Avian adenoviral (FAdV-1) ventriculitis in laying hens

Emily Rätsep, Emily Martin, Davor Ojkic, Elizabeth Black

Animal Health Laboratory, University of Guelph, Guelph, ON (Martin, Ojkic), Kemptville, ON (Rätsep); Elfrida Poultry, Caledonia, ON (Black)

AHL Newsletter 2024;28(4):16.

In the late summer of this year, there was an increase in mortality since housing of commercial brown laying hens. The flock was placed at 20.5 weeks, with 0.66% mortality over the ensuing two weeks. Necropsies conducted at 23 weeks of age revealed the majority of birds contained melenic content in the crops, proventriculi and ventriculi. Ulceration and erosions were also observed grossly in the ventriculi. Tissues submitted for histologic examination confirmed an ulcerative and erosive ventriculitis with patchy areas of necrosis (Fig. 1). Within these necrotic regions, there were large, basophilic intranuclear inclusions within the remaining viable epithelial cells. Fowl adenovirus (FAdV) PCR on ventriculus was positive. Hexon-gene sequencing was carried out to determine the FAdV strain, and it was a 100% match to FAdV-1 (CELO).

While fowl adenoviruses are widespread and endemic worldwide, in Ontario they are most commonly associated with necrotizing hepatitis (inclusion body hepatitis). However, since the early 1990s, a FAdV-associated ventriculitis with intranuclear inclusions has been reported in both domestic chickens (broilers and layers) and captive bobwhite quail in multiple countries, including: Japan, Poland, Italy, Germany, Korea, the United Kingdom, the United States of America and Morocco. In each of these cases, reduced weight gain and increased mortality were commonly noted, with grossly apparent melenic crop and gizzard content and proventricular/ventricular ulceration observed on necropsy. In these cases, histological findings confirmed the ulcerative and necrotizing ventriculitis, and large intranuclear inclusion bodies were often observed in mucosal epithelial cells. In all reported cases, the results of ancillary testing showed involvement of FAdV-1. While other FAdV strains were concurrently recovered in some cases, notably FAdV-8a, the few subsequently performed in-vivo trials noted that infection with similar gross and histological findings could be induced in birds with FAdV-1. Some reports indicate that vaccination against FAdV-1 provided protection in young broiler birds.

While these outbreaks noted increased mortality associated with FAdV-1 infection, outbreaks appeared to be sporadic and affected a relatively small proportion of the population. In each case, these outbreaks were described as occurring randomly over a period of years within the affected country, and marked sustained outbreaks were not reported.

Therefore, while ulcerative and necrotizing ventriculitis associated with FAdV-1 infection is only sporadically reported, it should be kept in mind as a differential diagnosis for increased mortality in laying hens or broilers with hemorrhagic/melenic crop and gizzard content. To our knowledge, this appears to be the first report of FAdV-1-associated ulcerative ventriculitis in laying hens in Ontario, Canada. 

Figure 1. Ulcerative and necrotizing ventriculus with intranuclear inclusion bodies in a laying hen. There is ulceration and loss of the superficial mucosa, and remaining epithelial cells contain large basophilic intranuclear inclusions (arrows). H&E stain, 20x.

References

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