Seroepidemiological and virological studies on virus-induced tumors in chickens in Egypt

Extensive epidemiological studies were conducted over four years to investigate the real cause and prevalence of virus-induced tumors among commercial meat-and egg-type chicken breeds, as well as native varieties of different age-groups and localities. Criteria used to establish an etiological diagnosis in problem flocks included, besides flock history, gross, histopathological and cytological examinations, virus isolation in chicken embryo fibroblast cultures [Line O] and identification by enzyme-linked-immunosorbent assay [ELISA] and/or indirect immunofluorescence [IFA], antigen detection in thin tissue sections by IFA, and reticuloendotheliosis virus [REV] proviral DNA detection in blood or tumor tissue by polymerase chain reaction [PCR]. Moreover, chicken flocks were examined for viral antigen and/or antibody in plasma, egg albumin or serum by ELIA. The results achieved indicated that Marek's disease virus [MDV], lymphoid leukosis virus [LLV], and REV were the common causes of neoplasms as single or mixed infections with variable incidence among the flocks. The sources of infection in the investigated flocks is discussed in the light of the obtained results

Administration of non activated infectious bursal disease oil-emulsion vaccine to commercial layer chickens at different ages

Commercial layer chickens of different ages carrying maternal antibody levels to infectious bursal disease [IBD] were inoculated with a full dose a commercial inactivated oil-emulsion IBD vaccine, and then challenged with very virulent IBD virus [vvIBDV] at 7 and 14 days post-vaccination [PV]. The results revealed complete absence of vaccinal protection [0%] one week PV and poor vaccinal protection [10- 50%] two weeks PV, when vaccination adopted weekly during the period from 7 up to 35 days of age. However, survivors during this period showed bursal lesions and significant [P <0.05] bursal atrophy two weeks PV despite vaccinal protection conferred against mortality