Immunogenicity and protective efficacy of a gE, gG and US2 gene-deleted bovine herpesvirus-1 (BHV-1) vaccine.

The efficacy and safety of a gene-deleted bovine herpesvirus-1 (BHV-1) vaccine was determined in a bovine herpesvirus challenge trial in calves. Three different doses of the vaccine were administered intramuscularly at 10(5), 10(6) and 10(7) PFU/ml and compared to a commercial vaccine and non vaccinated control calves. Challenge was performed by intranasal aerosolization with the Cooper strain of BHV-1 (3 x 10(4) PFU/ml). The non-vaccinated calves shed significantly (P < 0.05) more virus than all other groups on days 4, 8 and 10 post challenge. By day 14 post challenge, antibody titers for BHV-1 of calves vaccinated with 10(7) PFU/ml were significantly (P < 0.05) higher than the commercial or non-vaccinated calves. Clinical scores of non-vaccinated calves were significantly (P < 0.05) higher than all other groups on days 4-14 post challenge. With both radioimmunoprecipitation and competitive enzyme-linked immunosorbent assays (C-ELISA), calves in the gene-deleted vaccine groups mounted comparable specific responses against gB, gC and gD post vaccination as calves in the commercial vaccine group, but in a dose dependent manner. These data suggest that the gene-deleted BHV-1 vaccine tested may be used as an effective vaccine in controlling BHV-1 infections.

Development of an antigen-capture enzyme-linked immunosorbent assay for detection of enterovirus in commercial turkeys.

Diagnosis of enterovirus infection in turkey poults is currently done using electron microscopy. We have developed an antigen-capture enzyme-linked immunosorbent assay (ELISA) for use in diagnosis of enterovirus infection in turkey intestinal contents. Intestinal contents from naturally and experimentally infected turkey poults were evaluated for the presence of astrovirus and enterovirus by immune electron microscopy (IEM). The results were compared with the findings obtained using the ELISA for the presence of enterovirus. The ELISA, using the samples from the naturally infected poults, had a sensitivity of 0.963 and a specificity of 0.879. The Kappa value of 0.834 for the naturally infected samples and 0.97 for the experimentally infected samples showed excellent agreement between the ELISA and IEM for detection of enterovirus. Our results indicate that the ELISA is a rapid, sensitive, and specific method for diagnosis of turkey enterovirus infection.

Experimental infection of specific-pathogen-free turkey poults with single and combined enterovirus and group A rotavirus.

This study was designed to investigate the effects of orally administered single and combined enterovirus and group A rotavirus in specific-pathogen-free poults of different ages. Clinical signs, body-weight gain, D-xylose absorption, and morphometric analysis revealed that poults given the combined enterovirus/rotavirus inoculum were more severely affected than poults that received either inoculum alone. The poults developed a malabsorption syndrome early in the disease process, but by day 8 postinoculation poults had regained normal intestinal absorptive capacity. Poults inoculated with enterovirus alone at 2 and 3 weeks of age were more severely affected, as shown by some of the parameters measured, than those inoculated at 3 days of age.

Single-stranded genomic RNA from turkey enterovirus-like virus.

Previously, we described a disease syndrome in young turkeys caused by an enterovirus-like virus. The virus was designated an enterovirus-like virus based on size, morphology, and intracytoplasmic crystalline arrays of virus. In the present study, further characterization of the virus was performed to ascertain its classification. The virus has a buoyant density of 1.33 g/ml in CsCl and single-stranded RNA genome of approximately 7.5 kilobases. These combined characteristics indicate that this agent is an enterovirus.

Further observations on enterovirus infection in specific-pathogen-free turkey poults.

To evaluate sites of enterovirus replication and to characterize the resulting lesions, twenty 4-day-old specific-pathogen-free (SPF) turkey poults were orally inoculated with an enterovirus. Twenty uninoculated SPF poults served as controls. Inoculated poults were depressed, had ruffled feathers, watery droppings, and pasted vents. Gross lesions were dilated thin-walled ceca with foamy yellow fluid. Immune electron microscopy of the gastrointestinal tract contents revealed an enterovirus with an average diameter of 23.5 nm. Immunoperoxidase and indirect immunofluorescent antibody assays revealed intracytoplasmic staining in enterocytes of the duodenum, jejunum, and ileum. This correlated with the scanning electron microscopy findings, which showed the most lesions in the jejunum and ileum. The ileum had prominent cell outlines because of rounded, distinct, bulging epithelial cells. Histopathology revealed slight shortening of villi and increased crypt depth in the intestines of inoculated poults. Our findings indicate that the small intestine is the site of turkey enterovirus replication, and the gross and microscopic changes observed are determined to result from viral damage to the enterocytes.

Use of dairy herd improvement monthly summary data to monitor intervention strategies in a dairy herd experiencing suboptimal reproductive performance and reduced milk production.

An 87-cow dairy herd with a history of high milk production was visited because of reduced reproductive performance and decreasing milk production. Cows that had recently delivered calves were thin, and many cows had evidence of previous episodes of laminitis. A ration that provided an unfavorable forage-to-concentrate ratio was being fed. In addition to various diagnostic efforts, management changes that were made included alteration of the ration and installation of a computer-operated feeder. After the initial visit, the herd was monitored for 30 months by the use of Dairy Herd Improvement monthly herd summary data. Several potential strengths and weaknesses of using selective production and reproduction monthly summary statistics were illustrated by this study. Milk production, as monitored by mature-equivalent production and average relative value-milk, continued to increase throughout the 30 months after intervention. Reproductive performance, as indicated by first-service conception rate, did not begin to improve until the final 6 months of the monitoring period. Overall, in addition to assisting in diagnostic efforts. Dairy Herd Improvement monthly herd summary data may be used to establish goals, provide comparisons, and maintain producer interest after practitioner intervention in herd management.

A small round virus associated with enteritis in turkey poults.

In a natural outbreak of enteric disease in turkey poults, Salmonella, group D rotavirus, astrovirus, and a small (18-24 nm) round virus were detected in the gut contents. Except for the small virus, the pathogenic potential of the other agents is recognized. In experiments, the small round virus was shown to be transmissible and pathogenic in specific-pathogen-free turkey poults.