Causes of Egg Drop Syndrome (EDS 76)

Egg drop syndrome (EDS 76)
Occurrence: Worldwide, though not reported in
chicks in US. The virus has been isolated from
non-symptomatic migratory ducks in the US.
Species affected: Laying chickens, ducks,
guinea fowl.
Age affected: Adult.
Causes: Avian adenovirus.
Effects: Incubation period is 7-9 days. Loss of
colour in pigmented eggs, thin-shelled, soft-
shelled or shell-less eggs and a reduction in
production up to 40%. Watery albumin and
reduction in egg size. Inappetance, dullness
and diarrhoea may occur.



Causes
Egg drop
syndrome is
an acute to
chronic
disease
affecting
laying birds,
ie. laying
chickens,
ducks and guinea fowl. It is
caused by the avian adenovirus,
which is 70-75nm in length. All
chickens are susceptible, but
brown layers are most
susceptible.
It can spread vertically through
the embryonated egg, by
faecal-oral routes, and by
contaminated water. Wild
ducks, geese, gulls, owls,
storks, swans and egrets can
transmit the virus mechanically.

Clinical signs
There is a 7-9 day incubation
period. Signs include loss of colour in
pigmented eggs, thin-shelled, soft-shelled or
shell-less eggs and a reduction in production up
to 40%. Watery albumin and a reduction in the
size of the egg, inappetance, dullness and
diarrhoea may occur.
Postmortem lesions
Lesions include inactive ovaries and atrophied
oviducts, uterine oedema, exudate in the shell
gland, flaccid ovules and a mild splenomegaly
(enlarged spleen).

Diagnosis
Clinical signs, gross lesions, and inclusion
bodies in the epithelial cells of the shell gland
are diagnostic.
Isolation and identification of
haemagglutination virus in embryonated duck
eggs is also important.
Immunofluorescent staining of fluids with
specific conjugated antisera, and the
Haemagglutination-inhibition test and ELISA to
check for antibody in blood are also helpful. It
simulates IB.

Treatment & control
Prevention
Biosecurity is important. A killed vaccine can
be given during the pullet-rearing phase to help
prevent the disease.