Paramyxoviridae Flashcards
What are some general properties of paramyxoviriae
- pleomorphic (filamentous and spherical forms)
- virions are enveloped
- diameter of about 150nm
- covered w glycoprotein spikes
- herringbone shaped helically symmetrical nucleocapsid
- single strand of linear, negative sense, ssRNA, 13-19kb
what are 5 important viral proteins of paramyxoviridae?
F- fusion protein HN- hemagluttinin neuraminidase M-matrix protein P- phosphoprotein N - nucleoprotein L- polymerase
What is the role of attachment spike protein in paramyxoviridae?
attachment of viruses to host cell
elicit neutralizing antibodies, induce protective immunity
t/f - the attachment protein varies b/w genera of paramyxoviridae
true
which genera of paramyxoviridae have hemagglutinin-neuraminidase as their attachment protein? what does HN do?
Genera: Respirovirus, Avulavirus, Rubulavirus
- cause hemagglutination
- has neuraminidase; virion release, destruction of mucin inhibitors
which genera of paramyxoviridae have hemagglutinin as their attachment protein? what does it do?
genus morbillivirus
-hemagglutination, but NO NEURAMINIDASE
which genera of paramyxoviridae have G-protein as their attachment protein? what does it do?
henipavirus, pneumovirus, metapneumovirus
- no hemagglutination
- no neuraminidase
describe paramyxoviridae membrane fusion.
fusion protein, present in all genera, mediates the fusion of the viral envelop with the plasma membrane of the host cell. Virus penetration by this process is not dependent on a low pH environment.
Cell-to-cell spread of viruses occurs this way, big part of presistent infection (immune response evasion)
cause syncytium formation, elicits neutralizing antibodies
t/f Matrix (M) protein is important for virion stability
true
what does Nucleoprotein (N or NP) do?
bind to RNA, protection of genomic RNA
what is transcriptase complex made of?
Large(L) protein
phosphoprotein(P)
cysteine-rich protein (V)
t/f - paramyxoviruses replicate in the nucleus
false - replicate in cytoplasm of cells
what are some major histological features of paramyxoviridae infections? how about the genus morbillivirus specifically?
acidophilic cytoplasmic inclusions, made of ribonucleoproteins
formations of syncytia
morbillivirus specifically: characteristic acidophilic intranuclear inclusions
what are the five main genera of subfamily paramyxovirinae?
- Respirovirus
- Avulavirus
- rubulavirus
- morbillivirus
- henipavirus
what are the two main genera of the subfamily pneumovirinae?
- pneumovirus
- metapneumovirus
what condition is caused by respirovirus?
bovine parainfluenza virus-3 respiratory disease
what is the host and the transmission of BPV3 Respiratory disease?
host is cattle and sheep
transmission is primarily aerosol, but also occurs by ingestion of contaminated fomites (nasal discharge)
what is the pathogenesis of BPV3 respiratory dz?
epithelial cells of respiratory tract targeted
infection results in necrosis and inflammation in small airways in the lungs - bronchitis and bronchiolitis
predispose animal to bacterial invasion/pneumonia
clinical signs of BPV3 respiratory disease
uncomplicated cases result in mild respiratory dz
- calves and lambs: fever, lacrimation, serous nasal discharge, dyspnea, and coughing. recovery in 3-4 days
- bovine pneumonia: role in initiating so-called shipping fever aka bovine respiratory dz complex. w/ other viruses or as sole pathogen, predisposes animals to secondary bact infection(especially Mannheimia haemolytica)–> bact bronchopneumonia
how do you diagnose BPV3 respiratory dz?
- virus isolation from nasal discharge
- id in nasal discharge and resp tissues by FAT and ELISA
- paired sera(acute/convalescent):antibodies quantitated by VN test, HI test, ELISA
- RT-PCR
how do you control BPV3 respiratory dz?
inactivated or live modified(attenuated) vaccines, usually combo with other pathogens. intranasal or parenteral
is newcastle dz reportable?
YES
what causes newcastle dz?
Avulavirus: avian paramyxovirus serotype 1
what are the differences b/w low and high virulence strains of avian paramyxovirus serotype 1?
- low: produce precursor F proteins cleaved only by a trypsin-like protease which have a restricted tissue distribution and are usually distributed extracellularly.
