Can high-voltage pig pens stop China's swine fever?
One farm that was wired up saw none of its pigs died from the deadly virus despite being in Hubei, a province badly hit by swine fever
Scientists are planning a high-voltage electricity experiment at a farm in southwestern China to create cleaner conditions for animals and explore whether doing so could help halt the African swine fever pandemic.
Cables will be installed around pens housing about 2,000 pigs to create an electric field – an invisible force surrounding an electric charge – which the scientists believe will purify the air. They aim to test whether a method already believed to improve animal welfare can restrict the spread of the pandemic, which has decimated China’s hog herd.
The experiment will be conducted at a medium-sized hog farm in Chengdu, in China’s largest pig-rearing province, Sichuan.
Led by Professor Liu Binjiang, a government scientist in northeastern China, it was inspired by Liu’s work on a national “electro culture” program that has been shown to benefit crops by using a combination of electric field and artificial lighting to stimulate plant growth and reduce diseases.
This time, Liu and collaborators will generate a static electric field of 50 kilovolts – more than 400 times the voltage in a standard US household plug.
They believe the high-voltage discharges could break down chemicals such as ammonia that generate unpleasant odors, reduce biological aerosol by 50 to 90 percent, kill germs and generate negatively charged particles in the air that bind to air-polluting chemicals and make them harmless.
Despite the high voltage, the volume of electrons in the cable will be extremely low, at about 1 microampere, producing an electric field that would not be harmful to animals or staff, according to the researchers.
“The air quality [for the pigs] should improve when the device is powered up,” Liu said. “Electricity is one of the many ways to improve living conditions for farm animals. We have a long to-do list.”
When the high-voltage electricity was used to improve air quality at a farm in central China’s Hubei – one of the provinces hit worst by African swine fever – none of its pigs died from the virus, according to Liu.
It had been deployed to enhance animal welfare and prevent airborne diseases such as foot and mouth, but the lack of African swine fever cases was a surprise. It led the team to hypothesise that the electric field had caused a change in the environment that prevented the virus thriving.
The deadly African swine fever pandemic has tended to spread more easily among pigs living in dirty, unhealthy conditions, according to some studies.
Liu’s team’s hypothesis required further testing, however. One popular theory on the fast spread of the virus in China blamed the use of kitchen waste as feed. Some hog farms used restaurant leftovers that may have contained pork products from infected areas.
Other researchers also proposed flies, ticks or even mosquitoes as disease-bearing hosts, while trucks carrying pigs around the country may have contributed to its spread over long distances. But airborne transmission has been limited, it is believed.
The electric field idea was initially developed to boost plant production. In what was billed as the world’s largest electro-cultural experiment, involving vegetable greenhouse farms with a combined area of more than 3,600 hectares (8,895 acres), Chinese researchers used it to increase crop production significantly while reducing the use of chemical fertilizers and pesticides.
Liu said the Sichuan study could provide new data – to be analyzed by government research institutes including the Chinese Academy of Agricultural Sciences – to verify various hypotheses about viral transmission of a disease that has defied containment.
The swine fever has spread to every populated continent except the Americas. It originated in Sub-Saharan Africa, where the first outbreak was reported in 1907, before spreading to Europe and Central Asia in recent decades. China first detected it last August in Shenyang, in the northeastern Liaoning province, and since then nearly all of its provinces have been affected, with millions of pigs culled to control the outbreak.
Pork prices have soared, and top government veterinary Professor Li Defa estimated in September that the virus had resulted in economic losses of 1 trillion yuan (US$143 billion) for China. The pork crisis has even weakened China’s bargaining power in trade negotiations with other countries, including the United States.
The African swine fever virus has an abnormally large body, containing more DNA strains than most viruses. This gives it better adaptability to changes in environment. It can also mutate faster to cheat pigs’ immune systems.
With no drug available that can relieve the symptoms, mortality remains nearly 100 percent.
Li Baoming, a professor at China Agricultural University and director of Beijing Engineering Research Centre for Livestock and Poultry Healthy Environment, was not involved in the Chengdu experiment, but said electric field could indeed improve the air quality in a pigsty by reducing the amount of floating particles in the air. He said, though, that there remained the problem of particles sticking to surfaces and animals.
He said that the “lucky” pig farm in Hubei remained an isolated case and that, to prove the effectiveness of an electric field in fighting African swine fever, “we need to see more evidence”.