Bayesian evaluation of clinical diagnostic test characteristics of visual observations and remote monitoring to diagnose bovine respiratory disease in beef calves.

Accurate diagnosis of bovine respiratory disease (BRD) in beef cattle is a critical facet of therapeutic programs through promotion of prompt treatment of diseased calves in concert with judicious use of antimicrobials. Despite the known inaccuracies, visual observation (VO) of clinical signs is the conventional diagnostic modality for BRD diagnosis. Objective methods of remotely monitoring cattle wellness could improve diagnostic accuracy; however, little information exists describing the accuracy of this method compared to traditional techniques. The objective of this research is to employ Bayesian methodology to elicit diagnostic characteristics of conventional VO compared to remote early disease identification (REDI) to diagnose BRD. Data from previous literature on the accuracy of VO were combined with trial data consisting of direct comparison between VO and REDI for BRD in two populations. No true gold standard diagnostic test exists for BRD; therefore, estimates of diagnostic characteristics of each test were generated using Bayesian latent class analysis. Results indicate a 90.0% probability that the sensitivity of REDI (median 81.3%; 95% probability interval [PI]: 55.5, 95.8) was higher than VO sensitivity (64.5%; PI: 57.9, 70.8). The specificity of REDI (median 92.9%; PI: 88.2, 96.9) was also higher compared to VO (median 69.1%; PI: 66.3, 71.8). The differences in sensitivity and specificity resulted in REDI exhibiting higher positive and negative predictive values in both high (41.3%) and low (2.6%) prevalence situations. This research illustrates the potential of remote cattle monitoring to augment conventional methods of BRD diagnosis resulting in more accurate identification of diseased cattle.

The use of lung biopsy to determine early lung pathology and its association with health and production outcomes in feedlot steers.

The objectives of this study were to determine if percutaneous lung biopsy can be used to characterize early pathologic changes in bovine lung associated with bovine respiratory disease (BRD), to determine if specific infectious respiratory pathogens can be identified in association with these changes, and to determine whether pulmonary pathology at arrival and at the time of initial diagnosis are associated with health and production outcomes. One hundred auction-market derived crossbred steer calves from a commercial feedlot in southern Alberta were included in this study. A percutaneous lung biopsy technique was used to obtain lung samples from the right middle lung. Steers were sampled 295 times yielding 283 samples with 210 (74%) containing lung tissue. Overall, histopathological changes were observed in 20 (9.5%) of lung biopsy samples. There were too few samples with pathology to reveal an association between lung pathology and subsequent health events. In general, percutaneous lung biopsy can be done safely on feedlot steers in a commercial feedlot setting with few clinical side effects. This technique did not prove useful as a diagnostic tool or prognostic indicator for early BRD. However, it may be useful for the diagnosis of BRD in targeted populations of commercial feedlot steers.

Les objectifs de la présente étude étaient de déterminer si une biopsie pulmonaire obtenue par voie transcutanée pouvait être utilisée afin de caractériser dans les poumons bovins les changements pathologiques hâtifs associés aux maladies respiratoires bovines (MRB), de déterminer si des agents infectieux pathogènes spécifiques au système respiratoire peuvent être identifiés en association avec ces changements, et de déterminer si les pathologies pulmonaires à l'arrivée et au moment du diagnostic initial sont associées avec les résultats de production et de santé. Cent bouvillons de race croisée issus d'encans et élevés dans un parc d'engraissement commercial du sud de l'Alberta ont été inclus dans cette étude. Une technique de biopsie pulmonaire transcutanée a été utilisée pour obtenir des échantillons de poumon du lobe pulmonaire médial droit. Les bouvillons ont été échantillonnés 295 fois produisant 283 échantillons avec 210 (74 %) contenant du tissu pulmonaire. Des changements histopathologiques ont été observés dans 20 (9,5 %) des échantillons de biopsie pulmonaire. Il y avait trop peu d'échantillons avec des pathologies pour démontrer une association entre une pathologie pulmonaire et des conséquences subséquentes sur la santé. En général, la biopsie pulmonaire transcutanée peut être faite de manière sécuritaire sur des bouvillons d'embouche en parc d'engraissement commercial avec peu d'effets cliniques secondaires. Cette technique ne s'est pas avérée utile comme outil diagnostique ou indicateur de pronostic pour les MRB hâtives. Toutefois, elle pourrait être utile pour le diagnostic de MRB dans des populations ciblées de bouvillons d'embouche en parc d'engraissement.(Traduit par Docteur Serge Messier).

The development of a novel percutaneous lung biopsy procedure for use on feedlot steers.

The purpose of this study was to develop a percutaneous lung biopsy technique to be used on steers in a commercial feedlot setting. Thirty-four crossbred steer and heifer calves from a commercial feedlot in southern Alberta were used in this study. The calves originated from the auction market and all were chronically affected with bovine respiratory disease (BRD). A technique was developed to obtain a lung sample from the right cranioventral lung lobe, intercostal space (ICS) 2, using a manual or an automatic biopsy instrument with a 14- or 12-gauge (ga) biopsy needle. Overall, lung parenchyma was successfully harvested in 55.9% of experimental animals and in 55.0% of lung biopsy trials. Compared with postmortem diagnosis, the biopsy resulted in the same pathologic diagnosis for 75% of biopsy samples when evaluated using standardized criteria by the same veterinary pathologist. The success rate was 61.5% and 42.9% in a hospital or field setting, respectively. With an automatic instrument, lung was recovered from 57.9% and 37.5% of samples obtained using a 12- or 14-ga biopsy needle, respectively. One experimental animal or 2.9% of the total had fatal complications from the procedure. In a commercial feedlot setting, the procedure took 20 min for each animal. Percutaneous lung biopsy of the right cranioventral lung lobe may be a viable technique when used on feedlot steers affected with chronic pneumonia. These findings suggest that using an automatic instrument with either a 14- or 12-ga biopsy needle may yield lung samples that are suitable for histopathological evaluation. However, this technique needs to be further evaluated in a field setting.

A multiplex polymerase chain reaction assay for the identification of Mannheimia haemolytica, Mannheimia glucosida and Mannheimia ruminalis.

The objective of this study was to design a multiplex PCR assay to identify Mannheimia haemolytica, Mannheimia glucosida and Mannheimia ruminalis. The multiplex PCR included primer sets HP, amplifying a DNA region from an unknown hypothetical protein, Lkt and Lkt2, amplifying different regions of the leukotoxinD gene, and 16S to amplify universal bacterial sequences of the 16S rRNA gene. Based on positive amplification, isolates were delineated as M. haemolytica (HP, Lkt, 16S), M. glucosida (HP, Lkt, Lkt2, 16S), or M. ruminalis (HP, 16S). The validity of the assay was examined against 22 reference strains within the family Pasteurellaceae and 17 field isolates (nasal) that had been collected previously from feedlot cattle and tentatively identified as M. haemolytica based on morphology and substrate utilization. Additionally, 200 feedlot cattle were screened for M. haemolytica using multiplex PCR. Forty-four isolates from 25 animals were identified as M. haemolytica. The PCR assay positively identified all M. haemolytica, as confirmed by phenotypic tests and clustering based upon cellular fatty acid methyl ester (FAME) profiles. Selected nasal isolates that exhibited evidence of haemolysis, but were M. haemolytica-negative based on PCR, were also confirmed negative by phenotypic and FAME analyses. The multiplex PCR assay required no additional phenotypic tests for confirmation of M. haemolytica, within the group of bacteria tested.