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  • Author or Editor: Lin Da Roden x
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Summary

Genetically altered stable nonreverting aromatic-dependent (aro -) Salmonella dublin, strain SL5631, was administered orally to healthy colostrum-fed calves as vaccine. Twenty-six calves were allotted to 4 groups. There were 2 experiments, each with a vaccinated and nonvaccinated control group. Skin testing with 0.1 ml of sonicated S dublin was performed 3 days prior to challenge exposure. The IgG and IgM titers to S dublin lipopolysaccharide (lps) antigen were determined by elisa on sera before initial vaccination and at 1.5 to 2 weeks after each vaccination.

In experiment 1, six calves received a dose of 1.7 × 1010 colony-forming units (cfu) of aro-S dublin SL5631 orally at 2 and 4 weeks of age. After the first vaccination, 2 of 6 calves developed fever, but all 6 calves continued to have normal appetite and mental attitude. Adverse changes were not observed after the second vaccination. At the time of challenge exposure at 6 weeks of age, all 12 calves were seronegative for IgG and IgM lps-specific antibodies, and the difference in percentage increase in skin test reaction at 48 hours was not significant. At 6 weeks of age, the 6 vaccinates and 6 controls were orally challenge-exposed with 1.5 × 1011 cfu of virulent S dublin T2340. Protection from challenge was not evident, as 3 of 6 controls and 5 of 6 vaccinates died after challenge exposure.

In experiment 2, eight calves received a dose of 5 × 1011 cfu of aro-S dublin SL5631 orally at 2, 3.5, and 5 weeks of age. The vaccine dose and volume (300 ml) were 30 times that of experiment 1. After each vaccination, some calves (7, 6, and 2 calves for first, second, and third doses, respectively) developed fever, but all calves continued to have normal appetite and attitude. At 7 weeks of age, the 8 vaccinates and 6 controls were orally challenge-exposed with 1.5 × 1011 cfu of virulent S dublin T2340 (same dose as experiment 1). At the time of challenge exposure, all 8 vaccinated calves had elisa titers to IgG and IgM lps-specific antibodies significantly above those of nonvaccinated calves (P < 0.01 and P < 0.05, respectively), 5 of 8 had a strongly posisitive skin test reaction to lps, and the group mean percentage increase in skin thickness 48 hours after intradermal injection was 135% (P = 0.01). The 6 control calves had negative elisa results and mean increase in skin thickness of 34%. Protection from challenge exposure was evident as vaccinates remained blood culture-negative, whereas 5 of 6 controls were blood culture-positive; vaccinates did not develop diarrhea, whereas all controls developed diarrhea. All vaccinates survived, but 3 of 6 controls died after challenge exposure (P = 0.05).

Failure of orally administered vaccine to protect calves in experiment 1 appeared attributable to insufficient antigenic stimulation when 1.7 × 1010 cfu of aroS dublin SL5631 was administered. In experiment 2, a larger number of vaccinal organisms given orally was able to induce a measurable systemic immune response and protection, but the vaccine volume makes it unlikely to be practical for field use.

Free access
in American Journal of Veterinary Research

SUMMARY

A commercially available Salmonella bacterin was administered to Holstein calves starting at 1 to 19 weeks of age. Serum samples were obtained before administering bacterin and at 2-week intervals thereafter. An elisa with Salmonella dublin lipopolysaccharide (lps) or S dublin whole cells as antigen, was used to measure specific IgG and IgM responses. Antibody responses to lps were not detected from calves < 12 weeks old inoculated with killed bacterin. Immunoglobulin responses to whole-cell antigen were detected from all age groups of calves inoculated with the same killed Salmonella bacterin. Calves < 11 weeks old are able to produce immunoglobulins to some whole-cell antigens, but are unable to produce anti-lps immunoglobulins when inoculated with killed Salmonella bacterin. This age-related response to killed Salmonella antigens may account, in part, for increased susceptibility to salmonellosis in calves < 12 weeks old. In comparison to the response for killed antigen, 8 calves given modified-live aromatic-dependent S dublin bacterin at 1 to 3 weeks of age had detectable anti-lps immunoglobulins after immunization, although the response was not as rapid and was of a lesser magnitude than that of older calves given killed Salmonella bacterin.

