Back in 1816, a French physician named René Laennec came upon an idea. The good doctor was frustrated by his limited ability to determine what was happening inside a patient’s body and, in response, invented a device for listing to the patient’s lung sounds. His invention, which consisted of a relatively simple shaped wooden tube, is regarded as the first stethoscope.
Medical historians consider the invention of the stethoscope a critical turning point in human medicine. Prior to Laennec’s innovation, doctors could only base their diagnosis and treatment decisions on a collection of gross symptoms. And about the only way to observe or diagnose internal pathology was through post-mortem examinations.
Those limitations sound familiar 200 years later, says Greg Quakenbush, DVM, when we look at how bovine respiratory disease (BRD) typically is diagnosed in feedyards and dairies. Farm crews observe and pull animals based on a variety of clinical signs including lethargy, labored breathing and nasal discharge, and perhaps measure rectal temperatures in the hospital. When treatments fail, veterinarians refine the diagnosis and identify the causative pathogens through necropsy findings.
Quakenbush is a technical services veterinarian with Geissler Corporation, the company that recently brought the Whisper Electronic Stethoscope to market after more than 10 years of development. The Whisper system, he says, can dramatically change the way veterinarians and feedyard or dairy crews diagnose BRD, manage and evaluate treatment protocols and, most importantly, reduce the performance losses and mortality associated with BRD.
Traditional diagnosis falls short
One of the most challenging aspects of controlling BRD is the difficulty in diagnosing the disease, particularly in its early stages when treatment is most effective. Multiple pathogens and environmental interactions result in a wide range of clinical signs. And some of the classic signs of BRD such as depression, fever or reduced appetite can result from conditions unrelated to BRD.
Numerous studies have shown a poor correlation between “respiratory pulls” in feedyards and actual signs of BRD in post-mortem examinations. When researchers examine cattle lungs at packing plants, they typically find a high percentage of lesions in cattle that were never pulled or treated for BRD, and lungs with no lesions from cattle that were diagnosed and treated.
Tom Noffsinger, DVM, with Production Animal Consultation in Nebraska, notes that in many feedyards, a rectal thermometer is the only objective diagnostic tool used to evaluate cattle for BRD. Most diagnoses rely on subjective observations, and even rectal temperature is not entirely reliable for diagnosing BRD. He became an early proponent of auscultation in feedyard hospitals, and data on more than 500,000 cattle from feedyards in Noffsinger’s practice group showed that using a conventional stethoscope at the hospital chute, along with rectal temperatures and observation of other clinical signs, improved the accuracy of BRD diagnosis significantly, with a 34 percent reduction in mortality rates compared with non-auscultated respiratory pulls. Interpretation of lung sounds from conventional auscultation can be subjective and inconsistent though, so Noffsinger, along with his Kansas colleague Wade Taylor, DVM, began to focus on making auscultation more objective and user-friendly for feedyard crews.
Eventually, they partnered with Geissler Corporation for engineering and software development for the Whisper system. The group spent nearly 10 years in developing the system, quantifying and validating the lung scores and building algorithms to convert lung sounds into digital audio signals, analyze key audio frequencies and translate the signals into visual graphics and accurate lung scores.
Using the Whisper system at the chute, the operator positions the stethoscope behind the elbow, over the apical lobe of the lung. Quakenbush explains that as BRD pathogens enter through the airways, the apical lobe typically is the first site of infection, so the Whisper algorithms are “trained” to that location.
A radio-frequency signal sends the audio from the stethoscope to the computer, and the image on the screen provides the operator with verification of a good reading and a visual representation of lung sounds. It takes a trained operator about eight seconds to obtain a lung score at chute-side using the system.
The Whisper lung scores indicate severity, duration and progression of disease, Noffsinger says. Caregivers can use the information to make objective treatment decisions and evaluate outcomes, potentially leading to reductions in BRD-related losses and more judicious use of antimicrobials.
Quakenbush says the feedyard records frequently show a significant percentage of respiratory pulls that exhibit lung scores of 1, indicating these animals might not have BRD but could be suffering from acidosis or other problems that looked like BRD to a pen rider. The veterinarian can decide to hold these animals for observation and appropriate treatment while treating those with lung scores of 3, 4 or 5 for BRD.
Quakenbush also believes the system can help support judicious antibiotic usage by reducing treatments in cattle that do not have BRD and by helping the veterinarian target the sick cattle with the most efficacious treatment. Noffsinger says he and other veterinarians have had good success treating mild BRD cases, such as those with lung scores of 2, with older, less-expensive antibiotics, while reserving the more-potent and more-expensive treatments for those with lung scores of 3 or higher.
