Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/9/2003
Publication Date: 10/12/2003
Citation: Fadly, A.M., Silva, R.F., Hunt, H.D. 2003. Detection of exogenous and endogenous avian leukosis viruses in commercial marek's disease vaccines. In: Proceedings of the 170th Annual Meeting of the United States Animal Health Association, October 9-16, 2003, San Diego, California. p. 524-525. Interpretive Summary:
Technical Abstract: Recently, scientists at USDA-ARS-ADOL in East Lansing, MI, were requested to test Marek's disease (MD) vaccines for possible contamination with avian leukosis virus (ALV), an avian retrovirus that can cause cancer-like disease and other production problems in chickens. Samples of MD vaccines manufactured by two different companies (A & B) were received from a breeder company; samples were also received directly from vaccine company B. Initially, samples tested positive by virus isolation for subgroup E (endogenous) ALV. However, upon re-passage, the vaccines also tested positive for exogenous (subgroup A) ALV. PCR and DNA sequencing of the envelope of isolated ALVs confirmed the results obtained from virus isolation assays that in addition to endogenous subgroup E ALV, an exogenous subgroup A ALV was also present in the vaccines tested. ADOL scientists held a meeting on July 20, 2003 during the World Veterinary Poultry Congress in Denver, CO and presented their findings to concerned parties including poultry breeders and growers, vaccine manufacturers, suppliers of specific-pathogen-free (SPF) eggs, and scientists from academia and government. The Denver meeting resulted in two major recommendations: 1) USDA-APHIS-CVB should work with vaccine manufacturers and SPF suppliers to determine source of contamination and to institute necessary safeguards to avoid such incidents in the future; ADOL should participate in the process by providing necessary advice and technical assistance; and 2) USDA-APHIS-CVB should work with vaccine manufacturers, SPF Suppliers and ADOL to determine needs for improving sensitivity and specificity of tests currently used for testing live-virus vaccines of poultry for contamination with ALVs.