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BRD is defined as a “disease complex”:
- It usually is caused by a variety of pathogens, both viral (Bovine Respiratory Syncytial Virus (BRSV), ParaInfluenza 3 (PI3), Adenovirus, Bovine Viral Diarrhea Virus (BVDV), and Infectious Bovine Rhinotracheitis (IBR)) and bacterial (Pasteurella multocida, Mannheimia haemolytica, Histophilus somni, Mycoplasma bovis).
- Parasitic (lungworm) and fungal (Aspergillus) agents are also pathogens.
- These pathogens interact with one another and the animal’s immune system to produce full-blown disease.
- Bacterial pathogens apparently cause the acute syndrome by invading the bovine respiratory tract that has been compromised by viral infections, environmental conditions and/or other stress factors.
Contributing to the disease complex is stress. Stressors include weaning, changes of feed, variation in ambient temperature and humidity, and weather.
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Clinical signs of BRD in cattle depend on many factors including the age of the animal, the causative organism(s) and thestage of the disease.
General signs:
- Fever - The connection between BRD and fever is extremely strong. BRD is one of the most common causes of fever - and fever is always one of the earliest signs of the BRD complex.
- Depression.
- Lack of appetite.
- Dullness
Respiratory signs:
- Rapid, shallow breathing.
- Coughing.
- In early BRD cases, the lungs and airways are generally painful, so the animal will try to clear the airway with mild, tentative, soft coughing.
- Loud, prominent coughing or “honking” indicates far more chronic, advanced cases, at which point treatment is difficult.
- Serous (watery), then purulent (pussy), and/or bloody nasal and eye discharge.
- Salivation.
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Diagnosis may be made on clinical signs and epidemiology, but additional examinations are often needed (e.g., tracheal washings, nasopharyngeal swabs, blood samples, post-mortem examinations).
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Treatment should always be specifically targeted to the disease and the symptoms (anti-infectious agents(Antibiotics and Sulfas), antiparasiticides, non steroidal anti-inflammatories, bronchodilators, mucolytics, oral rehydration fluids) in consultation with the attending veterinarian.
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The key to preventing respiratory disease is to reduce stress and to vaccinate against viruses and bacteria that cause disease.
- Vaccination with biological products targeting the viral and bacterial pathogens.
- Appropriate use of antibiotics labeled for control of BRD
- Good cattle handling and stress reduction
- Minimize exposure to environmental conditions that contribute to disease, such as dust, crowding, fumes (proper ventilation is a key - especially with dairy facilities).
- Provide adequate rest, feed and water (especially after shipping).
- Make sure animals receive adequate levels of essential nutrients such as vitamins and minerals.
- Nutritional soundness also helps prevent disease and improves immune function.
- Handle animals with care. Use low stress handling techniques.
- Reduce and/or minimize pen movements.
- Make sure bedding is clean and dry .
- Keep animals as clean and dry as possible.
- Avoid overcrowding.
- Maintain good housing and ventilation.
- Minimize heat stress.
- Make sure animals receive the right deworming program in areas affected by lungworm.
- Effective colostrum management
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- In the US beef industry, BRD continues to be the primary cause of morbidity and mortality in feedlots contributing to losses in performance, carcass quality and health.
- In the US dairy industry respiratory disease continues to play a major role in death losses in weaned calves and morbidity due to BRD affects survivability and reduced dairy performance later in life.
- Economic losses include death loss, decreased weight gain, and additional labor and treatment costs.
United States 
