Etiology:
- Trauma, injury, surgical incision
- Extension of infection from myocardium, pleurisy
- Bacterial infection:
- Cattle: Mannheimia hemolytica, black disease, Haemophilus spp, Tuberculosis, Pseudomonas aeruginosa, Mycoplasma spp, Klebsiella pneumonia, Actinobacillus suis
- Horses: Streptococcus equi, S. zooepidemicus, S. faecalis, Tuberculosis, Corneybacterium pseudotuberculosis, Actinobacillus equi,
- Sheep and goat: Pasteurella spp, Staphylococcus aureus, Mycoplasma spp
- Pigs: Pasteurellosis, Mycoplasma spp. especially Mycoplasma hyorhinis, Haemophilus spp. – Glasser’s disease and pleuropneumonia, Streptococcus spp., Salmonellosis
- Viral infection: EHV-1 infection, Feline infectious peritonitis, Canine distemper
- Fungal infection: Actinomycosis, coccidiodiomycosis