Topic 61 Swine influenza (RED)

Question 1

Definition of swine influenza

Answer 1

An acute, febrile disease with general and respiratory signs

Question 2

Occurrence of swine influenza

Answer 2

Sporadic, more frequent in autumn and winter

Question 3

Causative agent of swine influenza

Answer 3

Otrhomyxovirus, Influenzavirus A

Question 4

Influenza serotype causing swine influenza

Answer 4

H1N1
H3N2

Question 5

Which proteins are the serotypes of influensa made up of?

Answer 5

NA = Neuraminidase
HA = haemagglutinin

Question 6

What is the function of HA?

Answer 6

It is the virus surface protein, the antireceptor.

The virus binds to the surface of the cell where we find siliac acid protein which is the receptor.

Question 7

What is the function of NA?

Answer 7

Its an enzyme.
It is responsible for the release of the virus from the cell.
the enzyme cuts the connection between virus particles and the cell membrane

Question 8

How does the NA and HA determine serotypes of the influenza, how is it done?

Answer 8

They are hypervariable genes, meaning that most of the mutations happens at the HA and NA genes.
There are serial point mutations, causing a antigenic drift which will make the seasonal influensas

Question 9

How many types does the NA and HA have, that can cause influensa types?

Answer 9

18 HA types
11 NA types

They combine freely.
The combinations are due to the segmented genome and if two different influensa viruses meet in the same cell, we get a segment re-assortment

Question 10

Explain how a re-assortment of segments work

Answer 10

1. 2 different influensa viruses meets in the cell
2. They replicate, making copies of the genome segments and at the end, the virus assemble happens ⭢ The segments get into the capsid mixed up
3. At the end of the virus replication, we have one original type virus. But due to the virus re-assortments, we also have two new types.
4. The host already have antibodies working for the original type, but they body do not recognise the new viruses and we get severe clinical signs ⭢ This is what we call the antigenic shift

Question 11

Route of infection in case of swine influenza

Answer 11

Air-borne
Nose-to-nose contact and also by drinking water

Question 12

Morbidity and mortality of swine influenza

Answer 12

High morbidity - all are infected
Low mortality

!! A pig recovered from the swine influenza should not be kept for breeding !!

Question 13

Pathogenesis of swine influenza

Answer 13

1. Infection of respiratory mucosa
2. Replication in epithelial cells of mucus membranes
3. There is a tracheal and bronchial mucosa damage, which induce inflammation.
4. Due to the virus replication we see nasal discharge at the beginning, after some time we have a viremia
5. Without complications, the animal will recover within weeks

Question 14

Incubation time for swine influenza

Answer 14

1-3 days

Question 15

Clinical signs in case of swine influenza

Answer 15

Fever
Loss of appetite
The animal is laying down
Respiratory signs: cough, sneezing, nasal discharge, dyspnoea

Question 16

Post mortem lesions in case of swine influenza

Answer 16

Without the complications the mortality is low

The secondary infections causes the lesions
1. Upper respiratory tract inflammations
2. Lung oedema

Question 17

Diagnostic methods for swine influenza

Answer 17

We do nasal swab, and in case of dead animals we send the lungs

1. RT-PCR is a quick diagnosis
2. Virus isolation is time consuming

Question 18

Treatment of swine influenza

Answer 18

Resting in dust-free environment - let the immune response work
AB against the bacterial complications

Question 19

Control and prevention measures for swine influenza

Answer 19

1. Recovered gilts and boars should not be kept for breeding !!!
2. closed farming, separation of age groups
3. Vaccination

Question 20

Vaccination types in case of swine influenza

Answer 20

In endemic areas, inactivated vaccines is used