The Whisper database retains records of each examination, which become available to the veterinarian, feedyard manager and designated staff. At any time, veterinarians can, through password-protected online access, look at the previous day’s records from client operations, showing how many cattle were pulled and how many exhibited each of the five lung scores. They also can look at weekly records and access graphs showing short- or long-term trends in pulls or lung scores, and view records on individual animals to evaluate progress.
The value in the system, Quakenbush says, lies in the veterinarian using it as a diagnostic tool for individual treatment decisions, for tracking trends and refining protocols. In this way, it can help the consulting veterinarian build value into his or her service.
In Noffsinger’s client feedyards, he has noticed that in cases where crews have used conventional stethoscopes, it takes a little time to adjust to the Whisper system, as it picks up sounds and frequencies they have not heard before. Initially, crew members often use a conventional stethoscope to confirm the Whisper readings, but after a week or so they gain confidence in the system and trust it to help them make correct decisions. In yards where crews have not used auscultation, it takes time for workers to understand the importance of case definitions. They see an animal showing physical signs of BRD and expect a certain reading from Whisper, but reality doesn’t always match their expectations. In all the yards, hospital crews, the management team and the veterinarian need to learn how to fully utilize the dynamic reporting system to review hospital activity and use the data to manage high-priority pens.
North Platte Livestock Feeders, a 70,000-head operation in western Nebraska, uses the Whisper system in all five of its hospital facilities. Manager Dennis Stucky says his pen riders and hospital crews, with training from Noffsinger, have gained a better understanding of case definitions and disease trends. They use the lung scores for individual treatment decisions and also for decisions regarding management of entire pens, as they can determine early on whether an outbreak in a pen merits observation or more-aggressive treatment.
Noffsinger’s records from about a year of using Whisper in the North Platte operation, including pulls, re-pulls, case definitions, treatments and death loss, show some clear trends. Since adopting the system, the number of pulled cattle diagnosed in “other” categories, rather than BRD, has increased significantly, resulting in more-appropriate treatment for those cattle. The hospital crew also has significantly increased its use of older, less-expensive antibiotics, in cases where the Whisper lung score indicates cattle will respond. This has reduced treatment costs while minimizing re-pulls and case mortality in those cattle.
Validation through research
In a study of over 3,000 cattle, which Noffsinger summarized in a presentation at the recent national BRD symposium, researchers found a 6 percent correlation between body temperature and case-fatality rate, with a confidence interval of 2.5 to 9.5 percent. In contrast, the correlation between the Whisper lung score and case-fatality rate was 79.8 percent with a confidence interval of 78.5 to 81.1 percent.
In another trial, the number of false negatives with fever as a diagnostic test predictor (i.e., those that died and did not have a fever) was 608 head. The number of false negatives with a Whisper lung score of 1as a diagnostic test predictor was 210 head, a reduction of 65 percent. The number of false negatives with a combined fever and Whisper lung score was 102 head, which is 506 head or 83 percent fewer than fever alone as diagnostic test predictor, and 108 head fewer than Whisper lung score alone as a predictor of fatality.
Based on records from over 12,000 cattle in six feedyards, compiled over the course of more than one year, the Whisper lung scores were highly predictive of case-fatality rates. In fact, every increase in lung-score rating (1 to 5) translates to a 50 percent increase in the odds of mortality, Quakenbush says.
Researchers also have collected data on lung scores of cattle upon arrival at the feedyard. In one study on 1,800 cattle arriving during April and May, wide fluctuations in lung scores between shipments and days were observed. In some shipments, nearly all the calves had normal lung scores, while in others up to 40 percent had scores of 2 or higher. Quakenbush says this information could allow veterinarians to better assess risk upon arrival, treating only those cattle with lung scores indicating treatment. As public and regulatory pressure mounts to reduce antibiotic use, this process could help demonstrate that antibiotics administered upon arrival are for treatment rather than prevention of disease.
The Whisper Electronic Stethoscope was developed by Geissler Corporation and is marketed by Micro Technologies. Noffsinger says a Whisper stethoscope and compatible laptop computer costs about $1,000, and the operation pays a monthly service fee for data management, costs that are quickly exceeded by savings through more-objective diagnosis and effective treatment.
View this article, and features on the veterinary feed directive, jejunal hemorrhage syndrome, beef cow-calf nutrition consultation and more in the October digital edition of Bovine Veterinarian.