Etio-immuno-pathological studies on chicken infectious anemia: gangrenous dermatitis syndrome in pullets
Vachhani, Kapilkumar (2005) Etio-immuno-pathological studies on chicken infectious anemia: gangrenous dermatitis syndrome in pullets. Masters thesis, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand, Gujarat, INDIA.
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Studies were carried out to detect the etiological agents responsible for the mortality in commercial layer farms around Anand district during the period of November 2002, to October 2004 with considering the immunopathological aspect of the affected birds. The farms having mortality were visited for the collection of data like farm name, system of management, age of affected flocks, vaccination status, total strength of affected flocks, mortality, and for collection of materials like blood and dead carcass for postmortem examination and tissue collection. Total 17 flocks of 11 farms were visited having total strength of 123097 birds. From each flock 10 carcasses were collected for postmortem examination and tissue collection for histopathological examination, bacterial isolation, virus detection and relative organ weight comparisons with one normal healthy flock of same age group. The blood samples were collected from the 10 birds of each flock including healthy flock for haematology and NDHI titer. Results of present study showed that the all 17 flocks having outbreaks were reared in cage system. No outbreaks were recorded in deep litter system. All outbreaks were recorded during April to November with maximum incidence in the month of August indicating hot and humid weather predispose flocks to CIA - GDS. Mortality started in the age group of 8 – 11 weeks and continued for nearly five weeks. The over all mortality recorded in 17 flocks was 8.12 per cent which ranged from 2.55 to 22.94 per cent between different flocks. The skin was purple with loss of feather particularly in rump, breast, wing, head and thigh areas. The skin was moist and soft with haemorrhages and necrosis. Accumulation of serosanguineous exudates was noticed in subcutaneous tissues. The scaly lesion with haemorrhages and necrosis were noticed in toes. In internal organs, the bursa, thymus and spleen were atrophied, and liver showed enlargement. In some birds the necrotic foci on liver and spleen were noticed. There were diffuse or petechial haemorrhages on heart in few birds. The bone marrow was variably pinkish to whitish yellow. The kidneys were pale and enlarged. Histopathological changes included necrosis, haemorrhages with heterophilic infiltration and bacterial microcolonies in dermis and epidermis. Bursa of Fabricius showed atrophy of follicle with lymphoid depletion and interfolicular connective tissue proliferation. Spleen showed lymphoid depletion, necrotic foci, bacterial emboli and RE cell hyper plasia. The thymus showed severe lymphoid depletion and loss of demarcation between cortex and medulla. The bone marrow showed atrophy of haemetopoetic lineage with accumulation of lypocytes as a clear vacuoles. The organ body weight ratio of bursa, thymus and spleen showed significant reduction compared to that of normal healthy birds of same age. This supported gross and microscopic lesions of atrophy. The liver to body weight ratio was observed higher compare to normal. The haemorrhagic data like Hb, PCV, RBC’s and WBC’s counts were significantly decreased compare to that of normal birds. The DLC showed higher value of hetrophil and lower value of lymphocyte supporting the microscopic lesions of lymphoid depletion in thymus, bursa and spleen. The NDHI value during outbreaks and after outbreaks showed lower titer compared to healthy flock indicating lower humoral immune response. The DNCB test showed decreased skin thickness and in microscopic lesion less severe reaction than that of normal birds indicating lower cell mediate immune response. The bacterial isolation from the skin as well as spleen, liver and muscle revealed S. aureus indicating gangrenous dermatitis in all the flocks studied. The electrophoresis of the genomic DNA from the tissues of thymus, bursa. bone marrow and liver of affected flocks showed typical DNA laddering pattern of 180 bp and its multiplication indicating large scale apoptosis in these tissues due to CIAV infection. The virus detection from the pooled tissues of thymus, bursa, spleen, liver and bone marrow by PCR assay revealed presence of CIAV. The Restricted Enzyme analysis showed similar pattern of fragments that of Bangladesh strain viz. BD-3 CAV. 6.2 CONCLUSIONS Following conclusions could be drawn from the present study. 1) Cage birds are more susceptible to CIA-GDS compared to deep litter birds. 2) Incidences of CIA-GDS were recorded only during the period of April to August. 3) Outbreaks of CIA-GDS initiated in the age group of 8 to 11 weeks and continued for five weeks. 4) Average total mortality due to CIA-GDS was 8.12 per cent. 5) Gross and microscopic lesions observed in CIA-GDS were typically of mixed infection of chicken infection anemia and gangrenous dermatitis. 6) The organ body weight ratio of thymus, bursa and spleen showed significant decrease while liver showed significant increase when compared to that of normal healthy birds. This indicated atrophy of lymphoid organs. 7) The lower haematological values of Hb, PCV, RBC’s indicated anemic condition of the birds. 8) The low WBC’s count with lymphopenia and relative increase in heterophil count indicates the destruction of lymphocyte by CIAV. 9) The low NDHI titer and poor DNCB reaction as compared to normal birds indicated low humoral and cell mediated immunity in CIA – GDS affected flocks. 10) The bacterial isolation from all the 17 flocks revealed S. aureus which produced lesions of GD in previously immunosuppresed birds by CIAV. 11) The electrophoresis of genomic DNA showed large scale apoptosis in tissues indicating apoptosis as one of the importent phenomenon during CIA-GDS infection. 12) The PCR assay confirmed the presence of CIAV. The RE analysis showed similar DNA fragmenting pattern to that of Bangladesh strain BD-3 CAV.
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