A novel risk assessment tool for bovine respiratory disease in preweaned dairy calves

Due to the increased morbidity and mortality of bovine respiratory disease (BRD) in dairy calves, as well as an increasing urgency for the judicious use of antimicrobials in farm animals, a comprehensive risk assessment tool for BRD in preweaned dairy calves has been designed based on a longitudinal and a cross-sectional study. As a multifactorial disease complex in which immune function stressors increase susceptibility to respiratory pathology, risk management programs for environmental and husbandry practices may be an effective approach for BRD control. Practices of known or suspected effect on BRD in preweaned calves have been explored in 2 large studies correlating management factors to BRD prevalence (BRD 100 study) and incidence (BRD 10K study) and forming the scores presented here. Priority was given to results from multivariable over univariable model estimates. However, when used, univariable model estimates were adjusted for confounders or stratified by effect modifiers if necessary. Regression coefficients were translated into scores, which are presented in a field-ready tool consisting of (1) a risk assessment questionnaire, which identifies the herd-specific risk factors and the risk scores associated with each; (2) the California BRD scoring system to estimate the BRD prevalence at the time of risk assessment for future comparison with the prevalence after interventions; and (3) the BRD control and prevention herd management plan, which can be used to plan and track the interventions identified. Scores for 100 dairies across California were used to benchmark a dairy's risk on a spectrum. With the help of the risk assessment tool, dairy producers, calf managers, and veterinarians may be able to adjust management factors that affect BRD risk on a farm and objectively monitor BRD prevalence before and after management interventions. As a result, the BRD risk assessment tool described here is the first comprehensive effort for herd-specific BRD control and prevention.

Preweaning cost of bovine respiratory disease (BRD) and cost-benefit of implementation of preventative measures in calves on California dairies: The BRD 10K study

Bovine respiratory disease (BRD) is a multifactorial disease that is estimated to affect 22% of preweaned dairy calves in the United States and is a leading cause of preweaning mortality in dairy calves. Overall cost of calfhood BRD is reflected in both the immediate cost of treating the disease as well as lifetime decrease in production and increased likelihood of affected cattle leaving the herd before their second calving. The goal of this paper was to develop an estimate of the cost of BRD based on longitudinal treatment data from a study of BRD with a cohort of 11,470 preweaned dairy calves in California. Additionally, a cost-benefit analysis was performed for 2 different preventative measures for BRD, an increase of 0.47 L of milk per day for all calves or vaccination of all dams with a modified live BRD vaccine, using differing assumptions about birth rate and number of calves raised per year. Average short-term cost of BRD per affected calf was $42.15, including the use of anti-inflammatory medications in the treatment protocols across all management conditions. The cost of treating BRD in calves appears to have increased in recent years and is greater than costs presented in previous studies. A cost-benefit analysis examined different herd scenarios for a range of cumulative incidences of BRD from 3 to 25%. Increasing milk fed was financially beneficial in all scenarios above a 3% cumulative incidence of BRD. Use of a modified live vaccine in dams during pregnancy, examining only its value as a form of BRD prevention in the calves raised on the farm, was financially beneficial only if the cumulative incidence of BRD exceeded 10 to 15% depending on the herd size and whether the dairy farm was raising any bull calves. The cost-benefit analysis, under the conditions studied, suggests that producers with high rates of BRD may benefit financially from implementing preventative measures, whereas these preventative measures may not be cost effective to implement on dairy farms with very low cumulative incidences of BRD. The long-term costs of calfhood BRD on lifetime productivity were not factored into these calculations, and the reduction in disease may be associated with additional cost savings and an improvement in calf welfare and herd life.

Management factors associated with bovine respiratory disease in preweaned calves on California dairies: The BRD 100 study

The objective of this cross-sectional study was to determine how management practices on California dairies may be associated with bovine respiratory disease (BRD) in preweaned calves. A convenience sample of 100 dairies throughout California, providing a study population of 4,636 calves, were visited between May 2014 and April 2016. During each farm visit, in-person interviews with the herd manager or calf caretaker were conducted to collect information about herd demographics, maternity pen, colostrum and calf management, herd vaccinations, and dust abatement. A random sample of preweaned calves was identified and evaluated for the presence of BRD using a standardized tool. A survey-adjusted generalized linear mixed model with a logit link function was fitted with calf as the unit of analysis and dairy as the random effect. Mean study herd size (±SE) was 1,718 (±189.9) cows. Survey-adjusted estimates of breed types in the sample were 81.6% (±0.6) Holstein, 13.1% (±0.4) Jersey, and 5.3% (±0.5) crossbred or other purebred breeds, and calf sex proportions were 73.8% (±1.0) female and 26.2% (±1.0) male. Overall survey-adjusted BRD prevalence in the study herds was 6.91% (±0.69). Housing factors positively associated with BRD were metal hutches compared with wood hutches [odds ratio (OR) = 11.19; 95% confidence interval (CI) = 2.80–44.78], calf-to-calf contact in calves >75 d of age (OR = 9.95, 95% CI = 1.50–65.86), feeding Holstein calves <2.84 L of milk or replacer per day (OR = 7.16, 95% CI = 1.23–41.68), and lagoon water used for flushing manure under hutches compared with no flush (OR = 12.06, 95% CI = 1.93–75.47). Providing extra shade over hutches (OR = 0.08; 95% CI = 0.02–0.37), feeding calves at least 90% saleable milk (OR = 0.27, 95% CI = 0.13–0.54) or pasteurized milk (OR = 0.10; 95% CI = 0.03–0.36), and feeding >5.68 L of milk or replacer per day to Jersey calves (OR = 0.04; 95% CI = 0.01–0.28) were negatively associated with BRD. Our study identified management practices on California dairies with variability and that may contribute to differences in BRD prevalence, which will be incorporated into a risk-assessment tool to control and prevent BRD in preweaned dairy calves.

