Paramyxoviridae

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Overview

• Systemic infections - controlled by live monotypic vaccination
• Respiratory infections - not controled by live monotypic vaccinations

Classification

• Paramyxovirinae
  • Bovine Parainfluenza 3
  • Canine Parainfluenza 2
  • Murine Parainfluenza 1 (Sendai virus)
  • Newcastle Disease (NDV) - avian paramyxovirus serotype 1
  • Avian Paramyxoviruses serotypes 2-9
  • Reptilian Paramyxoviruses
  • Mumps
• Morbilliviruses
  • Canine Distemper (CDV)
  • Rinderpest
  • Pest de petit ruminant (PPR)
  • Measels
  • Seal virus - phocine distemper
  • Dolphin Morbillivirus
  • Hendra virus
  • Nipah virus
• Pneumovirinae
  • Bovine Respiratory Syncytial Virus (BRSV)
  • Turkey Rhinotracheitis Virus

Virus properties

Structure

• Negative sense RNA, unsegmented, single stranded
  • -> Reasortment and antigenic shift cannot occur
• HN spike contains:
  • Haemagglutinin (H)- attachment protein
  • Neuraminidase (N)
• Fusion glycoprotein (F) spike
  • -> Viral lipid bilayer can fuse directly with host plasma membrane
    • -> RNA released into cytoplasm
  • ->Syncytium (multinucleated giant cells) in lesions and cell culture
  • Host antibody response to this protein is most important
    • Best induced by live attenuated vaccines

Growth in vitro

• Allantoic cavity of 10-day-old eggs
• Followed by haemagglutination

In vivo

• Cell tropism for upper respiratory tract epithelium
  • All replicate in these cells
• Some replicate in the gut
• Most virulent replicate in lymphoid cells and neurons (Distemper, NDV)
• Links to the readiness to cleave Fo and Ho precursors in different cells

Antigenic differentiation

• Major conserved immunodominant virus-specific antigens on F and HN
  • -> Vaccines protect against all isolates of the same virus
• Minor morbillivirus-specific epitopes on F
  • Some crossprotectin between canine distemper, measels and rinderpest
• Minor variable epitopes of F, HN and NP
  • Allows antigenic fingerprinting

Canine Distemper Virus (CDV)

• Canine Distemper virus in rhinitis and Infectious canine tracheitis ?Paramyxovirinae, morbillivirus, also in chronic interstitial pancreatitis
  • May cause growth retardation lattice

{Canine distemper - a pantropic virus which has a suppressing effect on lymphoid tissue, and which may trigger latent Toxoplasmosis. After aerosol infection, the virus multiplies in the bronchial and other lymph nodes. It then spreads to a variety of epithelium depending upon the strain of virus including that of the respiratory and alimentary tracts, skin and later (1-5 wk. post infection) to the brain, causing a mucopurulent oculonasal discharge with keratitis and an interstitial pneumonia, a smelly sometimes bloody diarrhoea, eruptions on the skin including hyperkeratosis of the nose and pads, and encephalitis respectively. The essential feature of the last mentioned is demyelination particularly in the cerebellum resulting in ataxia. Convulsions, coma and paralysis may occur, and chorea (rhythmic motor movements) may be seen in recovered animals. Intracytoplasmic inclusions may be found in most affected tissues and inclusions persist longest in the brain (may be intranuclear) and the alveolar macrophages. Giant cells may be seen in the alveoli. The severity of the disease may vary; if enough neutralising antibody develops in the early stages, the virus maybe kept restricted largely to the lymph nodes. Severe clinical pneumonia follows secondary infection with Bordetella bronchiseptica.} From RVC respiratory notes 2006 by B.Smyth

Newcastle Disease Virus (NDV)

• Hosts
  • Gallinaceous birds, pigeons, parrots, finches
  • Subclinical carriers: ducks, ostriches
  • Causes conjunctivitis in humans

• Virulence
  • Disease ranges from subclinical respiratory tract infections -> torticollis -> haemorrhages and death

• Epidemiology
  • Air-born
  • Direct contact of poultry

• Diagnosis
  • Samples of trachea and gut of 20 birds are tested in eggs
  • HI using anti-NDV serum (to differentiate HA caused by avian influenza
  • Animal test: virulence of isolate tested by the speed it kills chicks
  • Sequencing the cleavage site of H gene
    • The more basic amino acids the more virulent the virus
    • Now replacing the animal test

• Control
  • Isolation of stock
  • Vaccination of chickens and racing pigeons
  • Surveillance of imported exotic birds
  • Notifiable disease
  • Infected premises to be culle and firebreak cull if spread

• Parainfluenza - 2 in rhinitis and Infectious canine tracheitis of dogs

• Parainfluenza - 3 in rhinitis of cattle
• Bovine respiratory syncytial virus in respiratory infection
• Hendra virus in respiratory infections

On line lecture by P. Russell

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