Genetic resistance of chickens to aflatoxin assessed with organ-culture techniques.

A chick tracheal-organ-culture model system was used to evaluate the sensitivity of various strains of chickens to aflatoxin B1. Tissues from different genetic stocks showed highly significant differences in in vitro sensitivity to aflatoxin. Tracheal tissues from brown-egg layers were most sensitive, meat-type birds intermediate, and white-egg layers most resistant. Within-category strains and sex differed significantly in sensitivity to damage by aflatoxin, with male chicks more resistant than female chicks.

Isolation and identification of a turkey respiratory adenovirus.

A virus with physical and biological characteristics of an adenovirus was isolated from turkey poults with respiratory disease. The virus was ether-resistant and incorporated [3H] thymidine. Electron microscopy revealed virions of icosahedral configuration, approximately 78 nm in diameter, within the nuclei of infected cells. The virus produced cytopathology in turkey kidney cells, but did not produce observable disease when inoculated into commercial turkey poults or specific-pathogen-free embryonated chicken eggs. Virus-neutralization tests indicated widespread exposure to the virus in North Carolina turkey populations.

Incidence and distribution of "avian adenovirus group II splenomegaly of chickens".

Forty-six percent of 3,585 serum samples from 174 broiler-breeder chicken flocks in 9 states were positive for the precipitating antibody of hemorrhagic enteritis (HE) of turkeys/marble spleen disease (MSD) of pheasants. Seroconversion was detected only in flocks 19 weeks of age and older. The percent of individual serum samples positive within a flock increased with the age of the flock.

Influence of some physical factors on survival of Marek's disease vaccine virus.

Cell-associated Marek's disease (MD) vaccine was suspended at dilutions normally used for vaccination in seven commercially available diluents and in tryptose phosphate broth. The stability of diluted vaccines was determined by assay in cell cultures subjected to 0 to 37 C for 0 to 90 minutes. Optimum holding temperatures for MD vaccine virus survival varied with the specific diluents employed. Some diluents afforded greatest survival when dilution was at 0 C and held at 0 C, while others performed best when dilution was at 25 C followed by cooling and holding at 0 C. Diluents which allowed greatest survival when tested at 37 C also performed well under other temperature regimes. Spectinomycin dihydrochloride pentahydrate and various buffering compounds were added to commercial diluents used for diluting MD vaccine. Additives producing osmolality of 745 mOsm/kg and higher markedly reduced vaccine virus survival. The adverse effects of high osmotic pressure were accentuated by extended holding time, elevated incubation temperature, and physical manipulations including mechanical mixing or expressing through a syringe and needle. Satisfactory MD vaccine virus survival was afforded by a commercial diluent especially formulated to accommodate the pH osmolality changes produced by adding spectinomycin dihydrochloride pentahydrate.

Homidium (ethidium) bromide inhibition of avian reovirus replication.

Homidium bromide inhibited replication of avian reovirus in cell culture. Inhibition was dose dependent, and the critical event required that the dye be present during the replicative viral cycle and was not attributable to a cellular function.

Use of Japanese quail embryo fibroblast cells for propagation and assay of turkey herpesvirus FC-126.

Japanese quail (Coturnix coturnix japonica) fibroblast cell culture monolayers were found to provide a very satisfactory system in which to propagate and assay turkey herpesvirus FC-126, which is used for production of Marek's disease vaccine. Japanese quail cells were more sensitive than duck cells and of approximately equal sensitivity to chicken cells. Foci of infection developed rapidly and uniformly, were of larger size, and were more easily discernible in quail cells than in chicken cells.

Neural disturbances in chickens caused by dietary T-2 toxin.

Graded concentrations of dietary T-2 toxin (0, 1, 2, 4, 8, and 16 mug/g) were fed to groups of 40 chickens. T-2 toxin was found to cause an abnormal positioning of the wings, hysteroid seizures, and impaired righting reflex in young chickens. The abnormal wing positioning occurred spontaneously or as the result of dropping from a height of 1 meter. The seizures could be elicited by rough handling or loud noises. The seizures and the abnormal wing posture would not occur again when the stimulus was repeated unless a rest period of 3 to 6 h was allowed. The loss of righting reflex could be demonstrated at any time. The total incidence of neural symptoms was dependent on the length of exposure to T-2 toxin and to its concentration. Neural toxicity occurred at dosages of 4, 8, and 16 mug per g of diet, which are the same doses that retard growth. This neural toxicity of T-2 toxin in chickens is similar to the neural disturbances associated with alimentary toxic aleukia, a nutritional toxicosis of humans produced by eating moldy grain. T-2 toxin has been implicated also in moldy corn toxicosis which has neural manifestations in horses and swine.