Clinical Diagnosis And Pathological Histological Observation Of Tumor Disease In Laying Hens In Some Areas Of Anhui Province

Avian Leukosis(AL),Marek's Disease(MD)and Reticuloendotheliosis(RE)are the three most common viral tumors in poultry farming.They can not only cause the decline of production performance and immune function of laying hens,acute or chronic death,but also often co-infection with other diseases,seriously endangering the development of poultry industry.In this study,52 laying hens suspected of oncology from different regions of Anhui Province were clinically diagnosed by gross examination,anatomical observation and molecular identification,and 3 cases of double infection of ALV-J and MDV were selected to focus on histopathological characteristics and antigen localization.The results are as follows:1.Clinical Diagnosis of 52 Suspected Tumor CasesBased on clinical symptoms and pathological findings,52 chicken farms were initially identified as positive for oncology.The symptoms of sick chickens were emaciation,depression,crown atrophy or purple spots,fluffy feathers,etc.It was observed that the center of crown of some laying hens was thickened,hardened and faded,and the abdominal circumference was significantly increased.The liver and spleen of visceral organs were diffuse enlargement,the surface of liver was densely distributed with large white spots of rice grains,thymus and glandular stomach bleeding,solitary,bulging tumor nodules could be seen on the surface and substance of heart,kidney and gastrointestinal tract,and the superficial and deep layers of pectoral muscle had white stripes accompanied by tumor nodules,and the muscle fibers lost luster and were gray-white.The positive rates of ALV-J,MDV,REV and CAV were 84.6%,63.5%,21.2%and 7.7%respectively.Triple infection,double infection and single infection accounted for 22.72%,61.36%and 15.90%respectively.Sequencing ALV-J 17 cases,MDV 15 cases and REV 6 cases respectively,and comparing them with reference strains published on GenBank.ALV-J-gp85 gene analysis showed that the homology between the identified strains was 84.7%-100%,and 75.6%-97.4%with the standard strain on GenBank.Nucleotide sequence analysis showed that the 695-724 base was deleted in some strains.The results of MDV-meq gene analysis showed that the homology between the identified strains was 94.7%-100%.Amino acid sequence analysis showed that there were many characteristic mutation sites.Compared with CVI988,GU2 and 814 attenuated vaccine strains,all identified strains(90 D?T,125 V?A,149?A,186 P?R)mutated,and some identified strains and supervirulent strains pC 12/130-10 mutated(98 A?T and 103Q?R).All identified strains accorded with the sequence characteristics of virulent strains or supervirulent strains.The results of REV-LTR gene analysis showed that the homology rate of 6 identified strains was 99.6-100%,and 98.4-100%with standard strains on GenBank.2.3 cases of histopathological characteristics and antigen distribution of co-infection of ALV-J and MDV.Three clinical cases of double infection of ALV-J and MDV were selected as the research objects.Pathological sections were made and HE staining was performed on the organs of the three cases.Microscopic examination showed that most of the tumor cells in the organs of the three cases showed focal distribution.Most of the tissues and organs were lymphoma and medulloblastoma,and a few were single lymphoma cells.Next were giant pleomorphic cell tumors and uncertain tumor cells.In addition to the focal distribution,the tumor cells were also infiltratively distributed in the interstitial space of various tissues.Two kinds of tumor cells could be seen in the same organs or even in the same section field of vision in the infected cases.Paraffin sections of the organs of three cases were made continuously.Indirect immunofluorescence staining was performed with monoclonal antibodies against two kinds of positive tumors.The results of double infection cases showed that ALV-J and MDV had the strongest positive signals in liver and spleen,followed by kidney,and the positive signals of antigens in other tissues were different.In summary,through the diagnosis and research of laying hens'oncology in Anhui,we preliminarily understood the epidemic situation of infectious oncology in laying hens in Anhui,the evolution direction of virus strains and the degree of gene variation,the basic types of tumor cells and the tissue distribution of antigens,which provided a reference for the diagnosis,prevention and control of hens' oncology in Anhui in the future.