CSI-Dairy: Bovine respiratory disease

 

Numerous ‘culprits’ on dairy farms combine to rob herd performance and injure a dairy’s bottom line. Identifying and arresting the offender isn’t always easy. In this month’s investigation, a new diagnostic tool provides the evidence necessary to solve the case.     

 

By Dr. Tom Shelton 

 

The sun was out, and the prospect of warmer weather was around the corner. Dr. Smith started his day with a routine herd pregnancy check at one of his larger clients. Dr. Smith met with Joe, the herdsman, on the 1,400-cow dairy. They happily discussed the farm’s successful pregnancy outcomes. With increasing reproduction rates and milk production, Joe commented that all was good on the operation. That is, with the exception of a few calves in the hutch that seemed “a little off.” 

 

Physical evidence

Dr. Smith went straight to the source – the calf hutches. On examination, he noticed a number of calves seemed depressed, even while lying down. Their heads were down, a few were coughing spontaneously and two had clear nasal discharge. They had not consumed all of their milk, were hesitant to get up and seemed unconcerned when examined closely in their hutch. Dr. Smith found numerous readings of 104.5° F. or greater on his digital thermometer. While listening to the lungs with his stethoscope, Dr. Smith detected increased lung sounds. All of the evidence pointed to early bovine respiratory disease (BRD), more commonly known as pneumonia.  

 

Identifying the bugs

There are several bacteria and viruses that could have been the cause. Dr. Smith advised Joe to use a relatively new diagnostic procedure called deep nasopharyngeal swabbing to identify the bug at fault. Joe was hesitant to invest in diagnostics because previous efforts had been futile or conducted too late to be effective. 

 

Dr. Smith explained this new diagnostic technique was his best shot at heading off the acute outbreak. A clean sample collected from the tonsils of a few calves with a guarded deep nasopharyngeal swab could be submitted for polymerase chain reaction (PCR) analysis, which identifies the pathogens by their genetic make-up. If samples could be collected right away, they would receive most of the results the next day.

 

Collecting evidence

Joe agreed to let Dr. Smith collect samples. Dr. Smith inserted a plastic-covered sterile swab through the nose of the calf down to the tonsils. He extended the sterile tip for collection, and then withdrew it to prevent contamination. Joe was surprised by how calm the calves were during this procedure. In some cases, they stayed on their feet and resumed eating. 

 

Test results

The next afternoon, Dr. Smith called Joe with the results. Evidence of an early calfhood virus and signs of the bacterium Pasteurella multocida, which is very common in early BRD cases, had been found. Fortunately, the virus could be addressed in their vaccination program. Dr. Smith explained that they were lucky, and were not dealing with Mycoplasma, a commonly-found bug which can be resistant to treatment.

 

Eliminating the bugs

Calves were treated with an antibiotic, and testing confirmed it was effective and pathogen sensitive. A culture revealed a sensitivity pattern to multiple antibiotics in an acute or early phase of the infection. This new method may yield a stronger correlation to treatment compared to necropsies. Sound vaccination protocols were implemented to eradicate viral issues.

 

Dr. Smith continued encouraging clients to use this new technology. He proactively tested BRD cases through several seasons, gaining a better understanding of how and when to set up vaccination and treatment protocols and follow the efficiencies of both. His clients reported the calf-health benefits realized by using this new method outweigh the costs, improving overall profitability. 

 

The unique ability to intercede in the face of an acute BRD outbreak has become a reality. Now, Dr. Smith better understands what bugs are present early in an outbreak. He has been able to collect enough information to recommend improved prevention and treatment protocols, resulting in healthier calves for his clients.

 

This cow-side investigation is a fictional story based on multiple real-world scenarios.

 

 

FYI

• Dr. Tom Shelton is a dairy technical services manager for Merck Animal Health. He lives in Utah and can be contacted at 208-867-3502 or tom.shelton@merck.com.

 

Each month, DairyBusiness Communications will check the case files of lead dairy
‘investigators’ to uncover another ‘CSI-Dairy’ mystery. Episodes are archived at www.dairybusiness.com.