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Abstract

Objective—To determine whether an interferon (IFN)-γ response sufficient to categorize cattle as positive for tuberculosis can be detected in blood collected at commencement of exsanguination at slaughter.

Animals—15 Holstein cows.

Procedures—12 cows were experimentally sensitized by SC injection with inactivated Mycobacterium bovis in mineral oil, which induced an immune response that mimicked natural infection with M bovis. Three nonsensitized control cows were injected SC with mineral oil alone. By 5 weeks after injection, only the 12 sensitized cows had positive results for tuberculosis with whole blood IFN-γ assay. At that time, all 15 cows were sent to slaughter and samples of blood were collected from each cow immediately before stunning and at commencement of exsanguination (within 90 seconds after stunning). A whole blood IFN-γ assay was performed on the samples. Conditional probability and paired t tests were used to analyze changes in the categorical test interpretation and qualitative IFN-γ production, respectively.

Results—All 12 sensitized cows had positive results for tuberculosis in samples obtained immediately before stunning, and 9 retained positive results for samples obtained at commencement of exsanguination. There was a significant decrease in the mean background-corrected IFN-γ ELISA optical density values for samples obtained at commencement of exsanguination.

Conclusions and Clinical Relevance—IFN-γ response sufficient to classify cattle as positive for tuberculosis could be detected in blood collected at commencement of exsanguination. These findings support further development and use of the IFN-γ assay on blood samples collected at exsanguination as part of a bovine tuberculosis surveillance program.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine prevalence of paratuberculosis among dairy cattle herds and to identify associated soil-related risk factors.

Sample Population

Serum and soil samples for 121 Michigan dairy herds.

Procedure

Blood samples were collected from cows at each farm and tested for Mycobacterium paratuberculosis, using an antibody ELISA. Soil samples were collected from pastures and exercise lots; pH and available iron content were determined. A questionnaire was administered to collect data regarding farm management practices and productivity.

Results

55% of the herds tested had ≥ 2 M paratuberculosis-positive cattle. Adjusting sample prevalence for distribution of herd size strata yielded a statewide herd prevalence of 54%. Of 3,886 cattle tested, 267 had positive results. Prevalence of test-positive cattle was 6.9%. For every part per million (ppm) increase in soil iron content, there was a 1.4% increase in the risk of a herd being test-positive. An increase in soil pH of 0.1 was associated with a 5% decrease and an increase in soil iron content of 10 ppm was associated with a 4% increase in the number of test-positive cattle. Application of lime to pasture areas was associated with a herd being only 10% as likely to be paratuberculosis positive and with a 72% reduction in number of test-positive cattle.

Conclusions and Clinical Relevance

Prevalence of paratuberculosis-positive dairy herds in Michigan (54%) was greater than expected, but prevalence of paratuberculosis-positive cattle (6.9%) was within anticipated values. These prevalences were associated positively with acidic soil and increased soil iron content. Application of lime to pasture areas was associated with reduced risk of paratuberculosis. (Am J Vet Res 1999;60:589–596)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether daily administration of pyrantel tartrate can prevent infection in horses experimentally challenged with Sarcocystis neurona.

Animals—24 mixed-breed specific-pathogen-free weanling horses, 10 adult horses, 1 opossum, and 6 mice.

ProcedureSarcocystis neurona-naïve weanling horses were randomly allocated to 2 groups. Group A received pyrantel tartrate at the labeled dose, and group B received a nonmedicated pellet. Both groups were orally inoculated with 100 sporocysts/d for 28 days, 500 sporocysts/d for 28 days, and 1,000 sporocysts/ d for 56 days. Blood samples were collected weekly, and CSF was collected monthly. Ten seronegative adult horses were monitored as untreated, uninfected control animals. All serum and CSF samples were tested by use of western blot tests to detect antibodies against S neurona. At the end of the study, the number of seropositive and CSF-positive horses in groups A and B were compared by use of the Fisher exact test. Time to seroconversion on the basis of treatment groups and sex of horses was compared in 2 univariable Cox proportional hazards models.

Results—After 134 days of sporocyst inoculation, no significant differences were found between groups A and B for results of western blot tests of serum or CSF. There were no significant differences in number of days to seroconversion on the basis of treatment groups or sex of horses. The control horses remained seronegative.

Conclusions and Clinical Relevance—Daily administration of pyrantel tartrate at the current labeled dose does not prevent S neurona infection in horses. (Am J Vet Res 2005;66:846–852)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine whether feeding a direct-fed microbial (DFM) to dairy calves would reduce total and antimicrobial-resistant coliform counts in feces and affect average daily gain (ADG).

