The Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, frequently supports veterinarians and producers investigating bovine respiratory disease. Because of the multiple etiologies often involved, many professionals refer to it as Bovine Respiratory Disease Complex (BRDC).
The impact of the disease varies by operation, but it affects both animal welfare and financial outcomes.
“Operations with a high prevalence of BRD spend a lot of time and effort treating ill individuals which can affect their bottom line,” said Resident Director of the laboratory in Canyon, Alexis Thompson, DVM, Ph.D., DACVPM.
“Presently, cattle are very expensive. Every day an individual is sick means that they are not growing at their potential, which is additional time on feed and at the lot. This in turn affects the number of animals available for harvest and may impact the price consumers see at the grocery store.”
Because so many factors and pathogens can be involved in this disease complex, timely, accurate diagnostics play a critical role in identifying what’s driving an outbreak and helping veterinarians and producers respond effectively.
What is BRDC?
BRDC develops when several factors line up at once. Stress, viruses, bacteria, and management changes can all play a role. Together, they weaken the animal’s immune defenses and allow bacteria in the respiratory tract to overgrow.
Common signs include:
- Fever
- Lethargy
- Nasal discharge
- Coughing
Often, viral infections occur first, damaging the respiratory system. Bacteria then take advantage of the favorable conditions and multiply, leading to pneumonia.
Spread and impact of BRDC
BRDC is highly contagious, especially when calves from different herds or housing locations are mixed together or comingled. BRDC most often occurs when recently weaned calves are moved into feedlots.
Thompson explains the contagious nature of Bovine Respiratory Disease in simple, relatable terms.
“Calves that are comingled are very similar to children going to kindergarten,” she said. “Every child brings germs from home that they are used to, but now they are in a new location and swapping germs with other children.”
Correspondingly, calves combining at a sale barn, backgrounding facility, or feedlot are often exposed to unfamiliar pathogens.
“When they encounter pathogens that they have never been exposed to, they get sick,” Thompson said.
This comparison highlights a key reality: BRD can spread fast, but it’s important to note that stress plays a major role in infection. Stressors weaken immunity and create ideal conditions for disease. Some stressors include:
- Weaning
- Shipping and transport
- Weather changes
- Dust and environmental conditions
- Castration
Diagnosing BRDC: Why testing matters
Identifying which pathogens are involved in an outbreak helps veterinarians and producers make better treatment and management decisions. TVMDL offers a bovine bacterial respiratory disease panel utilizing Polymerase Chain Reaction (PCR) technology that detects five common bacterial contributors:
- Histophilus somni
- Mannheimia haemolytica
- Pasteurella multocida
- Arcanobacterium (Trueperella) pyogenes
- Mycoplasma bovis
The TVMDL website provides helpful sampling and submission guidance, and diagnosticians in College Station and Canyon are always available to help clients navigate the process and choose the right testing approach.
“Knowing what pathogens we are dealing with in an outbreak can help guide our antimicrobial use,” Thompson said. “Additionally, it can help us in evaluating the risk factors in our population that may alter our management decisions, such as vaccinations or stocking densities.
A complex disease that requires a team approach
The multifactorial complexity of BRDC is why early recognition, good communication, and diagnostic support are essential. Veterinarians, producers, and diagnostic laboratories each play a role in reducing its impact.
“To ensure good antimicrobial stewardship, I hope that veterinarians and producers will submit samples from ill cattle before using antimicrobials,” Thompson said. “Additionally, reducing risk factors that cause stress in our cattle will hopefully reduce the number of animals that suffer from BRDC.”
For more information about TVMDL’s various test offerings, visit tvmdl.tamu.edu or call the College Station laboratory at 888.646.5623 or the Canyon laboratory at 888.646.5624.
Want more information on BRD? TVMDL is hosting a webinar in October covering BRD sample selection, testing, and result interpretation. Check out the Clinical Connections page to learn more and register.
