One-day-old chicks, inoculated intramuscularly (i.m.) with the chicken
anaemia virus (CAV) isolate 10343, showed depression of body weight g
ain and anaemia, particularly between days 14 and 21 post-inoculation
(p.i.). The weights of thymus and bursa were substantially reduced com
pared to controls at days 14 and 21 p.i. The histological lesions dete
cted in thymus, bursa, spleen and liver were similar in frequency at d
ays 14 and 21 p.i. Eosinophilic intranuclear inclusion bodies, lymphoc
yte depletion, and focal necrosis were detected in the thymus, spleen,
bursa and liver of more than 50% of the inoculated chicks at days 14
and 21 p.i. Focal necrosis and vacuolar degeneration in the liver, as
well as apoptosis in different organs were more evident at days 14 and
21 p.i. Ten-week-old broiler breeders, inoculated i.m, with isolate 1
0343 showed pathological changes that were less severe than the change
s shown by 1-day-old chicks. No anaemia could be detected in this grou
p. However, severe thymus atrophy, and histological lesions in bursa,
spleen, and liver, were also evident at days 14 and 21 p.i. in some of
the inoculated birds. Viral detection by immunofluorescence using a m
onoclonal antibody revealed a wide distribution of the CAV isolate. CA
V antigen was detected until day 21 p.i, in thymus, spleen, bursa and
liver. According to the severity of the lesions shown by 1-day-old chi
cks, the length of the period in which CAV antigen could be detected i
n tissues, and the fact that CAV isolate 10343 was capable of inducing
disease in 10-week-old chickens, it seems that this CAV isolate may b
e particularly virulent.