Efficacy of fenbendazole and ivermectin in treating gastrointestinal nematode infections in an Ontario cow-calf herd.

The objective of this randomized clinical trial was to compare performance of cow-calf pairs in southern Ontario treated with fenbendazole or ivermectin, or not treated, for gastrointestinal nematode infections. Treatments were administered to 128 cow-calf pairs over 2 years. Weights, body condition score, and fecal egg counts (FEC) were collected at treatment and at 28-day intervals. Treating calves with an anthelmintic was significantly advantageous compared with not treating, and there was no significant difference between treatment with fenbendazole or ivermectin. Neither treatment nor calf FEC had a significant effect on calf weaning weight. This could be the result of time of treatment, low initial FEC, or lack of power. Treatment affected cow FEC (P = 0.003). Cows in the ivermectin groups had the lowest FEC (P < 0.05), but because FEC were all low, biological significance is questionable. Additional work is needed to provide recommendations on when an anthelmintic should be used.

Efficacité du fenbendazole et de l'ivermectin pour traiter les infections à nématodes gastrointestinaux dans un troupeau de vaches-veaux en Ontario. L'objectif de cet essai clinique randomisé était de comparer les performances de paires de vaches-veaux dans le sud de l'Ontario traitées avec du fenbendazole ou de l'ivermectin, ou non-traitées, pour des infections à nématodes gastro-intestinaux. Les traitements furent administrés à 128 paires de vaches-veaux sur une période de 2 ans. Le poids, le pointage de l'état corporel, et le dénombrement des oeufs dans les fèces (FEC) furent colligés au moment du traitement et à des intervalles de 28 jours. Traiter des veaux avec un anthelmintique était significativement avantageux comparativement à ne pas les traiter, et il n'y avait pas de différence significative entre un traitement au fenbendazole ou à l'ivermectin. Ni l'un ou l'autre des traitements ou les FEC n'avaient un effet significatif sur le poids au sevrage des veaux. Ceci pourrait être dû au moment du traitement, un FEC initial peu élevé, ou un manque de puissance. Les traitements ont affecté les FEC des vaches (P = 0,003). Les vaches dans le groupe ivermectin avaient les plus bas FEC (P < 0,05), mais étant donné que tous les FEC étaient bas, la signification biologique est questionnable. Du travail supplémentaire est requis pour fournir des recommandations sur le moment où un anthelmintique devrait être utilisé.(Traduit par Dr Serge Messier).

Suitability of sentinel abattoirs for syndromic surveillance using provincially inspected bovine abattoir condemnation data.

BACKGROUND: Sentinel surveillance has previously been used to monitor and identify disease outbreaks in both human and animal contexts. Three approaches for the selection of sentinel sites are proposed and evaluated regarding their ability to capture overall respiratory disease trends using provincial abattoir condemnation data from all abattoirs open throughout the study for use in a sentinel syndromic surveillance system. RESULTS: All three sentinel selection criteria approaches resulted in the identification of sentinel abattoirs that captured overall temporal trends in condemnation rates similar to those reported by the full set of abattoirs. However, all selection approaches tended to overestimate the condemnation rates of the full dataset by 1.4 to as high as 3.8 times for cows, heifers and steers. Given the results, the selection approach using abattoirs open all weeks had the closest approximation of temporal trends when compared to the full set of abattoirs. CONCLUSIONS: Sentinel abattoirs show promise for integration into a food animal syndromic surveillance system using Ontario provincial abattoir condemnation data. While all selection approaches tended to overestimate the condemnation rates of the full dataset to some degree, the abattoirs open all weeks selection approach appeared to best capture the overall seasonal and temporal trends of the full dataset and would be the most suitable approach for sentinel abattoir selection.

Characteristics of Loads of Cattle Stopping for Feed, Water and Rest during Long-Distance Transport in Canada.

This study is the first comprehensive examination of long-haul cattle being transported across Canada and off-loaded for feed, water and rest. A total of 129 truckloads were observed at one of two commercial rest stations near Thunder Bay, Ontario. Data collected included information regarding the truck driver, the trailer, the trip, the animals and animal handling. The majority of the loads stopping were feeder calves (60.94%) while 21.09% were weaned calves, and the remaining 14.84% were market weight cattle. The truck loads surveyed were in transit for, on average, 28.2 ± 5.0 hours before stopping and cattle were rested for an average of 11.2 ± 2.8 hours. These data suggest that loads stopping at the rest station were adhering to the regulations stated in the Health of Animals Act, which outline a maximum of 48 hours in transit before a mandatory stop of at least 5 hours for feed, water and rest. There was a large amount of variability around how well recommendations, such as stocking density were followed. Further research is required to assess how well cattle are coping with long-distance transport under current regulations and industry practices.

