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Blog: African Swine Fever spread prompts vaccines search

27 March 2020 Dr. Alan Bullion

African swine fever (or ASF), is a highly contagious viral disease which affects domestic and wild pigs. The disease has become a global threat to the entire pig industry and beyond. Once infected, pigs with ASFV suffer from internal haemorrhaging and will ultimately die within 10 days.

There is no available vaccine or treatment for the disease yet, which means it is spreading across the globe and disrupting basic protein availability, consumption patterns and the international meat trade. However, ASF presents a significant opportunity for those involved in understanding the science of the disease and in developing interventions to combat its spread.

Disease Overview

ASF is endemic in many African countries, to which it was limited until 2007 when the ASFV entered the country of Georgia. It has since gone on to rapidly spread across Europe and now Asia, reaching China in August 2018. More recently, Cambodia, Hong Kong, Indonesia, South Korea, North Korea, Laos, Mongolia, Myanmar, Philippines, Timor Leste and Vietnam have all been affected.

The African swine fever virus (ASFV) affects all members of the pig family, including domesticated swine, European wild boars, warthogs, bush pigs and the giant forest hogs. ASF however does not currently pose a risk to human health as it cannot be transmitted to human beings.

The ASFV can be transmitted directly, indirectly through contaminated feed and fomites, or can be vector-borne and transmitted through ticks. Once the ASFV has been introduced, infected swine develop high viral loads which are easily shed and lead to further direct or indirect transmission via fomites, on items like contaminated clothing, shoes, equipment and vehicles. Infection through contamination (whether feed or, for example, mud on a transport vehicle) is considered to be of primary concern. This is why many European countries focused on raising awareness on biosecurity. This is also why there has been a drive to develop feed additives that can inactivate ASFV within feed.

Wild boar has also played an important role in spreading the disease; however, larger geographical leaps in the spread of the disease have been the result of human activity and the international transportation of domestic pigs. For example, the first outbreak of ASF outside Africa, was recorded in 1957 in Portugal, where it is presumed to have been caused by the feeding of pigs near Lisbon airport with food waste containing pork from Angola.

Implementation of ASF control methods varies among countries depending on the epidemiological status of the disease, that is whether its endemic or not, and the predominant type of pig production, traditional or backyard versus commercial.

Some of the most important biosecurity measures to prevent the entrance of ASF into a commercial farm include:

• Fences,

• Restriction of visitors and vehicles,

• Use of dedicated clothes and footwear,

• Safe disposal of carcasses,

• Avoiding the use of potential contaminated feed including swill.

• Introduction of new animals via quarantine and from well-known sources.

In fact, the Czech Republic demonstrated in 2017, after ASF was detected in two wild boars, how proper biosecurity measures can eliminate ASF. The country took various measures including increased passive surveillance, ban on hunting and wild boar feeding and enclosing the risk-area with "odour" and electric fences to ensure that the disease would remain contained and not spread any further throughout the country or the region. The last confirmed case of ASF in the Czech Republic was in February 2018.

Disease Impact

Broadly speaking, the presence of ASF has led to a dramatic decrease in pig populations leading to shortened supplies of pork, breeding stock, and in some cases significant price increases. This is most notable in China where the price of pork has increased significantly, and where the share prices of breeding companies also increased due to high demand for pork.

China, the US, Germany, Spain and Brazil are the world's top pig producers, producing over 60% of the world's pigs. Pig production in these countries is made up of specialised medium-to-large intensive commercial farms - except for China which we will move onto shortly.

In contrast, there are traditional or backyard operations which are more susceptible to ASF due to low implementation of adequate biosecurity measures and the use of swill feed which remains an important mode of transmission of the disease. It is worth noting that countries in which ASF is endemic are primarily reliant on backyard operations.

China has lost an estimated 50% of its pig population since the first reported case of ASF in 2018. Unlike the other top producing nations, China has a large share of backyard operations. It is reported that 85% of the herd population loss has occurred among small scale and backyard producers.

These losses have led to unprecedented shortages in the country's pork supply, which has altered global trade flows and will continue to do so for the foreseeable future. In order to cater for the increasing demand in the wake of production loss, global exports of pork are predicted to increase by 10% (at 10.4 million tonnes) in 2020 - a record high. Nonetheless, it is believed that even through the increase of imports, China will struggle to make up for its reduced production capacity due to ASF.

Vaccine Search

Vaccination is, in principle, the most effective way of controlling animal viral diseases through preventing mortality or reducing morbidity. Live attenuated vaccines for ASF were used in the 1960s in Spain and Portugal, but they led to the appearance of chronic forms of ASF.

All other approaches including inactivated viruses, recombinant proteins and DNA vaccines, have not yielded as yet, an effective and safe ASF vaccine. As a result of this, Animal Pharm has seen a global increase in the number of ASF-related technologies being patented in the last 10 years. Based on this trend, it is expected that patent filings and R&D funding will continue to grow over the next few years.

A mixture of both public and private-sector organisations appears as applicants (the owners) on ASF-related patents. Some notable applicants include the University of Yangzhou in China, which has been carrying out research on ASF as early as the mid-2000s and filed its latest ASF related patent in 2019.

It is estimated that the value of an ASF Asian market vaccine over a period of four years is likely be in the region of US$112 million. There has undoubtedly been an increase in patenting activity with respect to ASF related technologies filed globally over the past 10 years. Bearing in mind that patent filing data may not yet be fully disclosed for applications filed in 2019, the average increase of filings year-on-year appears to be around 13%. Based on this trend, Animal Pharm expects growth in both patent filings as well as private and public sector funding into related R&D to continue.

A mixture of both public and private-sector organisations appears to be applicants/assignees (the owners) on ASF-related patents. Some notable top-10 applicants/assignees include the University of Yangzhou (China), Qingdao Agricultural University (China), US Department of Agriculture, with a focus on the ASFV Georgia 2007 isolate, and Boehringer Ingelheim Vetmedica (DE). Some of these organisations either have, or are in the process of, commercialising their vaccine technologies. There are also other forms of interventions being developed, including genetically modified pigs which are resistant to ASF.

The European Commission estimates a timeline of around eight years with a probability of success varying between 50 and 80%. In the short-term, live attenuated vaccines (LAVs) are the most promising candidates, but further research is needed to confirm their safety and efficacy in long-term controlled experiments.

To find out more about the global trajectory of African Swine Fever, download a sample of our latest 111-page African Swine Fever report, authored by Ingentium Limited.

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