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  • Author or Editor: George W. Dilling x
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Summary

Serologic testing to detect persistent IgG titer directed at Salmonella lipopolysaccharide (lps) has proven useful in detecting Salmonella carrier cattle without clinical signs of disease and in seroepidemiologic studies. Although little cross-reactivity exists between most Salmonella serogroups, groups B (O1, 4 [5], 12) and D (O1, 9, 12) share somatic (lps cell wall) antigens O1 and O12, which results in some cross-reactions. This may be unimportant in most instances, because group-B and group-D carriers need to be identified and culled. It may be desirable in some situations, such as when trying to control S dublin, to determine which serogroup is present in a given herd. For this reason, a procedure to produce a pure O9 group-D antigen was developed.

Salmonella dublin (group D) was grown by use of standard procedures, and lps was extracted by use of the phenol-water method. The lps was then oxidized with sodium periodate, dialyzed, reduced with sodium borohydride, cleaved with hydrochloric acid, and again dialyzed. This procedure successfully cleaved the saccharides comprising O antigens 1 and 12, leaving a pure O9 elisa antigen. Sera from cattle vaccinated or naturally infected with S typhimurium, S agona, and S schwarzengrund (all group B), S montevideo (group C1), and S dublin (group D) were tested by elisa, using modified and unmodified antigens. When the elisa antigen used was the chemically modified (pure O9) group-D antigen, elimination of cross-reactions confirmed the structural loss of cross-reacting O1 and O12 antigens.

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

The normal microvascular permeability of the ascending colon in horses and the microvascular permeability of that segment after ischemia and reperfusion were investigated. Microvascular permeability was estimated by the ratio of lymphatic protein to plasma protein concentration (Cl/Cp) at high lymph flow rates in 8 adult horses in 2 equal groups: normal and ischemic (2-hour period). Lymphatic flow rates and lymph and plasma protein concentrations were determined. Intestinal biopsy specimens were obtained at the end of each experiment. Flow independent values were selected and compared by one-way anova, and the mean and sem of these values were determined. The mean Cl/Cp ratios for the flow independent part of each data set were as follows: normal = 0.36 ± 0.08; ischemic = 0.70 ± 0.08. These groups were significantly different (P ≤ 0.0001). Microscopic evaluation revealed mild congestion and edema in the normal group. The ischemic group had mild to moderate mucosal degeneration, with moderate to severe congestion and edema. We concluded that ischemia of the ascending colon, when followed by reperfusion, results in a significant increase in microvascular permeability.

Free access
in Journal of the American Veterinary Medical Association

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

Immunoglobulin reactions to Salmonella dublin in serum and milk from 4 groups of lactating cows were measured by an indirect elisa. The groups consisted of (1) cows that were natural carriers of S dublin in the mammary gland, (2) experimentally infected cows that did not become carriers, (3) cows inoculated with a commercial S dublin bacterin, and (4) cows used as S dublin-negative controls. Milk and serum samples were obtained at monthly intervals. Models for predicting carrier status were developed by use of stepwise logistic regression. Independent variables consisted of serum and milk IgG and IgM titers to S dublin lipopolysaccharide and a ratio of IgG to IgM. The utility of a single sample vs multiple samples obtained at 1-month or 2-month intervals was tested by comparison of goodness-of-fit χ2 P values for 8 models predicting carrier status.

Immunoglobulin reactions specific to S dublin were a significant predictor of carrier status (P < 0.001). Serum IgG titers specific for S dublin were the most important variable for predicting carrier status. Two serum IgG titers to S dublin obtained 2 months apart was a better predictor of carrier status than measurement of the IgG:IgM ratio from a single serum sample. Immunoglobulin recognizing S dublin epitopes also were detected in milk samples. In milk, performing 2 ELISA 60 days apart to determine IgG and IgM reactions to S dublin appeared to be useful for the prediction of carrier status, but was not as accurate as models for serum immunoglobulin reactions.

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