The effect of antimicrobial treatment and preventive strategies on bovine respiratory disease and genetic relatedness and antimicrobial resistance of Mycoplasma bovis isolates in a western Canadian feedlot.

Feedlot calves (n = 3784) were systematically randomized and allocated in a 2 × 2 factorial study to receive metaphylactic oxytetracycline (OTC) on arrival or no antimicrobial, as well as florfenicol once subcutaneously or twice intramuscularly (48 h apart) if diagnosed with bovine respiratory disease (BRD). Calves of different treatment groups were comingled and followed from placement to re-implantation (~100 days). Animals receiving OTC had a reduced risk of BRD, an increased risk of arthritis, and no significant differences in average daily gain, BRD relapse, overall mortality, or BRD mortality. There were no significant differences between treatment protocols. Deep nasal swabs (n = 233) taken at arrival (n = 122), treatment (n = 77), and swabs from lungs and joints at postmortem (n = 34) were cultured for Mycoplasma bovis from 61 animals ill or dying of chronic pneumonia and arthritis and from 61 healthy calves. There was significant variation in diversity among isolates (n = 51) between study years and different cattle. Metaphylaxis or antimicrobial treatment did not affect the diversity of isolates. Except for tilmicosin, isolates were largely susceptible to tested antimicrobials.

Effet du traitement antimicrobien et des stratégies préventives sur le complexe respiratoire bovin ainsi que la relation génétique et l'antibiorésistance des isolats deMycoplasma bovisdans un parc d'engraissement de l'Ouest canadien. Les veaux d'un parc d'engraissement (n = 3784) ont été systématiquement randomisés et répartis dans une étude factorielle 2 × 2 pour recevoir de l'oxytétracycline métaphylactique (OTC) à l'arrivée ou pas d'antimicrobien, ainsi qu'une injection sous-cutanée ou deux injections intramusculaires (à intervalle de 48 h) de florfénicol s'ils étaient diagnostiqués avec le complexe respiratoire bovin (CRB). Les veaux de différents groupes de traitement ont été regroupés pêle-mêle et suivis du placement à la réimplantation (~100 jours). Les animaux recevant l'OTC avaient un risque réduit de CRB, un risque accru d'arthrite et ne présentaient pas de différences significatives pour le gain de poids quotidien moyen, la rechute du CRB, la mortalité globale ou la mortalité associée au CRB. Il n'y avait aucune différence significative entre les protocoles de traitement. Des écouvillonnages nasaux profonds (n = 233) prélevés à l'arrivée (n = 122), au traitement (n = 77) et des écouvillonnages des poumons et des articulations post mortem (n = 34) ont été cultivés pour Mycoplasma bovis à partir de 61 animaux malades ou mourants de pneumonie chronique et d'arthrite et de 61 veaux en santé. Il n'y avait aucune variation significative dans la diversité des isolats (n = 51) entre les années d'étude et les différents bovins. La métaphylaxie ou le traitement antimicrobien n'a pas affecté la diversité des isolats. Sauf pour la tilmicosine, les isolats étaient largement sensibles aux antimicrobiens testés.(Traduit par Isabelle Vallières).

Comparison of covariate adjustment methods using space-time scan statistics for food animal syndromic surveillance.

BACKGROUND: Abattoir condemnation data show promise as a rich source of data for syndromic surveillance of both animal and zoonotic diseases. However, inherent characteristics of abattoir condemnation data can bias results from space-time cluster detection methods for disease surveillance, and may need to be accounted for using various adjustment methods. The objective of this study was to compare the space-time scan statistics with different abilities to control for covariates and to assess their suitability for food animal syndromic surveillance. Four space-time scan statistic models were used including: animal class adjusted Poisson, space-time permutation, multi-level model adjusted Poisson, and a weighted normal scan statistic using model residuals. The scan statistics were applied to monthly bovine pneumonic lung and "parasitic liver" condemnation data from Ontario provincial abattoirs from 2001-2007. RESULTS: The number and space-time characteristics of identified clusters often varied between space-time scan tests for both "parasitic liver" and pneumonic lung condemnation data. While there were some similarities between isolated clusters in space, time and/or space-time, overall the results from space-time scan statistics differed substantially depending on the covariate adjustment approach used. CONCLUSIONS: Variability in results among methods suggests that caution should be used in selecting space-time scan methods for abattoir surveillance. Furthermore, validation of different approaches with simulated or real outbreaks is required before conclusive decisions can be made concerning the best approach for conducting surveillance with these data.

