Difference between revisions of "Paramyxoviridae"

Revision as of 15:45, 9 December 2007

BACK TO VIRUSES

Overview

Systemic infections - controlled by live monotypic vaccination
Respiratory infections - not controled by live monotypic vaccinations
On line Paramyxoviridae lecture by P. Russell

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

Reptilian Paramyxoviruses

Infect central nervous system and lungs
Kill particularly snakes
Healthy reptiles may be carriers
Testing by serology - HI test
Aim to keep virus free collection and prevent spread back into the wild

Murine Parainfluenza - 1 (Sendai virus)

Endemic in many mouse colonies
Most mice show no symptoms due to maternal antibodies
But minor respiratory lesions may invalidate carcinogenic or toxicological studies
Immunological studies also confused due to virus activating NK cells via high circulating IF 3-4 days post-infection
Control achieved by:
- Purchasing specific pathogen free (SPF) mice
- Kill whole colony in an outbreak -> disinfection -> formalin fumigation

Canine Parainfluenza - 2

or Parainfluenza - 5
Infects dogs
May cause mild upper respiratory infection, rhinitis
- Virus shed for a short time only
Also part of kennel cough (Infectious canine tracheitis), together with Bordetella bronchiseptica
Control:
- Live attenuated vaccine may be incorporated in multivalent vaccines
  - Immunity is short-lived
  - Only reduces severity of clinical signs

Bovine Parainfluenza - 3 (PI-3)

Virulence varies with isolates
Cessation of ciliary clearance and epithelial necrosis predisposes to secondary bacterial infections -> cough
May cause rhinitis of cattle
With other agents causes calf pneumonia
- Together with managemental factors (overcrowding, poor ventilation, high humidity, deprivation of colostrum and stress caused by transport or mixing of stock)
Diagnosis
- Diseased lung tissue from dead animals or centrifuged cells from lung lavage
- Virus is too fragile for cell culture isolation (often inactivated intransport)
- Antigen detection by immunocytochemistry for intracytoplasmic viral inclusions containing labelled viral protein
- Serology: 4-fold rise in ELISA antibody in paired serum samples from several animals
Control
- Improve managemental factors
- All-in, all-out systems
- Some vaccination
  - Temperature sensitive mutant that replicates at 34^oC but not at 37^oC
  - Re-infection is common

Bovine Respiratory Syncytial Virus

Bovine respiratory syncytial virus in respiratory infection
Diagnosis is same as for PI-3

Hendra virus in respiratory infections