Calf Pneumonia Flashcards
Define ‘pneumonia’
An acute or chronic disease marked by inflammation of the lungs caused by viruses, bacteria, other MO’s and sometimes by physical/chemical irritants
What are the causes of BRD?
Bovine Resp. Syncytial Virus (BRSV) Infectious Bovine Rhinotracheitis (IBR) Parainfluenza virus 3 (PI3) Mycoplasma bovis, M. dispar Pasteurella spp., Mannheima spp., Histophilus spp.
What are the individual calf factors that can predispose to pneumonia?
Age, immunity, herd/calf BVDV status, housing environment
Describe the pathogenesis of bovine pneumonia
- Commensal colonisation
- Pre-disposing factors; stress, transport, virus, mycoplasma
- Decreased mucocillary clearance; impaired alveolar macrophage function
- Proliferation and inhalation of nasopharyngeal M. haemolytica, A1 colonisation of lung
- Release of leukotoxin, endotoxin and other virulence factors
- Mast cell degranulation, complement activation, cytokine release, infiltration and lysis of neutrophils and macrophages
- Fibrinous pneumonia
What are the bacterial spp. involved in BRD?
Mannheima haemolytica, Pasteurella mutocida, Histophilus somni
What are pasteurella virulence factors?
Lipopolysaccharide (LPS) - lipid A, bacterial lung damage, initiates complement and coagulation cascades which results in increased vascular permeability and coagulation. Accumulation of fibrin, oedema, inflammatory cells in lungs.
Lipooligiosaccharide (LOS)
How is Pasteurella infection diagnosed?
Isolation of bacteria from lower airways
Gram or geimsa stain - bipolar organisms
PM for absolute diagnosis
What are the general characteristics of H. somni?
Small to medium sized (0.5-1um) Gram -ve, coccobacilli Non-motile Fastidious Found on mucosal surfaces of cattle (host specific)
What specific diseases are caused by H. somni?
TEME (thromboembolic meningioencephalitis) - lesions consist of a fibrous meningitis with thrombosis and necrosis
Pneumonia with pleuritis and arthritis
Repro. failure - metritis, endometritis, late abortion, mastitis and vaginitis
What are the virulence factors of H. somni?
Endotoxin LOS
Extoxin - produces a weak haemolysin (survives inside bovine macrophages)
Host specificity - Fe limiting conditions cause bacteria to produce outer membrane proteins that obtain Fe from host transferrin
How is resp disease controlled?
Antibacterials
Vaccinations
Husbandry measures
How is pneumonia treated?
Antimicrobials - tetracyclines, macrolides, penicilllins, fluoroquinolones, sulphonamides
Define ‘biofilm’
Surface mounted, integrated communities of cells. Highly structured and physically dynamic. Protects bacteria from host defences and antimicrobial actions.
