Nature Sci. Rpts: Risk of African Swine Fever Virus Introduction into the United States

How ASF Spreads

#14,461

Although African Swine Fever can be transmitted directly from pig-to-pig, and can be carried by certain types of ticks, in many cases the virus has been spread by the movement of contaminated food products, animal feed or bedding, or other products to uninfected regions.

For the past year we've been following numerous reports (see here, here, here, and here) of the confiscation ASF-positive food products (see photo below) carried by travelers coming  from endemic regions, at ports of entry in Taiwan, South Korea, Japan, and Australia.

The illegal importation of food products also happens at a much larger scale, as we saw last March in USDA Statement On Seizure Of 1 Million Pounds Of Smuggled Chinese Pork.

While North American remains free from the ASF virus, the more inroads it makes around the globe, the more opportunities it will have to jump into our backyard (see USDA's A qualitative assessment of the likelihood of ASF virus entry to the United States. March 2019).

We've seen concerns raised by U.S. and Canadian Stakeholders (see ASF in China Prompts Call for Pork Producers to Think Feed Safety and Five Possible Pathways ASF Could Enter Canada) along with our own USDA, which recently released a 28-page ASF response plan.

None of this means that the importation of ASF to North America is inevitable, but it wouldn't be without precedent. Foreign Animal Dieases (FADs) - such as  highly pathogenic avian influenza (HPAI), Virulent Newcastle disease (vND),and foot-and-mouth disease (FMD) - are a constant threat.  

Six years ago we saw the arrival of another, far less dangerous porcine virus - PEDV  - which is believed to have originated from China (see mBio: PEDV - Porcine Epidemic Diarrhea Virus – An Emerging Coronavirus).

Despite the plans in place to contain the virus should it arrive, the success rate around the world thus far has been underwhelming. The economic impact, both to farmers and to consumers, could be enormous.

Given the stakes, the $64 question is: What are the odds that ASF contaminated food products will get past the customs checkpoints, and introduce the virus to the United States?

While it is not possible to come up with a solid answer to that question, a recent analysis - published in Nature's Scientific Reports - finds that the odds of it happening have increased significantly over the past couple of years.

I've only included the Abstract, so follow the link to read the report in its entirety.  When you return, I'll have a brief postscript.

Risk of African swine fever virus introduction into the United States through smuggling of pork in air passenger luggage

Cristina Jurado, Lina Mur, María Sol Pérez Aguirreburualde, Estefanía Cadenas-Fernández, Beatriz Martínez-López, José Manuel Sánchez-Vizcaíno & Andrés Perez

Scientific Reports volume 9, Article number: 14423 (2019) | Download Citation

Abstract

African swine fever causes substantial economic losses in the swine industry in affected countries. Traditionally confined to Africa with only occasional incursions into other regions, ASF began spreading into Caucasian countries and Eastern Europe in 2007, followed by Western Europe and Asia in 2018.

Such a dramatic change in the global epidemiology of ASF has resulted in concerns that the disease may continue to spread into disease-free regions such as the US. In this study, we estimated the risk of introduction of ASF virus into the US through smuggling of pork in air passenger luggage.

Results suggest that the mean risk of ASFV introduction into the US via this route has increased by 183.33% from the risk estimated before the disease had spread into Western Europe or Asia.

Most of the risk (67.68%) was associated with flights originating from China and Hong Kong, followed by the Russian Federation (26.92%). Five US airports accounted for >90% of the risk. Results here will help to inform decisions related to the design of ASF virus surveillance strategies in the US.

        (Continue . . . )


Getting good baseline data on the recente spread of ASF has been difficult. Many countries - including China and North Korea - treat any bad `economic news' as a national security issue, and rarely reveal the full extent of their losses.

Despite China officially reporting just over 1.17 million pigs lost, and only 158 outbreaks, outside experts have concluded that China's losses are easily 100 times greater.   

Last April, in African Swine Fever In China: Epizootic or An EpicZootic?, I wrote about this RaboResearch report, which estimated that between 150-200 million Chinese pigs have already been infected with ASF - more than all the pigs in Europe - and that China's pig production will drop 30% in 2019.

Rabobank's latest update (“African Swine Fever: A Global Update.”) - published August 22nd - has revised their estimates upwards to a 50% herd loss - or over 200 million head. 

While ASF doesn't impact human health directly, the economic impacts, resultant food insecurity, and potential political instability from these sorts of massive losses can be far reaching, and unpredictable. 

All of which makes it an epizootic to watch in the months ahead.