Experimental infection study
The
aim of the study was conducted to determine the pathogenicity of the
isolate. The specific pathogen free (SPF) duck embryos were obtained
from a hatchery (Harbin Veterinary Research Institute). Newly hatched
SPF ducklings were moved in SPF negative pressured isolators. Twenty
1-day-old SPF ducklings were infected by subcutaneous injection with 0.2
ml of the isolated virus (DAstV-SDZZ strain; 5×104.8TCID50/0.1ml) as the experimental group, while the other
ducklings (n = 20) were inoculated with sterile phosphate buffered
saline (0.2 mL) in the same manner as the control group. Clinical signs
and mortality of ducklings were monitored daily. Survival birds were
euthanized at 15 days after inoculation. Dead birds were necropsied
immediately for histopathological observation and virus identification.
All ducklings were bred and cared for in accordance with humane
procedures.