Since August 2018, there are many cases of African swine plague in China, which has caused huge economic losses to farmers. African swine fever is an infectious disease caused by African swine fever virus (ASFV) infecting domestic pigs and wild boars. This virus was born in Africa that deserves the name. How did it spread to the whole world and how did it come to China?
African swine fever virus first appeared in sub-Saharan Africa. In 1921, African swine fever was reported for the first time in Kenya, Africa. A retrospective study found that there was a case of African swine plague in Kenya in 1907. Initially, the main hosts of African swine fever virus were African wild boars and warts, and ticks that feed on wild boar blood became vectors.
Because adult wild boars seldom die from infection, African swine fever has not been sufficiently vigilant at first. But later in Africa, people engaged in pig industry found that domestic pigs were less resistant to the virus than wild boars. Once infected, no matter pups or adults, visceral organ bleeding and other symptoms would occur. The mortality rate was very high, and the transmission was particularly rapid. Pig farms suffered heavy losses.
For quite a long time, the Sahara Desert has blocked the northward spread of African swine fever. But after the middle of the 20th century, the virus began to spread in Europe, the Americas and Asia, as trade between people from all continents became more frequent. One reason why African swine fever virus can "travel around the world" is that it can survive for a long time under non-high temperature conditions, such as in frozen meat for several years, and in semi-cooked meat and ham or sausage without high temperature for about half a year.
In 1957, a flight from Angola, Africa, to Portugal, Europe, sent the remaining pork products on board as swill water to a pig farm in Portugal. This is believed to be the source of the African swine fever epidemic in Portugal. This is the first time that African swine fever has landed in Europe. Since then, there have been epidemics in Spain, France, Italy, Belgium, the Netherlands and other countries.
In the Americas, there was an outbreak of African swine plague in Cuba in 1971. It was reported that passengers arrived in Cuba with unquarantined sausages, which became the source of the outbreak of swine fever in Africa. The epidemic has caused heavy losses to Cuba and killed about 500 thousand pigs nationwide. Subsequently, African swine plague was also found in Brazil, Haiti and other American countries.
In 2007, African swine fever was introduced into the Caucasus. In June of that year, the Georgian health authorities first reported the discovery of African swine fever, which may originate from contaminated pork products flowing into the country. Subsequently, epidemics also occurred in Russia, Ukraine and other countries.
At present, more than 60 countries and regions in the world have reported the situation of African swine plague.
In August 2018, China first reported African swine fever. According to Huang Baoxu, deputy director of the Center for Animal Health and Epidemiology of China, molecular epidemiological studies showed that African swine fever virus (CSFV) introduced into China belonged to genotype II, with 99.95% homology with the whole genome sequence of the strains published by Georgia, Russia and Poland.
Huang Baoxu said: "Usually there are four main ways for African swine fever to be introduced across the border: international trade and smuggling of pigs and their products, pork and its products carried by international passengers, food and kitchen residues on international transport, and migration of wild boars."
Huang Baoxu believes that the possible ways of African swine fever introduced into China are also the above categories* He pointed out: "China has frequent exchanges and trade in goods with countries where African swine fever occurred; pork prices are higher than those of surrounding countries; smuggling activities continue; the number and population density of wild boar in border areas continue to increase."
Globally, African swine fever virus was more active in 2018. More than 5,800 outbreaks were reported in more than 20 countries, such as Russia, Romania and Poland. At the beginning of 2019, the Mongolia state also announced on January 14th that the 4 provinces of the country had African swine plague and had taken urgent measures.
African swine fever is rampant. Can pork still be eaten? People who like to eat pork don’t worry that African swine fever is not a zoonosis and that the virus will not infect humans. African swine fever virus is sensitive to high temperature. High temperature disinfection is helpful to prevent and control African swine fever when handling pork products.
