SAMATHA .V (MAJOR)SUDHARANI CHOWDHARY .CHJYOTHI SREE .CHMOLIKA KOTTAPU2024-06-222024-06-222023-03https://krishikosh.egranth.ac.in/handle/1/5810210770In the present study, fowl pox was diagnosed in 119 birds out of 128 suspected backyard chicken with an overall occurrence of 92.96% based on gross lesions, histopathology, ultrastructural and molecular studies. Fowl pox in backyard chicken was recorded in eight coastal districts of Andhra Pradesh and the highest occurrence of fowl pox was found in Krishna district (100%), followed by West Godavari (96.8%), Bapatla (93.75%), Konaseema (92.3%), Kakinada (90%), Prakasam (88.8% ), Anakapalli (75%) and Visakhapatnam (66.6%). The highest occurrence of fowl pox in the present study was in the winter season (47.9%), followed by summer (29.4%), and rainy seasons (22.7%). Occurrence of cutaneous form of fowl pox in backyard chicken was mostly seen in chicks of ≤ 9 weeks of age (97.10%), followed by adults aged > 28 weeks (92.30%) and growers aged 9-28 weeks (80.0%) whereas diphtheritic form of fowl pox was mostly noticed in chicks followed by growers and mortality rate was also highest in chicks when compared to others. Both cutaneous (85.71%) and diphtheritic forms (14.28%), of fowl pox was recorded in the present study. Among 102 cases of cutaneous form, highest occurrence of pock lesions were observed at the eye lids (33.4%), followed by beak (25.5%), corner of the mouth (11.77%), shank region (8.824%), feet (6.87%), comb and wattles (4.95%), at the wings (3.93%), cloacal aperture (2.95%) and ventral aspect of abdomen (1.97%). The highest occurrence of diphtheritic form was observed on mucous membrane of the laryngeal orifice (29.42%), trachea (29.42%), oral cavity (23.53%) and oesophageal tract (17.65%) in a total of 17 cases. Backyard chicken affected with fowl pox exhibited clinical signs like stunted growth, emaciation and decline in egg production in laying hens. Birds affected with cutaneous form of fowl pox revealed alopecia, ocular discharges, closure of eyes, blepharitis and blindness. Respiratory signs like nasal discharges, gasping and other clinical signs like swelling of infraorbital sinuses swelling of head, difficulty in swallowing and asphyxia were also noticed. Grossly, cutaneous form of fowl pox revealed pock lesions ranging from initial small erosions to large developed nodular, proliferative wart like projections on eyelids, beak, corner of mouth, comb, wattles, wings, shank region and feet, whereas nodular to purulent, cheesy patches at laryngeal orifice, trachea, oral cavity and oesophageal tract were noticed in diphtheritic form. In the present study, pock lesions from both cutaneous and diphtheritic forms of fowl pox cases revealed characteristic histopathological features. Majority of tissue sections from cutaneous form of fowl pox (25.5%) revealed severe congestion of blood vessels and haemorrhages in epidermis and dermis, ballooning degeneration of epidermal cells, hyperplasia of epidermis (acanthosis) in focal areas along with presence of medium to large singular or multiple intracytoplasmic eosinophilic inclusion bodies (Bollinger bodies). Degenerative changes and necrosis of the cells of uropygial glands and feather follicles were also seen in addition to numerous Bollinger bodies in 56 (54.9%) cases whereas liquefactive necrosis of epidermal cells, microabscess development and severe infiltration of heterophils was noticed in 18 (17.64%) cases. Proliferative wart like lesions (1.96%) exhibited finger like projections of epithelium due to severe hyperplasia and connective tissue proliferation. Superficial mineralised and necrotic layers were observed over the hyperplastic epidermal cells in large firm crusted nodules whereas increased fibrous connective tissue, increased collagen was noticed in epidermis and dermis in healing lesions. Microscopically, all the diphtheritic pock lesions revealed characteristic changes like severe congestion of blood vessels, haemorrhages and degeneration of epithelium of mucous membranes of oral cavity, tongue, oesophagus, trachea and laryngeal orifice along with presence of small to medium solid or ring shaped Bollinger bodies. Severe necrosis of mucosal cells was evident and was covered by haemorrhagic, fibrinoheterophilic exudate in purulent pock lesions. Diffuse loss of cilia from lining epithelium and disorientation of ciliated epithelium in focal areas in addition to proliferation of epithelial cells in mucosa of trachea was noticed. Demonstration of characteristic intracytoplasmic inclusion bodies was performed by Lendrum’s phloxine tartrazine stain that revealed both solid and lipid associated ring shaped inclusion bodies in skin and oesophageal sections. Four cutaneous pock samples collected from fowl pox affected birds were subjected to transmission electron microscopy and all the sections revealed medium to large intracytoplasmic inclusions in epidermal cells. A few affected cells revealed filaments and tonofibrils arranged as loose bundles in cytoplasm whereas various stages of viral particles were observed in cytoplasm of epithelial cells in all the sections. Majority of cells revealed degenerative changes in mitochondria like swelling of the organelle, partial loss of cristae and coalesced mitochondria forming large mitochondrion along with incorporated incomplete virions as an earliest evidence of inclusion body formation. Immature viral particles contained eccentric nucleoid surrounded by halo whereas mature viral particles contained typical inner dumbbell shaped core and two lateral bodies. Characteristic large inclusions contained more virions at the periphery than in central zone. Shedding of extra coats of the mature virions as the broken segments of inner membranes of inclusions resulted in rodlets. In the present study, inoculation of 10 day old embryonated chicken eggs with skin pock suspension resulted in death of embryo between 5 to 7 days of post inoculation. Grossly, the CAM showed severe congestion, haemorrhages, edema and necrosis in first, second and third passages respectively. Microscopically, congestion of blood vessels in ectoderm, edema in mesoderm and haemorrhages in mesoderm was observed on the CAM in the first, second and third passages respectively. Molecular diagnosis of fowl pox disease in skin, oesophagus, trachea and virus propagated CAM tissue samples by using primers specific for P4b gene of fowl pox virus obtained a desired amplicon of 578bp. Nucleotide sequencing and phylogenetic analysis of four cutaneous fowl pox samples revealed that they were in close relation with the FPV isolates from Singapore, North America and USA (KY464130, MH175285 and KC017961 with an identity of 97.28%, 97.21% and 97.16% respectively) when compared to FPVs isolated from Portugal, Brazil, Jammu and Kashmir and India (KM974727, KX863706, MF496042 and HM481406 respectively with an identity of 96.66% to 96.86%). In the present study fowl pox was diagnosed based on the gross, histopathology, electron microscopy and molecular studies in backyard chicken with an overall occurrence as 92.96%.EnglishThesis