Epidemiology of bovine respiratory disease (BRD) in preweaned calves on California dairies: The BRD 10K study

Bovine respiratory disease (BRD) is one of the leading causes of death in dairy heifers. The objective of this prospective cohort study was to characterize the epidemiology of BRD in preweaned dairy calves and to identify management practices associated with decreased risk of BRD. Dairies were chosen for the study based on management practices, location, size, and willingness to participate. A total of 6 dairies, ranging in size from 700 to 3,200 milking cows, in 6 counties across California's Central Valley, were enrolled in the study for at least 1 year. A total of 11,945 calves were born on the study dairies and followed until weaning. Incidence of BRD was estimated using treatment records. Trained study personnel performed comprehensive calf management surveys and estimated BRD prevalence on every dairy at least once every season. A shared frailty model was used to model the associations between management practices and BRD hazard. The final models included data from complete records of 11,470 calves. The overall BRD study period prevalence across the study herds was 22.8%. The mean BRD incidence density rate on all the study dairies was 0.17 BRD cases [95% confidence interval (CI) = 0.16-1.74] per calf-month at risk. The shared frailty model identified that feeding only waste or saleable milk (compared with use of milk replacer), feeding over 3.8 L of milk per day to calves under 21 d of age, frequent changing of maternity pen bedding, and administration of modified live or killed BRD vaccines to dams before calving significantly reduced the risk of BRD. Risk factors for BRD included housing calves in wooden hutches with metal roofs, compared with all-wood hutches, twin births, and perception of dust occurring "regularly," as reported by calf managers, compared with a perception of "no dust" in the calf-raising area. All 4 seasons were analyzed, and both summer (hazard ratio = 1.15; 95% CI = 1.01 to 1.32) and spring (hazard ratio = 1.26; 95% CI = 1.11 to 1.44) were associated with a higher risk of BRD compared with winter. The current longitudinal study identified specific housing and feeding practices that could be modified to decrease risk of BRD. In addition, season was observed to have a strong effect on calves' risk of developing BRD on California dairies.

Bovine respiratory disease (BRD) cause-specific and overall mortality in preweaned calves on California dairies: The BRD 10K study

Mortality in preweaned dairy calves is a significant source of economic loss for dairy producers. In particular, bovine respiratory disease (BRD) is a leading cause of death in preweaned dairy calves. The objectives of this study were to investigate management practices and their effects on mortality, both that specifically attributed to BRD and overall mortality due to all causes, in preweaned dairy calves. Rates of failure of passive transfer of immunity (FPT) are also reported. The study consisted of a convenience sample of 5 dairies across California, selected based on management practices, calf records, location, and size. Trained study personnel performed comprehensive calf management surveys on every dairy at least once every season. Calves were enrolled in the study at birth and followed until weaning. Mixed-effect logistic regression models were specified for the outcomes all-cause mortality (any death before weaning) and mortality attributed to BRD. The 2 final models included a total of 11,470 calves that were born on the study dairies and followed until weaning. The study cohort's overall crude mortality was 2.8%, with crude mortality of individual dairies ranging from 1.7 to 7.2%. The proportion of mortality attributed to BRD was 19.3%, with a range of 0 to 27.1% on the study dairies. Increasing the frequency of changing maternity pen bedding was associated with a decreased risk of mortality due to BRD. Calves diagnosed with BRD in the spring had an increased risk of mortality compared with calves born in the summer; mortality in calves with fall and winter BRD diagnoses did not different significantly from that in summer. Season of mortality was not significant in either model. Feeding ≥5.7 L of milk per day per calf (vs. ≤3.7 L/d) decreased the risk of mortality in calves over 21 d of age. Twins had a 68% increased risk of all-cause mortality compared with calves born as singletons. Both mortality models showed an association between administration of a modified live vaccine in dams (targeting BRD pathogens) and a decreased risk of mortality in calves. Using a serum total protein cut-off of 5.2 g/dL, 16.8% of calves had FPT, with a mean serum total protein concentration of 5.94 ± 0.06 g/dL across all calves sampled.

