Epidemiological Investigation Of Chicken Marek's Disease In Dongying Area And Improvement In Controlling Methods Of MD

Marek's disease (MD) is a highly infectious disease with hyperplasia of lymphocyte caused by herpes virus. It is often characterized with lynphocyte tumours in peripheric nerve, gonad, iris, muscle, skin and other viscera of chicken. There are a variety of MD viruses with different virulences, and promulgated quikly in many ways. The disease usually gives rise to high mortality in ckicken and brings great damage to poultry industry. Currently, inoculation of MD vaccines is the only way against the disease because of no efficient medicines for it. However, MD occurs more popularly in some areas because of the emergence of novel virulent MD virus (vMDV) or very virulent MD virus (vvMDV). To improve the method of controlling the disease effectively, the epidemiological investigation of chicken Marek's disease in Dongying areas of Shandong province was carried out, and meanwhile some experiments of immunological and pathological test were performed. The main results are shown as following:1. The epidemiological investigation of chicken Marek's disease was carried out in Dongying city, Guangrao, Kenli, Lijin and Huantai county, and Qingzhou, shouguang, Zhucheng and Binzhou cities of Shandong province, at the same time, clinic dissection, pathological determination and immunological assay were done to diagnose MD out of the chickens sampled. As result, 62 populations of chickens were shown to infect MD. Five clinic symptoms of pathological changes in nerve, viscera, eye, skin and their mixes were observed in the suscepts. Of which the pathological changes in viscera was more popular, the change in nerve was less than it. All of the varities of clinic pathological symptoms were summarized.2. In the trial of immune protective effecacy of chicken MD vaccines, the virulent MD virus of Jing-1 strain were utilized to challenge the birds that were inoculated with 6 vaccines: three cell-associated vaccines of the imported CVI988/Rispens and CVI988-â…  and domestic CVI988/Rispens, and three cell-free vaccines of HVT, GA+SB-1 and HVT+SB-1, to evaluate their protective effecacies, respectively. It showed that in the MDV challenge condition, two cell-associated vaccine of the imported CVI988/Rispens and CVI988-â…  could give more significantly effective protective potency to the chickens challenged with the MD virus Jing-1 strain than the others. Their protective indices (pI) arranged from 96.16-100%, while the PI of the domestic CVI988/Rispens vaccine was lower than the both. The MD mortality rate of birds at 80-day-old were 0 after vaccinatin with the three vaccines of the imported CVI988/Rispens, CVI988- â…  and domestic...