Free access
in American Journal of Veterinary Research

Summary

Cows and calves from a 1,600-cow drylot dairy were screened for IgG antibodies to Salmonella dublin lipopolysaccharide (lps), using an indirect elisa. The elisa was performed on milk samples from lactating cows and on sera from nonlactating cows and calves. Fecal samples were collected from calves and nonlactating cows for culture of Salmonella spp. All seropositive cattle were retested by culture and elisa 5 times at monthly intervals or until antibody concentration decreased. None of the cattle remained culture-positive and seronegative. Prior to and during the sample collection period, approximately 30% of calves < 8 weeks old died of S dublin infection. Vaccination of cows with a killed S dublin/S typhimurium vaccine at cessation of lactation was a routine management practice. The elisa-determined IgG response to vaccination had decreased by 50 days after vaccination.

Eight cows and 5 calves that maintained a high serologic response to S dublin were purchased and moved to a research facility for 6 months of intensive monitoring. Lactating cows were milked twice daily, and culture of milk and feces for Salmonella spp was performed 5 times/wk. Serum IgG antibodies to S dublin lps were measured weekly, using elisa. At the end of 6 months, all 13 cattle were necropsied and tissues were obtained for culture of Salmonella spp. All 8 cows and 5 calves maintained persistently high elisa titer for the 6 months of testing, and shed S dublin in the milk and/or feces during the same period. On this basis, they were termed S dublin carriers. Salmonella dublin was isolated from mammary tissue of 2 calves at necropsy, indicating that bacteremia may be a mode of mammary infection by S dublin.

Results of the study indicated serologic testing can be used successfully on a large dairy to identify S dublin carrier cattle. Using initial milk screening, 42 of 1,268 lactating cows were identified as suspect, requiring repeated serologic testing. One nonlactating cow, 7 of the 42 suspect lactating cows, and 5 of the 222 calves maintained an IgG response, and were found to be S dublin carriers. Carrier cows shed S dublin in 3.35% of fecal samples and 2.51% of milk samples, and carrier calves shed S dublin in 17.26% of fecal samples.

Free access
in American Journal of Veterinary Research

Summary

Milk samples were collected from all lactating cows on 60 dairies (mean number of cows/dairy, 584; range, 66 to 2,834) randomly selected from 701 California dairies enrolled in the Dairy Herd Improvement Association program. Samples were tested, by means of an elisa, for antibodies against Salmonella serogroup B, C1, and D1 antigens (somatic antigens 01, 4, 6, 7, 9, 12). Blood samples were collected from all cows with positive results and tested for serologic evidence of exposure to salmonellae. Samples for bacteriologic culture (pooled feces from 20 randomly selected calves, swabs of wet areas and feces from calf pens and dairy hospital pens, drag swab sample from wastewater lagoon, and samples of feed components) were also collected from all 60 dairies. Seven (11.7%) of the 60 dairies each had 1 sample that yielded Salmonella organisms (3 S typhimurium, 1 S dublin, 1 nonmotile Group D salmonella, 1 S derby, and 1 S oranienberg). Five of the Salmonella isolates came from the hospital pens and 2 came from calf pens. Thirty-three dairies did not vaccinate cattle against salmonellosis, and of these, 24 (72.7%) had ≥ 1 seropositive cow (titer ≥ 200), and 20 (61 %) had ≥1 persistently seropositive cow (titer for each of 2 blood samples collected ≥ 60 days apart was ≥ 200). Of the 27 dairies that did vaccinate cows against salmonellosis, 24 (89%) had ≥ 1 seropositive cow, and 21 (78%) had ≥ 1 persistently seropositive cow.

We concluded that studies that use of bacteriologic culture of fecal and environmental samples to determine the percentage of dairies with Salmonella-infected cows may underestimate the true percentage.

Free access
in Journal of the American Veterinary Medical Association