Regional management practices and prevalence of bovine respiratory disease in California's preweaned dairy calves

The objective of this cross-sectional study was to estimate the prevalence of bovine respiratory disease (BRD) in California preweaned dairy calves and identify management practices that are associated with BRD. A convenience sample of 100 dairies in the 3 distinct dairy regions of California was surveyed. Regions evaluated were Northern California (NCA), northern San Joaquin Valley (NSJV), and greater Southern California (GSCA). A questionnaire on calf management practices and demographic information was administered via in-person interviews at each dairy and a random sample of preweaned calves was evaluated using the California BRD scoring system on the same day. Prevalence of BRD varied between the 3 dairy regions: 9.30% in NCA, 4.51% in NSJV, and 7.35% in GSCA. Breed was not associated with BRD prevalence at the statewide level, but differences in prevalence were observed between breeds across the regions with a higher prevalence in NCA for Jerseys and in GSCA for Holsteins, compared with NSJV. Prevalence of BRD was not different between organic and conventional dairies. Colostrum management practices, including heat treatment and feeding colostrum from multiparous cows, varied by region and were associated with lower BRD prevalence. Calves housed in group pens, a practice observed primarily in NCA, had a higher BRD prevalence than those in individual housing. Feeding salable milk was also more common in NCA and was associated with lower BRD prevalence. Ground and road surfaces adjacent to the calf raising area were also variable by region, and paved surfaces were associated with lower BRD prevalence. Management practices associated with BRD varied across the state and may be addressed to inform the adoption and implementation of potentially protective management decisions on California dairies and other regions with similar dairy systems.

Outcome and prognostic factors in nonambulatory Hansen Type I intervertebral disc extrusions: 308 cases

Thoracolumbar intervertebral disc disease is the most common cause of caudal paresis in dogs (1). Whilst the pathogenesis of the extrusion has been widely studied, treatment protocols and prognostic factors relating to outcome remain controversial. Recent studies have examined a multitude of factors relating to time to regain ambulation after decompressive surgery. Most intervertebral disc herniations occur in the thoracolumbar region, causing upper motor neuron signs in the rear limbs, which are thought to have a more favourable prognosis compared to the lower motor neuron signs created by herniation of an intervertebral disc in the caudal lumbar region. Due to the potential disruption of the lumbar intumescence, lower motor neuron signs have been reported as having a less favourable prognosis. The purpose of this study was to evaluate the intervertebral disc space as a prognostic factor relating to ambulatory outcome and time to ambulation after decompressive surgery. Hansen Type I intervertebral disc extrusions were studied in 308 non-ambulatory dogs. Preoperative and postoperative neurological status, corticosteroid use, signalment, intervertebral disc space, postoperative physical rehabilitation, previous hemilaminectomy surgery, disc fenestration, return to ambulation, and time to ambulation were reviewed.

Comparison of radiographic arthritic changes associated with two variations of tibial plateau leveling osteotomy

Osteoarthritis (OA) progresses in the canine cranial cruciate ligament (CCL) deficient stifle. Progression of OA is also documented in canine patients after various surgical repair techniques for this injury. We evaluated the radiographic arthritic changes in canine stifle joints that have sustained a CCL injury, and compared radiographic OA scores between Tibial Plateau Leveling Osteotomy (TPLO.)surgery patients receiving a medial parapatellar exploratory arthrotomy for CCL remnant removal versus those receiving a limited caudal medial arthrotomy without removal of the CCL remnants. Medial/ lateral and caudal/cranial stifle radiographs were obtained before surgery, immediately following TPLO surgery and at 7–38 months (mean 20.5) after surgery. Sixty-eight patients (72 stifles) were included in the study. The cases were divided into two groups. The patients in group 1 (n = 49 patients, 51 stifles) had a limited caudal medial arthrotomy, and patients in group 2 (n = 19 patients, 21 stifles) had a medial parapatellar open arthrotomy. A previously described radiographic osteoarthritis scoring system was used to quantify changes in both of the groups. The age, weight, OA scores, initial tibial plateau angle, final tibial plateau angle, and the change in angle were compared between the groups. The results showed that there was significantly less progression of OA in the group that had the limited caudal medial, arthrotomy, versus a medial parapatellar open arthrotomy. There was a significant advancement of the OA scores of patients that had TPLO surgery.

Agreement Among 4 Sampling Methods to Identify Respiratory Pathogens in Dairy Calves with Acute Bovine Respiratory Disease

Background

Four sampling techniques commonly are used for antemortem identification of pathogens from cattle with bovine respiratory disease (BRD): the nasal swab (NS), guarded nasopharyngeal swab (NPS), bronchoalveolar lavage (BAL), and transtracheal wash (TTW). Agreement among these methods has not been well characterized.