- high: precursor F’s cleaved intracellularly by proteases present in cells lining mucous membranes. viruses replicate in more cell types
describe the five pathotypes of newcastle dz virus
1) asymptomatic enteric
2) lentogenic - less virulent
vND(virulent Newcastle dz)
3)mesogenic - moderately virulent
4/5)velogenic pathotype strains - highly virulent (viscerotropic and neurotropic)
Exotic Newcastle Dz(END): US name for velogenic viscerotropic
velogenics aren’t present in usa, but are brought in via illegally imported game chickens and exotic birds
what are the hosts of newcastle dz
most avians
- pigeons highly susceptible
- canaries, finches pretty resistant
- humans: conjunctivitis
transmission of newcastle dz occurs how?
Respiratory secretions and feces contain high concentrations of virus.
Virus is shed for up to 4 weeks in all secretions and excretions of birds that
survive the infection.
Major route of transmission:
Inhalation of aerosols and dust particles
Ingestion of contaminated feed and water
Contaminated fomites.
Mechanical spread between flocks is facilitated by the relative stability of the virus
and its wide host range.
Vertical transmission rare: reported for lentogenic virus strains
what’s the pathogenesis of Newcastle dz?
Initially it replicates in the mucosal epithelium of the URT and GIT, then one of two things can happen:
1) no further dz spread for lentogenic and enteric strains
2) vND: primary viremia –> spread to bone marrow and spleen –> secondary viremia –> infection of other target organs; lung, intestine, CNS
what are the clinical signs of visceroptropic velogenic newcastle dz?
respiratory, w/ depression, watery green diarrhea, and swelling of the head and neck
hemorrhages and ulcer-like lesions are seen in the digestive tract
mortaliy approaches 100% in all age groups
what are the clinical signs of neurotropic velogenic newcastle dz?
respiratory signs, followed by nervous signs of tremors, paralyzed wings and legs, twisted necks, circling, clonic spasms, and complete paralysis
cns lesions are encephalomyelitis, with neuronal necrosis
hemorrhages absent from GI tract
mortality approches 100% in all age groups
what are the clinical signs of mesogenic and lentogenic newcastle dz?
mesogenic: acute respiratory dz, reduced egg production, and uncommonly neuro signs; mortality aproaches 25% in young chickens, rare in adults
lentogenic: respiratory signs of gasping, coughing sneezing and rales predominate
the dz in turkeys is similar but usually less severe than that in chickens; there are signs of respiratory and nervous involvement
t/f - severe depression with a reluctance to stand or move is associated with viscerotropic velogenic ND
true
t/f - abnormal perching reflex is associated with newcastle dz
true
t/f - feather loss is associated w newcastle dz
false, ruffled feathers are associated
t/f - mild conjunctivitis and dehydration are associated with newcastle dz
false; severe acute conjunctivitis and edema are associated with newcastle dz
t/f - watery greenish diarrhea is associated with viscerotropic velogenic newcastle dz
true
t/f periorbital, facial and neck edema are associated with viscerotropic, velogenic newcastle dz
true
t/f - sometimes soiled vents with diarrhea are associated w/ viscerotropic velogenic newcastle dz
true
what are the three main tools to diagnose newcastle dz?
virus isolation, RT-PCR, and serology
What must be done to determine the virulence of newcastle dz?
intracerebral pathogenicity index in day old chickens (0.7 or more)
presence of a specified amino acid motif at the cleavage site of the fusion protein(F) precursor(FO).
what must be done to farms infected with newcastle dz?
quarantine and depopulation.
Newcastle DZ is REPORTABLE
what vaccinations are available for newcastle dz?
- live lentogenic vaccines, chiefly B1 and LaSota strains, are widely used and typically administered to poultry by mass application in drinking water of by spray
- oil adjuvanted inactivated vaccines are also used after live vaccine in breeders and layers
- fowlpox or turkey herpesvirus-vectored NDV vaccines are commercially available for chickens
what does newcastle dz cause in humans?
ndv can produce a transitory conjunctivitis in humans, and occurs primarily in laboratory workers and in members of vaccination teams
what major virus is from the rubulavirus genus?
canine parainfluenza virus-5
what is the canine parainfluenza virus responsible for?
one of several pathogens that cause kennel cough
how is CPiV-5 transmitted?
aerosolized microdroplet
what is the pathogenesis of CPiV?
the virus causes destruction of the ciliated epithelial cells of the respiratory tract, predisposing to secondary infections
What are the three main things which characterize rinderpest?
the 3 D’s: discharge, diarrhea, and death
what is the etiology of canine distemper?
canine morbillivirus
how many strains of canine morbillivirus are there? how are they classified?
