This is a disease discovered in the USA and only the chicken is naturally infected. The virus can remain latent (dormant) in the chicken for several months.

How common?

Unfortunately it is getting more so as people mix hens from different sources without quarantining them. The airborne route of transmission is the commonest. Beware of sales and auctions.


Respiratory signs are more severe in young chicks with growth retardation, and the reproductive problems are usually caused by very early exposure to the virus. A coronavirus is the cause which may locate in the respiratory or reproductive tract or the kidneys. Infection may not show symptoms or may show respiratory signs which last only a few days, or reproduction disease, mainly mis-shapen, wrinkly or shell-less eggs with watery whites.


Direct airborne transmission from the respiratory tract is most common but infected faeces can spread the virus and equipment is also implicated in transmission. The infection spreads rapidly in 1-3 days. If no other disease is present (especially mycoplasma) then the respiratory signs can last 10-14 days. A hen laying mis-shapen eggs may be shedding the virus.


Supportive treatment of antibiotics in the respiratory stage will prevent pathogenic bacteria multiplying. There is no treatment once the shell gland is affected.


If hens are kept regularly wormed, properly fed and with minimal stress, they may not succumb to the virus. A short respiratory problem is a warning sign. If action is taken early, the virus may not cause a shell problem.

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