Orthomyxoviridae

Question 1

What are the 4 genera of orthomyxoviridae?

Answer 1

• influenza A: human, swine, equine, canine, birds, seal
• influenza B: human
• influenza C; human, swine
• influenza D: swine, cow
• thogotovirus: tick borne viruses

Question 2

Influenza outbreaks in humans

Answer 2

• 1918: Spanish flu (H1N1) = 40 million deaths
• 1957: Asian flu (H2N2) = 2 million deaths
• 1968: Hong Kong flu (H3N2) = 1 million deaths
• 2009: H1N1

Question 3

Possible HA-NA combinations among type A influenza viruses

Answer 3

HA subtypes: 1-18
NA subtypes: 1-11
= 198 HA-NA combinations

Question 4

Antigenic drift

Answer 4

Accumulating point mutations in RNA segments coding for HA and H A

• results in minor antigenic changes in NA and HA
• new variants still possess same HA and NA subtypes
• linear progression
• horses, swine, equine

Question 5

Antigenic shift

Answer 5

Gene reassortment when one cell is infected with 2 different flu A viruses

Question 6

_____ facilitates emergence of pandemic strains

Answer 6

Reassortment

Question 7

Emergence of highly pathogenic avian influenza viruses

Answer 7

Associated with mutation at the cleavage site in HA molecule

• point mutations, nucleotide inserts, recombination
• all HPAIVs have been H5 or H7, but few H5 and H7 AIVs are HP (majority are LP)

Question 8

______ serves as a mixing vessel for influenza A viruses

Answer 8

Swine!

- have both receptors (alpha 2,3 and 2,6- linked sialic acid

Question 9

Avian influenza in US poultry

Answer 9

LPAI viruses

• no clinical illness, drop in egg production, respiratory disease
• poultry can become a reservoir!!

Question 10

HPAIV can cause severe respiratory disease as well as _______

Answer 10

Neurological disorders

Question 11

Interspecies transmission in birds

Answer 11

LPAI viruses are host adapted!

• LPAIVs cross species barriers with difficulty
• viruses replicate poorly in hosts
• require adaptation to new host

Question 12

Animal influenza vaccines

Answer 12

• equine: H3N8 and H7N7 inactivated
• swine: H1N1, H3N2 inactivated
• canine: H3N8 inactivated (no H3N2!!!)
• avian: only available for turkey in some US states

Question 13

What are 3 current challenges for influenza?

Answer 13

• natural history of H5 HPAI
• pathogenesis (genomic constellation)
• control: education, biosecurity, depopulation, vaccination

Question 14

Influenza viruses are divided into groups based on their ______

Answer 14

Antigenic differences in nuclear protein and matrix protein, and genetic variations
- influenza A is further classified based on antigenic difference among neuraminidase and hemagglutinin

Question 15

Influenza A genome

Answer 15

8 segmented, single stranded, negative sensed RNA

Question 16

What are the 4 major antigens of influenza?

Answer 16

H, N, M, and NP

- only antibodies to H and N glycoproteins are associated with resistance to infection

Question 17

Antigenic drift results in ________

Answer 17

Imperfect protection by old vaccines

- detected by 2-4 fold increase in HI titer between one isolate and the mutant recovered several years later

Question 18

Antigenic shift results in _______

Answer 18

No protection by old vaccines

Question 19

Birds that survive influenza infection can excrete the virus ______

Answer 19

Orally or in feces for at least 10 days

Question 20

Respiratory signs of avian influenza

Answer 20

Excessive lacrimation, sinusitis, diarrhea, edema of head, wattles, and comb

Question 21

What is the natural reservoir of avian influenza viruses?

Answer 21

Migratory waterfowl, wild ducks

Question 22

_____ or ______ contact of domestic flocks with wild migratory waterfowl is a frequent cause of epidemics

Answer 22

Direct or indirect

Question 23

T/F: viruses of low pathogenicity can mutate into highly pathogenic strains

Answer 23

True, after circulation in a poultry population

Question 24

The best specimen for diagnosis is _______

Answer 24

Nasal mucus taken at early stage or lung tissue obtained at necropsy

Question 25

What is one of the most prevalent respiratory disease in swine in North America?

Answer 25

Swine influenza

Question 26

What was the cause of Greyhound race dog fatalities in Florida in 2004?

Answer 26

Equine influenza A subtype H3N8

• first evidence of influenza A in dogs
• symptoms are usually mild respiratory distress, or pneumonia due to secondary bacterial infection