Isolation, identification and pathogenicity analysis of a virulent duck enteritis virus strain causing outbreaks in vaccinated duck flocks

Figures

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  Fig. 1. Clinical autopsy and PCR identification. (A) Clinical manifestations and macroscopic pathological alterations in ducks infected with DPV on a commercial duck farm in Henan Province: Affected ducks exhibited lacrimation with tear stains (red arrow), eyelid hemorrhage (yellow arrow), rectal and cloacal hemorrhage (green arrow), splenomegaly with infarction (blue arrow), esophageal hemorrhage and ulceration (white arrow), hepatic necrosis (orange arrow), proventricular papillary hemorrhage (purple arrow), and duodenal annular hemorrhage (black arrow). (B) Results of exogenous virus screening and identification (Lane 1 - 4: duck Tembusu virus; Lane 5 - 8: avian influenza virus; Lane 9 - 12: waterfowl-origin reovirus; Lane 13 - 16: duck hepatitis A virus (DHAV); Lane 17 - 20: duck circovirus; Lane 21 - 24: duck astrovirus). (C) PCR identification results of the samples (Lane 1 - 3 represent the collected samples, and Lane 4 is the negative control). (D) PCR identification results of duck embryo and allantoic fluid (Lane 1 - 3: Mixture of duck embryo liver and spleen; Lane 4 - 6: Allantoic fluid; Lane 7: Negative control). (E) Lesions in duck embryos infected with DPV: In the infected…

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  Fig. 2. Autopsy findings indicated: Ducks in both the challenged and contact-exposed groups exhibited typical clinical signs and lesions of duck plague, including periocular staining (tear tracks, red arrow), hepatic necrosis (orange arrow), splenomegaly (yellow arrow), annular hemorrhages in the intestines (green arrow), and petechial hemorrhages in the esophagus (blue arrow) and proventriculus (black arrow). In contrast, no abnormalities were observed in the control group.

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  Fig. 3. Pathological sections of organs (The scale is 100 μm; magnification for all images: 200 ×): Compared with the blank control group, ducks in both the challenged group and the contact-exposed group exhibited severe pathological changes, including marked hepatic necrosis, extensive congestion and necrosis in the splenic red pulp, prominent intestinal hemorrhage and inflammatory cell infiltration, conspicuous esophageal hemorrhage, and haemorrhage in the proventriculus.

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  Fig. 4. Analysis of All Genes. (A) Full-length nucleotide sequence similarity between the isolate and the reference strain. (B) Phylogenetic tree of the isolated strain.

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  Fig. 5. Nucleotide sequence homology between the virulence protein of the isolate and that of the reference strain.

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  Fig. 6. Amino acid site mutations within the virulence protein of the isolate.