Test 2- Asfarviridae

Question 1

Family Asfarviridae

Answer 1

 General Properties:

 Virions are enveloped.

 Possess a nucleocapsid core that is surrounded by internal lipid layers and a

complex icosahedral capsid.

 The genome consists of a single molecule of linear double-stranded DNA.

 Replication occurs primarily in the cytoplasm, although the host cell nucleus is involved in early stage of DNA replication.

T= 189-217- VERY COMPLEX

Question 2

African Swine Fever (ASF)

Etiology

Host

Answer 2

 Etiology:
 Sole member of Family Asfarviridae

 Only known DNA arbovirus- MULITPLYING IN AN ARTHOPOD VECTOR
 22 genotypes have been defined

 Variation in Virulence of Virus:
Some strains cause severe disease (100% mortality), while others cause transient disease or inapparent infection.

 Host:

 All breeds and types of domestic pigs and European wild boar.

 Inapparent infection in warthogs, bush pigs and giant forest hogs, which act as

reservoirs.

Question 3

African Swine Fever (ASF)

Economic Impact

Answer 3

 OIE List A Disease- REPORTABLE!

 Economic Impact

 Animal health

 High morbidity and mortality

 Highly contagious
 Import and export bans
 Quarantine and depopulation

 Required for eradication
 Can become prolonged epidemic

IF A CASE IS REPORTED, ALL OF THOSE PIGS MUST BE CULLED.

Question 4

African Swine Fever (ASF)

Geographical Distribution

Recent outbreaks

Answer 4

 Geographical Distribution:  Endemic:

 Most of sub–Saharan Africa

 Island of Sardinia (Italy)

 Recent outbreaks:

 2007, The Caucasus: Georgia, Armenia
 2009–2013, The virus has continued to spread within the Russian Federation

 2014, Poland, Latvia

Question 5

African Swine Fever (ASF)

 ASF Virus Stability:

Answer 5

 Virus survive at least 30 days in pens
 Very resistant to a wide range of pH (several hours at pH 4 or pH 13).
 Survive in chilled carcass for up to 6 months, 40C for 2 years.
 Highly resistant to putrefaction.
 Remains viable for long periods in blood, feces and tissues; especially infected,

uncooked or undercooked pork products.

 Can multiply in vectors (Ornithodoros sp.).

China has banned pork imports from Poland after it confirmed its first cases of African swine fever.

Question 6

African Swine Fever (ASF)

 Some Properties of ASF Virus :

Answer 6

 Although ASFV can be adapted to grow in cells from different species, it does not replicate readily in any species other than swine.

 Virus produces Cytopathic effects (some strains do not induce CPE): Syncytia, intracytoplasmic inclusion bodies.

Question 7

African Swine Fever (ASF)

Hemadsorption:

Answer 7

 Hemadsorption:
 Virus does not hemagglutinate. However, pig erythrocytes will adhere to the surface of pig monocyte or macrophage cells infected with ASF virus.
 This hemadsorption (HAD) is attributed to a virus specific protein that appears on plasma membrane of infected cells during late infection.

Question 8

Answer 8

Rosette formation of porcine erythrocytes can be observed in macrophages infected by ASF virus

Question 9

2 cycles of Transmission:

Answer 9

• Sylvatic cycle
• Domestic Cycle

Question 10

African Swine Fever (ASF)

 Transmission:

Answer 10

African Swine Fever (ASF)

 Transmission:

 Vector: Soft Ticks (Ornithodorus sp., specifically O. moubata in Africa)

 Ornithodorus sp. are biological vectors of the virus.
 Virus replicates in the tick, resulting in trans-stadial, transovarial, and sexual

transmission (male-to-female).
 Infected ticks may live for several years and capable of transmitting virus to pigs during each blood meal

Question 11

African Swine Fever (ASF)

Reservoirs Hosts (Sylvatic cycle)

Answer 11

• Warthog
• Giant Forest Hog
• Bush Pig

Question 12

African Swine Fever (ASF)

 Transmission:

 Sylvatic Cycle:

Answer 12

 Transmission of ASF virus between warthogs and soft ticks is known as the sylvatic cycle.

 ASF virus is maintained in a sylvatic cycle involving soft ticks and asymptomatic infection in wild pigs.

 After primary infection, young wild pigs develop a viremia with high enough

virus titers to infect ticks feeding on them.

 Older wild pigs are persistently infected, but rarely develop viremia.

Question 13

ASF

Transmission:
 Domestic Cycle:

diagram

Answer 13

Question 14

African Swine Fever (ASF)

 Domestic Cycle:

Answer 14

 Domestic Cycle:
Primary outbreaks of African swine fever in domestic swine can result from:

 Bite of infected tick

 Direct contact with infected animal (oronasal spread)

 Indirect contact on fomites

 Virus spreads to new areas when pigs are fed uncooked scraps that contain

infected pork.

 Aerosol spread

 Mechanical transmission through biting flies.

 All body fluids and tissues contain large amounts of infectious virus
 Pigs that survive infection may become carriers and shed virus in secretions and

excretions.

Question 15

African Swine Fever (ASF)

 Pathogenesis:

Sites of Virus Replication:

Answer 15

 Pathogenesis:
The effects of ASF virus are primarily hemorrhages and apoptosis. There is Leukopenia, Lymphopenia, Thrombocytopenia

 Sites of Virus Replication:
 Pharyngeal mucosa, tonsils, etc

 Endothelial cells
 Megakaryocytes
 Macrophages, etc

Question 16

African Swine Fever (ASF)

 Pathogenesis:

 Apoptosis of host cells:

Mechanisms related to Hemorrhages:

Answer 16

African Swine Fever (ASF)

 Pathogenesis:

 Apoptosis of host cells:
 p54 protein (encoded by virus) directly induces apoptosis of host cells.  ASF infected macrophages release cytokines & apoptotic mediators.  Apoptosis of both lymphocytes and mononuclear phagocytic cells.

