Paramyxoviridae
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BACK TO VIRUSES
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
- -> Viral lipid bilayer can fuse directly with host plasma membrane
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
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
- Live attenuated vaccine may be incorporated in multivalent vaccines
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 34oC but not at 37oC
- Re-infection is common
Bovine Respiratory Syncytial Virus (BRSV)
- Pathogenesis:
- More serious than PI-3
- Causes [Respiratory Viral Infections - Pathology#Respiratory syncytial virus|respiratory infection]]
- Replicates in nasal epithelium -> throughout upper respiratory tract -> bronchial tree
- Syncytia form -> shed into bronchioles
- Complications include emphysema and oedema, drop in milk yield in adult cattle
- Epidemiology:
- Subclinical reinfections are important in spreading disease
- More than 70% of cattle in the UK have antibodies to BRSV
- Diagnosis is same as for PI-3
- Control
- Improve husbansry as in PI-3
- Vaccines are available but not effective as need to stimulate cytotoxic T-cells
- Reference: Bryson, 1999, Update on calf pneumonia, CPD Veterinary Medicine, 1,3, 90-95
Canine Distemper Virus (CDV)
- Hosts: dogs, ferrets, seals, lions, mink
- Has been a major pathogen of dogs prior to vaccination
- Variable mortality depending on virulence
- May occur subclinically
- Involvement of central nervous system generally results in death
- Pathogenesis:
- Aerosol infection
- Infects alveolar macrophages or oropharynx
- Multiplies in the bronchial and other lymph nodes, infects monocytes and dendritic cells
- Viraemia
- Spreads via monocytes to a variety of epithelium depending upon the strain of virus
- Respiratory and alimentary tracts, skin and later (1-5 wk. post infection) to the brain
- Clinical signs:
- Mucopurulent oculonasal discharge
- Keratitis
- Interstitial pneumonia
- Severe clinical pneumonia follows secondary infection with Bordetella bronchiseptica
- Smelly sometimes bloody diarrhoea
- Eruptions on the skin including hyperkeratosis of the nose and pads (hardpad)
- Demyelination (especially in cerebellum) -> incoordination or muscle tremors -> paralysis and coma or convulsions -> death
- Encephalitis
- Secondary pyogenic infections associated with immunosuppression and damage to epithelia
- Recovered animals may have persistent or spasmodic chorea
- 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.
- Diagnosis:
- May present as series of infections
- Immunocytochemistry of inclusion bodies
- Intracytoplasmic inclusions may be found in most affected tissues
- Inclusions persist longest in the brain (may be intranuclear) and the alveolar macrophages
- Sections of fixed bronchial tissue, lung, macrophages, bladder may be used or nasal or conjunctival epithelium from live animals
- Giant cells may be seen in the alveoli
- Control:
- Live attenuated virus vaccines given at 10 and 12 weeks of age
- Some now given at 7 and 10 weeks to allow socialisation
- Homeopathic vaccines do not work
- Live attenuated vaccines may kill some wildlife therefore Iscom vaccine is used in seal sanctuaries
- Live attenuated virus vaccines given at 10 and 12 weeks of age
- Can contribute to Infectious canine tracheitis
- May be involved in chronic interstitial pancreatitis
- May cause growth retardation lattice
- May also trigger latent Toxoplasmosis due to suppressing effect on lymphoid tissue
Hendra Virus
- Equine Paramyxovirus
- Causes respiratory infections with respiratory distress and paralysis
- Potentially zoonotic (beware palpating inside the throat for obstruction)
Nipah Virus
- Infects pigs and humans
- Humans exposed to pig blood are at risk