เข าใจโรค เข าใจเช อ ASF อ.สพ.ญ.ดร. ยลยง ว นวงษ

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1 เข าใจโรค เข าใจเช อ ASF อ.สพ.ญ.ดร. ยลยง ว นวงษ ภาคว ชาเวชศาสตร และทร พยากรการผล ตส ตว คณะส ตวแพทยศาสตร มหาว ทยาล ยเกษตรศาสตร 1

2 ASF 2

3 China: 2018 Korea: 2018 In Shenbei New District, Shenyang City, Liaoning Province 47 cases and 47 pigs dead local authorities culled 913 pigs (Arias et al., 2017) 3

4 African swine fever (ASF) A highly contagious viral disease of all pigs (family Suidae) High fever, hyperemia, severe hemorrhages and high mortality rate Very similar to acute CSF and HP-PRRS No vaccine or effective treatment No effective neutralising Ab 4

5 African swine fever virus Genus Asfivirus, Family Asfarviridae (ASF And Related Virus) A large complex multilayer virus Icosahedral, enveloped DNA virus, kbp Only DNA arbovirus (transmitted by arthropod vectors) Pippa Hawes IAH 5

6 Structure of ASFV p72: The viral capsid, antibody and CTL target p54: Transmembrane, involved in virus particle maturation, antibody target p32: Immunogenic, implicated in virus internalization, antibody target (Sánchez-Vizcaíno et al., 2009) 6

7 Molecular Epidemiology Partial p72 sequencing B646L gene encoding p72 capsid protein More than 20 genotypes Genotype I: West Africa, Europe (endemic in Sardinia, Italy), central and south America and the Caribbean Genotype II: South-eastern Africa, Caucasus region, Ukraine (Simulundu et al., 2018) 7

8 Transmission and Dissemination Direct contract (between sick or carrier and healthy animals ) Parenteral exposure Oronasal exposure Indirect contract By David Almquist Contact with Contaminated objects (fomites) By vectors: Ornithodoros ticks 8

9 Transmission and Dissemination Routes of shedding: - Blood, tissues, secretions and excretions (such as oronasal fluid, urine, feces) Very stable and persistent in the environment At least 30 days in pens ~ 140 days in some pork products 9

10 Viral replications 10

11 Oronasal routes Viral exposures Tick bite Main Target Cells: monocytes/macrophages Rapidly spreads to the main sites of secondary replication i.e.,lymph nodes, bone marrow, spleen, lung, liver, and kidney Systemic distribution (4-8 days post infection) Blood coagulation disturbances - Damage to endothelial cells - Impairment of thrombocytopoiesis Severe bleeding and Thrombocytopenia Effect on red blood cells; hemadsorption 11

12 Immune response 1. Impaired immune system Inhibits host signalling pathways; block transcription of host immunomodulatory genes Inhibits the action of apoptosis 2. Resulting in immune modulation and immune suppression 3. ASFV can escape from the host immune system 4. Results in carriers showing no clinical symptoms 12

13 Pathogenicity Incubation period: Natural infection: 5-21 days Experimental infection: 2-5 days Vary in pathogenicity: High to low virulence forms Highly virulence - Peracute - Acute form Moderate virulence - Subacute form Low virulence - Chronic form (Seroconversion) Clinical develop Sudden death <7 days 5-30 days 1 month Mortality 100% 100% 20-40% adults 70-80% young animals 30% (pregnant sows, young animals) 13

14 Clinical signs and lesions Acute disease Sudden death with few clinical signs High fever (up to 42 C) Hyperaemia and cyanosis (seen as reddening) of the skin, particularly ears and snout Depression and loss of appetite Vomiting and diarrhea (sometimes bloody) Abortions 14

15 Clinical signs and lesions Subacute and chronic disease More common outside of Africa Various signs: slight fever, depression Transitory thrombocytopenia, leukopenia Numerous hemorrhagic lesions Necrosis in areas of skin, chronic skin ulcers, arthritis, pericarditis, adhesions of lungs Abortion 15

16 Available from: 16 african-swine-fever-recognizing-the-disease-in-field_5521/

17 Available from: african-swine-fever-recognizing-the-disease-in-field_5521/ 17

18 CSFV Extensive hemorrhage 18

19 Differential diagnosis African swine fever(asf) Classical swine fever(csf) Highly pathogenic strain of porcine reproductive and respiratory syndrome (HP-PRRS) Systemic salmonellosis Erysipelas 19

20 Diagnostic methods Virus detection (OIE protocol) Immunological methods: Fluorescent antibody test (FAT) Ag captured ELISA Viral isolation: Primary cultures of pig monocytes or bone marrow cells Haemadsorption test PCR 20

21 Diagnostic methods Antibody detection (OIE protocol) anti-asfv antibodies are detectable from about 6 days post-infection Enzyme-linked immunosorbent assay Indirect fluorescent antibody (IFA) test Immunoblotting test 21

22 ELISA: 2010 to 2015 An indirect ELISA Coated with three recombinant proteins (p32, p62, and p72) 6,184 samples (230 farms) 71 samples (1.15%) showed unclear results However, repeated confirmatory tests were negative

23 Vaccine development 23

24 Vaccine Live-attenuated virus vaccine Stimulates both cellular antibody response and confer protection Safety concern Risk of long-term viral persistence Inactivated and subunit vaccine (recombinant protein, DNA vaccine, virus vector) Safety Can induce antibody responses, but not confer strong protection May delay in the onset of disease 24

25 Prevention and control No vaccine available No effective treatment Biosecurity is the main prevention strategy Culling (stamping out) is the main control strategy 25

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