Serum concentrations of haptoglobin and haptoglobin-matrix metalloproteinase 9 (Hp-MMP 9) complexes of bovine calves in a bacterial respiratory challenge model

Background

Serum haptoglobin (Hp) and haptoglobin matrix metalloproteinase 9 complexes (Hp-MMP 9) have been identified as biomarkers with diagnostic potential in cattle with conditions resulting in an acute inflammatory response. The purpose of this study was to evaluate potential diagnostic applications of serum Hp and Hp-MMP 9 concentrations in calves with BRD and establish a timeline for their detection in calves experimentally challenged with Bibersteinia trehalosi and Mannheimia haemolytica. Thirty-five cross bred dairy calves were inoculated via tracheal catheterization with either a PCR confirmed leukotoxin negative B. trehalosi isolate, a PCR confirmed leukotoxin positive B. trehalosi isolate, a Mannheimia haemolytica isolate, a combination of leukotoxin negative B. trehalosi and M. haemolytica, or a negative control. Serum samples were collected throughout the study. Calves were euthanized and necropsy performed on day 10 post inoculation.

Results

M. haemolytica inoculated calves had increased lung involvement. Serum Hp and Hp- MMP 9 concentrations were elevated compared to the other treatment groups. Increases in serum Hp and Hp-MMP 9 concentrations for the M. haemolytica group were significantly different from other study groups on day 7 of the study. B. trehalosi inoculated calves did not have increased lung involvement compared to control calves, but the leukotoxin positive B. trehalosi group demonstrated increased serum Hp-MMP 9 concentrations from day 3 to the end of the study compared to the pre-inoculation concentrations.

Conclusion

Serum Hp-MMP 9 concentration is a useful diagnostic tool for detecting early pulmonary inflammation in calves challenged with B. trehalosi and M. haemolytica. Serum Hp-MMP 9 may also be a useful tool in detecting subclinical pulmonary inflammation in challenged calves.

Corneal sensitivity in healthy bovine calves

OBJECTIVE

To evaluate corneal sensitivity as measured by the corneal touch threshold in healthy bovine calves.

ANIMALS STUDIED

Twelve clinically normal male calves with predominantly Holstein genetics and a median age of 76.5 days (range, 67-92 days).

PROCEDURES

Corneal touch threshold (CTT) of the central cornea was measured in both eyes of each calf using a Cochet-Bonnet aesthesiometer.

RESULTS

The mean ± standard deviation corneal touch threshold of all eyes was 1.33 ± 1.1 g/mm(2) (range, 0.62-66.15 g/mm(2) ), corresponding to a filament length of 34.56 ± 8.02 mm (range, 14-47.5 mm). There was no significant difference between fellow eyes.

CONCLUSIONS

Cochet-Bonnet aesthesiometry was well tolerated in all 12 calves using a modified head restraint. Calves in this study may have a relatively sensitive central cornea compared to adult cattle and some other species; however, wide variation among individuals and eyes may be possible. Studies utilizing larger calf populations are necessary to establish reference ranges.

Evaluating approaches to measuring ocular pain in bovine calves with corneal scarification and infectious bovine keratoconjunctivitis-associated corneal ulcerations

