Severe acute respiratory symptoms with coughing, dyspnea, and gasping were reported in
two flocks of 9-day-old Pekin ducklings from different provinces. Gross lesions, white
exudate and mucous membrane congestion in the trachea as well as blue to purple color
changes and sclerosis in lungs were observed. Histological lesions revealed that the
trachea and bronchial epithelium were hyperplastic and infiltrated by neutrophil
granulocytes. Egg drop syndrome virus (EDSV) was differentially diagnosed using
polymerase chain reaction, and the strains were isolated from tracheas and lungs by
inoculation of 10-day-old embryonated duck eggs. The virus isolates were designated
strain D11-JW-012 and D11-JW-017. The clinical and pathological signs were reproduced
by intra-tracheal inoculation of the isolates in 3-day-old ducklings. Although the two
isolates produced similar clinical signs, pathological lesions and ciliostasis, the D11-JW-
017 strain resulted in more severe clinical signs with progressive symptoms compared to
those of D11-JW-012 strain-infected ducklings. We suggest that different EDSV strains
with mild or severe to moderate pathogenicity coexist and have potential risks in poultry.
Hereby, we report an EDSV infection in ducklings.