The efficacies of trivalent (Md11/75C + SB-1 + HVT), bivalent (SB-1 + HVT), and turkey herpesvirus (HVT) vaccines against Marek's disease (MD) were compared in commercial broiler flocks in four trials involving 11 farm locations and 486,300 chickens. In all four trials, chickens receiving polyvalent vaccines had lower leukosis (MD) condemnation rates than chickens vaccinated with HVT alone; when data were summarized for each vaccine type in each trial, condemnation rates for the bivalent- or trivalent-vaccinated groups were 56-96% (mean 78%) lower than those for HVT-vaccinated chickens. Polyvalent vaccination was clearly mor efficacious than HVT in 8 of 11 individual farms, although it did not always reduce leukosis condemnations to acceptable levels. Body weights of chickens vaccinated with polyvalent vaccines did not differ consistently from those vaccinated with HVT. Chickens inoculated with the trivalent vaccine had slightly lower overall leukosis condemnation rates (0.24%) than those inoculated with the bivalent vaccine (0.45%) in trials 1-3, where direct comparisons were made. Bivalent vaccines containing either 1,500 or 200 plaque-forming units of SB-1 virus were equally effective; thus, HVT may need to be supplemented with only small amounts of SB-1 to obtain the benefits of protective synergism. SB-1 virus did not appear to carry over from polyvalent-vaccinated flocks to subsequent HVT-vaccinated flocks in the same houses, even when old litter was used.

The objective of this study was to compare the survival of non-O157 Shiga toxin–producing Escherichia coli (STEC) with E. coli O157:H7 during pepperoni production. Pepperoni batter was inoculated with 7 log CFU/g of a seven-strain STEC mixture, including strains of serotypes O26, O45, O103, O111, O121, O145, and O157. Sausages were fermented to pH ≤4.8, heated at 53.3°C for 1 h, and dried for up to 20 days. STEC strains were enumerated at designated intervals on sorbitol MacConkey (SMAC) and Rainbow (RA) agars; enrichments were completed in modified EC (mEC) broth and nonselective tryptic soy broth (TSB). When plated on SMAC, total E. coli populations decreased 2.6 to 3.5 log after the 1-h heating step at 53.3°C, and a 4.9- to 5-log reduction was observed after 7 days of drying. RA was more sensitive in recovering survivors; log reductions on it were 1.9 to 2.6, 3.8 to 4.2, and 4.6 to 5.3 at the end of cook, and at day 7 and day 14 of drying, respectively. When numbers were less than the limit of detection by direct plating on days 14 and 20 of drying (representing a 5-log kill), no more than one of three samples in each experiment was positive by enrichment with mEC broth; however, STEC strains were recovered in TSB enrichment. Freezing the 7-day dried sausage for 2 to 3 weeks generated an additional 1- to 1.5-log kill. Confirmation by PCR revealed that O103 and O157 had the greatest survival during pepperoni productions, but all serotypes except O111 and O121 were occasionally recovered during drying. This study suggests that non-O157 STEC strains have comparable or less ability than E. coli O157 to survive the processing steps involved in the manufacture of pepperoni. Processes suitable for control of E. coli O157 will similarly inactivate the other STEC strains tested in this study.

During a 2 1/2 year study on the effect of experimentally-induced infectious bursal disease (IBD) in White Leghorns, a system for scoring microscopic lesions was developed. Microscopic changes in the bursa of Fabricius, thymus, spleen, and kidney were studied to create a lesion score for each organ. No changes occurred in the cecal tonsil and few, if any, changes occurred in the liver. The system was useful in evaluating the severity of pathologic and inflammatory changes in each organ during the course of the disease. Lesion scores for the bursa ranged from 0 for normal bursae to +4 for severely affected bursae. The lesion scores for the thymus, spleen, and kidney ranged from 0 to +3. The criteria for scoring lesions in the thymus were: 0 equaled no change; +1- cortex had a few empty spaces, pronounced hyperemia with some heterophil infiltration, especially in the medulla; +2- cortex had an increase in the number of empty spaces and increased heterophil infiltration, and the cortex and medulla had decreased hyperemia; +3- cortex had numerous round aggregations (12 to 16 mu in diameter) of cell debris and pyknotic nuclei, a definite decrease in the lymphocyte density in the cortex, and decreased hyperemia in cortex and medulla. This lesion scoring system was useful in determining the severity of IBD in different-aged progeny from IBD-immune and nonimmune dams.

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The experiment involved 392,955 broilers from breeders vaccinated with a commercially available killed infectious bursal disease (KIBD) virus vaccine (Treatments 1 and 2) and 373,371 broilers from breeders not vaccinated with a KIBD virus vaccine (Treatment 2). The broilers from the KIBD-vaccinated breeders were divided into two treatment groups: Treatment 1 consisted of 209,457 broilers and Treatment 2 consisted of 183,498 broilers. Treatment 2 broilers were vaccinated at 10 days of age intraocularly with a commercially available modified liver infectious bursal disease virus (IBD-MLV) vaccine. Broilers in all three treatments were raised on commercially contracted farms serviced by the same company representative. Broiler performance was based on mortality, body weight, feed efficiency, condemnations, and how each farm ranked with respect to contract settlements. Compared with birds in Treatments 2 and 3 respectively, Treatment 1 broilers had 1.65% and 0.89% less mortality; 0.22 lbs. and 0.09 lbs. increased weight per bird; 0.03 and 0.03 increased feed efficiency; 0.09% and 0.32% fewer air sacculitis condemnations; and 0.57% and 0.83% fewer total condemnations. Treatment 1 broilers ranked in the top 37%; Treatment 2 ranked in the bottom 36%; and Treatment 3 ranked in the lower 57% of contract settlements for all broilers processed. The results clearly showed that Treatment 1 broilers outperformed Treatment 2 amd 3 birds and that the IBD-MLV vaccine had a detrimental effect on Treatment 2 broilers.