Infectious bovine keratoconjunctivitis (IBK) is a common ocular disease in cattle, associated with a 6.8 to 13.6 kg decrease in weaning weight. Antibiotic therapy is available but it is unclear if pain mitigation as an adjunct therapy would reduce the weight loss associated with IBK. Before assessing the impact of pain mitigation therapies, it is first necessary to validate approaches to qualifying ocular pain. The objective of this study was to evaluate approaches to qualifying ocular pain in bovine calves (Bos taurus) with IBK. Our a priori assumption was that scarification or corneal ulcerations consistent with IBK are painful compared to normal eyes. To quantify this difference in pain, we assessed 4 tools: pressure algometry-mechanical nociceptive threshold (PA-MNT), corneal touch thresholds (CTT) obtained with the use of a Cochet-Bonnet aesthesiometer, and assessment for the presence of blepharospasm and photophobia as metrics for pain. Using a 1-eye randomized controlled challenge trial, 31 calves with healthy eyes were randomly allocated to treatment groups, and then a left or right eye was randomly assigned for corneal scarification and inoculation with Moraxella bovoculi or Moraxella bovis. A repeated measures analysis of variance was used for PA-MNT, with significance set at P < 0.05. A log (base 10) transformation was used to stabilize the variance, and Tukey's t tests were used to test differences between assessment days for each landmark. Calves had statistically significantly lower PA-MNT scores (which indicates more pain) the day after scarification relative to baseline measurements (4 d before scarification). For example, at 1 landmark the median PA-MNT (kg/force) prescarification was 4.82 (95% confidence interval [CI]: 3.92-5.93) and 3.43 (95% CI: 2.79-4.22) postscarification. These data suggest PA-MNT may be a tool for quantifying ocular pain in calves. No differences (P < 0.1) in PA-MNT scores between scarified and not-scarified eyes were detected for any landmark on any day. This result suggests that the pain response occurs over the entire face, not just the affected eye. Corneal ulcerations consistent with IBK were not associated with statistically significant differences in PA-MNT or CTT at eye or calf levels. Not surprisingly, scarified eyes were more likely to exhibit blepharospasm and photophobia compared to healthy eyes. Due to blepharospasm, the use of the Cochet-Bonnet to evaluate corneal sensitivity by CTT was of limited value.

Risk associated with transportation and lairage on hide contamination with Salmonella enterica in finished beef cattle at slaughter

Transportation of cattle to the slaughter plant could influence hide contamination with Salmonella enterica. Fecal and hide samples were obtained from 40 lots of cattle at the feedlot and again at the slaughter plant. Potential risk factors for hide contamination were evaluated. A multilevel Poisson regression model was used to determine whether transportation and lairage were associated with hide contamination by Salmonella. Cattle with hide samples positive for Salmonella at the feedlot had twice the risk of having positive slaughter hide samples compared with cattle without positive feedlot hide samples (relative risk [RR], 1.9). Cattle transported in trailers from which samples positive for Salmonella were collected had twice the risk of having positive slaughter hide samples compared with cattle transported in culture-negative trailers (RR, 2.3). Cattle transported for long distances had twice the risk of having positive hide samples at slaughter compared with cattle transported shorter distances (RR, 2.3). Cattle held in lairage pens contaminated with feces had twice the risk of having positive slaughter hide samples compared with cattle held in clean pens (RR, 1.8). Cattle held off feed longer than 18 h before loading had twice the risk of having positive slaughter hide samples compared with cattle held off feed for shorter times (RR, 1.7). Cattle that were agitated during loading had twice the risk of having positive slaughter hide samples compared with cattle that were calm (RR, 2.2). These findings suggest that variables associated with transportation and lairage can impact the presence of Salmonella on the hides of cattle at slaughter.

Impact of transportation and lairage on hide contamination with Escherichia coli O157 in finished beef cattle

Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157. A study was initiated to investigate the influence of transportation and lairage on shedding and hide contamination of E. coli O157. Fecal and hide samples were obtained from 40 pens of harvest-ready beef cattle at the feedlot prior to transport and again at the slaughter plant immediately after slaughter. Potential risk factors for hide contamination at the feedlot, during transport, and at slaughter were evaluated. A multilevel Poisson regression model was used to evaluate if transportation and lairage were associated with hide contamination by E. coli O157 in finished beef cattle. Lots of cattle held in E. coli O157-positive lairage pens had eight times greater risk of having positive slaughter hide samples compared with cattle held in culture-negative pens (relative risk, 8.0; 95% confidence interval, 1.6 to 38.8). Lots of cattle that were held in lairage pens contaminated with feces had three times greater risk for positive slaughter hide samples compared with cattle held in clean pens (relative risk, 3.1; 95% confidence interval, 1.2 to 7.9). Lots of cattle that were transported for long distances (> 160.9 km) had twice the risk of having positive hide samples at slaughter compared with cattle transported a shorter distance (relative risk, 2.4; 95% confidence interval, 1.1 to 5.1). These findings suggest that transportation and lairage should be considered in E. coli O157 control strategies.

