By Group 05

1. By Group 05

2. Introduction • African swine fever (ASF) is one of the most serious diseases affecting domestic pigs, warthog, European wild bores and bush pigs. African swine fever (ASF) is the disease caused by African swine fever virus(ASFV).

3. History • ASF was first described in Kenya in the 1920s as an acute haemorrhagic fever which caused mortality approaching 100 per cent in domestic pigs. • It was noted that disease outbreaks occurred when domestic pigs came into close contact with wildlife species, particularly warthogs • Initial reports were from countries in East and southern Africa where the virus is recognized to have been present in its wildlife hosts for a very long time • The first spread of ASF outside Africa was to Portugal in 1957 as a result of waste from airline flights being fed to pigs near Lisbon airport • Then the Outbreaks of ASF were reported subsequently in a number of other European countries.

4. Symptoms and Signs • Reddening of the ears is a common sign of African swine fever in pigs. • Pigs develop a high fever 40-42°C • Gradually lose their appetites and become depressed • The swelling around the kidneys and the muscle hemorrhages are typical of pigs with African swine fever.

5. If they are white skinned pigs their extremly (nose, ears, tail and lower legs) become cyanotic (blue-purple colour) and discrete haemorrhages appear in the skin particularly on the ears and flanks

6. Diagnosis • Laboratory tests • Virus isolation from serum, spleen, kidney or lymph nodes. • Virus antigen demonstration by direct immuno-fluorescence tissues. • PCR(Polymerase chain reaction) is a sensitive test to detect viral genetic material. • Serological (antibody) tests on serum from recovering pigs, 8-21 days after infection.

7. Diagnosis cont…. • Blood splashes (ecchymosis) may be present in the skin of legs or abdomen. • The spleen is often enlarged and there can be excess fluid in the abdominal, pleural and pericardial cavities. • Oedema of the gall bladder and mesentery of the colon is also quite typical of ASF. • In chronic cases, lungs may show focal lesions caused by necrosis and even mineralization.

8. Prevention & Control Sanitary prophylaxis ASFV-recovered carrier swine and persistently infected wild pigs require special consideration in controlling the disease. Free countries • Careful import policy for animals and animal products • Proper disposal of waste food from aircraft or ships coming from infected countries • Efficient sterilization of garbage

9. Prevention & Control cont….. In outbreaks • Rapid slaughtering of all pigs and proper disposal of cadavers and litter is essential. • Thorough cleaning and disinfection. • Designation of infected zone, with control of pig movements. • Detailed epidemiological investigation, with tracing of possible sources (up-stream) and possible spread (down-stream) of infection. • Surveillance of infected zone, and surrounding area

10. Prevention & Control cont….. Infected countries • Avoid contact between pigs and soft tick vectors or their habitats (Africa) – i.e. prevent pigs from wandering. Medical prophylaxis • No treatment. • No vaccine to date.

11. Aetiology Classification of the causative agent • African swine fever virus (ASFV) is a DNA virus in the AsfarviridaeFamily; genus Asfivirus • Virulence of ASFV isolates vary greatly • ASFV: large, double-stranded DNA virus which replicates in the cytoplasma of infected cells • As the virus progresses through its life cycle most if not all of the host cell’s organelles are modified, adapted or in some cases destroyed

12. Aetiologycont… • Resistance to physical and chemical action • Temperature: Highly resistant to low temperatures. Heat inactivated by 56°C/70 minutes; 60°C/20 minutes. • pH: Inactivated by pH <3.9 or >11.5 in serum-free medium. Serum increases the resistance of the virus, e.g. at pH 13.4 – resistance lasts up to 21 hours without serum, and 7 days with serum. • Survival: Highly resistant to environmental factors: Remains viable for long periods in blood, faeces and tissues; especially in infected, uncooked or undercooked pork products. Can multiply in vectors (Ornithodoros sp.).

13. Epidemiology Hosts • African wild swine (warthogs (Phacochoerusaethiopicus), bush pigs (Potamochoerussp.), giant forest hogs (Hylochoerusmeinertzhageni) are usually inapparently infected and act as reservoir hosts of ASFV in Africa • Hosts that demonstrate disease: domestic pigs (Susdomestica), European wild boar, and American wild pigs • Ticks of the genus Ornithodorosare considered the natural arthropod host and there exists some speculation that ASFV is a virus of arthropods and that mammalian species, such as domestic swine, represent “accidental hosts”

14. Epidemiology cont….. Transmission • Direct transmission by oronasal spread (sometimes aerosol if short distance)  contact between sick and healthy animals • Indirect transmission on fomites (premises, vehicles, implements, clothes) • ASFV can be found in all tissues and body fluids, but particularly high levels are found in the blood  massive environmental contamination if blood is shed during necropsies or pig fights or if pig develops bloody diarrhea • ASFV often spreads to new areas when pigs are fed uncooked scraps that contain ASFV-infected pork (e.g. pigs that have been fed intestines of guinea that had eaten infected ticks)  important way that the virus spreads to new countries (ASFV can remain infectious for 3–6 months in uncooked pork products)

15. Epidemiology cont….. • Biological vectors: soft ticks of the genus Ornithodoros(only DNA virus transimtted by arthropodes)  in tick populations: transstadial, transovarial, and sexual transmission occur  In Africa: ASFV is thought to cycle between newborn warthogs and the soft ticks that live in their burrows (Warthog can serve as a natural reservoir of the virus without sign of disease)  Individual ticks can apparently remain infected for life and infected soft tick colonies can maintain this virus or years • Other bloodsucking insects such as mosquitoes and biting flies may also be able to transmit the virus mechanically  Animals which have recovered from either acute or chronic infections may become persistently infected, acting as virus carriers; especially in African wild swine, and in domestic pigs in enzootic areas

16. THREAT TO WILDLIFE • In endemic areas, it is difficult to eliminate the natural reservoir in warthogs; however, control of the soft tick vectors is important in preventing the disease • In wildlife such as warthogs, European wild boar, American wild pigs, bush pigs, Cause death in 2-10 days on average Mortality • There is no vaccine against ASFV and this limits the options for disease control to wildlife and domestic animal.

17. THREAT TO WILDLIFE • Transboundary spread also occurs through movements of infected wildlife such as warthogs and bushpigs, together with the soft tick vector • The extensive free-ranging pig husbandry systems in large parts of Asia would complicate the implementation of control measures. In addition, potential wild pig reservoirs of ASF exist in these regions

18. Conclusion • The African swine fever is one among the very challenging and demanding diseases as it cost a lot of money to control since it neither has vaccine nor cure. And for poor countries especially most of the African countries it may lead to extinction and poverty as the level of technology is very poor hence it may take very long time detect the disease outbreak.

19. Reference • http://www.oie.int/wahis/public.php?page=home • http://www.pighealth.com

20. Presenters • LOTHA R. MOLLEL • LINDA HILGERS • LIGHTNESS TUNGU • JOSEPH MZIRAY • DAVIS RUNYORO • MACOKECHA BEST NASHON