370
Possible Existence of Fowl Paralysis
old chicks. Most of the cases occur soon after the pullets are in full lay, after
the first moult and after the breeding season in the case of cockerels. It
has been suggested that the disease may not be infectious or contagious as
only a few birds in a flock become affected at a time and by the end of a season
from 5 to 50 per cent of the whole flock may have suffered. But, Williams.
Gildow and Lampman [1938] have stated that it is transmitted by contact
and that up to 40 per cent of pullets from susceptible flocks became affected
when placed with affected chicks. Chicks from paralysis-affected stock are
more resistant than those from paralysis-free stock and those bred from pullets
are more susceptible than those bred from two-year old hens.
Symptoms and lesions will depend upon the parts and the nerves involved.
Affected fowls may, therefore, show a variety of symptoms. The paralysis
form is first shown by drooping of one or both wings, partial
lameness in one or both legs, or paralysis in one wing and one leg.
In the beginning lameness may pass off only to recur again. In ad-
vanced cases as the affected parts get completely paralysed the bird is unable
to move and lies in a helpless condition, often with one leg stretched forward as
far as possible and the other stretched backward to its full length. Frequently
the digits are paralysed and incapable of being extended—-a ' clutching claw '
attitude. At other times the leg appears incapable of being extended upon
the thigh. Many other types of paralysis may be observed depending on the
nerves involved and muscles supplied by them. The muscles of the affected
leg or wing shrink and cause the part to be withered. The affected birds
usually remain bright in appearance until the disease is well advanced. The
normal reddish grey eyes are changed to grey-pale pearly eyes. In addition
the ' diaphragm ' action of the iris, i.e. visual accommodation fails and the
pupil gets distorted and fixed becoming oval in shape and fails to respond to
bright light. The visual power of the eyes is lost and the birds may become
completely blind. Occasionally birds may be found exhibiting signs of paraly-
sis of the head and neck when the brain and spinal cord are involved. The head
may hang over to trail on the ground, the neck may jerk spasmodically. In
severe cases somersault movement takes place when the bird is handled. When
the digestive tract is involved indigestion occurs and it may cause loss of condi-
tion. The crop may be found flaccid and distended. Usually diarrhoea
occurs but as the disease progresses constipation and impaction of the various
parts of the alimentary tract may occur. Collections of lymphoid cells may
occur in organs like liver, kidney and lungs and produce consequent symptoms.
Occasionally gasping may be noticed. Kidney lymphomata sometimes cause
direct pressure on the leg nerves because of their increase in size. Tumours
which are often associated with this disease may be found in any part of the
body Affected birds do not usually die in large numbers but may linger
for weeks or sometimes months provided they get access to food. Sometimes
an anaemic or leukaemic condition may also be noticed when the affected birds
appear pale about the head, show loss in weight, and become gradually weaker
and die.
On post mortem examination the most constant changes are to be found
in the nervous system. The nerves supplying the affected legs and wings are
found to be enlarged. Barber [1939] has described a method of diagnosis