PATHOLOGICAL AND MOLECULAR DIAGNOSIS OF CHICKEN INFECTIOUS ANEMIA IN COMMERCIAL CHICKEN
Loading...
Files
Date
2024-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
SRI VENKATESWARA VETERINARY UNIVERSITY, TIRUPATI - 517 502. (A.P.) INDIA
Abstract
In the present study, a total of 217 commercial chicken among 50 chicken flocks
were suspected for CIA based on history and clinical signs. CIA was diagnosed in 135
birds including 116 layers (71.6%) and 19 broilers (34.5%) with an overall prevalence
of 62.2% based on hematology, gross lesions, histopathology, electron microscopy and
molecular studies.
Out of 116 CIA cases in layers the highest prevalence was recorded in East
Godavari (90.47%), followed by Chittoor (81.81%), Kakinada (80%) and lowest in
Eluru (52.38%). The prevalence of CIA in broilers was found highest in East Godavari
(39.1%) followed by Chittoor (38.88%) with lowest prevalence in Visakhapatnam
(21.42%). In the present study, age wise prevalence of CIA in commercial chicken
showed highest prevalence in layer growers of 5-16 weeks of age (79.8%) and the
lowest prevalence in layer chicks aged ≤4 weeks age (27.2%).
Concurrent infections with other bacterial (36.3%), viral (24.2%), protozoal
(28.7%) infections were noticed with overall occurrence of 48.88%. Concurrent
infections were confirmed in layer growers (55.17%), layer adults (42.30%) followed
by broiler chicken (42.1%) and layer chick (33.33%).
The commercial chicken affected with chicken infectious anemia exhibited pale
comb and wattles, anorexia, generalised weakness, decline in egg production and
ruffled feathers. Blood samples collected randomly from the birds suspected for CIA
grossly appeared as watery contents and there was a significant decline in the
Hemoglobin concentration (5.56 ± 0.29 g/dl), PCV (17 ± 0.79 %) and TEC (1.46 ±
0.09 x 106/µL) in CIA affected flock when compared to that of healthy flocks.
Grossly, CIA affected chicken exhibited small, shrunken thymus and bursa. Pale
pink to yellow discoloration of bone marrow of femur along with oily jelly to watery
like consistency was observed. Atrophy of spleen was noticed in many cases whereas
enlarged pale livers and swollen pale kidneys were observed in few cases. Petechiae to
patchy hemorrhages on thigh muscle, breast muscles and in the oral cavity were also
noticed. Cytologically, bone marrow collected from affected chicken revealed presence
of vacuolar spaces due to replacement of hematopoietic tissue by adipose tissue.
Thymus sections revealed multiple hemorrhages along with moderate to severe
depletion of lymphocytes in cortex and medullary areas and apoptotic changes in
nucleus like pyknosis and karyorrhexis in thymic lymphocytes whereas few
lymphocytes exhibited the presence of eosinophilic, intranuclear inclusion bodies. All
the sections from bone marrow of femur revealed aplasia of all cell types including
granulocytic, agranulocytic and hemopoietic precursors along with complete
replacement of bone marrow by adipose tissue in the form of vacuolar spaces.
Hemocytoblast cells with more cytoplasm and large nuclei revealed eosinophilic,
intranuclear inclusions.
Bursa of Fabricius showed moderate atrophy of lymphoid follicles, cystic
changes in bursal follicles. Spleen revealed moderate to severe lymphoid depletion in
white pulp along with proliferation of macrophages, reticular cells and hemosiderosis.
Severe congestion of blood vessels, multiple hemorrhagic foci and degenerative
changes were noticed in tissue sections of liver and kidneys.
In the present study, different concurrent infections were noticed in 66 CIA
affected commercial chicken. Marek’s disease was confirmed in a total of 16 cases
revealing neoplastic nodules on liver and heart. Tissue imprints revealed numerous
pleomorphic cells and histologically, infiltration of neoplastic lymphoid cells in hepatic
parenchyma and myocardium was noticed. Different bacterial diseases included
fibrinopurulent serositis (12), gangrenous dermatitis (7) and Fowl Cholera (5).
Protozoal infections like intestinal and caecal coccidiosis (19) were also recorded.
Fibrinous pericarditis revealed fibrinous exudation along with inflammatory cell
infiltration in pericardium and samples collected from these lesions yielded
characteristic green metallic sheen colonies on EMB agar confirming E.coli.
Gangrenous dermatitis appeared as dark, moist lesions at the base of the wing
indicating blue wing. Necrotic and inflammatory changes were evident in subcutaneous
tissue and lesions yielded Gram positive cocci suggestive of Staphylococcal infection.
Multiple hemorrhagic foci on epicardium and numerous necrotic foci on liver were
noticed in Fowl cholera. Microscopically, hemorrhages and necrotic changes were
observed in heart and liver. Tissue imprints of heart revealed presence of bipolar
organisms and swabs collected revealed non hemolytic colonies on blood agar
suggestive of Pasteurellosis. Distended intestinal segments and caeca along with
hemorrhagic and necrotic contents were suspected for coccidiosis. Intestinal and caecal
mucosal scrapings revealed presence of different stages of coccidia suggestive of
Eimeria Spp. Severe hemorrhages and necrosis in mucosa and submucosa along with
presence of different stages of coccidia was evident.
Five thymus and three bone marrow samples collected from CIA affected birds
were subjected to TEM and revealed severe scarcity of cells and presence of apoptotic
changes in the nuclei and intranuclear viral inclusions. Apoptotic thymocytes revealed
chromatin aggregation as large, dark condensed masses that abut the nuclear membrane.
Bone marrow samples revealed large adipose cells replacing the bone marrow whereas
few electron dense viral aggregates in the nucleus of hemocytoblast are also observed.
In the present study, molecular diagnosis of CIA disease in commercial chicken
was carried out using thymus, bone marrow, spleen and liver tissue samples for
amplification of VP1, VP2 and VP3 genes of Chicken infectious anemia virus by
specific primers and yielded amplicons of size 1390 bp for VP1 gene, 713 bp and 367
bp for VP2 and VP3 genes respectively confirming the presence of CIA viral DNA in
the samples.
In conclusion, the present study has defined characteristic gross and microscopic
features of CIA in commercial chicken and diagnosis was done based on PCR by
amplification of VP1, VP2 and VP3 genes of CIAV.