LEC 17 - Orthomyxviruses Flashcards
Characteristics: Influenza Type A
Broad host range
Characteristics - influenza type B
Humans
Seals
Characteristics Influenza Type C
Minor disease in humans and pigs
What is the structure of the influenza envelope?
Contains spikes with hemagglutinin + neuraminidase
What is the genomic structure of influenza?
Segmented
ssRNA (-)
What two proteins are contained in the envelope?
M1 + M2
Describe M1
Envelope matrix protein
Describe M2
Ion channels
What is the flu virus sensitive to?
Heat
Acid
Solvents + Detergents
What is bound to the RNA of influenza?
RNA polymerase complex
What is the components of the influenza nomenclature?
Virus type + Host + Geographic origin + Strain # + Year
(H + N subtype)
What are the pandemic vaccines?
Avian influenza
H 5 + 7 + 9
What are the regular vaccines?
B
H1 (Russian)
H3 (Avian)
H2 (Hong kong)
What is needed to start the replication process with influenza?
HA spikes bind to sialic acid receptors on cell = viral host range + tissue trophisms
How does the influenza virus enter the cell?
Receptor-mediated endocytosis
Vesicle acidified
M2 allows H+ ions to transverse membrane
Leads to conformation change in HA allowing membrane fusion
Nucleocapsid release from M1 to host
When is the maturation of the influenza virus complete?
Virions bud through host membrane lipid rafts w/ inserted viral spike + matrix protein
What is critical for viron release?
viral NA
What is the function of viral NA?
Cleaves sialic acid receptors that would otherwise bind + trap virus
What must happen to hemagglutinin inorder to allow for infection?
Viral protein must undergo postranslational cleavage
Describe HPAI
Highly pathogenic avian influenza have HA forms that are cleaved by a wider array of proteases
What are the common symtpoms seen with HPAI influenzas?
Produce severe uniformly fatal disease affecting most organs
What two things occurs within a virus that allow it to be so diverse and change so quickly?
Antigenic drift + shift
Describe antigenic drift?
Point mutation
Describe antigenic shift
Resssortment of genome segments
What happens with antigenic shift that allows for influenza virus to be so dangerous?
Bird virus + human virus mist in swine cell and by a hybrid virus that is more pathogenic
Where does the low pathogenicitic virus tend to target?
Intestinal epithelium
Few disease symtpoms seen
What is the method of transmission of the influenza type A virus?
Fecal-oral
What is the common reservior for the influenza type A virus?
Water fowl
What does equine influenza cause?
Respiratory disease
What is the main equine influenza type?
H3N8
What is the improtance of the flu vaccine with the equine influenza?
Counters antigenic drift
What symptoms are seen with equine influenza?
Fast onset
Reddening nasal mucosa + discharge
Fever
Paroxysmal cough
How long does it take a horse to normally recover from equine influenza?
2 to 3 weeks
What are the signs there is a secondary bacterial infection with EIV?
Purulent nasal exudate
Bronchiopneumonia
Where does EIV replicated?
Respiratory tract epithelium
Effects of EIV on upper respiratory tract
Destroys ciliated cells
= inflammation + discharge
Effects of EIV on lower respiratory tract
Traceitis + Bronchitis + Bronchointersitial pneumonia
with congestion alveolar edema
How is EIV diagnosed?
Clinical symptoms + rtPCR
Nasal or Oropharyngeal areas
Virus culture in eggs or cells lines w/ trypsin
How is EIV controlled?
Biosecurity
Antibiotics for secondary infections
Watching horses that travel often
When is the EIV infections most prevalent?
April to October — race season
What was the first recognized swine flu?
H1N1
What is the generic pathogenesis of swine flu?
Progressive necrotic, attack on epithleium in respiratory tract
Progression rate of swine flu
Short incubation period
Abrupt disease onset
Symptoms of swine flu
Fever
Huddling
Respiratory distress w. paroxysmal cough
Nasal discharge
What are the two major variants of H1N1?
US strain - similar to original
European strain - avian reservior derived strain
Where is it thought that mixing of the flu viruses most likely occurs?
Pigs
What is the used to diagnose swine flu?
rt-PCR
Rapid test kits
Virus isolation
What is typed via PCR?
Hemagglutinin
Neuramindase
When are outbreaks of swine flu most common?
Fall and winter
What is the general epidemology of swine flu?
Explosive spread
No carrier state known
Big economic impact
What is the key to controlling the swine flue?
Vaccination
What is the goal of the swine flu vaccine?
To prevent clinical disease
The vaccine does not prevent infection or shedding
Why can’t we control all infections with a vaccine that contains H1,2,3 + N1,2?
Vaccinate sows - maternal antibodies decline
Vaccines do not stop infection
Constant shift/drift allow flu virus to stay
Virus get to pigs from other sources
What is another name for the avian flu?
Fowl plague
What is the reservoir for the avian flu?
Waterfowl
What are the symtpoms of a HPAI strain of AVI?
Sudden ddeath without any previous signs
What are the symptoms of AVI?
Respiratory distress
No eggs
Lacrimation
Diarrhea
Edema of head and neck
Cyanosis of comb + wattle
Tremors
Stargazing
When does the LPAI strain of AVI cause problems?
In Turkeys
What symptoms are seen with LPAI strains of AVI?
Respiratory distress
Decrease in egg laying
Anorexia
Where does AVI replicate?
Intestinal + respiratory tracts
What does the most virulent forms of HPAI AVI produce in a chicken?
Virema
Multifocal lymphoid/visceral organ necrosis
What is the two key roles of HA in the infection process of AVI?
Attachment
Fusion of host + viral membranes
What is HA a large determinant of?
Pathogenicity
What changes the virulence of AVI?
Changes in the AA sequence of the cleavage site
What is the change at the AA sequence in AVI that causes it to be a LPAI?
one basic AA at the cleavage site
Where does HPAI strains of AVI tend to replicate in the body?
Liver
Lungs
Kidneys
Brains
How is AVI detected?
rt-PCR to detect viral M gene
+’s = tested for H5/H7 genes
+’s = Clocal/tracheal swabs cultured
What is a notifiable disease when it comes to AVI?
HPAI
or LPAI with H5 or H7
Where is waterfowl shedding AVI from?
Feces
How is AVI controlled?
HPAI is watched for closing with rapid mass culling when virus is detected
