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July 01, 2020

African swine fever eradication may depend on climate

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Eradicating African swine fever in European boars may require a mix of culling and carcass removal, depending on climate conditions, according to a recent article.

Authors from institutions in Scotland and Spain examined the potential to reduce risk of disease spread from wild boars that survive initial infection and carcasses of those that die. They compared conditions in Estonia and Spain, the latter of which has higher temperatures and more abundant scavengers, such as vultures, that degrade carcasses more quickly.

“Our model study indicates that in Estonia, culling alone is unlikely to eradicate the disease without eradicating the host population, whereas in Spain culling could potentially eradicate the disease without eradicating the host,” the article states. “The difference is that in Estonia infected carcasses remain in the environment, acting as a long-term source of infection and increasing the difficulty of eradicating the disease.”

The authors published their report April 3 in Scientific Reports, an open-access journal from Nature Research.

“Our study indicates that multiple control methods should be applied in parallel to eradicate ASF without eradicating the population,” the article states. “This will be of particular relevance in regions where wild boar hunting is an important industry that supports rural communities.”

The article indicates ASF can persist in low-density populations, at 1%-3% prevalence, for several years following an epidemic. The virus transmits through contact in social groups and where wild boars congregate, such as water holes, as well as through contaminated carcasses.

ASF is highly lethal, and analysts estimate outbreaks in China may have killed hundreds of millions of pigs since August 2018. The virus previously spread through wild boars and domesticated pigs in the Caucasus, Eastern Europe, and Russia.

U.S. swine veterinarians have been bolstering disease defenses in anticipation of a domestic outbreak.