Associations of antimicrobial uses with antimicrobial resistance of fecal Escherichia coli from pigs on 47 farrow-to-finish farms in Ontario and British Columbia

This study assessed the associations between antimicrobial use and other management practices in pigs and antimicrobial resistance in generic Escherichia coli recovered from feces of weaner and finisher pigs on 39 purposefully selected farrow-to-finish farms in Ontario and 8 in British Columbia. Antimicrobials (n = 13), most frequently penicillins and tetracycline, wer dministered to different age groups of pigs on study farms through various routes of administration. Logistic regression was used to model risk factors to antimicrobial resistance in fecal E. coli of pigs for the following antimicrobials: ampicillin, apramycin, carbadox, cephalothin, chloramphenicol, kanamycin, neomycin, nitrofurantoin, spectinomycin, streptomycin, sulfamethoxazole tetracycline, and cotrimoxazole (trimethoprim and sulfamethoxazole). Use of antimicrobials in weaner pigs compared with use in finisher pigs was associated with resistance in most models. There was phenotypic evidence of different mechanisms of resistance selection, including direct selection [use of carbadox was associated with carbadox resistance (OR = 6.48)]; cross-resistance [use of spectinomycin was associated with streptomycin resistance (OR = 2.29)]; and possible co-selection [ceftiofu use was associated with tetracycline resistance (OR = 6.12)]. These results provide further evidence that use of antimicrobials in pigs selects for resistance among fecal E. coli within and between classes of antimicrobials.     

Generating confidence intervals for composition-based landscape indexes

Many landscape indexes with ecological relevance have been proposed, including diversity indexes, dominance, fractal dimension, and patch size distribution. Classified land cover data in a geographic information system (GIS) are frequently used to calculate these indexes. However, a lack of methods for quantifying uncertainty in these measures makes it difficult to test hypothesized relations among landscape indexes and ecological processes. One source of uncertainty in landscape indexes is classification error in land cover data, which can be reported in the form of an error matrix. Some researchers have used error matrices to adjust extent estimates derived from classified land cover data. Because landscape diversity indexes depend only on landscape composition – the extent of each cover in a landscape – adjusted extent estimates may be used to calculate diversity indexes. We used a bootstrap procedure to extend this approach and generate confidence intervals for diversity indexes. Bootstrapping is a technique that allows one to estimate sample variability by resampling from the empirical probability distribution defined by a single sample. Using the empirical distribution defined by an error matrix, we generated a bootstrap sample of error matrixes. The sample of error matrixes was used to generate a sample of adjusted diversity indexes from which estimated confidence intervals for the diversity indexes were calculated. We also note that present methods for accuracy assessment are not sufficient for quantifying the uncertainty in landscape indexes that are sensitive to the size, shape, and spatial arrangement of patches. More information about the spatial structure of error is needed to calculate uncertainty for these indexes. Alternative approaches should be considered, including combining traditional accuracy assessments with other probability data generated during the classification procedure.     

Resistance of Thrips tabaci to pyrethroid and organophosphorus insecticides in Ontario, Canada

Onion thrips, Thrips tabaci Lindeman, were collected from commercial onion fields in 2001, 2002 and 2003 to assess resistance to lambda-cyhalothrin, deltamethrin and diazinon. In 2001, six of eight adult populations were resistant to lambda-cyhalothrin, with resistance ratios (RR) ranging from 2 to 13.1 and four of these were also resistant to deltamethrin, with RR ranging from 19.3 to 120. Three of four adult populations were resistant to diazinon with RR ranging from 2.5 to 165.8. In 2002, four of seven nymphal populations and three of six adult populations were resistant to deltamethrin, with RR ranging from 4.3 to 72.5 and 9.4 to 839.2, respectively. Only one of six nymphal populations and one of five adult populations were resistant to diazinon, with RR of 5.6 and 2.3, respectively. In 2003 diagnostic dose bioassays, 15 of 16 onion thrips populations were resistant to lambda-cyhalothrin and all were resistant to deltamethrin. Eight of the 16 were resistant to diazinon. These results indicate that insecticide resistance is widespread in onion thrips in commercial onion fields in Ontario.     