Objective

To evaluate agreement among TTW and NS, NPS, or BAL for identification of viral and bacterial pathogens in dairy calves with BRD.

Animals

One hundred dairy calves with naturally acquired BRD.

Methods

Calves were sampled by all 4 methods. Viral agents were identified by real‐time RT‐PCR, bacteria were identified by aerobic culture, and Mycoplasma bovis (M. bovis) isolates were speciated by PCR. Agreement among TTW and NS, NPS, or BAL was evaluated by calculating the kappa statistic and percent positive agreement. McNemar's exact test was used to compare the proportions of positive results.

Results

Agreement among TTW and NS, TTW and NPS, and TTW and BAL, was very good for identification of P. multocida, M. haemolytica, and M. bovis. For bovine respiratory syncytial virus (BRSV), agreement with TTW was moderate for NS, good for NPS, and very good for BAL. For bovine coronavirus (BCV), agreement with TTW was moderate for NS and NPS, and good for BAL. McNemar's test was significant only for BCV, indicating that for this pathogen the proportion of positive results from NS and NPS could not be considered comparable to TTW.

Conclusions and Clinical Importance

This study provides guidance for veterinarians selecting diagnostic tests for antemortem identification of pathogens associated with BRD.

Survey of management practices related to bovine respiratory disease in preweaned calves on California dairies

In the spring of 2013, a survey of California (CA) dairies was performed to characterize management practices related to bovine respiratory disease in preweaned calves, compare these practices across geographic regions of the state, and determine the principal components that explain the variability in management between herds. The questionnaire consisted of 53 questions divided into 6 sections to assess management practices affecting dairy calves from precalving to weaning. The questionnaire was mailed to 1,523 grade A licensed dairies in CA and 224 responses (14.7%) were collected. Survey response rates were similar over the 3 defined regions of CA: northern CA, northern San Joaquin Valley, and the greater southern CA region. The mean size of respondent herds was 1,423 milking cows. Most dairies reported raising preweaned calves on-site (59.7%). In 93.3% of dairies, preweaned calves were raised in some form of individual housing. Nonsaleable milk was the most frequent liquid diet fed to preweaned heifers (75.2%). Several important differences were identified between calf-raising practices in CA and practices reported in recent nationwide studies, including herd sizes, housing practices, and sources of milk fed to heifers. The differences between the CA and nationwide studies may be explained by differences in herd size. Regional differences within CA were also identified. Compared with the 2 other regions, northern CA dairies were found to have smaller herds, less Holstein cattle, calves remained with dams for longer periods of time after calving, were more likely to be certified organic dairies, and raised their own calves more often. Principal component analysis was performed and identified 11 components composed of 28 variables (questions) that explained 66.5% of the variability in the data. The identified components and questions will contribute to developing a risk assessment tool for bovine respiratory disease in preweaned dairy calves.

A double-blind block randomized clinical trial on the effect of zinc as a treatment for diarrhea in neonatal Holstein calves under natural challenge conditions

Diarrhea is the leading cause of death in neonatal calves and contributes to major economic losses. The objective of this double-blind randomized clinical trial was to evaluate the effect of oral inorganic or organic zinc supplementation as a treatment for neonatal diarrhea in calves. Seventy nine 1 to 8 day old male Holstein calves on a California calf ranch were block randomized to one of 3 treatments within 24h from their first onset of diarrhea. Calves received a daily dose of either a placebo composed of 80 mg of zinc-free powder, 381.54 mg of zinc methionine (Met) (equivalent to 80 mg of zinc), or 99.69 mg of zinc oxide (ZO) (equivalent to 80 mg of zinc) in 2L of a zinc-free oral rehydration solution (ORS). Calves were treated once daily until normal fecal consistency or for a maximum of 14 days. Upon enrollment and exit, calves were weighed, and blood, feces, and liver biopsies were collected for trace mineral analysis. Fecal samples at enrollment and exit were tested for E. coli K99, Cryptosporidium spp., rotavirus and coronavirus. Pre-treatment liver zinc concentrations for the 71 calves in the placebo, zinc Met, and ZO treatment groups were 710.6 (SEM=147.7), 852.3 (SEM=129.6), and 750.7 (SEM=202.9)mg/kg dry weight (DW), respectively. Exit liver zinc concentrations for the calves in the placebo, zinc Met, and ZO treatment groups were 728.9 (SEM=182.9), 1141.0 (SEM=423.8), and 636.8 (SEM=81.5)mg/kg dry weight, respectively. Although statistically non-significant, there were clinically important findings identified for each of zinc Met and ZO treatments. Calves treated with zinc Met gained on average 40 g/day during a diarrhea episode compared to a weight loss of 67 g/day on average in the placebo-treated calves (Power 19.9%). Calves treated with ZO had 1.4 times higher hazard of clinical cure compared to calves in the placebo group (Power 5.3%). Calves that were fecal positive to cryptosporidium spp. at enrollment and treated with zinc Met had higher odds of testing negative at exit compared to placebo calves (Odds Ratio (OR)=16.0). In contrast, calves treated with ZO tended to recover (fecal score=1) one day earlier compared to calves treated with a placebo (8.5 d vs. 9.7 d). The current trial identified clinically important findings that warrant further research to investigate zinc's therapeutic effect for calf diarrhea.

