16. Orthomyxovirus Infections

What type of virus are orthomyxoviruses?

RNA

How many genera are there in Orthomyxovididae?

5

What are the genera in Orthomyxoviridae?

1. influenza A
2. influenza B
3. influenza C
4. Thogoto virus
5. Isavirus

What species are affected by influenza A?

humans, other mammals (pigs, seals, horses leopard, racoon, dog, ferret, cat, tiger, bat), birds (chickens, ducks, turkeys, ostrich, water fowl, emu, quail)

What species are affected by influenza B?

human, pig, seal

What species are affected by influenza C?

human, pig

What species are affected by influenza D?

human, pig, horse, cattle, camel, sheep, goat

Which type of influenza causes the most severe disease?

influenza A

How are influenza A classified?

basis of surface proteins: haemagglutinin (H) and neuraminidase (N)

Compare influenza B to influenza A

influenza B is much less common than A; mutates at rate 2-3 times lower than A

Describe the effect of influenza C

can cause severe illness and local epidemics, however is less common and usually just causes mild disease in children

What are examples of influenza A diseases?

avian influenza, equine influenza, swine influenza

What are the reservoir species of avian influenza?

wild ducks

Describe the transmission of avian influenza

virus is excreted via upper respiratory tract;

orofecal, direct, indirect, vertically

What species does avian influenza affect?

all birds worldwide; may mutate and infect mammals (including humans)

What is the significance of low virulence strains of avian influenza?

reduced appetite, respiratory clinical signs, reduced egg production

What is the significance of moderate virulence strains of avian influenza?

mortality: 30-70%

What is the significance of high virulence strains of avian influenza?

general fatal disease; can affect humans and mammals

What are the clinical signs of avian influenza in birds?

reduced activity, reduced water and feed intake, reduced egg production, RT signs and secretions, head oedema, cyanosis, and bloody cloaca

What are the clinical signs of avian influenza in mammals?

coughing, sneezing, lacrimation, face oedema, sinusitis, some die with no symptoms (in case of increased virulency)

What are the strains of equine influenza?

EIV-1 (H7N1), EIV-2 (H3N8)

How is equine influenza transmitted?

inhalation of respiratory secretions

What is the pathogenesis of equine influenza?

replicate in upper and lower respiratory tract epithelium and cause inflammation

What are the clinical signs of equine influenza?

pyrexia, mucopurulent nasal discharge, submandibular lymphadenopathy, dry cough, depression, anorexia

How long is the incubation period in equine infuenza?

1-3 days

What are the complications of equine influenza if there is no recovery?

secondary bacterial infections: vasculitis, myositis, pneumonia, myocarditis

What diagnostic methods are used for equine influenza?

clinical signs, HIT, VNT, KIT

What treatments are used for equine influenza?

rest, supportive NSAIDs, ATBs, vaccines, hygiene

What are the major circulating swine influenza viruses?

H1N1, H1N2, H3N2

How does swine influenza affect humans?

does not spread effectively to humans

How does swine influenza spread?

by air and especially affects suckling pigs

What is the incubation period of swine influenza?

1-3 days

What are the clinical signs of swine influenza?

RT signs are cough, sneeze, rhinitis, nasal discharge, lethargy, and anorexia

What is the pathology of swine influenza?

catarrhal bronchopneumonia, secondary bacterial infections

What diagnostic methods are used for swine influenza?

IF, HIT, RT-PCR, neuraminidase inhibition test, ELISA

What is the neuraminidase inhibition test?

identifies N-glycoprotein subtype or subtype specificity of Abs to virus

What is the treatment and prevention of swine influenza?

good nutrition and hygiene; don’t transfer sick animals