Comparison of two laparoscopic suture patterns for repair of experimentally ruptured urinary bladders in normal neonatal calves

OBJECTIVE: To compare 2 laparoscopic suture patterns for repair of experimentally ruptured urinary bladders in normal neonatal calves. STUDY DESIGN: Experimental surgical study. ANIMALS: Thirty male Holstein calves. METHODS: A bladder defect was created in 24 anesthetized calves (day 0). They were randomly divided into 4 groups (n=6/group). In groups 1 and 3, the defect was closed laparoscopically using a one layer full thickness simple continuous (FTSC) suture pattern (pattern A). In groups 2 and 4, the defect was closed laparoscopically in 2 layers using a FTSC suture pattern followed by Lembert continuous suture pattern (pattern B). Groups 1 and 2 calves were euthanatized at the end of the surgery and groups 3 and 4 at day 10. Six healthy calves were also euthanatized and used as a control group. The bladders were harvested and tested for bursting strength (BS). The surgical time (ST) data from the two groups for each pattern were pooled. A Student t-test was used to compare ST data. For the BS data, a 2-factor ANOVA test with post-hoc Student t-test was used to determine if treatment, time, or treatment-time interaction was significant. A Dunnett's test was used to compare BS of the 4 treatment groups to the control group. P<.05 was considered significant. RESULTS: Mean ST was significantly shorter for pattern A than for pattern B. In all treatment groups, the mean bladder BS (MBBS) was significantly lower than the MBBS for the control group. The MBBS was significantly lower for group 1 than for group 2. There was no significant difference in the MBBS between groups 3 and 4. CONCLUSION: In this study, a 1-layer laparoscopic closure technique had advantages compared with 2-layer laparoscopic closure technique. Further work is required before a 1-layer laparoscopic closure technique can be recommended clinically. CLINICAL RELEVANCE: One-layer bladder closure is fast and safe in clinically normal calves and permits additional research to evaluate its safety in foals and clinical ruptures.     

Canine digital tumors: a veterinary cooperative oncology group retrospective study of 64 dogs

We compared clinical characteristics and outcomes for dogs with various digital tumors. Medical records and histology specimens of affected dogs from 9 veterinary institutions were reviewed. Risk factors examined included age, weight, sex, tumor site (hindlimb or forelimb), local tumor (T) stage, metastases, tumor type, and treatment modality. The Kaplan-Meier product limit method was used to determine the effect of postulated risk factors on local disease-free interval (LDFI), metastasis-free interval (MFI), and survival time (ST). Outcomes were thought to differ significantly between groups when P < or = .003. Sixty-four dogs were included. Squamous cell carcinoma (SCC) accounted for 33 (51.6%) of the tumors. Three dogs presented with or developed multiple digital SCC. Other diagnoses included malignant melanoma (MM) (n = 10; 15.6%), osteosarcoma (OSA) (n = 4; 6.3%), hemangiopericytoma (n = 3; 4.7%), benign soft tissue tumors (n = 5; 7.8%), and malignant soft tissue tumors (n = 9; 14%). Fourteen dogs with malignancies had black hair coats, including 5 of the 10 dogs with MM. Surgery was the most common treatment and, regardless of the procedure, had a positive impact on survival. None of the patient variables assessed, including age, sex, tumor type, site, and stage, had a significant impact on ST. Both LDFI and MFI were negatively affected by higher T stage, but not by type of malignancy. Although metastasis at diagnosis correlated with a shorter LDFI, it did not have a significant impact on ST. On the basis of these findings, early surgical intervention is advised for the treatment of dogs with digital tumors, regardless of tumor type or the presence of metastatic disease.     

Radiographic and clinical changes of the tibial tuberosity after tibial plateau leveling osteotomy

OBJECTIVE: To investigate radiographic changes of the tibial tuberosity after tibial plateau leveling osteotomy (TPLO) surgery and identify clinical findings and risk factors associated with such changes. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Hundred and eighty-six client-owned dogs (219 stifles) that had TPLO surgery. METHODS: Patient data retrieved included radiographic changes of the tibial tuberosity during re-examination, age, body weight, whether unilateral or single-session bilateral surgery had been performed, location of the anti-rotational pin, approximate tibial tuberosity area, and approximate average tibial tuberosity width. RESULTS: Fracture with resulting caudal displacement of the proximal tibial tuberosity (1.4%; 3 of 219) occurred less frequently than non-displaced tibial tuberosity fractures (7.3%; 16 of 219). Age, weight, average tibial tuberosity width, location of the anti-rotational pin, and single session bilateral surgery were identified as risks factors for non-displaced fracture. Weight divided by the square of the average tibial tuberosity width may be a stronger risk factor than either weight or average tibial tuberosity width alone. CONCLUSIONS: Dogs undergoing single session bilateral TPLO surgery are at greater risk for developing non-displaced tibial tuberosity fractures. The non-displaced tibial tuberosity fracture does not appear to adversely affect outcome or lead to tibial tuberosity avulsion. Significant risk factors for fracture of the proximal tibial tuberosity with caudal displacement were not identified. CLINICAL RELEVANCE: Factors including age, weight, tibial tuberosity thickness, and conditions that may enhance strain on the tibial tuberosity, such as single-session bilateral procedures, may increase risk of fracture.     

