A live streptomycin-dependent Pasteurella multocida (Serotype 3) vaccine was found to protect turkeys orally and parenterally against homologous challenge.
An enzyme-linked immunosorbent assay (MYCO-ELISA) was developed to detect antibodies to Mycoplasma gallisepticum (MG) in chicken sera. The assay was standardized in terms of optimum antigen concentration, serum dilution, conjugate dilution and incubation temperature, and time. The MYCO-ELISA antigen was prepared from MG whole bacterial cell or its disrupted cell suspension. Both preparations showed strong affinity for binding or adsorbing to the surface of polystyrene wells of the microtiter plate. The MYCO-ELISA was more sensitive than the hemagglutination-inhibition test. However, cross-reactions were observed with sera from M. synoviae (MS)-infected birds.
The pathogenesis of infectious bursal disease (IBD) in chickens neonatally chemically bursectomized (CB) by cyclophosphamide and subsequently inoculated with various numbers of bursal cells was examined. CB chickens inoculated with at least 62.5 X 10(6) bursal cells were as susceptible to IBD clinical manifestations (as determined by gross and microscopic evaluation of bursal tissues, virus recovery from spleen, and antibody titer) as intact chickens following inoculation with virus at 5 weeks of age. In contrast, CB chickens inoculated with 2.5 X 10(6) or fewer bursal cells were refractory to the IBD clinical manifestations compared with intact chickens or CB chickens inoculated with 62.5 X 10(6) or more bursal cells. Results from this study suggest that the availability of a large number of bursal cells is an essential factor in the development of IBD.
Mibolerone, an androgen analog (17 beta-hydroxy-7-alpha, 17-dimethylestr-4-en-3-one), induces a slow but progressive involution of the bursa of Fabricius when fed to chickens at microng levels during the first 7 weeks of life. Chickens receiving mibolerone remained immunologically competent, evidenced by: 1) their antibody response to nonreplicating antigens and infectious antigens; 2) the number of antibody-producing cells in their spleens; 3) the stimulation of their peripheral leukocytes with the plant mitogen phytohemagglutinin; and 4) their capacity to resist challenge with Marek's disease virus and Newcastle disease virus after vaccinations with turkey herpes-virus and the B-1 LaSota strain. This, coupled with the fact that it prevents experimental lymphoid leukosis, makes mibolerone a potential agent to be used under field conditions for the control of lymphoid leukosis.
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