there are at least ten strains, based on differences in the hemagglutinin gene.
what 3 strains of canine morbillivirus are regarded as highly virulent and neurotropic?
snyder hill
A75/17
R252
How does canine morbillivirus (distemper) persist in different temperatures?
in warm climates, the virus will not persist in kennels after infected dogs have been removed
in near freezing temperatures (0-4 C) the virus survives in the environment for weeks
how resilient is canine morbillivirus in the face of most disinfectants?
ordinary disinfectants can inactivate the virus
what are the hosts of canine morbillivirus (distemper)
domestic and wild dogs
raccoon, panda, ferret, mink, bears, etc
CNS infections in exotic felidae
how is canine morbillivirus transmitted?
inhalation of infected droplets
transplacental infections can occur from viremic dams
what cell types does canine morbillivirus replicate in?
macrophages
t and b lymphocytes
epithelial cells
nervous tissue
what is the pathogenesis of canine morbillivirus?
1) the virus replicates in the macrophages in URT tissues, then spreads to tonsils and regional lnn.
2) after multiplication in the lymph nodes, the virus enters the bloodstream, circulating in b and t lymphocytes.
3) virus spreads to lymphoid tissues in body; GALT, mesenteric lymph nodes, kupffer’s cells of the liver
4) virions formed in these sites are then carried by blood mononuclear cells during secondary viremia
5) further spread of CDV to epithlial and CNS tissues on day 8-9 PI occurs hematogenously, and depends on the dog’s cell-mediated and humoral immune response
How does the cell mediated and humoral response influence the outcome of infection?
in dogs with >1:100 antibody titers, on day 8 or 9, there is no more spread of virus, and it is cleared from lymphoid tissues. the infection remains subclinical.
In dogs with low antibody titers and poor cell-mediated immune response by day 14 post-infection: virus spreads to many tissues including the epithelium of the GI tract, respiratory tract and genitourinary tract.
t/f - In canine morbillivirus, invasion of CNS occurs when the viremia is of sufficient magnitude.
true - details to know:
Infection of the central nervous system occurs relatively late in the course of infection.
Dogs producing anti-envelope antibodies appear to prevent persistent infection of CNS.
describe acute canine distemper virus encephalitis
occurs in young and immunosuppressed animals, and
is characterized by direct viral replication and injury to CNS.
Acute noninflammatory demyelination in microglial and astroglial cells
describe subacute to chronic CDV encephalitis
characterized by reduced expression
of CDV antigen and a strong upregulation of inflammatory response.
The immune reaction rather than virus replication causes demyelination
at this stage.
Chronic perivascular cuffing with demyelination
what are the late complications of CDV?
Observed in old dogs. These may also be seen in dogs with no history of earlier acute
or subacute disease.
Hardpad disease: Hyperkeratosis of foot pads and the nose due to virus
multiplication in the skin.
Old Dog Encephalitis:
Extremely rare, chronic , progressive inflammatory disease of gray matter of
cerebral hemispheres and brainstem of CNS.
Occurs in immunocompetent animals with persistent virus in their neurons in
a replication defective form.
Often marked by ataxia, compulsive movements such as head pressing.
what are the signs of canine distemper in an old dog?
Clinical signs:
1) Transient fever usually occurs 3–6 days after infection with leukopenia
(especially lymphopenia).
2) A second febrile response indicates serious phase of the infection,
accompanied by profound leukopenia.
3) Serous or mucopurulent nasal discharge, conjunctivitis, and depression.
4) Some dogs show primarily respiratory signs, whereas others develop
gastrointestinal signs:
Respiratory signs reflect inflammation and injury to the upper respiratory
tract and large airways. Productive cough; bronchitis and interstitial
pneumonia may follow.
Gastrointestinal involvement: vomiting and watery diarrhea.
Both respiratory and GI signs may be complicated by secondary bacterial
infection.
5) Dogs surviving the acute phase may have hyperkeratosis of the footpads and
epithelium of the nasal planum. Hyperkeratosis of the nose and footpads is often
found in dogs with neurologic manifestations
what is the greatest diagnostic tool for CDV?
Immunofluorescent assay or reverse transcriptase (RT) PCR
describe canine distemper control and vaccination
Control:
Control of canine distemper virus infection is based on adequate diagnosis,
quarantine, sanitation, and vaccination.
The virus is very fragile, and susceptible to standard disinfectants.
