Outbreak Of Marek’s Disease In A Vaccinated Broiler Breeding Flock During Its Peak Egg-laying Period And Preparation Of Reference Antigen And Antisera

Marek’s disease (MD) is caused by Marek’s disease virus (MDV), one of the family Herpesviridae. MD was first reported in 1907 by Josef Marek and characterized by T-cell lymphomas in the peripheral nerves or organs in chicken at the age of 10-12-week-old. MDV currently spreaded worldwide and can cause serious economic losses. We reported a case of MD in a breeding flock of 30-week-old vaccinated broilers by AGP, IFA and histopathological diagnosis, while ALV and REV were excluded. We also prepared the reference antigen and antisera of MDV according to the OIE official method, which will provide effective methods and materials for MD diagnosis.1. Outbreak of Marek’s Disease in a Vaccinated Broiler Breeding Flock During Its Peak Egg-laying PeriodOutbreaks of Marek’s disease (MD), caused by Marek’s disease virus (MDV), primarily occur in 10-12-week-old hens. Here we reported a case of MD in a breeding flock of 30-week-old vaccinated broilers by AGP, IFA and histopathological diagnosis, while ALV and REV were excluded. The virus was isolated from the blood lymphocytes and named MDV-AH1410. Sequence analysis of the pp38, meq, and gB genes revealed that strain MDV-AH1410 had molecular features consistent (99.7%-100.0%homology) with some virulent, previously identified MDV. Our data provide evidence that not only is MDV becoming more virulent, but that the period of its onset in chickens is expanding.2. Preparation of Reference Antigen and AntiseraWe choose an international reference strain RB1B as candidate strain. The virus was purified by limited dilution method and identified by PCR. The reference antigen of MDV was prepared according to the OIE official method. Purification analysis of the virus showed that other viruses such as CAV. ALV、REV、EDS-76V、GPV、IBV、ILTV、IBDV were not found.The prepared antigen only reacted with the antisera to MDV in AGP test. The titer was 1:4. The reference antisera to MDV was made in day old SPF chickens challenged intraperitoneally with MDV-RB1B (2000PFU). The antisera reacted with only MDV but not with other viruses such as ALV、GPV、REV、IBV、IBDV、NDV、AIV、EDS-76V. The IFA and AGP titer of the antisera were 1:1600 and 1:4 respectively.Both the antigen and antisera were packaged by vacuum freeze-drying technology after adding 1% BSA in the antigen and 0.01% Merthiolate in the antisera. The antigen and antisera of MDV were futher analyzed sterility, mycoplasma contamination, uniformity, stability and so on. The references antigen and antisera were finally obtained. It will provide effective method and materials for the diagnosis of MDV.