Feather insights could curb spread of poultry virus

Producing poultry with limited capacity to shed virus in their feather dust could help improve protection against a highly contagious viral infection, research shows.

Roslin scientists have found that while vaccination and genetic resistance protected individual birds from Marek’s disease, only vaccination significantly reduced the amount of virus released into the environment through feather dust, confirming previous findings.

However, current vaccine developments and breeding programmes focus on genes linked to survival and tumour resistance in individual birds, and overlook traits linked to reduced virus spread within flocks.

Feather viral load in birds could be used as a measure to inform breeding programmes and support improved vaccine development, the study team suggests.

Flock-level protection

Researchers sought to identify how virus shedding patterns of infected birds might help manage Marek’s disease, a virus that can trigger cancer-like tumours in poultry. Current vaccines and genetic selection for resistance help prevent illness and death, but do not completely stop virus transmission between birds.

Scientists studied whether vaccination or greater genetic resistance reduces the transmission of the deadly virus to susceptible flock mates, and improves overall survival of the flock.

Hens that had been vaccinated or bred to resist Marek’s disease were less likely to become ill or die following infection compared with unvaccinated or susceptible birds, they found.

Researchers found that vaccinated hens also shed significantly lower levels of virus into the environment.  Although nearly all unvaccinated birds became infected, those exposed to vaccinated birds were less likely to develop disease or die, suggesting that vaccination provided a herd immunity effect within the flock.

In contrast, hens bred for higher resistance to developing Marek’s disease, did not shed less virus into the environment and had no protective effect on their susceptible flock members.

Measuring transmission

Because Marek’s disease virus is shed through feather follicles, feather samples offer a simple, non-invasive way to estimate how much virus a bird is releasing.

Feather viral load could be used as a practical, non-invasive measure to guide breeding programmes and support the development of improved vaccines to curb the spread of this deadly virus.

Selecting birds with lower feather viral load could help reduce the amount of virus circulating within poultry environments and slow down virus evolution,  the research team says.

This study was published in Avian Pathology, in collaboration with colleagues from the US National Poultry Research Center, the Swedish University of Agricultural Sciences, and INRAE, France.

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Research publication