Developing a Rapid, Chute-Side Diagnostic Test to Inform BRD Treatment

Background

Bovine respiratory disease (BRD) continues to be the biggest animal health challenge to the Canadian cattle feeding sector. Data compiled over time suggests morbidity and mortality due to respiratory disease continues to increase despite introduction of new antimicrobials and a newer generation of vaccines over the last two decades.

Many technologies have been examined to help in the detection and diagnosis of respiratory disease. Despite this, traditional visual pen checking followed by rectal temperature assessment is still the standard management strategy used to diagnose sick cattle. However, this approach has long been recognized to lack sensitivity and specificity (approximately 62% sensitive and 63% specific), leading to a high percentage of false-positive and false-negative diagnoses.

The objective of this study was twofold. The first objective was to test a prototype of a proprietary technology, the visual interference color assay (VICA), for its ability to measure haptoglobin, an inflammatory protein produced in response to infection, as a point-of-care test in a commercial feedlot setting. A second objective is to evaluate haptoglobin for its ability to predict animals requiring antibiotic therapy for BRD. The use of a confirmatory test in conjunction with visual pen checking and rectal temperature assessment will improve health outcomes and reduce antibiotic use by focusing treatment on those animals that warrant it.

Objectives

• To determine if use of haptoglobin, an inflammatory biomarker, is a predictor of both the need for antimicrobial treatment for BRD as well as the severity to improve health outcomes in a commercial feedlot setting
• To demonstrate that the visual interference color assay technology is rapid, robust and can be used chute side

What they did

Part one of the study tested the visual color interference assay (VICA) technology as a point of care device in a commercial feedlot. In two small pilot studies, researchers demonstrated the chute-side technology accurately measured haptoglobin, but due to sample handling requirements, it took longer than desirable (approximately 3 minutes). This was considered too long to keep up with the workflow, particularly during the fall run, so the researchers elected to sample the cattle as planned and perform the analysis in a lab setting.

Part two evaluated haptoglobin as a marker for respiratory disease. For this part of the study approximately 480 fall placed calves that were pulled for treatment of respiratory disease (380) or served as controls (100) were sampled for haptoglobin analyses. Animals that were pulled for BRD had rectal temperature recorded and those ≥43.3oC were treated with an antibiotic and returned to the home pen while those <40.3oC were returned to the home pen untreated. Animals that relapsed at least once and animals that died within 90 days were included in the analysis.

What they learned

The population of animals sampled was divided into five health cohorts for analysis:

• Control (C); no symptoms of BRD
• No Treatment (NT); pulled for BRD but not treated (temp. < 43.3oC)
• Pneumonia (P); pulled and treated for BRD (temp. ≥43.3oC)
• Pneumonia Relapse (P2); treated at least twice for BRD
• Died (D); animals that subsequently died following treatment for BRD

Statistically different haptoglobin levels were found between the groups. Increasing levels of haptoglobin were associated with increasing disease severity. As expected, the control population was lowest followed by calves pulled but not treated, and then those treated for BRD. Animals that relapsed or died were similar, but both were higher than the single BRD treatment group. This supports previous work demonstrating haptoglobin is a good marker of BRD and correlates with disease severity.

It is important to note that haptoglobin data was from a single sample taken at first pull or when pulled as controls. Differences measured between animals that survived following treatment and those that relapsed or died provides the opportunity to manage that high-risk group differently at the time of first treatment. This may include a different antibiotic regime, longer duration of therapy or use of other supportive treatments.

Experience gained from the pilot studies with the VICA technology provided useful feedback on how to optimize the process to work chute side in a commercial feedlot setting. This involved engaging a biomedical engineering firm to assist with the redesign of the sample handling device. This has been completed, and additional testing of the prototype was expected to commence in Fall 2025.

What it means

With cattle prices at record levels, the cost of lost productivity and mortality to respiratory disease has never been higher. The traditional method of pen checking relies on visual assessment for disease detection, followed by rectal temperature measurement for disease confirmation. However, once animals are presented for evaluation, multiple studies have shown that rectal temperature alone is an unsatisfactory diagnostic tool, highlighting the need for a reliable confirmatory test. This study found significant differences in serum haptoglobin levels within the health cohorts examined and supported other research showing it can assist in predicting health outcomes. Work is ongoing to refine the VICA assay to improve speed with the goal of using the technology chute side.