Category:Bordetella species

Overview

• B. bronchiseptica infects a wide range of animal species worldwide
• B. avium resticted to birds
• Normal inhabitants of upper respiratory tract
• Cause repsiratory diseases including rhinitis, tracheitis, bronchitis and bronchiolitis
• Exogenous or endogenous infection
• Poor survival in the environment
• Transmission between animals
• Young animals particularly susceptible
• Predisposing factors include stress and concurrent infections
• High morbidity; low mortality

Characteristics

• Gram negative rods
• Strict aerobes
• Grow slowly
• Catalase and oxidase positive
• Non-lactose fermentors
• Grow on MacConkey agar
• Toxigenic strains agglutinate mammalian red blood cells
• Identical S form LPS in all strains of B. bronchiseptica - 1 diagnostic antigen
• B. bronchiseptica haemolytic, whereas B. avium not
• Affinity for ciliated respiratory epithelium

Pathogenesis and pathogenicity

• Use pathogenicity factors such as filamentous haemagglutanin (only B. bronchiseptica), fimbriae and pertactin to adhere to ciliated respiratory epithelium
• Produce toxins:
  • Adenylate cyclase (leucocyte toxin - kills phagocytes) (only B. bronchiseptica)
  • Tracheal cytotoxin (inhibits DNA synthesis in ciliated cells)
  • Dermonecrotic toxin
• Pathogenicity factors activated by environment and genetic changes
• Regulatory locus, BvgAS, mediates the activation
• Phase variation: genetic switch of Bvg locus allows transciption of pathogenicity factors
• Phenotypic modulation: temperature, magnesium ions and nicotinic acid affect expression of pathogenicity factors
• Bvg positive allows expression of pathogenicity factors and toxins and colonisation
• Bvg negative may allow survival in the environment with production of flagellae
• Mucosal IgA prevent attachment of bacteria to cilia, but clearance from the respiratory tract may take weeks
• Carrier animals are a source of infection

Diagnosis

• Samples include nasal swabs, tracheal aspirates and exudates
• Cultured on blood agar and MacConkey agar
• Biochemical profiles
• Slide agglutination tests for virulence of isolates

Infectious canine tracheitis/Kennel cough

• B. bronchiseptica acts as a primary pathogen in Infectious canine tracheitis
• Frequently isolated from dogs with respiratory disease
• Often found with viruses or mycoplasma
• Adheres to ciliated epithelial cells in the trachea
• Colonisation and proliferation in trachea
• Releases toxins causing epithelial necrosis and prevents ciliary clearance
• Irritation to tract causes coughing
• Mortality rates low
• Peribronchial inflammation and bronchopneumonia

can result in unvaccinated puppies or immunosuppressed dogs

• Severe pneumonia following secondary infection e.g. with Streptococci
• Fatal bronchopneumonia if occurs secondary to canine distemper virus
• Transmission via respiratory secretions by direct contact or aerosol and on fomites
• Clinical signs:
  • Develop within 3-4 days; persist for up to 2 weeks
  • Coughing
  • Gagging
  • Mild serous oculonasal discharge
• Treatments includes antibiotics if coughing persists or bronchopneumonia develops
• Live intranasal vaccines
• Also found in respiratory tract of cats; can cause pneumonia in kittens; vaccine available

Atrophic Rhinitis

• B. bronchiseptica causes Atrophic rhinitis of pigs in association with Pasteurella multocida
• Colonises nasopharynx
• Infection must occur during first few weeks of life
• Produces dermonecrotic toxin which damages osteoblasts, preventing bone formation
• Leads to turbinate atrophy without distortion of the snout in uncomplicated infections
• Atrophic rhinitis results when Pateurella multocida colonises and produces osteolytic toxin, leading to bone resorption
• Malformation of snout in growing pigs as well as poor growth
• increases with high stocking density and poor ventilation
• Vaccine available

Turkey coryza

• A highly infectious upper respiratory tract infection of poults caused by B. avium
• High morbidity, low mortality
• Infection spread by direct contact, aerosol and from the environment
• Rhinotracheitis
• Mucus accumulation in the nares
• Swelling of maxillary sinuses
• Beak breathing, lacrimation, sneezing
• Predisposes to infection with E. coli
• Treatment with antibiotics
• Bacterin and modified live vaccines available