Test 2- Asfarviridae Flashcards

1
Q

Family Asfarviridae

A

 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

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2
Q

African Swine Fever (ASF)

Etiology

Host

A

 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.

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3
Q

African Swine Fever (ASF)

Economic Impact

A

 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.

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4
Q

African Swine Fever (ASF)

Geographical Distribution

Recent outbreaks

A

 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

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5
Q

African Swine Fever (ASF)

 ASF Virus Stability:

A

 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.

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6
Q

African Swine Fever (ASF)

 Some Properties of ASF Virus :

A

 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.

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7
Q

African Swine Fever (ASF)

Hemadsorption:

A

 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.

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8
Q
A

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

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9
Q

2 cycles of Transmission:

A
  • Sylvatic cycle
  • Domestic Cycle
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10
Q

African Swine Fever (ASF)

 Transmission:

A

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

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11
Q

African Swine Fever (ASF)

Reservoirs Hosts (Sylvatic cycle)

A
  • Warthog
  • Giant Forest Hog
  • Bush Pig
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12
Q

African Swine Fever (ASF)

 Transmission:

 Sylvatic Cycle:

A

 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.

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13
Q

ASF

Transmission:
 Domestic Cycle:

diagram

A
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14
Q

African Swine Fever (ASF)

 Domestic Cycle:

A

 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.

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15
Q

African Swine Fever (ASF)

 Pathogenesis:

Sites of Virus Replication:

A

 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

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16
Q

African Swine Fever (ASF)

 Pathogenesis:

 Apoptosis of host cells:

Mechanisms related to Hemorrhages:

A

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.

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17
Q

African Swine Fever (ASF)

 Clinical Signs:

A

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.

18
Q
A
19
Q

African Swine Fever (ASF)

 Clinical Signs:
 Acute form:

A

 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

20
Q
A

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).

21
Q

African Swine Fever (ASF)

Acute form

A
  • Bloody, mucoid, foamy nasal discharge
  • Mucous membranes of the eyes are deeply congested
  • Marked hyperemia of the distal limbs
  • Cutaneous hemorrhage
22
Q

African Swine Fever (ASF)

clinical signs

chronic forms

A

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

23
Q
A

Necrotic exudate is sloughing from the lesion

chronic form ASF

24
Q
A

African Swine Fever

Lung: Interlobular Edema

25
Q
A

African Swine Fever

Congestion of the fundic portion of the Stomach

26
Q
A

African Swine Fever

Enlarged friable spleen [blackberry jam spleen]

VERY CHARACTERISITIC

27
Q
A

African Swine Fever

Enlarged [Top] and Normal [Bottom] Spleen

28
Q
A

Cut surface of enlarged Spleen

29
Q
A

ASF

Kidney: Petechial and
Ecchymotic Hemorrhages

30
Q
A

ASF

Hepatogastric Lymph Nodes

31
Q
A

Cut surface of Hepatogastric Lymph Nodes

32
Q
A

Hydropericardium and Diffuse Hemorrhage in the Myocardium

33
Q
A

Chronic African Swine Fever

Cutaneous Lesion

34
Q
A

Chronic African Swine Fever

Fibrinous Pericarditis and Myocardial Hemorrhage

35
Q
A

Chronic African Swine Fever

Granulomatous Pneumonia

36
Q
A

Chronic African Swine Fever Pulmonary Consolidatio

37
Q

African Swine Fever (ASF)

 Diagnosis:

A

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

 Hemadsorption TEST

 Serology: FAT, Immunodiffusion

 PCR to detect viral DNA

38
Q

ASF Immunity

A

 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.

39
Q

African Swine Fever (ASF)

 TO PREVENT ASF:

A

 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.

40
Q

African Swine Fever (ASF)

 DURING AN OUTBREAK:

A

 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

41
Q

In adult pigs

A

No viremia

virus goes to lymphoid tissue