Test 2- Asfarviridae Flashcards
Family Asfarviridae
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
African Swine Fever (ASF)
Etiology
Host
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.
African Swine Fever (ASF)
Economic Impact
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.
African Swine Fever (ASF)
Geographical Distribution
Recent outbreaks
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
African Swine Fever (ASF)
ASF Virus Stability:
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.
African Swine Fever (ASF)
Some Properties of ASF Virus :
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.
African Swine Fever (ASF)
Hemadsorption:
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.
Rosette formation of porcine erythrocytes can be observed in macrophages infected by ASF virus
2 cycles of Transmission:
- Sylvatic cycle
- Domestic Cycle
African Swine Fever (ASF)
Transmission:
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
African Swine Fever (ASF)
Reservoirs Hosts (Sylvatic cycle)
- Warthog
- Giant Forest Hog
- Bush Pig
African Swine Fever (ASF)
Transmission:
Sylvatic Cycle:
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.
ASF
Transmission:
Domestic Cycle:
diagram
African Swine Fever (ASF)
Domestic Cycle:
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.
African Swine Fever (ASF)
Pathogenesis:
Sites of Virus Replication:
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
African Swine Fever (ASF)
Pathogenesis:
Apoptosis of host cells:
Mechanisms related to Hemorrhages:
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.
African Swine Fever (ASF)
Clinical Signs:
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.
African Swine Fever (ASF)
Clinical Signs:
Acute form:
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
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).
African Swine Fever (ASF)
Acute form
- Bloody, mucoid, foamy nasal discharge
- Mucous membranes of the eyes are deeply congested
- Marked hyperemia of the distal limbs
- Cutaneous hemorrhage
African Swine Fever (ASF)
clinical signs
chronic forms
Chronic form:
Emaciation & Stunting
Swollen joints
Ulcers and reddened or raised necrotic skin foci Pneumonia
Necrotic exudate is sloughing from the lesion
chronic form ASF
African Swine Fever
Lung: Interlobular Edema
African Swine Fever
Congestion of the fundic portion of the Stomach
African Swine Fever
Enlarged friable spleen [blackberry jam spleen]
VERY CHARACTERISITIC
African Swine Fever
Enlarged [Top] and Normal [Bottom] Spleen
Cut surface of enlarged Spleen
ASF
Kidney: Petechial and
Ecchymotic Hemorrhages
ASF
Hepatogastric Lymph Nodes
Cut surface of Hepatogastric Lymph Nodes
Hydropericardium and Diffuse Hemorrhage in the Myocardium
Chronic African Swine Fever
Cutaneous Lesion
Chronic African Swine Fever
Fibrinous Pericarditis and Myocardial Hemorrhage
Chronic African Swine Fever
Granulomatous Pneumonia
Chronic African Swine Fever Pulmonary Consolidatio
African Swine Fever (ASF)
Diagnosis:
Virus isolation: Blood, spleen, visceral lymph nodes, tonsils
Hemadsorption TEST
Serology: FAT, Immunodiffusion
PCR to detect viral DNA
ASF Immunity
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.
African Swine Fever (ASF)
TO PREVENT ASF:
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.
African Swine Fever (ASF)
DURING AN OUTBREAK:
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
In adult pigs
No viremia
virus goes to lymphoid tissue
