Pathology and Microbiology of Respiratory Infections - Small Animals Flashcards
Normal flora in the lower respiratory tract (LRT)
normally sterile
Normal flora in the upper respiratory tract (URT)
Streptococci - α-haemolytic/non-haemolytic Streptococci - β-haemolytic Pasteurella Staphylococci coagulase-negative Staphylococci coagulase-positive E. coli Actinobacillus Proteus Bordetella Pseudomonas Neisseria Lactobacillus Clostridium Bacillus Mycoplasmas Chlamydophila
Viral infections of the lower respiratory
tract
viruses that cause infections of the URT frequently spread down the respiratory tract and may cause bronchitis + bronchiolitis
all viruses that cause infections of the URT or LRT can predispose to bacterial infections
primary vs secondary infection
Secondary infections more clinically important
affects previously damaged lung tissue due to viral or parasitic involvement, or is facilitated by environmental stress
pure vs mixed infection
some bacteria important as pure infections
others are involved in mixed infections where initial damage by one species allows invasion by more pathogenic species
Respiratory disease: Small animals
Bordetella Pasteurella β-haemolytic Streptococci Actinomyces & Nocardia Chlamydophila Mycoplasmas
bordetella bronchiseptica
Strict aerobe, Gram-negative rod, Slow growing (48 hours)
Normal inhabitant of upper resp. tract in animals
Exogenous or endogenous infection: survival outside the host is poor.
Associated with tracheobronchitis (kennel cough) bronchopneumonia following distemper.
vaccine available (not v.good)
bordetella bronchiseptica in cats
Serological evidence for early exposure
to B. bronchiseptica in kittens
Respiratory disease common
Involvement of B. bronchiseptica unclear
Cultured from 11% of cats; none from household pets
Vaccination with NobivacBb (Intervet)
B.bronchiseptica - Pathogenesis & Pathology
Initial trauma? viral infection
adhers to respiratory epithelium (cilia) of trachea
proliferation of B. bronchiseptica in the airway
release of toxins irritation & coughing
epithelial necrosis
peribronchial inflammation & interstitial pneumonia
severe pneumonia due to secondary invaders eg. β-h strep
b.bronchiseptica - pathogenicity
Adherence to resp. ciliated epitheliu - FHA, fimbriae, pertactin (OMP)
Toxins - Adenylate cyclase (leucocyte toxin), tracheal cytotoxin (inhibits DNA synth in ciliated cells), dermonecrotic toxin (ADP-ribosylation)
Pasteurella multocida
Gram-negative rod, Large grey mucoid colonies, Oxidase-positive
No growth on MacConkey
Strong catarrhal smell
Normal oral bacteria in the dog & other animals
Secondary infection - URT infections
Common bacteria infecting dog bite wounds
Capsular serotypes A and D
Vaccines inappropriate - too few opportunities to intervene
Pathology of Pasteurella multocida in dogs and cats
Severe suppurative pneumonia and pleuritis (empyaema)
Important in cats following bites or other infected wounds
Often part of mixed infections
enzoonotic pasteurellosis URT
purulent material filling sinuses
enzoonotic pasteurellosis - control
Bacterin vaccines fail to protect.
Long-term antimicrobial therapy (enrofloxacin) may be needed to control & even eliminate the infection.
enzoonotic pasteurellosis - LRT
multifocal pulmonary abscesses - foci of radiopacity
streptococcus
Found in normal URT
β-haemolytic streptococci highly virulent in the lung: S. zooepidemicus (also S. canis)
Lancefield grouping Groups C and G
M protein, toxins, capsule, superantigen
Simple vaccines not effective
Actinomyces viscosus
Gram-positive, filamentous, branching, Aerobic growth
Commensal in canine oral cavity
Cause of granulomatous thoracic infection in dogs
Localised granulomatous abscesses of skin
Chronic & progressive
nocardia spp.
Gram-positive rods, thin, short filaments, Partially acid fast (wax-like mycolic acid)
Growth within, and destruction of, macrophage
Chronic, progressive, suppurating, thoracic granulomas
Resistant to Penicillin and some other antimicrobials
Prolonged use of TMP, Tetracyclines, Ampicillin
pathology of norcardiosis
red-brown exudate in pleural cavity (strawberry milkshake appearance)
may become chronic with adhesion formation
exudate has sulphur granules
Chlamydophila felis
intracellular Gram-negative rods (no growth on lab media)
Conjunctivitis in cats, nasal discharge progress to interstitial bronchopneumonia
Detect by ELISA for antigen, PCR, Kosters or fluorescein-labelled antibody
Not seen in the dog (?)
Vaccination in the cat
mycoplasma spp.
Several mycoplasmas of the dog resp. tract are known.
M. cynos increasingly implicated in some KC infections.
canine nasal aspergillosis
Aetiology - Aspergillus fumigatus
Diagnosis - Radiology, Endoscopy, Serology, Culture, Microscopy
Treatment - Surgical delivery of antifungal
nasal aspergillosis - pathology
Nasal turbinates progressively destroyed by chronic granulomatous (and eosinophilic) infl
may be yellow-green mycotic exudate in caudal nasal cavity
Numerous fungal hyphae (filaments) on histopathological examination
