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BEIJING (AP) – Scientists are working to develop a vaccine to protect the world's pork stocks, a deadly virus ravaging Asian hog herds.
Farmers have long mastered its spread by quarantining and killing infected animals, but the devastating march of the disease in East Asia is intensifying the search for another solution.
The virus was not considered a high priority by researchers until its appearance last year in China, home to half of the swine population, probably in Eastern Europe and Russia. Since then, it has spread to other Asian countries, including Vietnam and Taiwan, killing millions of pigs en route. Although it does not make you sick, the disease is highly contagious and deadly for pigs.
"Today's situation, facing this global threat, puts a lot more emphasis on this research," said Dr. Luis Rodriguez, who heads the US government's laboratory on exotic animal diseases at Plum Island, in New York. New York State.
One way to develop a vaccine is to kill a virus before injecting it into an animal. The deactivated virus does not make the animal sick, but it encourages the immune system to identify the virus and produce antibodies against it. However, this approach is not always effective for all viruses, including the one that causes African swine fever.
That's why scientists are working on another type of vaccine, made from a weakened rather than dead virus. With African swine fever, the puzzle is to figure out exactly how to modify the virus.
In Vietnam, where the virus killed 3.7 million pigs in six months, the government said this summer that it was testing vaccines but was giving little details about its program. In China, the government said scientists were working on a vaccine that genetically alters the virus, an approach that US scientists have also pursued.
The US Department of Agriculture said it recently signed a confidential agreement with a vaccine manufacturer to continue its research and develop one of three Plum Island candidate vaccines. The candidates were made by genetically modifying the virus to suppress certain genes.
But before a vaccine is available, it must be tested on a large number of pigs in secure facilities with isolation pens, waste and carcass incinerators and decontamination showers for staff, said Linda Dixon, a biologist at the Pirbright Institute in London, who studies viral diseases in livestock. The process takes between two and five years, she said.
In-depth testing is needed to ensure that vaccines containing weakened viruses do not cause unwanted side effects.
In the 1960s, for example, Spain and Portugal tested such a vaccine after outbreaks of African swine fever. The treated pigs seemed fine at first, but then lesions broke out on their skin, arthritis blocked their joints and the animals did not get fat, said Jose Manuel Sanchez-Vizcaino Rodriguez, who heads a laboratory on African swine fever at the university. to Madrid.
The two countries finally eradicated the disease by applying strict health protocols, quarantining and killing infected and carrying pigs.
Even if vaccines become available, they may not work anywhere in the world. Vaccines developed against the virus in China and Europe, for example, may do nothing in sub-Saharan Africa, where the disease has been around for longer.
A vaccine may be more desirable in places where the disease is prevalent, said Daniel Rock, who previously headed Plum Island's African swine fever program. Other countries might prefer the quarantine and destruction method.
This could be the case in the United States, where health officials have taught pork producers to recognize and report potential symptoms, including bleeding, lethargy and loss of appetite.
According to Rock, the spread of the disease worldwide has made the vaccine option a top priority in the United States.
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Candice Choi brought back from New York. Follow Sam McNeil on Twitter: @stmcneil
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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
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