Exam 2 - Family: Asfarviridae

Question 1

Family: Asfarviridae

Answer 1

African Swine Fever (ASF)

Question 2

Family: Asfarviridae - Properties

Answer 2

Virions are enveloped, nucleocapsid core, internal lipid layers, single molecule of linear double-stranded DNA, replication in the cytoplasm

Question 3

ASF - Properties

Answer 3

• Only known DNA arbovirus that is able to replicate within an arthropod vector
• OIE List A Disease - Reportable Disease
• Remains viable for long periods in blood, feces, and tissues; especially infected, uncooked or undercooked pork products
• Produces cytopathic effects: synctia, intracytoplasmic inclusion bodies

Question 4

ASF - Hemadsorption (HAD)

Answer 4

• Virus does not hemagglutinate
• This HAD is attributed to a virus specific protein that appears on plasma membrane of infected cells during late infection

Question 5

ASF - Transmission - Sylvatic Cycle

Answer 5

• Reservoirs: warthog, giant forest hog, and bush pig

- Transmission of ASF virus between warthogs and soft ticks

Question 6

ASF - Transmission - Domestic Cycle

Answer 6

• Bite of infected tick
• Direct contact with infected animal
• 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

Question 7

ASF - Transmission - Vector

Answer 7

• Soft ticks
• Ornithodorus spp., specifically O. moubata in Africa
• Virus replicates in the tick either trans-stadial or transovarial and sexual transmission

Question 8

ASF - Hosts

Answer 8

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 9

ASF - Distribution

Answer 9

Endemic in sub-saharan Africa and island of sardninia (Italy)

(def. of endemic: regularly found among particular people or in a certain area.)

Question 10

ASF - Pathogenesis

Answer 10

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

Question 11

ASF - Site of Virus Replication

Answer 11

• Pharyngeal mucosa, tonsils, etc.
• Endothelial cells
• Megakaryocytes
• Macrophages

Question 12

ASF - Apoptosis of host cells

Answer 12

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

Question 13

ASF - Mechanisms related to Hemorrhages

Answer 13

• 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

Question 14

ASF - Clinical signs - Peracute

Answer 14

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

Question 15

ASF - Acute

Answer 15

• High fever
• Moderate anorexia
• Erythema
• Cyanotic skin blotching on the ears, tails, lower legs or hams
• Respiratory distress
• Recumbency
• Vomiting
• Diarrhea: initially mucoid and later may become bloody
• Abortion: sometimes the first event seen in an outbreak
• Death

Question 16

ASF - Chronic form

Answer 16

• Emaciation and stunting
• Swollen joints
• Ulcers and reddended or raised necrotic skin foci
• Pneumonia

Question 17

ASF - Diagnosis

Answer 17

• Virus isolation: blood spleen, visceral lymph nodes, tonsils
• Hemadsorption
• Serology: FAT, immunodiffusion
• PCR to detect viral DNA

Question 18

ASF - Immunity

Answer 18

• Infected pigs do not neutralize the virus, hence, humoral response does not seem to have substantial protective value
• Vaccine creations are unsuccessful