36. African swine fever.

Question 1

Is African Swine Fever notifiable?

Answer 1

Yes

Question 2

African Swine Fever: Summary

Answer 2

• Acute viral disease of domestic swine & wild boar
• Fever, general symptoms & extensive haemmorrhages
• High mortality

Question 3

African Swine Fever:

1. Family
2. Genus

Answer 3

1. Family: Asfarviridae
2. Genus: Asfivirus

Question 4

African Swine Fever: Aetiology

Answer 4

• Arbovirus: Spread & replication in ticks
• Direct transmission by saliva
• Ø Virus neutralisation: Persistent infection & shedding
• Highly resistant

Question 5

African Swine Fever: Susceptible species

Answer 5

• Swine
• Wild boar
• African pig species

Question 6

African Swine Fever: Disinfection

Answer 6

• 2% NaOH
• 0.3% formalin
• Hypochlorite for 30 min
• Iodine

Question 7

African Swine Fever: Epidemiology

Answer 7

Europe, Asia & America: Live pigs, pork & ticks

Question 8

African Swine Fever: Pathogenesis

Answer 8

1. Infection
2. Primary replication in tonsils & Ln
3. Viraemia for months
4. Spleen, Ln, BM & blood vessel endothelium
5. Replication: Monocyte, macrophage, endothelium, hepatocyte
6. Type III Hypersensitivity Reaction

Question 9

African Swine Fever: How can CSx be categorised?

Answer 9

By their level of virulence:

1. Low virulence
2. Moderate virulence
3. High virulence

CSx may be milder in wild boar in comparison to domesticated pigs

Question 10

African Swine Fever: Incubation & CSx of a high-virulence infection

Answer 10

Incubation: 2-3 days

• Sudden death (Ø Nervous signs)
• Depression
• Skin lesions

Question 11

African Swine Fever: Incubation & CSx of a moderate-virulence infection

Answer 11

Incubation time: 1 week

• Fever
• Depression
• Anorexia
• Skin lesions
• Abortion
• High mortality in sows

Question 12

African Swine Fever: Incubation & CSx of a low-virulence infection

Answer 12

Incubation time: 1 week

• Sometimes asymptomatic
• Multifocal skin necrosis
• Swelling of carpal & tarsal joints
• Abortion
• Seroconversion
• Pneumonia

Question 13

African Swine Fever: Pathology (Acute​)

Answer 13

• Hyperaemia & petechial haemorrhages everywhere
• Black LNs
• Pulmonary oedema
• Hyperaemic splenomegaly (black)

Question 14

African Swine Fever: Pathology (Chronic)

Answer 14

• Splenic & lymphoid hyperplasia
• Fibrin-rich fluid in all serous cavities
• Pneumonia
• Skin necrosis

Question 15

African Swine Fever: Dx

Answer 15

Based on epidemiology, CSx & PM lesions

• Virus detection: PCR, IF, haemabsorption & virus isolation
• Antibody detection: ELISA & Western blot

Question 16

African Swine Fever: DDx

Answer 16

• Classical Swine Fever
• PDNS
• Acute Swine Paratyphoid
• Diamond Skin Disease
• Aujeszky’s Disease

Question 17

African Swine Fever: Prevention & Control

Answer 17

NOTIFIABLE DISEASE

• Ø Vaccine
• Epidemiological measures & tick control
• Disease-free countries: Stamping-out; disinfection & leave for 1 month before repopulating followed by 1-month movement restriction.

Question 18

African Swine Fever: Differentiate from Classical Swine Fever

Answer 18

Similar CSx & pathology

Differentiate with the “4 pigs test”:

1. Vaccinate & infect
2. If 2 were vaccinated against CSF but all die - ASF infection!