Loading...
Theses
Browse
1 results
Search Results
ThesisItem Open Access Studies on natural outbreaks of Marek’s disease in vaccinated domestic fowl with special reference to PCR based diagnosis(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2005-07) Agrawal, Vishal Shyamsundar; Shukla, S.K.The present investigation was undertaken to study the prevalence, clinico biochemical changes, histopathological changes, frequency of organ involvement, pathogenicity testing and PCR based diagnosis of Marek’s disease (MD). The samples and data were collected by personal visits to the poultry farms located in U. S. Nagar district of Uttaranchal. Incidence of MD ranged between 0.59 – 26.31% with an average of 9.17% in all the 7 farms. Mortality in birds gradually decreased as the age advanced. Maximum mortality was found during first part of laying phase. Clinical signs includes typical posture of one leg stretched forward and one backward, leg paralysis, incoordination, off feed, gradual reduction in body weight, prominent keel bone, curling of toes, torticollis and thickening and paleness of comb. Post mortem lesions included thickening of sciatic nerve with loss of striation and tumourous lesions or diffuse enlargement of visceral organs. Microscopically, most of the organs revealed loss of normal architecture, which was evident by degeneration and necrosis and massive pleomorphic cell infiltration. Reduction in Hb, PCV, heterophils, MCV and MCH and increase in TLC, ESR, lymphocytes were noticed. However no alteration in TEC, monocytes, eosinophils and basophils and MCHC values was recorded. Elevated plasma total protein, globulin, cholesterol, LDH, creatinine kinase, creatinine, BUN AST, ALT, AKP levels and decrease in A:G ratio were observed. No alteration in albumin and creatinine kinase MB levels was noticed. Plasma sodium, potassium and magnesium values were significantly higher with low calcium level in the infected birds. However, no alteration in plasma phosphorus level in infected birds was noticed. Investigation revealed 64% of the feather follicle samples positive for MD precipitinogen by standard antiserum. PCR by using specific primers for gA gene of MDV 1 amplify antigen A gene fragment of pathogenic MDV from feather, blood, liver, spleen. The amplified DNA product of 314 bp was detected on agarose (1.7%). HVT specific primers amplified none of the DNA isolated from infected samples. The probable reasons for the vaccination failures are early infection of chicks with virulent strain, maternal antibodies interfering with vaccinal immunity, mutation of MDV to vMDV, rearing of birds of multiple ages on same premises, mismanagemental practices, excessive dilution of vaccine, immunosuppression and lack of biosecurity measures.