Randomized noninferiority clinical trial evaluating 3 commercial dry cow mastitis preparations: I. Quarter-level outcomes

The study objective was to compare the efficacy of 3 commercial dry cow mastitis formulations regarding quarter-level prevalence of intramammary infections (IMI) postcalving, cure of preexisting infections over the dry period, prevention of new infections during the dry period, and risk for a clinical mastitis case between calving and 100d in milk (DIM). A total of 1,091 cows (4,364 quarters) from 6 commercial dairy herds in 4 different states (California, Iowa, Minnesota, and Wisconsin) were enrolled and randomized to 1 of the 3 treatments at dry-off: Quartermaster (QT; 1,000,000 IU of procaine penicillin G and 1 g of dihydrostreptomycin; Pfizer Animal Health, New York, NY), Spectramast DC (SP; 500 mg of ceftiofur hydrochloride; Pfizer Animal Health), or ToMorrow Dry Cow (TM; 300mg of cephapirin benzathine; Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO). Quarter milk samples were collected for routine bacteriological culture before dry cow therapy treatment at dry-off, 0 to 6 DIM, and 7 to 13 DIM and an on-farm record-keeping system was used to retrieve data on clinical mastitis cases. Noninferiority analysis was used to evaluate the effect of treatment on the primary outcome, risk for a bacteriological cure during the dry period. Multivariable logistic regression techniques were used to describe the effect of treatment on risk for presence of IMI postcalving and risk of a new IMI during the dry period. Cox proportional hazards regression was used to describe the effect of treatment on the risk and time for quarters to experience an episode of clinical mastitis between calving and 100 DIM. The overall crude quarter-level prevalence of infection at dry-off was 19.2%. The most common pathogen isolated from milk samples at dry-off was coagulase-negative Staphylococcus, followed by Aerococcus spp. and other Streptococcus spp. Noninferiority analysis showed no effect of treatment on risk for a cure between dry-off and calving [least squares means (LSM): QT=93.3%, SP=92.6%, and TM=94.0%] and secondary analysis showed no effect of treatment on risk for presence of an IMI at 0 to 6 DIM (LSM: QT=16.5%, SP=14.1%, and TM=16.0%), risk for development of a new IMI between dry-off and 0 to 6 DIM (LSM: QT=14.8%, SP=12.3%, and TM=14.2%), or risk of experiencing a clinical mastitis event between calving and 100 DIM (LSM: QT=5.3%, SP=3.8%, and TM=4.1%). In conclusion, no difference was observed in efficacy among the 3 products evaluated when assessing the aforementioned quarter-level outcomes.

Streptococcal infection in dogs: a retrospective study of 393 cases

Streptococcus spp are opportunistic pathogens that normally reside in the upper respiratory, intestinal, lower urinary, and genital tracts but can cause localized infection or septicemia in dogs of all ages. A retrospective study of streptococcal infection in 393 dogs was conducted to identify the species of Streptococcus isolated, determine demographics of affected dogs, and characterize the disease processes associated with infection. The major streptococcal species isolated were S canis (88 cases, 22.4%), S dysgalactiae ssp equisimilis (13, 3.3%), and S equi ssp zooepidemicus (4, 1.0%). Sex was not a risk factor (P > .30). Fetuses and neonates were more likely to have streptococcal infection than were other age groups (P < .001). Streptococcal septicemia was considered an important cause of abortion and neonatal death and was isolated from all samples submitted for aerobic culture from dogs in that age group. There was a seasonal trend, with dogs more likely to have streptococcal infection in summer months. In dogs for which a disease process was identified, streptococcal infection was associated with dermatitis (29 dogs), pneumonia (24 dogs), adult septicemia (13 dogs), and fetal/neonatal septicemia leading to abortion or neonatal death (16 dogs). Identification of other clinically significant bacterial, viral, fungal, and parasitic organisms was common (267 of 393 dogs, 68%), especially in dogs with dermatitis or pneumonia. Infection with Streptococcus spp should be considered in the differential diagnosis in cases of abortion, septicemia, dermatitis, and pneumonia in dogs. Clinical significance of isolation of streptococcal organisms should be interpreted in context of clinical signs and pathologic findings.

