Overview of cholera swine in Africa

African swine cholera is thought to have appeared since 1907 and was first described in 1921 in Kenya. The disease spread throughout the African region until 1957, when a report appeared in Portugal. Since then, the disease began to spread across European countries in the 1980s and recently appeared in Russia, China, and Japan.

Every day there are reports of outbreaks of African swine outbreaks around the world. The last day there was a report on African swine cholera in China, dated September 7, 2018 in Anhui province, and to date, about 40,000 infected pigs have been culled to control the outbreak. African swine cholera has become an existing risk for the pig industry in Southeast Asian countries, including Vietnam.

What is African swine cholera (ASF)?

The African swine flu virus (ASF) is a viral DNA, belonging to the Asfarviridae family. This is a virus completely different from the Classical swine fever virus (CSFV), a type of viral RNA, belonging to the Flaviviridae family. ASF mainly infects pig macrophages and causes serious disease for pigs and wild pigs. ASF is inactive at 60 ^° C for 20 minutes, pH = 11.5. The common antiseptic chemicals are capable of killing viruses such as ether, chloroform, NaOH 0.8%, chlorine 3%, formalin 0.3% and iodine-containing compounds. Viruses have a long-term survival ability in the blood, in tissue and non-cooked or raw meat products. Soft ticks (belonging to Ornithodoros genus) play the role of disease vectors.

Pigs infected with cholera virus of African pigs have a 100% death rate - (illustrated image).

Does African pig cholera affect humans or other animals?

The cholera epidemic of African pigs does not spread to humans but is likely to cause disease and cause many pigs to die resulting in heavy losses to the pig industry.

Clinical symptoms of ASF

Clinical manifestations of severe or mild illness depend on the virulence of the virus. High virulence virus often causes disease in too acute and acute with death rate up to 100%. The average virulence virus causes acute and acute disease with a mortality rate of about 60% while chronic and hermaphroditic diseases are usually caused by low virulence with a mortality rate of 2 - 10%. Sickle pigs in acute form often show signs such as: High fever (41-42 ^o C), stop eating, lie down, increase respiratory frequency, vomit and watery eyes, and runny nose. Pigs appear hematomas or hemorrhages in the ears, abdomen, groin, tail and legs. Pigs have constipation and diarrhea, droppings or blood (it may be observed on the base of the tail). In terms of lesions during the examination, the subcutaneous hemorrhage, hemorrhage and haemorrhage can be seen in the lymph nodes, causing the lymph nodes to become purple and purple like blood clots (especially lymph nodes near the stomach, liver and kidney). Sinuses include the heart of yellow water, pleural effusion, fluid accumulation in the abdominal cavity. Congestive pulmonary or hemorrhagic hemorrhage, bronchial gas with foam. Kidney kidney hemorrhage points. The stomach and intestines also hemorrhage into spots or into patches.

How to diagnose ASF disease?

African swine disease in clinical symptoms is difficult to distinguish from classic swine cholera, it must be diagnosed differently in the laboratory. The diagnostic method can identify the virus directly by detecting antigen by fluorescent antibody, cell culture, or detected by chemical polymerase chain reaction (PCR). Serological tests such as direct fluorescence antibodies or ELISA can be determined via ASF antibodies in blood samples taken after 8-21 days of infected pigs.

How is ASF spread?

The transmission of ASF is complex, including many factors, but the main route of transmission is known: people traveling from places of potential risk of disease and people transporting contaminated food. from diseased areas, for long distances, and in direct contact between wild pigs carrying diseases or pigs carrying diseases at close distances.

Other infectious factors such as bugs in subtropics, contaminated water, food and vehicles transporting contaminated food, and transmission routes are similar to other viruses.

Can food and ingredients make food spread of ASF?

ASF virus is highly resistant and can last for 6 months and every year in materials, such as infected pork products are not cooked, and it lasts longer if the product is frozen. It was also found to cause infection within at least 30 days in a pigsty that was abandoned due to disease.

Processed or unprocessed foods, cooked from pork and harvested grains from infected areas from wild pigs will present a risk of disease. ASF virus is moderately resistant to heat and acid environment. Non-heat raw foods such as corn, corn cobs, hay, straw or grain drying from risk areas should not be used. A recent study (Dee et al., 2018) recommended that ASF virus can survive 30 days of transport in dried feed ingredients such as soybean residues or in some feed additives. These studies have not been verified by the research team and the representativeness of the model used for research is still controversial.

The focus on preventing infection should start from the key points in the production chain, from infected pig cells or contaminated materials.

What are the risks associated with transportation?

When the ASF virus is highly resistant, a major risk of infection is transmitted directly from transport from ASF-infected areas. Therefore, experts recommend that prior to entering an uninfected area the means need to be cleaned with antiseptic on the outside border.

Can humans infect and spread ASFs?

People have a major involvement in the spread of disease over large distances, for example, people carry infected meat products such as sausages or raw materials, hunting equipment from areas with epidemic ASF.

Farmers and farm workers: should focus on biosecurity, avoiding direct or indirect contact with pigs with leftovers

For hunters: to neutralize ASF virus, hunting equipment must be cleaned of dust and mud and then put into an environment with a temperature of at least 60 degrees C for at least 30 minutes or treated with medicine antiseptic works on viruses (such as Virkon S 1% or 2% chlorit solution) depending on the manufacturer's recommendation.

How to disable AVF virus?

1. Temperature: the temperature can disable the virus is above 60 degrees C for 30 minutes.
2. PH : PH 11.5 can neutralize virus without serum. Serum increases the resistance of the virus, for example at pH 13.5, the virus can withstand 21 hours without serum and up to 7 days of serum.
3. Chemicals / disinfectants: viruses sensitive to ether, clor. The virus is neutralized by sodium hydroxide (xut) 8/1000, hypochlorite 2.3% chlorine (30 minutes) and formalin 3/1000 (30 '), ortophenyphenol 3% (30'), iodine mixture. Virkon S is recommended as commercial antiseptic to prevent ASF virus.

How to prevent ASF virus

So far, there is no vaccine to prevent this disease because:

1. The understanding of viral receptors in target cells is quite limited.
2. Complexity in the viral genome.
3. Lack of information about the link between pathogenicity and epidemiological factors of the disease.

Therefore, to assess the prevention of this disease, it is necessary to follow the disease prevention and control process as follows:

1. Accurate monitoring of epidemiological situation. Systematically guide epidemiological investigations in the event of epidemics occurring from the top down source and possibly from the bottom up of the infection.
2. Apply strict biosecurity measures to test adaptation to specific target groups (such as feed plants, pig farms, hunters, truck drivers, etc.).
3. Strict control of the supply system and focus on preventive testing to avoid contamination from contaminated materials and heat treatment stages.
4. Avoid having pigs raised in direct contact with wild boar, with bugs and other wild animals: should have fences in camps, factories, facilities and must control pets.
5. Stop transporting and controlling sperms and embryos to avoid spreading and spreading the disease.
6. Building a control area around the infected facility and supervising the transport of pigs in the area. Treatment of removing sick pigs in the camp. It is important to avoid pigs from hunting or wild boar because they are at higher risk of infection.
7. Pork and carcasses must be destroyed by burning, burying and infected establishments must handle comprehensive disinfection, full of antiseptic drugs.