Week 41: Fowl Adenovirus Appears to Rarely Spread Through Eggs
A new doctoral thesis from the Swedish University of Agricultural Sciences (SLU) and the Swedish National Veterinary Institute (SVA) provides new insights into how fowl adenovirus (FAdV) spreads among Swedish broiler chickens and their parent flocks. The virus can cause severe liver damage and lesions in the gizzard.
How was the research conducted?
The thesis brings together several studies involving healthy and diseased Swedish broiler chickens and breeding birds. One study analysed blood samples from 1,910 parent birds, along with tissue samples from a total of 1,029 embryos and chicks that died before hatching.
What is new?
The virus was detected in young parent birds as early as six weeks of age, and 94% of the examined flocks had developed antibodies by 16 weeks of age. However, FAdV was not detected in any of the examined embryos or chicks that died before hatching.
The findings suggest that parent birds typically become infected and develop immunity before they begin laying eggs. These antibodies may then help protect their offspring against transmission through the egg. Horizontal transmission between birds and through the poultry house environment may therefore play a more important role than previously assumed
Strength of evidence
Moderate to relatively strong for Swedish commercial broiler lines. The research includes extensive data based on serology, PCR testing, necropsies, and viral sequencing. The absence of detectable virus in 1,029 samples is a significant finding, but it does not prove that vertical transmission through eggs never occurs. The researchers also emphasise that high antibody levels do not always guarantee protection.
What does this mean for backyard flocks?
The findings primarily concern commercial broiler chickens and cannot automatically be applied to other breeds. Nevertheless, they reinforce the importance of cleaning, quarantine, and controlling potential routes of transmission, including equipment, footwear, and other contaminated materials.