 Mechanisms related to Hemorrhages:
 Vascular damage from degeneration of vascular endothelium.
 Disseminated intravascular coagulation (DIC)
 Infection and necrosis of megakaryocytes
 Activation and extensive destruction of monocytes and macrophages.  Thrombocytopenia & coagulation defects lead to:

Edema, Infarction, Exudation and Hemorrhages in many organs and tissues.

Question 17

African Swine Fever (ASF)

 Clinical Signs:

Answer 17

Peracute, acute, subacute, and chronic forms of ASF occur, and mortality rates vary

from 0 to 100%.

 Peracute:
Pigs may die suddenly, or 1-3 days course of high fever, hyperpnea, hyperemia before death.

Question 18

Question 19

African Swine Fever (ASF)

 Clinical Signs:
 Acute form:

Answer 19

 Acute form:

 High fever
 Moderate anorexia
 Erythema
 Cyanotic skin blotching on the ears, tail, lower legs or hams.- purplish BLUE on ears, near tail

 Respiratory distress
 Recumbency
 Vomiting
 Diarrhea: initially mucoid and later may become bloody.
 Abortion: sometimes the first event seen in an outbreak.
 Death

Question 20

Answer 20

Acute form:

African Swine Fever (ASF)

In white-skinned pigs, the ears, tail, legs and underside appear deeply flushed and may develop a bluish tinge (cyanosis).

Question 21

African Swine Fever (ASF)

Acute form

Answer 21

• Bloody, mucoid, foamy nasal discharge
• Mucous membranes of the eyes are deeply congested
• Marked hyperemia of the distal limbs
• Cutaneous hemorrhage

Question 22

African Swine Fever (ASF)

clinical signs

chronic forms

Answer 22

 Chronic form:
 Emaciation & Stunting
 Swollen joints
 Ulcers and reddened or raised necrotic skin foci  Pneumonia

Question 23

Answer 23

Necrotic exudate is sloughing from the lesion

chronic form ASF

Question 24

Answer 24

African Swine Fever

Lung: Interlobular Edema

Question 25

Answer 25

African Swine Fever

Congestion of the fundic portion of the Stomach

Question 26

Answer 26

African Swine Fever

Enlarged friable spleen [blackberry jam spleen]

VERY CHARACTERISITIC

Question 27

Answer 27

African Swine Fever

Enlarged [Top] and Normal [Bottom] Spleen

Question 28

Answer 28

Cut surface of enlarged Spleen

Question 29

Answer 29

ASF

Kidney: Petechial and
Ecchymotic Hemorrhages

Question 30

Answer 30

ASF

Hepatogastric Lymph Nodes

Question 31

Answer 31

Cut surface of Hepatogastric Lymph Nodes

Question 32

Answer 32

Hydropericardium and Diffuse Hemorrhage in the Myocardium

Question 33

Answer 33

Chronic African Swine Fever

Cutaneous Lesion

Question 34

Answer 34

Chronic African Swine Fever

Fibrinous Pericarditis and Myocardial Hemorrhage

Question 35

Answer 35

Chronic African Swine Fever

Granulomatous Pneumonia

Question 36

Answer 36

Chronic African Swine Fever Pulmonary Consolidatio

Question 37

African Swine Fever (ASF)

 Diagnosis:

Answer 37

 Virus isolation: Blood, spleen, visceral lymph nodes, tonsils

 Hemadsorption TEST

 Serology: FAT, Immunodiffusion

 PCR to detect viral DNA

Question 38

ASF Immunity

Answer 38

 Immunity:

 Although infected pigs produce virus-specific antibodies, sera from infected pigs do not neutralize the virus , hence humoral immune response does not seem to have substantial protective value.– HUMORAL RESPONSE IS NOT VERY HELPFUL- PREVENTION IS BETTER THAN CURE

 Therefore, attempts to develop a vaccine have so far been unsuccessful.

Question 39

African Swine Fever (ASF)

 TO PREVENT ASF:

Answer 39

 TO PREVENT ASF:

 Pig farmers and field personnel should be aware of ASF, able to recognize ASF and know what to do if they suspect ASF.

 Pigs should be kept in well-constructed pig sties under hygienic conditions with

controlled entry to the piggery.

 Movement of pigs inside the country and especially across international borders should be controlled.

 Pigs should not be fed swill that might contain remains of pigs. To ensure safety, swill should be boiled for 30 minutes and cooled before feeding.

Question 40

African Swine Fever (ASF)

 DURING AN OUTBREAK:

Answer 40

 DURING AN OUTBREAK:

 IMMEDIATELY NOTIFY AUTHORITIES (ANIMAL HEALTH DEPARTMENT)

 infected and suspected infected farms must be placed in quarantine;

 no movement of pigs or any products of pig origin should be allowed;

 all infected and in-contact pigs must be slaughtered;

 carcasses must be burnt or buried deeply on site;

 vehicles should be disinfected on entering and leaving farms;

 personnel should ensure that shoes, clothes and equipment are disinfected

between farms

Question 41

In adult pigs

Answer 41

No viremia

virus goes to lymphoid tissue