ANIMALS 21 preweaned Holstein heifer calves.

PROCEDURES The study had a randomized complete block design. Within each block, 3 consecutively born calves were randomly assigned to 1 of 3 treatment groups within 24 hours after birth (day 0). Calves were fed the DFM at 1.0 g (DFM1; n = 7) or 0.5 g (DFM2; 7) twice daily or no DFM (control; 7) from days 0 through 29. A fecal sample was collected from each calf daily on days 0 through 3 and then every other day through day 29. Fecal samples were cultured, and mean numbers of total coliforms and coliforms resistant to ampicillin, ceftiofur, and tetracycline were compared among the 3 treatment groups. Calves were weighed on days 0 and 29 to calculate ADG.

RESULTS Mean total fecal coliform counts did not differ significantly among the 3 treatment groups. Mean ceftiofur-resistant and tetracycline-resistant coliform counts for the control group were significantly lower, compared with those for the DFM1 and DFM2 groups. Mean ADG did not differ significantly between the DFM1 and DFM2 groups; however, the mean ADG for all calves fed the DFM was 0.15 kg less than that for control calves.

CONCLUSION AND CLINICAL RELEVANCE Results suggested that the DFM fed to the preweaned calves of this study did not reduce total or antimicrobial-resistant coliform counts in feces.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether cats exposed at a residence were infected with Mycobacterium bovis, whether the tuberculin skin test can identify cats infected with M bovis, and whether an ELISA could identify tuberculosis-infected cats.

Animals—20 domestic cats exposed to a cat with laboratory-confirmed disseminated M bovis infection.

Procedure—Cats were administered a tuberculin skin test and monitored for 72 hours. Blood and fecal samples were collected. Cats were then euthanatized, and postmortem examinations were performed. Tissues were examined grossly and histologically for signs of mycobacteriosis. Pooled tissue samples and fecal samples were submitted for mycobacterial culture. Blood samples were examined for evidence of tuberculosis by use of a comparative ELISA.

Results—4 cats had positive responses for the ELISA, and 2 cats had suspicious responses. All tuberculin skin tests yielded negative results. No gross or histologic lesions of tuberculosis were detected in any tissues, and mycobacteria were not isolated from tissues or feces obtained from the 20 cats.

Conclusions and Clinical Relevance—All cats that had positive or suspicious responses for the ELISA were offspring of the cat with tuberculosis. Evidence of tuberculosis was not seen in other cats at the residence, the owner, or the attending veterinarian. The most likely source of tuberculosis for the infected cat was through the consumption of M bovis-infected wildlife carcasses or offal. Because M bovis is endemic in wildlife in northeastern Michigan, there is a risk of exposure to tuberculosis in companion animals, their owners, and attending veterinarians. (Am J Vet Res 2002;63:1507–1511)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether certification in a Milk and Dairy Beef Quality Assurance Program (MDBQAP) was associated with a reduced risk of having antibiotic residues in milk and to define specific management factors that may have predisposed dairy farms to having violative antibiotic residues in milk.

Sample Population

124 dairy farms in Michigan that had ≥ 1 violative residue in milk during 1993 and 248 randomly selected control farms in Michigan that did not have violative residues in milk during 1993.

Procedure

A pretested structured questionnaire was mailed to case and control farms. A conditional multivariate logistic regression model was developed to determine risk factors associated with having a violative antibiotic residue in milk.

Results

Certification in the MDBQAP did not significantly reduce the risk of having a violative antibiotic residue. Annual treatment of > 10% of a herd for metritis was associated with a reduced risk of having a violative residue. Evidence suggested that a routine request for a milk processor to perform residue testing was associated with a decreased risk of having had a violative antibiotic residue, but routine on-farm residue testing was associated with an increased risk of having had a residue.

Conclusions and Clinical Relevance

MDBQAP certification was associated, although not significantly, with a reduced risk of having violative antibiotic residues in milk. Risk factors significantly associated with violative antibiotic residues are addressed by various critical control points in the MDBQAP and may be indicators for strengths and weaknesses of MDBQAP. (Am J Vet Res 1999;60:1312–1316)

Free access
in American Journal of Veterinary Research

Abstract

Objectives—To determine historical events leading to establishment of bovine tuberculosis in the white-tailed deer population in the northeastern corner of the lower peninsula (NELP) of Michigan and describe factors relevant to the present outbreak of bovine tuberculosis in Michigan.

Sample Population—Cattle and white-tailed deer in Michigan from 1920 to 1990.

Procedures—A search of extant historical documents (eg, scientific journals, books, public reports, and correspondence and internal reports from governmental agencies) was conducted. Factors investigated included the number of cattle and prevalence of tuberculosis, deer population and density levels, and changes in regional environments affecting the population and management of cattle and wild deer.

