Final Exam - Orthomyxoviridae

Question 1

HPAI

Answer 1

High Pathogenicity Avian Influenza Virus (HPAI)

Question 2

LPAI

Answer 2

Low Pathogenicity Avian Influenza Virus (LPAI)

Question 3

Reservoirs for LPAI A Viruses

Answer 3

Aquatic birds; they replicate in intestinal epithelium of these birds with no over disease and are excreted with fences

Question 4

Genus: Influenza A

Answer 4

contains human, equine, swine and domestic poultry viruses

Question 5

Genus: Influenza B

Answer 5

contains human viruses

Question 6

Genus: Influenza C

Answer 6

contains human and swine viruses that rarely cause disease

Question 7

Genus: Thogotovirus

Answer 7

Contains tick borne viruses which infect livestock and humans in Africa, Europe, and Asia.

Question 8

Isavirus

Answer 8

Has only one member, infectious salmon anemia virus. Also has hemagglutinin esterase and F protein

Question 9

Classification of Orthromyxoviruses

Answer 9

There are 16 hemagglutinin (H) and 9 Neuraminidase (N) types

Question 10

Two types of glycoprotien spikes for Influenza A and B

Answer 10

Homotrimer HA and homotetramer NA

Question 11

Influenza C lack neuraminidase

Answer 11

have only 1 type of glycoprotein spikes - the hemagglutinin is multifunctional - esterase molecule

Question 12

Surface HA structure, performs 3 functions:

Answer 12

1. receptor binding
2. membrane fusion
3. receptor cleavage

Question 13

Structure of the Influenza A Virus

Answer 13

Lipid envelope derived from the host cell. Envelope harbors hemagglutinin (HA), the neuraminidase (NA) and M2 protein. M1 - matrix protein lies beneath the lipid layer.

Question 14

Transmission

Answer 14

In aquatic birds the virus is shed in feces - fecal oral transmission is common. In poultry - ingestion and inhalation. In mammals - aerosols, droplets and fomites.

Question 15

Thogotoviruses - Tranmission

Answer 15

Are transmitted by ticks and replicate in both in the ticks and mammals

Question 16

Isavirus - Transmission

Answer 16

Transmitted in water - gill being the important route

Question 17

Antigenic change in orthomyxoviruses

Answer 17

1. Genetic shift - changes in antigenic setup due to reassortment of gene segments
2. Genetic drift - changes in antigenic setup due to point mutations (nucleotide substitution, deletion, insertions).

Question 18

Equine Influenza Viruses

Answer 18

Respiratory Disease. Affects horses, donkeys, and mules world wide. It is the most important viral respiratory disease or horses.

Question 19

Equine Influenza Virus - Pathogenesis

Answer 19

Virus replicates in the epithelial cells of the upper and lower respiratory tracts. Ciliated epithelial lining is destroyed by virus replication leading to inflammation and exudate formation including nasal discharge.

Question 20

Equine Influenza Virus - Clinical signs

Answer 20

Morbidity is high - symptoms visible within 24-48 hours after infection. Fever, inappetence and depression, reddening of the nasal mucosal, conjunctivitis, serous nasal discharge with dry paroxysmal cough, mucopurulent nasal discharges.

Question 21

Animals at Risk of Infection

Answer 21

Race horses, breeding stock, show jumper, horses sent to sales are at high risk of infection with equine influenza virus. Equids are the only source of equine influenza viruses.

Question 22

Equine Influenza Virus - Diagnosis

Answer 22

Acute disease is very characteristic and straight forward. RT-PCR is a diagnostic test of choice - highly specific. Nasal and pharyngeal swabs collected early in infections are samples of choice. Virus isolation - swabs should be protected from desiccation (transportation medium).

Question 23

Equine Influenza Virus - 10 day old chicken embryos

Answer 23

Can be used to detect virus in allantoic and amniotic fluids of infected chicken embryos using standard hemagglutination test.

Question 24

Equine Influenza Virus - Prevention and Control

Answer 24

Isolation, cleaning, vaccination (inactivated vaccines or live vectored vaccines), retrospective serology.

Question 25

Swine Influenza Viruses

Answer 25

Pigs are considered as a "mixing vessel" for influenza viruses because of their ability to become co-infected with both human and avian strains of influenza viruses.

Question 26

Swine Influenza Viruses - Pathogenesis

Answer 26

Highly contagious virus. Replication in the upper respiratory tract. Airway plugging, peribronchial and perivascular mononuclear cell infiltration.

Question 27

Swine Influenza Viruses - Symptoms

Answer 27

Appears in many animals at the same time. Fever > 42C. Nasal discharge at later stages of disease. Not fatal if animals are kept warm and stress free. Some animals may develop severe pneumonia and die.

Question 28

Swine Influenza Virus - Diagnosis

Answer 28

Virus identification. Deep nasal swabs. Embryonated chicken eggs can be inoculated. Hemagglutination inhibition (HI) test for detection. ELISA. RT-PCR. A four fold or greater increase in titre between the first and second sample is suggestive of a recent infection.

Question 29

Swine Influenza Virus - Control

Answer 29

No feasible therapeutic options. Commercial vaccines (whole virus, inactivated and are adjuvanted). They do NOT consistently confer crossprotection against new subtypes. Swine influenza viruses are economically important due to losses arising from the requirement to cull infected pigs.

Question 30

Avian Influenza Virus

Answer 30

Most devastating infection in chicken referred to as "fowl plague". Are economically important due to losses arising from the requirement to cull infected birds. A REPORTABLE DISEASE!

Question 31

Notifiable Avian Influenza (NAI)

Answer 31

An infection of poultry caused by any influenza A virus of the H5 or H7 subtype any AI virus that causes at least 75% mortality. Divided as HPNAI or LPNAI.

Question 32

Avian Influenza Pathogenesis

Answer 32

Influenza virus replicates int he intestinal and respiratory tracts. Viremia leads to multifocal lymphoid and visceral organ necrosis. Pancreatitis, myocarditis, myositis, encephalitis, and hemorrhage.

Question 33

HPAI - Clinical Features

Answer 33

A highly virulent strains of AI can cause sudden death without symptoms. Cessation of egg production, diarrhea, edema of the face, head and neck, cyanosis of combs or wattles, torticollis

Question 34

LPAI - Clinical Features

Answer 34

May cause considerable losses due to decreased egg production

Question 35

Avian Influenza Virus - Diagnosis

Answer 35

RT-PCR to detect matrix protein (M) gene, H5 and H7 genes. Virus isolation, agar gel immunodiffusion, ELISA, Hemagglutination inhibition assay

Question 36

Avian Influenza Virus - Control

Answer 36

Surveillance, biosecurity, and depopulation. Segregate poultry from wild birds. Vaccination has not been used to control HPAI.