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SUMMARY

A double-blind randomized clinical trial was undertaken to determine the value of parenterally administered Streptococcus equi M-protein vaccine in foals during an epizootic of strangles. Weaned mixed-breed foals (n = 664) housed on 2 adjacent feed-lots (A and B) arrived over a 5-day period, 2 weeks before primary vaccination. Foals in lot B (n = 114) were randomly administered vaccine (n = 59) or saline solution (placebo; n = 55) on 3 occasions at biweekly intervals. Foals in lot A (n = 450) were given 1 dose of vaccine (n = 225) or placebo. The following clinical observations were scored blindly by a single observer for all foals in lot B and for 120 (randomly sampled) foals in lot A on a single day, 2 (lot B) and 6 (lot A) weeks after final vaccination: cervical lymphadenopathy, type of bilateral nasal discharge, and palpable swelling at injection site(s). Bacteriologic culture of nasal swab specimens or lymph node aspirates from selected foals with clinical disease yielded Sequi. Cervical lymphadenopathy was observed in 17 of 59 (29%) vaccinates and 39 of 55 (71%) nonvaccinated controls in lot B and in 32 of 60 (53%) vaccinates and 29 of 60 (48%) controls in lot A. Contingency χ2analysis confirmed significantly lower cervical lymphadenopathy rate (χ2= 18.5; P < 0.001) and prevalence of mucopurulent nasal discharge (χ2= 11.4; P < 0.01) for vaccinates in lot B only. Swelling(s) at the vaccine injection site were palpated in 44% of lot B and 29% of lot A vaccinates vs < 2% of placebo controls. In the face of intense natural exposure, foals inoculated 3 times with M-protein vaccine were less than half as likely to have clinical signs of strangles as were nonvaccinated horses.

Free access
in American Journal of Veterinary Research

Summary

Cell-mediated immunity was evaluated in intestinal, respiratory, and systemic lymphoid tissues of pigs exposed when 11 days old to virulent transmissible gastroenteritis virus (tgev), attenuated tgev, or porcine respiratory coronavirus (prcv), 3 antigenically related porcine coronaviruses with distinct enteric and respiratory tissue tropisms. Mononuclear cells were prepared from mesenteric lymph nodes (mln), bronchial lymph nodes (bln), and spleens of pigs and tested for virus-specific responses by use of lymphocyte proliferation assays. Vigorous mln and bln proliferation responses to virulent tgev and prcv, respectively, at postinoculation days 8 to 24 were strongly associated with prior detection of tgev in rectal swab samples and prcv in nasal swab samples. Gastrointestinal disease and intestinal virus replication, assessed on the basis of rectal virus shedding, were almost exclusively found in the virulent tgev-inoculated pigs, even though virulent tgev and a high dose of attenuated tgev elicited the highest proliferation responses in mln. Pigs exposed to prcv or attenuated tgev did not have clinical signs of disease, and only 1 pig given a high dose of attenuated tgev shed virus in feces. Porcine respiratory coronavirus replicated in the respiratory tract after either oronasal or aerosol inoculation of virus and induced strong bln, but not mln, proliferation responses. A high dose of attenuated tgev (4 × 108 plaque-forming units) was more effective than a lower dose of attenuated tgev (7 × 106 plaque-forming units) in eliciting significant lymphocyte proliferation in mln and bln. Cellular immune function, assessed on the basis of mitogen-induced proliferation of lymphocytes, was comparable for all 3 sources of lymphocytes and was not adversely affected by exposure to any of the 3 coronaviruses, nor did it vary with age of the pigs. The tissue tropism of tgev and prcv was associated with induction of virus-specific cell-mediated immune responses, as evidenced by substantial lymphocyte proliferation responses in mln and bln, mucosa-associated lymph nodes adjacent to the primary sites of virus replication. The failure of prcv strain ISU-1 to replicate in the intestinal tract correlated with poor virus-specific cellular immune responses in mln.

