The Epidemiological Investigation And The Establishment Of GIS Warning Systems Of Avian Tumor Diseases In Shandong Province

As the worldwide disease, avian tumor diseases that seriously endanger the development of poultry industry have important economic significance. The main tumor diseases are Marek's disease (MD), Avian leukosis (AL) and Reticuloendotheliosis (RE). These three tumor diseases are prevalent around the world, causing enormous economic losses. And reports about immune failure and the emergence of the more virulent strain increase unceasingly. Therefore, effective precaution and control of these diseases will be the emphasis of our study and one of the great challenges.In order to master the information of these tumor disease timely, to find the correlation between the occurrence of tumors and viral infection and environmental factors, a systematical investigation for poultry tumor diseases in Shandong Province have been done using the methods such as serology, clinical diagnosis, histopathology, immunohistochemistry, PCR detection and environment investigation. The results were used to establish a complete early warning system which could be effective in preventing avian tumor disease in our province.The methods of Agar diffusion test and ELISA were used for detecting the antigens or antibodies of MD, AL and RE in serology in AA Breeders (above 4-week-old) in Shandong Province. In addition, Hemagglutination and Hemagglutination Inhibition tests for NDV antibodies were adopted in order to study the relationship between these conventional disease and tumor disease. The results showed that MD average antigen-positive rate was 3.38%, while the AL, RE average antibody positive rates were 10.31% and 40.36%.The data of Hemagglutination and Hemagglutination Inhibition tests showed the antibodies of Newcastle disease was generally low in the region where high incidences of these virus tumor disease were tested. The results showed these tumor virus could cause affected chickens immune suppression, so antibody-producing capacity were declined for NDV vaccine and others.The 57 chickens were collected in Shandong Province and examined in our laboratory. All birds were bled, killed and necropsied. Histopathological observations and immunohistochemistry results revealed a diffuse presence of MDV, ALV-J and REV antigen in livers, spleens, kidneys, proventriculus or bone marrow in some birds. 38.6% of chickens were MDV antigen positive; 54.39% of chickens were positive for ALV-J antigen in the bone marrow, liver and kidneys and other organs; 28.07% of chickens were positive cases for the REV antigen; 12.28% of chicken were double-positive for MDV+ALV-J, 5.26% of chicken were double-positive for MDV+REV, 8.77% of chicken were double-positive for ALV-J+REV and 3.51% of chicken were triple-positive for MDV+ALV-J+REV. PCR analyses revealed the presence of MDV, ALV-J or REV proviral sequences in DNA of these birds. The MDV, ALV-J and REV positive rates were 43.86%, 64.91% and 33.33%; MDV+ALV-J double-positive rate was15.79%; MDV+REV double-positive rate was 10.53%; ALV-J+REV double-positive rate was12.28% and MDV+ ALV-J+REV triple-positive rate was 7.02%.The tumor sites were mainly found in the liver, spleen, proventriculus and kidney. They were consistent with Immunohistochemical experiments. The result of Immunohistochemistry showed that the strongest antigen positive signal was in liver, spleen. Immunohistochemistry and PCR test results show that MDV, ALV-J and REV were epidemic in our province. The antigens can be detected using PCR in some birds without clinical symptoms because of the characteristics of sensitivity and specificity of PCR. And early infection can be identified by PCR. Immunohistochemistry determined the distribution and metabolic dynamics of antigen by immunostaining for MDV,ALV-J and REV monoclonal antibody.The study revealed PCR positive rates were higher than immunohistochemical positive rate. The double-positive rate of Immunohistochemistry and PCR of MDV, ALV-J and REV were 33.33%, 52.63%, 21.05% respectively, indicating that early infection and mixed infection chickens may be existed in chickens.In order to find the correlation between the occurrence of tumors and viral infection and environmental factors, 20 chicken farms were investigated. According to analysis of the data we investigated, farm environment and managements were so important. It was particular attention to vaccination, temperature, humidity, ventilation, densityand other issues.The survey found that there was a direct or indirect relationship beyween neoplastic diseases and vaccine contaminating. In addition, the region where temperature and humidity were too high or too low, the positive rate of tumor was so high. The choice of sites of farm would be combined with the region's topography, climate."Shandong Province poultry tumor disease GIS early warning system" was established in our study using of geographic information system (GIS) technology, based on the basis of geographic database, integrated with the epidemiological databases of avian tumor disease. Further study are going on to find the relation between disease occurrence and source of infection, route of transmission, susceptible animals by the geographical distribution and trends of these tumor disease in Shandong Province based on GIS. The scientific basis could be provided to control these avian tumor disease by the analysis of the system.