Biochemical and hormonal changes associated with experimental infection of chicks with infectious bursal disease virus

Host stress response is important for the pathogenesis of the deadly amphibian disease, Chytridiomycosis, in Litoria caerulea

Chytridiomycosis, a disease caused by Batrachochytrium dendrobatidis, has contributed to worldwide amphibian population declines; however, the pathogenesis of this disease is still somewhat unclear. Previous studies suggest that infection disrupts cutaneous sodium transport, which leads to hyponatremia and cardiac failure. However, infection is also correlated with unexplained effects on appetite, skin shedding, and white blood cell profiles. Glucocorticoid hormones may be the biochemical connection between these disparate effects, because they regulate ion homeostasis and can also influence appetite, skin shedding, and white blood cells. During a laboratory outbreak of B. dendrobatidis in Australian Green Tree Frogs, Litoria caerulea, we compared frogs showing clinical signs of chytridiomycosis to infected frogs showing no signs of disease and determined that diseased frogs had elevated baseline corticosterone, decreased plasma sodium and potassium, and altered WBC profiles. Diseased frogs also showed evidence of poorer body condition and elevated metabolic rates compared with frogs showing no signs of disease. Prior to displaying signs of disease, we also observed changes in appetite, body mass, and the presence of shed skin associated with infected but not yet diseased frogs. Collectively, these results suggest that elevated baseline corticosterone is associated with chytridiomycosis and correlates with some of the deleterious effects observed during disease development.

In vitro effects of some steroidal hormones on the replication of avian pneumovirus

The effects of testosterone, oestradiol, progesterone and cortisone on the in vitro replication of avian pneumovirus in tracheal organ cultures (TOC) were investigated. Samples of cell-associated and cell-free virus from TOC, grown in medium containing these hormones, were taken at selected intervals. Progesterone and cortisone caused a slight increase in cell-associated virus. Testosterone and oestradiol caused a slight delay and decrease in virus replication when compared with the controls. All groups shared the same time interval to reach peak cell-free virus titre, 96 h post inoculation. In comparison with the controls, only a small drop (0.25-0.50 log10) in the peak of virus titre was observed in the hormone treated groups.