Free access
in American Journal of Veterinary Research

Summary

Over a period of 3 summers, 21 colostrum-fed Holstein bull calves, 1 to 3 days old, were assigned to 7 replicates, each consisting of 3 calves. Within each replicate of 3 calves, 2 were selected at random, to be given 100,000 to 146,000 sporulated coccidia oocysts (principally Eimeria bovis) orally 60 hours after arrival at the college research farm. On the thirteenth day after coccidia inoculation, 1 of the 2 calves that had been given coccidia and the third calf that had not been inoculated, were given coronavirus by intranasal and oral routes. Calves were observed daily, and consistency of feces was scored visually. Nasal swab specimens for indirect immunofluorescent antibody testing for coronavirus and fecal samples for oocyst determination were obtained approximately every third day. Of 7 calves that were given only coronavirus, 3 developed diarrhea of short duration. Of 7 calves that were given only coccidia oocysts, 6 developed diarrhea. All 7 calves inoculated initially with coccidia and subsequently with coronavirus developed diarrhea. For 5 of 7 replicates, calves that were given coccidia and coronavirus developed diarrhea first. When overall severity, measured by fecal score and by blood in the feces, was compared, calves inoculated with coccidia followed by coronavirus were more severely affected (P < 0.05) than were calves that were given only coronavirus. Calves that were given only coccidia oocysts appeared more severely affected than calves that were given only coronavirus, but differences were not significant. Calves that were given either coccidia alone, or coccidia followed by coronavirus, had more severe lesions of mucosal degeneration/epithelial necrosis and inflammation (P < 0.05) than did calves that were given only coronavirus. Lesions, however, were generally most severe in calves that were given coccidia and coronavirus. In 4 calves, fibrinopurulent typhlitis and/or colitis were observed; 3 of these observations were made in calves that were given coccidia followed by coronavirus. These observations indicate that, although coronavirus infection in young calves is common and may be mild in calves given adequate colostrum, when combined with coccidia (principally E bovis) infection, resultant clinical signs of disease and lesions may be more severe than those associated with infection attributable to either coronavirus or coccidia alone.

Free access
in American Journal of Veterinary Research

SUMMARY

Five newborn isolation-reared colostrum-deprived calves were inoculated orally and intranasally when they were 20 to 30 hours old and challenge exposed when they were 21 days old with a suspension of virulent bovine coronavirus (bcv). Blood, feces, nasal swabs, tears, saliva, and bronchoalveolar lavage (bal) fluids were collected from each calf prior to inoculation and then weekly for 5 postinoculation weeks. An elisa was used to quantitate the immunoglobulin isotype titers of bcv antibodies in all samples, An immunoblot assay was used to determine the antibody isotype responses to bcv structural proteins in all the samples, except saliva.

At postinoculation days 2 to 3, all calves had severe watery diarrhea, shed bcv in their feces, and had evidence of bcv replication in their upper respiratory tract. After challenge exposure, no calves became ill and no evidence of bcv replication in the respiratory or intestinal tracts was detected. At postinoculation week 1, IgM responses to the N protein were seen in mucosal secretions (except nasal fluid) and feces. At postinoculation weeks 2 and 3, IgA was predominant in mucosal secretions and feces directed toward all the bcv proteins (except the E2 protein in bal fluid). After challenge exposure, an increase (or failure to decrease) in most IgA and some IgG1 titers to bcv proteins was seen. The increases in IgA titers were to all viral proteins in all mucosal secretions and feces, except to the N and E1 viral proteins in feces. The IgGl titer increases were to the E2 proteins in tears and bal fluid and to the E3 protein in bal fluid. In serum, IgM to the N and E3 proteins appeared first, followed by IgGl to mainly the N and E2 proteins, and then more moderate and slower IgG2 and IgA responses. Challenge exposure resulted in an increase (or failure to decrease) in IgGl reactions to all bcv proteins; in IgG2 reactions to E2 and E3 proteins; in IgA reactions to E1, E2, and E3 proteins; and IgM reactions to the N protein only. The N protein elicited the greatest antibody responses, followed by the E2 and E3 proteins, and least by the E1 protein in serum, feces, or mucosal secretions. The E1 and E2 proteins elicited no detectable IgM responses in serum or mucosal secretions.