Increased annexin A1 and A2 levels in bronchoalveolar lavage fluid are associated with resistance to respiratory disease in beef calves.

Strategies to control bovine respiratory disease depend on accurate classification of disease risk. An objective method to refine the risk classification of beef calves could be economically beneficial, improve welfare by preventing unexpected disease occurrences, refine and reduce the use of antibiotics in beef production, and facilitate alternative methods of disease control. The objective of this study was to identify proteins in bronchoalveolar lavage fluid (BALF) of stressed healthy calves that predict later disease outcome, serve as biomarkers of susceptibility to pneumonia, and play a role in pathogenesis. BALF was collected from 162 healthy beef calves 1-2 days after weaning and transportation. Difference in gel electrophoresis (DIGE) and mass spectrometry were used to compare proteins in samples from 7 calves that later developed respiratory disease compared to 7 calves that remained healthy. Calves that later developed pneumonia had significantly lower levels of annexin A1, annexin A2, peroxiredoxin I, calcyphosin, superoxide dismutase, macrophage capping protein and dihydrodiol dehydrogenase 3. Differences in annexin levels were partially confirmed by western blot analysis. Thus, lower levels of annexins A1 and A2 are potential biomarkers of increased susceptibility to pneumonia in recently weaned and transported feedlot cattle. Since annexins are regulated by glucocorticoids, this finding may reflect individual differences in the stress response that predispose to pneumonia. These findings also have implications in pathogenesis. Annexins A1 and A2 are known to prevent neutrophil influx and fibrin deposition respectively, and may thus act to minimize the harmful effects of the inflammatory response during development of pneumonia.

Laboratory and postmortem diagnosis of bovine respiratory disease.

Pathologic and laboratory investigations are essential when identification of the specific cause of bovine respiratory disease is needed. Considerations for planning a diagnostic investigation include the goals of the inquiry, the potential impact of the diagnosis, the plausible causes based on the clinical and epidemiologic appearance, and the relative merits of the available diagnostic strategies. This review uses 4 cases to outline different approaches to laboratory diagnosis. The postmortem examination is described, along with the patterns and gross appearance of lesions, considerations for effective sampling from appropriately selected animals, and reasons for discrepant or negative laboratory test results.

Suitability of bovine portion condemnations at provincially-inspected abattoirs in Ontario Canada for food animal syndromic surveillance.

BACKGROUND: Abattoir condemnations may play an important role in a food animal syndromic surveillance system. Portion condemnation data may be particularly useful, as these data can provide more specific information on health outcomes than whole carcass condemnation data. Various seasonal, secular, disease, and non-disease factors have been previously identified to be associated with whole carcass condemnation rates in Ontario provincial abattoirs; and if ignored, may bias the results of quantitative disease surveillance methods. The objective of this study was to identify various seasonal, secular, and abattoir characteristic factors that may be associated with bovine portion condemnation rates and compare how these variables may differ from previously identified factors associated with bovine whole carcass condemnation rates. RESULTS: Data were collected from the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and the Ontario Cattlemen's Association regarding "parasitic liver" and pneumonic lung condemnation rates for different cattle classes, abattoir compliance ratings, and the monthly sales-yard price for commodity classes from 2001-2007. To control for clustering by abattoirs, multi-level Poisson modeling was used to investigate the association between the following variables and "parasitic liver" as well as pneumonic lung condemnation rates: year, season, annual abattoir audit rating, geographic region, annual abattoir operating time, annual total number of animals processed, animal class, and commodity sales price. CONCLUSIONS: In this study, "parasitic liver" condemnation rates were associated with year, season, animal class, audit rating, and region. Pneumonic lung condemnation rates were associated with year, season, animal class, region, audit rating, number of cattle processed per year, and number of weeks abattoirs processed cattle. Unlike previous models based on whole carcass condemnations, commodity price was not associated with partial condemnations in this study. The results identified material-specific predictor variables for condemnation rates. This is important for syndromic surveillance based on abattoir data and should be modeled and controlled for during quantitative surveillance analysis on a portion specific basis.

Factors associated with whole carcass condemnation rates in provincially-inspected abattoirs in Ontario 2001-2007: implications for food animal syndromic surveillance.

