A labeled avidin-biotin enzyme-linked immunosorbent assay (LAB-ELISA) for detecting antibody to infectious laryngotracheitis (ILT) virus in chicken sera was developed and compared with ordinary ELISA. Purified ILT virus, biotin-labeled anti-chicken IgG rabbit IgG conjugate, and horseradish-peroxidase-labeled avidin were used in the LAB-ELISA. When sera from farm chickens were tested by serum neutralization (SN) and two kinds of ELISA, the correlation rate between SN and LAB-ELISA was 50/50 (100%), and that between SN and ordinary ELISA was 39/50 (78%). In LAB-ELISA, all of the sera that were antibody-negative by SN had low absorbance (A) values (below 0.05), and the A values were closely correlated with the SN indexes. In ordinary ELISA, however, the sera antibody-negative by SN had various A values ranging from 0.06 to 0.32. LAB-ELISA had much lower nonspecific reactions than ordinary ELISA against sera from ILT-negative chickens, even when chickens were 30 weeks old. ILT antibody production after ILT vaccination could be detected by LAB-ELISA. A values peaked 5 weeks postinoculation and were maintained for 17 weeks.
Effect of enterotoxigenic Escherichia coli (ETEC) K99-Specific monoclonal antibody (MCA) to neonatal calves was evaluated experimentally in 27 colostrum-deprived Holstein calves. Calves were challenged orally by ETEC-K99 strain B44 2 hours after oral administration of various doses of MCA. The MCA was not able to prevent diarrhea, but a dose response was noted between administrated herds. Also the grade of diarrhea, the incidence of clinical dehydration and clinical depression decreased in MCA treated groups compared with the control group which did not receive MCA. The mortality rate was also significantly lower (P<0.05) in the treated groups compared with controls. Jpn. Vet. Med. Assoc., 42, 411•`416 (1989).
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