Vaccination:
Successful immunization of pups with canine distemper modified live virus
(MLV) vaccines depends on the lack of interference by maternal antibody
Alternatively, measles virus vaccine induces immunity to canine distemper virus
in the presence of relatively greater levels of maternal distemper antibody.
Remember:
MLV vaccines should not be used in late-pregnant or early-lactation bitches.
MLV vaccines can produce postvaccinal illness in some immunosuppressed dogs.
what does morbillivirus cause in ruminants?
Peste des petits ruminants (PPR)
aka Goat Plague
t/f - PPR aka Goat Plague is a reportable dz
True
describe the lineage of PPR viruses
Peste des petits ruminants virus has been grouped into four distinct lineages based
on the sequence of the F protein.
Lineages 1 and 2 occur in West Africa
Lineage 3 in East Africa, the Middle East, and southern India
Lineage 4 extends from the Middle East to Tibet
what is the host of PPR?
Host: Goats and Sheep.
More severe in goats than in sheep.
how is PPR transmitted?
Infection is primarily by inhalation
There is no carrier state in goats and sheep
describe the pathogenesis of ppr
Inhalation–> Retropharyngeal mucosa–> Viremia–> damage to alimentary, respiratory and lymphoid systems.
Infected cells undergo necrosis, resulting in mucosal erosions and lymphopenia.
Death may occur from severe diarrhea and dehydration, before respiratory lesions become severe
what are the clinical signs of PPR?
The acute form of the disease is seen in goats and similar to rinderpest, except that severe respiratory distress is a common feature of PPR.
Early, the nasal discharge is serous; later, it becomes mucopurulent and gives a putrid odor to the breath.
Extensive erosions and necrosis in the mucosal lining of the oral cavity, and also in esophagus, abomasum, and small intestine (necropsy)
Profuse catarrhal conjunctivitis, high fever, necrotic stomatitis
Diarrhea may be profuse
Bronchopneumonia
Pregnant animals may abort
how do you diagnose PPR?
Clinical signs: Necrotic lesions in mouth, profuse diarrhea
Necropsy: Streaks of congestion with “zebra-striped” appearance in large intestine.
Field conditions: Agar-gel immuno-diffusion test and the PPR penside test
ELISA
RT-PCR
describe how to control PPR
Local and federal authorities should be notified when PPR is suspected.
Eradication is recommended when the disease appears in previously PPR-free
countries.
Attenuated vaccine has been prepared in Vero cell culture
what is the etiology of Bovine Respiratory Syncytial Dz?
genus pneumovirus
two antigenic subtypes based on differences of the G protein.
describe the hosts and transmission of BRSV
cattle of all ages, but mostly <6 months of age
Bovine respiratory syncytial virus (BSRV) infection occurs most often during the winter months, when are housed in confined conditions.
Virus spreads rapidly, probably through aerosols or droplets of respiratory tract excretions.
describe the pathogenesis of BRSV
Pathogenesis:
BSRV causes rhinitis, tracheitis, bronchitis, bronchiolitis & mild interstitial
pneumonia.
The pathogenesis of fatal pneumonia due to BSRV may be associated with an
immune mediated mechanism (hypersensitivity reaction mediated by IgE).
The severe highly fatal form of the disease, known as “malignant form” or “the
Paroxystic Respiratory Distress Syndrome (PRDS) , has been associated with extensive
pulmonary mast cell degranulation.
Gross lesions include a diffuse interstitial pneumonia with subpleural and interstitial
emphysema along with interstitial edema
what will you see in BRSV infections on histological samples?
Syncytial cells in bronchiolar epithelium and lung
parenchyma.
Intracytoplasmic inclusion bodies.
Edema, and hyaline membrane formation
what are the clinical signs of BRSD?
Fever (104–108°F [40–42°C]), depression, decreased feed intake, increased
respiratory rate, cough, and nasal and lacrimal discharge are common.
Dyspnea, possibly with open-mouthed breathing, later stages of disease.
Secondary bacterial pneumonia is a frequent occurrence
describe diagnosis and control of BRSD
Diagnosis:
Clinical signs
Necropsy: Dramatic distension of lungs by edema, alveolar hyperinflation,
emphysema.
Histopathology
Virus isolation: Transtracheal aspirate. Difficult as virus is fragile.
Specimens should not be frozen.
FAT test or immunohistochemical staining
RT-PCR
VN test on paired sera (convalescent and acute samples)
Control:
Immunity is incomplete and transient following natural BRSV infection of
calves