Estimated compliance for removal of specified risk materials from 18 U.S. beef packing plants

The removal of 18,345 specified risk materials was observed during audits of 18 U.S. beef processing facilities that, in total, account for over 90% of total U.S. beef slaughtered. Audited plants varied in capacity (280 to 6,000 head per day) and processed both "fed (young cattle)" and "nonfed (mature cows/bulls)" cattle. When all observations for removal of specified risk materials were combined from plants and adjusted for type of cattle processed, overall compliance with specified risk material removal regulations was 98.08%. A 100% compliance rate for removal of brains and distal ileums was recorded based on a total of 600 observations for removal of brains and a total of 2,400 observations for removal of distal ileums. Observations for removal of dorsal root ganglia were collected from 16 of the 18 plants, and overall compliance for dorsal root ganglia removal was 99.6% (4,783 of 4,800). Fifteen of the 16 plants were 100% compliant. For tonsils, data from 18 plants were collected, and tonsils were correctly removed from 92.8% (4,777 of 5,145) of tongues and heads. Data for spinal cord removal were collected from 18 plants, and the spinal cord was removed completely in line with U.S. Department of Agriculture-Food Safety and Inspection Service regulations for 99.43% of the observations. Based on the results of this study, packing plants have demonstrated that they are complying with regulations for removal of specified risk materials from beef meat products intended for human consumption greater than 98% of the time. To continue to assure food safety and consumer confidence, continued vigilance and provision of training programs for plant workers are essential.

Prevalence of and risk factors for Escherichia coli O157 in market-ready beef cattle from 12 U.S. feedlots

Determination of Escherichia coli O157 prevalence immediately prior to shipment and harvest is an important facet of the ecology of this organism, which requires further elucidation. As part of a larger study to measure the effects of within-pen prevalence of E. coli O157 on subsequent carcass contamination, fecal samples from 15 pens of cattle in each of 12 different feedlots in three states (Colorado, Nebraska, and Montana) were collected from June through September 2002. Thirty fresh fecal samples were collected from each pen floor within 36 h of shipment to slaughter. Fecal samples underwent standard enrichment, immunomagnetic separation, and isolation procedures for E. coli O157. Multivariable logistic regression was used to determine which factors best predicted pen-level positive culture results, and to estimate the magnitude of association between each factor and the outcome, while adjusting for other factors in the model. Thirteen (86.7%) of the 15 pens had at least one positive sample, and the within-pen prevalence of E. coli O157 in positive pens ranged from 3.3% to 77.8%. The odds of E. coli O157 positive fecal samples from cattle fed brewers grains were six times that for cattle not fed brewers grains. The odds of E. coli O157 positive fecal samples from pens of cattle from Central Nebraska was nine times that for pens of cattle from Eastern Colorado. These data demonstrate that the presence of E. coli O157 in fecal samples from finished feedlot cattle is associated with feeding of brewers grain and geographic location. Additional studies to further characterize geographic distribution of E. coli O157 and to investigate pen-level intervention strategies should be conducted.

