Kansas State professor works to develop ASF vaccine

Published on Jan. 25, 2020

Near the end of 2019, three Kansas State University (KSU) professors received a grant from the U.S. Department of Agriculture (USDA) to fight important animal diseases. One of these professors was Jishu Shi, professor of vaccine immunology and director of U.S.-China Center for Animal Health in KSU’s College of Veterinary Medicine. 

            During the Jan. 15 episode of KSU’s Agriculture Today podcast, Shi explained he will use the $640,720 grant to work toward developing a vaccine for African Swine Fever (ASF). 

African swine fever

            ASF is a highly contagious hemorrhagic viral disease affecting domestic and wild pigs and was discovered nearly 100 years ago in Africa. 

            “About 60 years ago, ASF moved to Europe and was contained and eradicated for the most part. There is still a small island in Spain with ASF,” Shi explains. “Then 12 years ago, it moved to Russia, then to eastern European countries and finally into Asia.” 

            Shi notes the first detected outbreak occurred in China in August 2018.

            “At the time, I don’t think people in China realized the damage caused by ASF would be so severe,” Shi says. “The swiftness of the damage has been devastating to the hog industry in China and elsewhere.” 

            In fact, ASF outbreaks have swept the East with cases reported in China, Vietnam, Republic of Georgia, Armenia, Russia, Azerbaijan, Ukraine, Belarus, Lithuania, Poland, Latvia, Estonia, Romania, Czech Republic, Belgium, Laos, Myanmar, Cambodia, Mongolia, North Korea, South Korea and the Philippines. 

            According to the World Organization for Animal Health (OIE), the epidemiology of ASF is complex and varies depending on the environment, types of pigs in production systems, presence or absence of tick vectors and the presence or absence of wild hogs.

            Transmission routes can include direct contact with infected domestic or wild pigs, indirect contact through ingestion of contaminated material or contaminated fomites or biological vectors, notes OIE.

            Clinical signs and mortality rates of ASF vary according to the virulence of the virus and species of pig. Acute forms of ASF are characterized by high fever, depression, anorexia and loss of appetite, hemorrhages in the skin, abortion, cyanosis, vomiting, diarrhea and death within six to 20 days. Mortality rates can be as high as 100 percent.  

ASF vaccine research

            “ASF is really a biosecurity issue at first, because keeping it out of our country in the first place is the best way to prevent it,” Shi states. “Once it is in, there are a lot of factors affecting how we control it.” 

            As far as vaccine goes, Shi notes about five years ago, several laboratories around the world started studying a way to develop an ASF vaccine. 

            “So far, there is no safe, efficacious and commercial vaccine for ASF which has really inhibited the way we control the disease,” Shi explains. 

            Similar to the other laboratories, Shi says KSU’s research is dedicated to finding a safe, efficacious vaccine that can be produced on a commercial level.

            “The ASF virus is very specific and has presented us with a lot of challenges to figure out,” Shi says. 

            “In our project we are working on three areas of vaccine development,” he explains. “First we have to work on the virus. Our approach is a modified live virus so we need to figure out which part of the virus can be diluted and still make it safe and efficacious.” 

            The second part of their research, according to Shi, is to develop an accompanying differentiation of infected from vaccinated animals (DIVA) test for the ASF live virus DIVA test developed by the USDA’s Agricultural Research Service (ARS). 

            “The reason it is important to separate vaccinated and infected animals is because vaccinated animals can still be used in the food chain while infected animals cannot,” Shi explains. 

            The third part of their research is to develop a stable cell line supporting the replication of those vaccine candidates, according to Shi.

            “We are in the process of making a new cell line which can support the growth of the virus and allow us to make a vaccine on a large commercial scale,” he says. 

            Hannah Bugas is the assistant editor for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.