Layers: FDN and avian hepatitis E

Focal duodenal necrosis and avian hepatitis E are causing problems in laying hens
calendar icon 1 July 2024
clock icon 2 minute read

Editor's note: The following contains content from presentations made during the 2024 Western Poultry Disease Conference.

Focal duodenal necrosis

Focal duodenal necrosis (FDN), an intestinal disease, causes significant economic losses to the table egg industry. However, the etiology and pathogenesis are still unclear, said Yu-Yang Tsai.

Tsai and fellow students at the University of Georgia presented results from a preliminary challenge experiment aimed at replicating the specific lesions of FDN in commercial layers.

Thirty laying hens were divided into five groups. Each group was subjected to 14 days of daily oral challenge using different bacterial cocktails, which included E. coli, Clostridium perfringens, Enterococcus faecium, Gallibacterium anatis, and Clostridium colinum, followed by a one-week pause.

At seven-day intervals, necropsy was performed to examine for pathological changes in the duodenum. Lesions observed included mucosal hyperemia, red foci/patches, and erosions. A notable increase in lesion scores was observed in each treatment group at each interval sampled.

Histopathological analysis revealed villous tip necrosis with mucosal exudate mixed with different shaped bacteria. This pilot study offers valuable insight into replicating FDN in layers.

Avian hepatitis E

Egg laying poultry flocks starting at 40 weeks of age in different states in the U.S. have been dealing with clinical signs, mortality, and economic losses that resemble avian hepatitis E virus infections.

Rodrigo Gallardo, researcher at the University of California-Davis, and fellow researchers at UC-Davis and the University of Maryland screened several flocks for the presence of hepatitis E antibodies. A seroprevalence of 23% was found in the screened flocks.

In addition, a RT-qPCR was used to detect the presence of the virus in liver, spleen, gallbladder, and bile. Upon detection of the virus in organs, an isolation process was started in embryonated SPF eggs via IV and LMH cells.

Since the hepatitis virus shows a fastidious growth behavior in conventional virological cells, the researchers worked on getting the full genome sequence of two avian hepatitis E viruses from bile and liver. The results of this sequencing effort ended in the detection of genotype 2 which was previously reported in the U.S. and genotype 3, new to the country, concluded Gallardo.

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