Since 1990, highly virulent infectious bursal disease virus (IBDV), which induces high mortality, has been infecting even vaccinated flocks in Japan. We report the efficacy of three live vaccines that are available in Japan. Two mildly attenuated strains (A and B) and one intermediate strain (C) were each tested both in specific-pathogen-free (SPF) chickens and in commercial chickens that have maternal antibodies against IBDV. Chickens were vaccinated at 20 days old and challenged with highly virulent IBDV 10 days post-vaccination. Protection was determined 7 days after challenge by measuring bursa/body weight ratios, histopathological lesions, and antibody responses to IBDV. All three lie vaccines conferred protection to SPF chickens. However, only vaccine C protected 100% of vaccinated commercial chickens against highly virulent IBDV; Vaccines A and B respectively protected three-fourths and none of vaccinated commercial chickens from severe bursal lesions. Vaccines A, B, and C and highly virulent IBDV induced bursal lesions in 3%, 0%, 23%, and 61% of inoculated commercial chickens, respectively. These results suggest that serological determination of the optimum vaccination time for each flock is required to effectively control highly virulent IBDV in the field. The optimum vaccination timing could be approximated by titrating the maternal IBDV antibodies of 1-day-old chicks by an enzyme-linked immunosorbent assay or by an agar gel precipitin test.
To determine a suitable source of tumor cells that would readily adapt to in vitro growth, attempts were made to culture lymphoid tumor cells in soft agar from several neoplastic organs from chickens with lymphoid leukosis. Of 10 tumors from 7 chickens, cells from only two--both from enlarged bursae--were grown successfully. The remaining 8 tumors failed to propagate. The two cell lines thus established have been propagated by serial passage for more than two years in continuous culture. The two cell lines grow as single, free-floating cells in suspension. Morphologically they are usually round, about 8-10 microns in diameter, and have the characteristics of lymphoblastoid cells. They propagate to a maximum concentration of about 1-2 X 10(6)/ml and release infective virus of subgroup A to titers as high as 10(7) TCID/ml. Their leukosis/sarcoma virus susceptibility phenotype is C/E. Lymphoid tumors developed on chorioallantoic membranes (CAM) of 10-day-old embryonated eggs of the BK line 7 days after inoculation, whereas no tumors developed on CAMs from the 15I line.
Sixty-one Japanese quail from eight flocks with problems of recurring outbreaks of lymphoproliferative diseases resembling Marek's disease (MD), were examined aetiologically. Gross lymphomatous lesions were seen in 17 of the quail and 11 out of 56 quail had MD virus (MDV) feather tips antigens. MDV antibody was detectable in only one of 22 quail. None of 9 quail had antibodies against reticuloendotheliosis virus (REV). No MDV was isolated from the total 42 materials of quail using cell culture technique. No REV and avian leukosis virus (ALV) were isolated from some of them. However, specific-pathogen-free chicks inoculated with the blood materials revealed MD. and four MDVs were recovered from them. The isolates proved free from REV and ALV. The isolates were placed into serotype 1 by the indirect immunofluorescent antibody test. These results indicate that MDV is aetiologically involved in the present outbreaks of lymphoproliferative disease in Japanese quail.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.