated from the infected birds. As found with other amantadine-resistant variants, the structure of the matrix gene was altered in the resistant isolates. These results demonstrate that amantadine resistance is widespread among avian influenza viruses of the H5 subtype, that drug sensitivity in cell culture does not necessarily reflect responses to amantadine in ovo and in vivo, and, as previously found, amantadine-resistant derivatives of H5 strains may be isolated from birds protected by the drug.

Automated monitoring system for determining embryo movement and death times following virus infection.

Abstract: SUMMARY. Design and performance information is presented on an automated embryomonitoring system for intact eggs. The computer-based system has been used successfully for several months to characterize viral pathogenicity in embryonated eggs. Features include electronic sensing of embryo movement, automatic quantification of the amount of movement, and automatic recording of the results on electronic media. The system does not require that eggs be removed from the incubator or that the incubator be opened during the course of an experiment, as is necessary with the manual candling technique. It has greatly improved discrimination of viral pathogenicity effects in fertile eggs because of its sensitivity and reduced intervals between observations. One important potential application involves using the system to measure the effects on virulence of mixing closely related variants of the same strain of virus that differ in pathogenicity, which is the biological scenario most likely approximating a natural disease outbreak.