Results—High deer numbers and severe winter feed shortages resulting from habitat destruction in the NELP in 1930 contributed to the transmission of tuberculosis from cattle to deer. Starvation increased the susceptibility of deer to infection and modified behavior such that exposure to infected cattle was increased. Relocation of deer resulted in spread of infection to other sites, including locations at which spatial clusters of tuberculosis presently exist. Ribotyping of Mycobacterium bovis from a human patient suggests that the strain of M bovispresently infecting white-tailed deer in the region is the same strain that affected cattle farms at that time.

Conclusions and Clinical Relevance—Feeding deer to maintain numbers above the normal carrying capacity of the NELP led to deer depending on consumption of livestock feed for survival during winter and increased contact with domestic cattle. This practice should be avoided.

Full access
in American Journal of Veterinary Research

Abstract

One of the important human health benefits of keeping pets may be to serve as an early warning system for indoor childhood exposure to toxic chemicals such as per- and polyfluoroalkyl substances (PFAS). The stain-resistant properties and environmental stability of PFAS make them a preferred choice for protective coatings and lubricants, and they have been used for years in various manufacturing and industrial processes around the world. Although the use of PFAS has arguably improved many commercial products, they have been linked to adverse health outcomes such as developmental delays, liver damage, immune suppression, disruption of endocrine and reproductive systems, and some cancers. The current body of literature suggests that serum PFAS levels in dogs and cats are analogous to their human counterparts and that household pets experience similar changes in blood chemistry markers. The proximity of small children and household pets to PFAS-treated carpets and floors, in addition to their tendency to put things into their mouths, potentially allows pets to serve as sentinels for household PFAS exposure. To assess the suitability of pets as indicators for exposure, researchers need to understand the most likely sources of PFAS exposure for household pets and identify the biomarkers of biological effects in those animals. Understanding these parameters may alert veterinary clinicians to potential sources of contamination in the home and ultimately protect the lives of the children and animals who live there.

Open access
in American Journal of Veterinary Research

Summary

In rats infected with the cestode Taenia taeniaeformis, hepatomegaly results from development of parasitic cysts in the liver. Diffuse nodular mucosal hyperplasia in the glandular region (corpus and antrum) of the stomach, and gross thickening of the intestinal mucosa also result. Between postinfection days (PID) 21 and 84, radiologic observations were made after oral administration of a barium sulfate suspension in T taeniaeformis-infected rats and in age/sex-matched controls. There was radiographic evidence of hepatic enlargement at PID 21. Enlargement of the gastric folds was first observed along the greater curvature of the stomach at PID 35. Fimbriation of small intestinal mucosal surfaces resulted from thickening of the intestinal villi and was observed in the duodenum at PID 21. Intestinal motility was assessed, and contractions were counted, using image intensification fluoroscopy, then were recorded on videotape. There were no significant differences between control and infected rats for gastric emptying time, intestinal transit time, and number of intestinal contractions per minute. Barium contrast radiography clearly indicated large gastric folds, thickening of the small intestinal villi, and hepatic enlargement, and was useful for assessing gastrointestinal motility.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the likelihood of false-positive results when testing milk samples from individual cows by use of 3 commercially available assays (Penzyme Milk Test and the SNAP β-lactamand Delvo- SP assays) labeled for use with commingled milk.

Sample Population—Milk samples from 111 cows with mild clinical mastitis.

Procedure—Cows were randomly assigned to the control (no antimicrobials) or intramammary treatment group. Posttreatment milk samples were collected at the first milking after the labeled withholding period or an equivalent time for controls, randomly ordered, and tested twice by use of each assay and once by use of high-performance liquid chromatography. Sensitivity, specificity, and positive and negative predictive values were determined for each assay. Concordance of results for the same sample was assessed for each assay by calculating κ.

Results—Sensitivities of the Delvo-SP and SNAP β-lactam assays were > 90%, whereas the sensitivity of the Penzyme Milk Test was 60%. Positive predictive values (range, 39.29 to 73.68%) were poor for all 3 assays. Concordance of test results was excellent for the SNAP β-lactam and Delvo-SP assays (κ = 0.846 and 0.813, respectively) but was less for the Penzyme Milk Test (κ = 0.545).

Conclusions and Clinical Relevance—Because of the low positive predictive values, these 3 assays may not be useful for detecting violative antimicrobial residues in individual milk samples from cows treated for mild clinical mastitis. However, repeatability of each assay was considered good to excellent. (Am J Vet Res 2001;62:1716–1720)

Full access
in American Journal of Veterinary Research