The effect of computed tomographical gantry angle on the measurement of the canine intercondylar notch

This study was conducted to evaluate the clinical application of computed tomography of the canine femoral intercondylar notch. The canine femoral intercondylar notch is angled 12 degrees from the dorsal plane and obliqued 7 degrees proximolateral to distomedial in the sagittal plane. Measurements of the notch were performed with eight, 12, and 16 degrees of gantry tilt. With the exception of proximal opening notch angle, significant differences were not detected in measurements referenced to 12 degrees of gantry tilt. Evidence from this study indicated that a +/- 4 degree variation in gantry tilt angle from a desired angle of 12 degrees did not significantly affect clinical interpretations of intercondylar notch measurements or notch width index ratios.

Outcome and prognostic factors in non-ambulatory Hansen Type I intervertebral disc extrusions: 308 cases

Thoracolumbar intervertebral disc disease is the most common cause of caudal paresis in dogs. Whilst the pathogenesis of the extrusion has been widely studied, treatment protocols and prognostic factors relating to outcome remain controversial. Recent studies have examined a multitude of factors relating to time to regain ambulation after decompressive surgery. Most intervertebral disc herniations occur in the thoracolumbar region, causing upper motor neuron signs in the rear limbs, which are thought to have a more favourable prognosis compared to the lower motor neuron signs created by herniation of an intervertebral disc in the caudal lumbar region. Due to the potential disruption of the lumbar intumescence, lower motor neuron signs have been reported as having a less favourable prognosis. The purpose of this study was to evaluate the intervertebral disc space as a prognostic factor relating to ambulatory outcome and time to ambulation after decompressive surgery. Hansen Type I intervertebral disc extrusions were studied in 308 non-ambulatory dogs. Preoperative and postoperative neurological status, corticosteroid use, signalment, intervertebral disc space, postoperative physical rehabilitation, previous hemilaminectomy surgery, disc fenestration, return to ambulation, and time to ambulation were reviewed.

Comparison of radiographic arthritic changes associated with two variations of tibial plateau leveling osteotomy

Osteoarthritis (OA) progresses in the canine cranial cruciate ligament (CCL) deficient stifle. Progression of OA is also documented in canine patients after various surgical repair techniques for this injury. We evaluated the radiographic arthritic changes in canine stifle joints that have sustained a CCL injury, and compared radiographic OA scores between Tibial Plateau Leveling Osteotomy (TPLO)surgery patients receiving a medial parapatellar exploratory arthrotomy for CCL remnant removal versus those receiving a limited caudal medial arthrotomy without removal of the CCL remnants. Medial/lateral and caudal/cranial stifle radiographs were obtained before surgery, immediately following TPLO surgery and at 7-38 months (mean 20.5) after surgery. Sixty-eight patients (72 stifles) were included in the study. The cases were divided into two groups. The patients in group 1 (n = 49 patients, 51 stifles) had a limited caudal medial arthrotomy, and patients in group 2 (n = 19 patients, 21 stifles) had a medial parapatellar open arthrotomy. A previously described radiographic osteoarthritis scoring system was used to quantify changes in both of the groups. The age, weight, OA scores, initial tibial plateau angle, final tibial plateau angle, and the change in angle were compared between the groups. The results showed that there was significantly less progression of OA in the group that had the limited caudal medial, arthrotomy, versus a medial parapatellar open arthrotomy. There was a significant advancement of the OA scores of patients that had TPLO surgery.

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.

Monoclonal antibody-based competitive enzyme-linked immunosorbent assay for detection of morbillivirus antibody in marine mammal sera

A competitive enzyme-linked immunosorbent assay (cELISA), using two monoclonal antibodies (MAbs), was developed and compared with the standard virus neutralization test (VNT) for detecting antibodies against canine distemper virus (CDV) and phocine distemper virus (PDV) in sera from dogs and various species of marine mammals. The test depends on the blocking of MAb binding to solid-phase antigen in the presence of positive serum. Test conditions were optimized by using control VNT-negative and -positive sera specific for CDV and PDV. A positive cutoff value of 30% inhibition, which represents the mean cutoff of a VNT-negative population (n = 623) plus 2 standard deviations, was adopted for the test. A total of 736 serum samples were tested by the new cELISA and by the VNT as the "gold standard." An unexpected but useful finding was the ability of this CDV- and PDV-specific cELISA to also detect antibodies against the related pair dolphin morbillivirus and porpoise morbillivirus. Based on a subpopulation of 625 sera used in statistical analyses, the overall sensitivity and specificity of cELISA relative to those of the VNT were 94.9 and 97.7%, respectively. Because the cELISA proved to be nearly as sensitive and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for suspect CDV or PDV cases and would also be useful for epidemiological surveillance of morbilliviral infections in marine mammal populations.

An indirect enzyme-linked immunosorbent assay for diagnosis of American canine hepatozoonosis

American canine hepatozoonosis (ACH), caused by Hepatozoon americanum, is an emerging tick-borne disease of dogs. An indirect enzyme-linked immunosorbent assay (ELISA) that should facilitate diagnosis of infection and study of the epidemiology of ACH has been developed using H. americanum sporozoites as antigen. Efficacy of the new test as a diagnostic tool was compared with that of skeletal muscle biopsy, the current gold standard for confirming H. americanum infection. Results show that the test is sensitive (93%) and specific (96%) and that it is as reliable as histopathologic examination of skeletal muscle for detecting infection. The ELISA would be suitable as a routine laboratory test for diagnosis of ACH.