External coaptation

External coaptation includes the use of casts, splints, bandages, or slings to help stabilize fractures or luxations, reduce postoperative swelling, or help to protect wounds. Although each of these can be highly effective, it is very important to understand the various types of devices available and the indications for each. Inappropriate use of an external coaptation device can lead to unsatisfactory results.     

A comparison of two intramuscular doses of xylazine-ketamine combination and tolazoline reversal in llamas

OBJECTIVE: To evaluate the anesthetic and cardiorespiratory effects of two doses of intramuscular xylazine/ketamine in llamas, and to determine if an intramuscular injection of tolazoline would shorten the anesthesia recovery time. STUDY DESIGN: Prospective randomized study. ANIMALS: Six castrated male llamas. METHODS: Each llama received a low dose (LD) (0.4 mg kg(-1) xylazine and 4 mg kg(-1) ketamine) and high dose (HD) (0.8 mg kg(-1) xylazine and 8 mg kg(-1) ketamine). Time to sedation, duration of lateral recumbency and analgesia, pulse, respiratory rate, hemoglobin oxygen saturation, arterial blood pressure, blood gases, and the electrocardiogram were monitored and recorded during anesthesia. Three llamas in each treatment were randomized to receive intramuscular tolazoline (2 mg kg(-1)) after 30 minutes of lateral recumbency. RESULTS: Onset of sedation, lateral recumbency, and analgesia was rapid with both treatments. The HD was able to provide at least 30 minutes of anesthesia in all six llamas. The LD provided only 30 minutes of anesthesia in two out of six llamas. Respiratory depression and hypoxemia were seen in the HD treatment during the first 10 minutes of lateral recumbency. Two llamas were severely hypoxemic during this period and were given nasal oxygen for five minutes. Heart rate decreased, but there were no significant changes in blood pressure. Tolazoline significantly shortened the duration of recumbency in the HD treatment. CONCLUSIONS: The HD provided more consistent clinical effects in llamas than did the LD. Intramuscular tolazoline shortens the duration of lateral recumbency in llamas anesthetized with this combination. CLINICAL RELEVANCE: Both doses appear to be very effective in providing restraint in llamas. The LD may be used for procedures requiring a short period of anesthesia or restraint. The HD could be used when a longer duration of anesthesia is desired. Supplemental oxygen should be available if using the HD. Tolazoline (IM) shortened the recovery time with this combination in llamas.     

Use of a polymerase chain reaction assay to detect bovine leukosis virus in dairy cattle

OBJECTIVE: To evaluate the use of a polymerase chain reaction (PCR) assay in detecting bovine leukosis virus (BLV) in adult dairy cows. DESIGN: Prospective study. ANIMALS: 223 adult dairy cows. PROCEDURE: Cows were tested for BLV status by use of an ELISA and a PCR assay. Sensitivity, specificity, predictive values of positive and negative tests, and the percentage of cows correctly classified by PCR assay were calculated. Ninety-five percent confidence intervals were calculated for sensitivity and specificity. RESULTS: Sensitivity and specificity were 0.672 and 1.00, respectively. Prevalence of BLV in this herd was 0.807. Predictive value of a positive test was 1.00, and predictive value of a negative test was 0.421. The percentage of cows correctly classified by PCR assay was 73.5%. CONCLUSIONS AND CLINICAL RELEVANCE: A positive PCR assay result provided definitive evidence that a cow was infected with BLV. Sensitivity and negative predictive value for PCR assay were low. Consequently, PCR assay alone is unreliable for routine detection of BLV in herds with high prevalence of the disease.