3. Olds (3rd exam)

Question 1

To what virus families do these diseases belong?
(a) Kennel Cough
(b) Porcine Parvovirus
(c) Infectious laryngotracheitis
(d) Chicken anemia
(e) Cowpox
(f) Foot & Mouth (FMD)
(g) Canine distemper

Answer 1

(a) Adeno
(b) Parvo
(c) Herpes
(d) Circo
(e) Pox
(f) Picorna
(g) Paramyxo

Question 2

Why does the circovirus need to infect cells in the crypts of Lieberkuhn?

Answer 2

• There is a high rate of cellular proliferation at the crypts of Lieberkuhn.
• The crypts contain stem cells that can differentiate to produce a number of different cell types, including enterocytes.
• Circovirus can induce immunosuppression by damaging these cells as they are responsible for the normal injury and repair mechanisms of the intestinal epithelial layer.

Question 3

Give 3 reasons why canine parvovirus can easily infect an entire litter.

Answer 3

1) Parvovirus infections target actively dividing cells which are present in puppies

2) Environmental stability (naked) makes it highly transmissible. Is not easily killed by ordinary disinfectants (should be 1:30 bleach solution)

3) Since the puppies are still nursing, risk of vertical transmission is high

4) There is a high risk for the spread of infection through direct contact since puppies stay
together.

Question 4

Draw and illustrate the rolling circle mechanism of viral genome replication.

Answer 4

Origin of replication – located between the start sites of the 2 major ORFs

cap gene/ORF1 = encodes VP1 (capsid protein)

rep gene/ORF2 = synthesis of VP2 (protein phosphatase)

ORF3 = encodes VP3 (apoptin) = protein responsible for the triggering of the cell to commit suicide

ILLUSTRATION?

Question 5

Draw and explain how early, intermediate, and late genes are transcribed and translated
into proteins.

Question 6

Give 5 clinical signs of Infectious laryngotracheitis

HERPES

Answer 6

1. Head shaking w/ coughing
2. Nasal ocular discharge
3. Dyspnea
4. Bloody mucus expectoration
5. Depression

Infectious laryngotracheitis

Question 7

Give 5 clinical signs of African Swine Fever.

ASFAR

Answer 7

1. Petechial hemorrhages in ear
2. Enlarged gastrohepatic lymph node
3. Enlarged spleen
4. High fever
5. Lethargy

Question 8

How do papilloma viruses cause the formation of tumors.

Answer 8

Rapid outward cellular differentiation (tumor) occurs due to the proliferative epithelial thickening caused by papillomavirus

Question 9

What happens if parvovirus infects the piglet and why:

(a) 25 days
(b) 70 days
(c) 110 days

Answer 9

(a) 25 days: resorption
(b) 70 days: mummification
(c) 110 days: stillbirth

This is caused by SMEDI (Stillbirth, mummification, embryonic death, and infertility) syndrome, which is a reproductive disease in swine caused by porcine parvovirus wherein the virus is capable of infecting and destroying both embryos and fetuses.

The degree of infection directly correlates to the time of infection, at 70 days gestation or longer, the fetus will already form an immune response against PPV due to the maternal antibodies produced by the sow.

Question 10

Discuss how does parvovirus reach its target cells.

Answer 10

• Parvovirus enters the host body through the** oronasal route**, and
• first infects the tonsils and
  lymph nodes.
• It then travels through the bloodstream causing viremia,
• which then reaches the gut after 4-6 days where it will destroy intestinal epithelial cells in the Crypt of Lieberkuhn.

Question 11

Draw and illustrate the pathogenesis of canine adenovirus

Answer 11

1. CAV-1 enters the** vascular endothelial cells** in the eye causing mild uveitis.
2. It reaches the **aqueous humor **via the uveal tract and forms a viral-antibody complex.
3. Severe uveitis and loss of endothelium and aqueous pump occurs upon complement fixation on virus-immune complexes which then leads to the

4.** influx of aqueous** into the cornea.