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New diagnostic tool for BRD can change vaccine protocols

Tom Shelton Published on 27 February 2015

A new technology is helping to identify what viruses or bacteria are causing early bovine respiratory disease (BRD) – thanks to a timelier, more accurate and less-invasive diagnostic test.

Deep nasal pharyngeal swab collections, combined with updated molecular diagnostics in the form of real-time reverse transcriptase polymerase chain reaction technology, is one of the newest diagnostic advances in dairy animal health.

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Deep nasal pharyngeal swabs are helping to identify some viruses that are hard to culture, and consequently have not been associated with early BRD, as well as the opposite, excluding some viruses that were believed to be related to early BRD.

Traditionally, bronchial alveolar lavages or trans-tracheal washes are techniques that require anesthesia and collection of fluid from the lungs in acute cases of pneumonia. These are invasive and time-consuming approaches.

Alternatively, tissue samples from expired animals can be sent to the diagnostic lab for culture and sensitivity. This submission determines what pathogens are present at the time of death, not necessarily the ones that initiated the problem.

This new approach provides a more accurate assessment of what is happening at the start of clinical symptoms and can yield a very quick analysis of what pathogens are causing the problem.

This allows veterinarians and producers to determine a more accurate vaccine and treatment approach. Deep nasal pharyngeal swabs are a non-invasive, repeatable, accurate, quick and semi-quantitative determination of the cause of pneumonia.

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The tonsils in the pharyngeal area (throat) of calves less than 6 months old have proven to harbor the same pathogenic organisms that induce the early signs of pneumonia in the lungs.

Using the guarded sterile swab (only the tip contacts the tonsil area), we are able to collect a relatively clean sample that avoids the contaminants in the external nasal cavity. This also gives us an idea of the level of infection and what antibiotics may provide the best result for treatment in the case of bacterial problems.

This concept has been validated by correlating the pathogens we find in the throat with those found in the lungs at the first sign of pneumonia.

This technology is applied to calves showing early signs of pneumonia, collecting samples before we treat them and overnighting the samples to one of several labs that have the capability and primers (molecular keys) to determine the pathogens.

In the case of all of the viruses and some of the bacteria, we may have an answer the next day. An added advantage for bacterial identification is a relatively unadulterated (cleaner) sample that lends itself to easier culture and sensitivity results, which may be better aligned with the antibiotic of choice to treat in the face of an outbreak.

The long-accepted belief that bovine respiratory viruses initiate most bacterial pneumonias has proven to be true in some cases but may be less important in others. Identifying two viruses that are hard to culture and went undetected have now proven to be common.

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Conversely, viruses previously believed to be common, including infectious bovine rhinotracheitis and bovine viral diarrhea, have been found to be rare in early BRD cases in young dairy calves before they are commingled.

The utilization of deep nasal pharyngeal swab diagnostic testing provides many opportunities:

1. Understand what viruses are present in young calves, providing the ability to attempt disease control either through passive transfer of protective antibodies or active immunization, whichever lends itself to better control for the particular pathogen.

2. Identify the early bacterial problems and determine their sensitivity to specific antibiotics in a timely manner, so we can intercede in the face of an outbreak rather than waiting for deaths, submissions and lab results, which take time and may not reflect the populations that initiated the disease.

3. Sample populations on a seasonal basis or set timing to monitor both pathogen populations and expected response to treatment protocols – or, conversely, sample calves when response to treatment declines below expectations.

4. Utilize these results to support environmental controls, hygiene and sanitation to reduce exposure.

5. Realign vaccine protocols in both adult and neonatal animals to increase both economic and metabolic efficiencies, in some cases by eliminating antigens previously considered to contribute to early respiratory problems and now are found to be less significant, or initiate vaccine protocols that provide a more specific application.

As we apply and expand our molecular diagnostic technologies, and combine this with what we are learning in the way of vaccine consequences to production (metabolic cost) and better ways of presentation by pathogen and age of vaccination, we can combine mucosal (in most cases intranasal) with traditional parenteral (subcutaneous or intramuscular) to provide the most efficient protection and performance.

This involves creating the most efficient means for both onset and duration of protection while allowing for maximum growth, utilization of expensive feedstuffs (feed efficiencies) and maximum performance, whether it be growth or milk production.

We are in the early stages of utilizing this technology, and many more applications will be identified as utilization increases. Already, the results have allowed us to increase our sophistication in the approach we use to vaccinate young animals.

In some cases, we can omit vaccines and in others include a more timely application, which all contributes to the bottom line of efficient production.

Talk to your veterinarian to see if this new technology makes sense on your operation. The more we can learn about what’s causing sickness in our animals, the better we can manage their health and performance.  PD

Tom Shelton
  • Tom Shelton
  • Senior Technical Services Vet
  • Merck Animal Health

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