1. Infectious Agents:
* Viruses:
* Bovine respiratory syncytial virus (BRSV): A major contributor to BRD, often causing initial infection and making cattle more susceptible to bacterial infections.
* Infectious bovine rhinotracheitis (IBR) virus: Causes upper respiratory tract infections, making cattle more vulnerable to other pathogens.
* Parainfluenza virus type 3 (PI3V): A common cause of coughing and respiratory distress, often in calves.
* Bovine viral diarrhea virus (BVDV): Can suppress the immune system, making cattle more susceptible to other infections, including pneumonia.
* Bacteria:
* Mannheimia haemolytica: A major cause of severe pneumonia, often associated with viral infections.
* Pasteurella multocida: Another significant bacterial pathogen that can lead to pneumonia, especially in calves.
* Histophilus somni: Can cause various infections, including pneumonia, especially in calves.
* Mycoplasma bovis: A common cause of chronic pneumonia and respiratory problems.
2. Environmental Factors:
* Stress: Transportation, weaning, overcrowding, cold weather, and poor ventilation can compromise the immune system and make cattle more susceptible to infection.
* Dust and Poor Air Quality: Dusty environments can irritate the lungs, making them more susceptible to infection.
* Poor Nutrition: Inadequate nutrition weakens the immune system and increases susceptibility to respiratory diseases.
3. Predisposing Factors:
* Age: Calves and young cattle are more susceptible to pneumonia due to their developing immune systems.
* Breed: Certain breeds may be more prone to respiratory problems.
* Immune Status: Cattle with weakened immune systems are more susceptible to infection.
4. Management Practices:
* Poor Hygiene: Unsanitary environments can facilitate the spread of pathogens.
* Lack of Vaccination: Vaccination against key pathogens can help prevent or reduce the severity of pneumonia.
Important Note: Pneumonia in cattle is often a complex interplay of these factors. It's rarely caused by a single agent, and multiple pathogens often work together to cause disease.
Understanding the causes of pneumonia in cattle is crucial for developing effective prevention and treatment strategies. By addressing the contributing factors, producers can significantly reduce the risk of this costly disease.