Quantification of hepatic and renal cortical echogenicity in clinically normal cats

OBJECTIVE

To quantitatively determine echogenicity of the liver and renal cortex in clinically normal cats.

ANIMALS

17 clinically normal adult cats.

PROCEDURE

3 ultrasonographic images of the liver and the right kidney were digitized from video output from each cat. Without changing the ultrasound machine settings, an image of a tissue-equivalent phantom was digitized. Biopsy specimens of the right renal cortex and liver were obtained for histologic examination. Mean pixel intensities within the region of interest (ROI) on hepatic, renal cortical, and tissue-equivalent phantom ultrasonographic images were determined by histogram analysis. From ultrasonographic images, mean pixel intensities for hepatic and renal cortical ROI were standardized by dividing each mean value by the mean pixel intensity from the tissue-equivalent phantom.

RESULTS

The mean (+/- SD) standardized hepatic echogenicity value was 1.06 +/- 0.02 (95% confidence interval, 1.02 to 1.10). The mean standardized right renal cortical echogenicity value was 1.04 +/- 0.02 (95% confidence interval, 1.01 to 1.08). The mean combined standardized hepatic and renal cortical echogenicity value was 1.02 +/- 0.05 (95% confidence interval, 0.99 to 1.04).

CONCLUSIONS AND CLINICAL RELEVANCE

Quantitative determination of hepatic and renal cortical echogenicity in cats is feasible, using histogram analysis, and may be useful for early detection of diffuse parenchymal disease and for serially evaluating disease progression.

Oral pharmacokinetics of fenbendazole in llamas, South American Camelids

Llamas, South American Camelids are increasingly popular in the United States, as a source of fiber, livestock guard, and pack animals. Gastrointestinal parasites have been identified as a major health problem in all classes of livestock including llamas. Currently, there are no approved anthelmintics available for use in llamas. In this study, the pharmacokinetics of a single, oral administration of fenbendazole paste at a minimum target dose of 5mg/kg, with an upper limit of <10mg/kg, was evaluated in llamas. Plasma fenbendazole concentration time profiles were best described by a single compartment model. After oral administration of fenbendazole, T(max) and Cp(max) were 28.39+/-12.80h, and 0.28+/-0.17µg/ml, respectively. The T(1/2alpha) and T(1/2beta) were 16.25+/-11.67 and 36.00+/-25.00h, respectively. The apparent volume of distribution (V(d)) and the area under the curve (AUC) were 11.28+/-4.66l/kg, and 22.52+/-8.67µgh/ml, respectively. The results of this preliminary study indicate that when the paste formulation of fenbendazole is administered orally to llamas, its rate of absorption appears to be very similar to that of other ruminants including sheep, goats, and cattle as indicated by the time required to reach peak plasma concentrations. It was also found that the rate of elimination of fenbendazole was prolonged in llamas as compared to sheep, goats, and cattle.

Herpesvirus papio 2: alternative antigen for use in monkey B virus diagnostic assays

BACKGROUND AND PURPOSE

Serologic testing for antibody to monkey B virus (BV) in macaque sera is problematic due to the biohazardous nature of BV and BV antigens. Herpesvirus papio 2 (HVP2), a herpesvirus of baboons, is more closely related genetically and antigenically to BV than is human herpes simplex virus 1 (HSV1). The potential for use of HVP2 relative to HSV1 as an alternative test antigen for detection of anti-BV antibody in macaque sera was assessed.

METHODS

Standard ELISA formats were developed, using BV-, HVP2-, and HSV1-infected cell extracts. Performance of the HVP2 and HSV1 tests was assessed relative to that of the BV test.

RESULTS

Using the BV antigen ELISA, 349 sera from 7 macaque species were tested, and results were classified as positive (253), negative (94), or suspect (2). The ELISA using HVP2 antigen detected 98.0% of BV-positive sera (248 of 253), whereas the HSV1-based ELISA detected only 96.0% (243 of 253). All three ELISAs identified the same two samples as suspect, and the HSV1 ELISA identified three additional BV-positive sera as suspect.

CONCLUSIONS

The HVP2 antigen-based ELISA was equal in sensitivity and specificity to the BV antigen-based ELISA and was superior to the HSV1 ELISA for detection of BV-positive macaque sera. In addition, the HVP2 ELISA has greater laboratory safety, compared with BV antigen use for ELISA testing.

