Asfarviridae

Question 1

African Swine Fever: etiology

Answer 1

Sole member of family asfarviridae

Only known DNA arbovirus

Question 2

African Swine Fever: Host

Answer 2

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:

Answer 3

OIE list A disease
Endemic: most of sub saharan africa
Island of sardinia Italy
Recent outbreaks Eastern Europe and Russia
Virus continued to spread within russian federation

Question 4

African Swine Fever: Stability

Answer 4

Virus survive at lease 30 days in pens
Very resistant to a wide range of pH
Survive in chilled carcass
Highly resistant to putrefaction
Remains viable for long periods in blood, feces and tissues; uncooked or undercooked pork products
Can multiply in vectors

Question 5

African Swine Fever: Hemadsorption

Answer 5

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 6

African Swine Fever: Transmission

Answer 6

Vector: Soft ticks (Ornithodoros sp, specifically O. moubata in Aftica)
They are biological vectors of the virus
Virus replicates in the tick, resulting in trans-stadial, transovarial, and sexual transmission (m to f)
Infected ticks may live for several years and capable of transmitting virus to pigs during each blood meal
Reservoirs hosts (sylvatic cycle): Warthog, Giant forest hog, bush pig

Question 7

African Swine Fever: Transmission cycles

Answer 7

Pig to pig or pig to tick to pig
tick to warthog (no viremia, in various Lymphoid tissues)
to juvenile warthog (sig viremia) back to tick

Question 8

African Swine Fever: Transmission- Sylvatic cycle

Answer 8

Transmission of ASF virus between warthogs and soft ticks is known as sylvatic cycle
ASF virus is maintained in a sylvatic cycle involving sodt 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 9

African Swine Fever: Transmission- Domestic cycle

Answer 9

Pig: excretion
Pig: viremia to soft tick to other pig
Pig direct contact secretions blood loos
Pig to pig through fomites, meat products/waste food

Primary outbreaks 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 10

African Swine Fever: pathogenesis

Answer 10

The effects of ASF virus are primarily hemorrhages and apoptosis
There is Leukopenia, lymphopenia, thrombocytopenia

Question 11

African Swine Fever: pathogenesis- apoptosis of host cell

Answer 11

p54 protein (encoded by virus) directly induced apoptosis of host cel
ASF infected macrophages release cytokines and apoptotic mediators
Apoptosis of both lymphocytes and mononuclear phagocytic cells

Question 12

African Swine Fever: pathogenesis- mechanisms related to hemorrhages

Answer 12

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 and Coagulation defects lead to: edema, infarction, exudation and hemorrhages in many organs and tissues

Question 13

African Swine Fever: clinical signs

Answer 13

Peracute: pigs may die suddenly
Acute: high fever,
-cyanotic skin blotching on ears, tail, lower legs or hams
-resp distress
-diarrhea: initially mucoid and later bloody
-abortion: sometimes the first event seen in an outbreak
-death

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

Question 14

African Swine Fever: clinical signs- chronic

Answer 14

Emaciation and stunting
Swollen joints
Ulcers and reddened or raised necrotic skin foci
Pneumonia
Enlarged friable spleen
Cutaneous lesion

Question 15

African Swine Fever: Immunity

Answer 15

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
Therefore attempts to develop a vaccine have so far been unsuccessful

Question 16

African Swine Fever: prevention

Answer 16

Pig farmers and field personnel should be aware of ASF, able to recognize and know what to do if suspected
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 esp 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 min and cooled before feeding

Question 17

African Swine Fever: during an outbreak

Answer 17

Immediately notify authorities (animal health department)
Infected and suspected infected farms must be places 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