Model Shows Culling, Carcass Removal Key to Containing ASF

May 6, 2020 — 

While countries in Europe and Asia have adopted various plans to prevent the introduction of African swine fever (ASF) or contain its spread, a new mathematical model from a team of researchers in the U.K. and Spain has identified two effective tactics. [Source: National Hog Farmer 5 May 2020]

ASF is a highly infectious virus that causes severe, usually fatal disease in domesticated pigs and wild boars. There is currently no treatment or vaccine. Wild boars are free ranging and can carry and spread ASF.

The team reported that culling and fast removal of animal carcasses are critical for the eradication of the disease, according to an announcement from Heriot-Watt University in Scotland.

Professor Andy White and his Heriot-Watt University mathematics research team worked with the SaBio group of the Spanish Game Resources Institute (IREC), UCLM & CSIC in Ciudad Real, Spain, to develop the new model.

The virus is not a threat to humans, but it can have a profound socioeconomic impact on areas with outbreaks.

"African swine fever can rapidly devastate pig populations. There are outbreaks in China, Poland, Belgium and the Baltic states at the moment. In China, it has wiped out around 40% of the country's pig population," White said.

"Wild boar transmit the disease, and their numbers are on the rise in Europe. There are several populations in the U.K., and here, too, numbers are increasing," he added. "Our mathematical model was used to understand the different ways that the virus could be transmitted.

"To match the data, we showed that infection needed to occur in three ways. Through contact between susceptible and infected wild boar, through contact between susceptible wild boar and infected carcasses and via individuals that survive the initial infection but succumb to the disease after several months," White explained.

"Our new model also considered biosecurity measures that can help mitigate the spread of an outbreak. A combination of culling and the removal of infected carcasses is the most effective way to eradicate the virus without also eradicating the host population," he said. "It is important to act quickly: Early implementation of these measures will reduce infection levels while maintaining a higher host population density. In some cases, this could prevent the virus from establishing in a wild boar population."

The model also suggests that it may be easier to control ASF in warmer climates.

"Higher temperatures lead to faster degradation of infected carcasses, which also reduces the severity of an outbreak," White said.

According to the announcement, some regions provide supplemental feed to wild boars in order to increase their density. The model suggests that this should be avoided when ASF is a threat, because it leads to a more pronounced epidemic outbreak and persistence of the disease in the long term, White said.

The new model was published in Scientific Reports.