Canine hepatozoonosis: comparison of lesions and parasites in skeletal muscle of dogs experimentally or naturally infected with Hepatozoon americanum

We report previously undescribed, early lesions in skeletal muscle of dogs experimentally infected with Hepatozoon americanum by ingestion of laboratory-reared, infected Amblyomma maculatum. The earliest muscle lesion was recognized at the first interval of examination 3 weeks following exposure. The lesion consisted of a large, modified host cell whose cytoplasm frequently contained a demonstrable parasite. In skeletal muscle, the cell was consistently located between muscle fibers or in loose connective tissue adjacent to those fibers. Evidence suggesting that the parasite arrives in muscle and other tissue within the host cell cytoplasm is presented. Mucopolysaccharide encystment of the host cell, absent at this early stage, was acquired gradually and approached maximal development 26 weeks post exposure. Completion of the asexual cycle as evidenced by the presence of parasites entering vascular lumens within granulomas and also by the presence of gamonts in peripheral blood leukocytes, occurred within 28-32 days postexposure. Progression of the parasite cycle from meront to passage of zoites into vessel lumens of granulomas can occur in 11 or fewer days. The density with which parasitic lesions occur in one named skeletal muscle compared to other named muscles, although somewhat variable, was not significantly different in either experimentally induced or natural infections. The distribution of developmental stages of the parasite/lesion in four experimental infections (969 lesions) is compared with those in eight dogs with natural infections (557 lesions).

Shedding and transmission of baboon Herpesvirus papio 2 (HVP2) in a breeding colony

Baboons in a captive breeding colony were monitored twice a year, and new additions were screened on arrival for shedding of Herpesvirus papio 2 (HVP2) and serologic reactivity to the agent. For 128 individual animals tested over a period of 1.5 years, shedding of infective virus was detected in 13 of 342 swab specimens (3.8%), each of these incidents representing shedding by a different animal. Among long-term colony animals, infective virus was recovered on only two occasions (5 of 236 swab specimens from five individuals). In all but one instance, animals shedding virus were infants, not adults, and all animals were shedding virus in the oral cavity. One of these five instances was an isolated case, but four (three infants and one adult) were clustered within a single breeding group. Molecular analyses of the HVP2 isolates from this cluster indicated that they likely arose from a single common source, probably the mother of one of the infants. None of 31 wild-caught baboons added to the colony during this period were found to be shedding infective virus, despite 93.5% of them being seropositive for HVP2. In contrast, 6 of 18 adult baboons (all seropositive) transferred into the colony from another breeding colony were found to be shedding HVP2 either orally (3 of 6) or genitally (3 of 6). In addition, 2 of 8 juvenile baboons in this shipment were found to be shedding virus in the oropharynx. Overall, 10 of 13 instances of HVP2 isolation were from the oropharynx rather than the genital tract, and 6 of 13 baboons shedding virus were infants or juveniles rather than adults. These results suggest that, although venereal transmission of HVP2 occurs among adult animals, oral infection of young, sexually immature baboons is not uncommon.

Dairy cow culling strategies: making economical culling decisions

The purpose of this report was to examine important economic elements of culling decisions, to review progress in development of culling decision support systems, and to discern some of the potentially rewarding areas for future research on culling models. Culling decisions have an important influence on the economic performance of the dairy but are often made in a nonprogrammed fashion and based partly on the intuition of the decision maker. The computer technology that is available for dairy herd management has made feasible the use of economic models to support culling decisions. Financial components--including profit, cash flow, and risk--are major economic factors affecting culling decisions. Culling strategies are further influenced by short-term fluctuations in cow numbers as well as by planned herd expansion. Changes in herd size affect the opportunity cost for postponed replacement and may alter the relevance of optimization strategies that assume a fixed herd size. Improvements in model components related to biological factors affecting future cow performance, including milk production, reproductive status, and mastitis, appear to offer the greatest economic potential for enhancing culling decision support systems. The ultimate value of any culling decision support system for developing economic culling strategies will be determined by its results under field conditions.

Dairy Herd Management Program

The Dairy Herd Management Program has served both dairymen and veterinarians very well over the past several years under a variety of conditions. A number of veterinarians have used the Dairy Herd Management Program to provide computerized dairy record service to their clients. In many of these situations, clients have decided to purchase a computer system of their own after discovering the value of having improved, computerized dairy records. The Dairy Herd Management Program is able to efficiently handle data from large dairies without disrupting daily record-keeping routines. With this data, useful reports are generated that measure actual reproductive performance against target levels or goals. Because the Dairy Herd Management Program focuses on specific time intervals and includes data from culled cows, trends or drops in reproductive performance are more quickly detected so that corrective action can be taken to minimize economic losses. The Dairy Herd Management Program's strong points include batch entry of data, an inclusive yet flexible Vet Check List of cows to be examined, and a detailed, comprehensive Reproductive Summary report. Its major weakness is the lack of a custom report generator for specific situations or conditions. This problem is being addressed in the new version. With the improvements scheduled for the new version, the Dairy Herd Management Program should be able to meet all of the needs of dairy managers and veterinarians alike, as well as become a powerful tool for conducting dairy reproductive field trials and research.