Assessment and modification of a Western blot assay for detection of central nervous system tissue in meat products in the United States

Health hazards associated with meat contaminated by the bovine spongiform encephalopathy agent have led to the development of tests for the presence of this agent. The objective of this study was to optimize a neuron-specific enolase Western blot assay for use in the United States. We compared the original test with a modified protocol to evaluate the detection limit for the presence of central nervous system (CNS) tissue in experimentally inoculated samples and compared and evaluated the utility of these tests for detecting CNS tissue in retail sausages. Sensitivity and specificity of the original and modified protocols were evaluated using the kappa statistic to assess agreement between the results of the two protocols. The original protocol resulted in 100% specificity and 92% sensitivity for raw samples and 92% specificity and 72% sensitivity for cooked samples. The modified protocol resulted in 92% specificity and 89% sensitivity for raw samples and 83% specificity and 75% sensitivity for cooked samples. The kappa statistic for protocol comparison was 0.94 for raw samples and 0.74 for cooked samples. Both protocols correctly identified CNS tissue in positive controls for each replicate. Although the Western blot technique should be considered for screening for the presence of bovine CNS tissue in meat samples, the techniques should be further optimized to address problems of low sensitivity. A test with higher sensitivity is needed to protect consumers from food safety threats associated with bovine CNS tissue.

Immunologic responses to West Nile virus in vaccinated and clinically affected horses

OBJECTIVE

To compare neutralizing antibody response between horses vaccinated against West Nile virus (WNV) and horses that survived naturally occurring infection.

DESIGN

Cross-sectional observational study.

ANIMALS

187 horses vaccinated with a killed WNV vaccine and 37 horses with confirmed clinical WNV infection.

PROCEDURE

Serum was collected from vaccinated horses prior to and 4 to 6 weeks after completion of an initial vaccination series (2 doses) and 5 to 7 months later. Serum was collected from affected horses 4 to 6 weeks after laboratory diagnosis of infection and 5 to 7 months after the first sample was obtained. The IgM capture ELISA, plaque reduction neutralization test (PRNT), and microtiter virus neutralization test were used.

RESULTS

All affected horses had PRNT titers > or = 1:100 at 4 to 6 weeks after onset of disease, and 90% (18/20) maintained this titer for 5 to 7 months. After the second vaccination, 67% of vaccinated horses had PRNT titers > or = 1:100 and 14% had titers < 1:10. Five to 7 months later, 33% (28/84) of vaccinated horses had PRNT titers > or = 1:100, whereas 29% (24/84) had titers < 1:10. Vaccinated and clinically affected horses' end point titers had decreased by 5 to 7 months after vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE

A portion of horses vaccinated against WNV may respond poorly. Vaccination every 6 months may be indicated in certain horses and in areas of high vector activity. Other preventative methods such as mosquito control are warranted to prevent WNV infection in horses.

Radiofrequency (electrosurgical) ablation of articular cartilage: a study in sheep

The objective of this study was to examine the effect of a bipolar ablation probe on experimentally roughened articular cartilage and compare it with the traditional mechanical shaving technique using the knee joint of sheep. Twenty-eight skeletally mature ewes were divided randomly into two groups: one group was treated with a rotating shaving device and another group was treated using the bipolar ablation probe (Bipolar Arthroscopic Probe; Electroscope, Inc, Boulder, CO). Animals were killed at 0, 6, 12, and 24 weeks, and histological sections of the experimental limbs were compared with sections of the opposite limb using a modified Mankin scale. The following variables were used to determine scores: surface (0-6), cells (0-4), hypocellularity (0-3), matrix staining (transitional zone [0-4], radiate zone [0-4], and focal empty lacunae or hypereosinophilic cells (0-3). Differences in scores for all response variables were calculated as treated limb minus sham limb. Response variables were formed: score >0 recoded as 1 (favorable response treated better than sham), score of 0 recoded as 2 (neutral response no differences), and score <0 recoded as 3 (unfavorable response treated worse than sham). Bipolar ablative probe-treated limbs had 14.29% favorable responses and 35.71% favorable or neutral responses, whereas shave-treated limbs had 0% favorable and only 7.14% favorable or neutral responses. For all variables, bipolar ablative probe-treated limbs had more favorable responses. The less severe histological change in the bipolar ablative probe-treated joints compared with the shave-treated joints suggests that bipolar ablation of articular cartilage may be a better treatment for chondromalacia than the usual shaving methods of debridement. Further, there were no pathological changes in the subchondral bone.