Our findings indicate that there may be local antibody production at mucosal sites of viral replication, as well as antibody production at associated systemic sites resulting in serum antibodies. Immunoglobulin A antibodies on mucosal surfaces to some or all of the bcv proteins may be important in protection from bcv reinfection.

Free access
in American Journal of Veterinary Research

Sciences, Oklahoma State University. Additional samples and nasal swab e specimens were obtained from certain calves determined to be PI via ACE for virus isolation and titration. Virus isolation and subtyping —To isolate BVDV, serum samples were

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

Blood, feces, and nasal swabs specimens were collected 12 to 24 hours after birth and then 3 times/week (blood only once per week) from one group of 10 calves until they were 10 weeks old and from a second group of 10 calves until they were 10 to 20 weeks old. Colostrum was collected from all calves’ dams and tears from 5 randomly selected calves in the first group. All fecal and nasal specimens were assayed for bovine coronavirus (bcv) antigens by elisa. Nasal epithelial cells were examined for bcv antigens by direct immunofluorescence. Isotype antibody titers to bcv in all samples from 5 calves in group 1 were evaluated by elisa. Zinc sulfate turbidity (zst) values were determined on the first serum samples taken from all calves in group 1. To determine whether any correlation existed between zst values, isotype antibody titers to bcv (12 to 24 hours after birth), number of respiratory sick days, number of enteric sick days, or days to first shedding of virus, a Spearman rank order correlation coefficient was done.

Bovine coronavirus respiratory tract and enteric tract infections were common on this farm. Most initial infections developed when calves were 1 to 3 weeks old; however, there were also multiple incidences of shedding of viral antigens or seroconversions at later times during the study. Persistence of infection or reinfection of the upper respiratory tract with bcv was common.

Colostral antibody titers to bcv (IgG1) were in all cows at moderate amounts; however, calf serum antibody titers and zst values (12 to 24 hours after birth) were highly variable. Significant correlations were found between zst values and bcv IgG1, IgG2, and IgA serum antibody titers (12 to 24 hours after birth); and number of respiratory sick days and zst values, IgG1, IgG2, and IgA serum antibody titers (12 to 24 hours after birth). All calves in group 1 had serum antibody IgM titer increases to bcv when they were 1 to 2 weeks old and many had subsequent IgA, IgG2, and IgG1 serum antibody titer increases in the first 4 weeks. Six calves had a second serum antibody titer increase with IgM or IgA isotypes when they were 5 to 9 weeks old. In the second group, IgM, IgA, and IgG serum antibody titers were increased > fourfold in 6 of 9, 8 of 9, and 5 of 9 calves, respectively. Most calves had passive IgG1 bcv antibodies in their nasal secretions or tears when they were 1 week old and all calves had at least one transient increase in active IgM antibody titers followed by a sharp and persistent increase in IgA titers. All calves had bcv antibodies (IgG1, IgA, or IgM) in their feces when they were 1 week old and at least one transient increase in fecal IgM (4 of 5 calves) or IgA (3 of 5 calves) antibody titers in the 9-week period.

Free access
in American Journal of Veterinary Research

embryonated chicken eggs) from 2 of the 4 nasal swab specimens that had positive results when tested by use of the real-time RT-PCR assay; the virus was designated as Eq/CO. After the diagnosis was established, initial (acute) serum samples were obtained from

Full access
in American Journal of Veterinary Research
in American Journal of Veterinary Research

inoculation, pigs were intranasally inoculated with PRRSV MN-30100 or MN-184 according to a described method. 11 Control pigs were anesthetized and sham-inoculated with sterile saline solution via the same intratracheal procedure. Nasal swab specimens were

Full access
in American Journal of Veterinary Research

isolation performed on serial serum samples and nasal swab specimens. Three 9-month-old Angus crossbred bulls were inoculated with BHV1 and commingled with the heifers to provide exposure to BHV1. However, prior to initiation of the study, these bulls were

Full access
in Journal of the American Veterinary Medical Association