BACKGROUND: Ontario provincial abattoirs have the potential to be important sources of syndromic surveillance data for emerging diseases of concern to animal health, public health and food safety. The objectives of this study were to: (1) describe provincially inspected abattoirs processing cattle in Ontario in terms of the number of abattoirs, the number of weeks abattoirs process cattle, geographical distribution, types of whole carcass condemnations reported, and the distance animals are shipped for slaughter; and (2) identify various seasonal, secular, disease and non-disease factors that might bias the results of quantitative methods, such as cluster detection methods, used for food animal syndromic surveillance. RESULTS: Data were collected from the Ontario Ministry of Agriculture, Food and Rural Affairs and the Ontario Cattlemen's Association regarding whole carcass condemnation rates for cattle animal classes, abattoir compliance ratings, and the monthly sales-yard price for various cattle classes from 2001-2007. To analyze the association between condemnation rates and potential explanatory variables including abattoir characteristics, season, year and commodity price, as well as animal class, negative binomial regression models were fit using generalized estimating equations (GEE) to account for autocorrelation among observations from the same abattoir. Results of the fitted model found animal class, year, season, price, and audit rating are associated with condemnation rates in Ontario abattoirs. In addition, a subset of data was used to estimate the average distance cattle are shipped to Ontario provincial abattoirs. The median distance from the farm to the abattoir was approximately 82 km, and 75% of cattle were shipped less than 100 km. CONCLUSIONS: The results suggest that secular and seasonal trends, as well as some non-disease factors will need to be corrected for when applying quantitative methods for syndromic surveillance involving these data. This study also demonstrated that animals shipped to Ontario provincial abattoirs come from relatively local farms, which is important when considering the use of spatial surveillance methods for these data.

Mycoplasma bovis in respiratory disease of feedlot cattle.

Mycoplasma bovis has recently emerged as an important cause of chronic caseonecrotic bronchopneumonia, arthritis, and tenosynovitis in beef cattle. Mycoplasma bovis can act as a primary pathogen, yet many cases are coinfected with other bacteria or viruses, and evidence suggests that M. bovis colonizes and perpetuates lung lesions that were initiated by other bacteria, such as M. haemolytica. Mycoplasma bovis elicits a robust humoral immune response, but the resulting antibodies are not protective because of the variable surface proteins, and vaccines have not yet been shown to prevent disease. Mycoplasma bovis infections are responsible for a high proportion of the chronic disease occurring in feedlots, and the welfare of such animals is an important aspect of feedlot health management.

Objective structured clinical examinations (OSCEs) as a summative evaluation tool in a ruminant health management rotation for final-year DVM students.

The objective structured clinical examination (OSCE) has been used for 10 years at the Ontario Veterinary College, University of Guelph, to evaluate the clinical competencies in ruminant health management of final-year DVM students. The performance of these students in the summative assessment, which includes the use of OSCEs, was compared to their formative assessment, given at the end of the rotation. Specifically, classification of students' performance as poor (bottom 10% of the grade range versus "serious deficits") or superior ("A grade" versus "exceeds expectations") was compared. Agreement between the two types of assessment is slight, regardless of whether assessing diagnostic process skills or technical skills--and regardless of whether all students were assessed or only those enrolled in food-animal or mixed streams in their final year--which suggests that the two assess different types of skills. OSCEs are a useful and viable tool for objectively assessing clinical skills in ruminant health management.

The effect of prepartum injection of vitamin E on health in transition dairy cows.

The objective of this study was to investigate parenteral vitamin E for the prevention of peripartum disease in dairy cows. A randomized clinical trial was conducted in 21 commercial dairy herds. Cows (n = 1142) were randomly assigned to receive either a single subcutaneous injection of 3000 IU of vitamin E, or placebo, 1 wk before expected calving. Serum alpha-tocopherol was significantly increased in treated cows at 7 and 14 d, but not at 21 d after injection. Overall, there were no significant differences between treatment groups in the incidence of retained placenta, clinical mastitis, metritis, endometritis, ketosis, displaced abomasum, or lameness. However, there was a conditional benefit of treatment for reduction of the incidence of retained placenta. Cows with marginal pretreatment vitamin E status (serum alpha-tocopherol to cholesterol mass ratio < 2.5 x 10(-3)) that received an injection of vitamin E tended to have reduced risk of retained placenta. However, in cows with adequate serum vitamin E, there was no reduction in the incidence of any disease. For clinical application, primiparous animals were most likely to benefit from prepartum injection of vitamin E.