n the last couple of years it had seemed as if ASF had almost disappeared, at least from public awareness. But that is not the case. In their latest report published in June 2024, WOAH states that ASF “continues to represent a global threat” and highlights the importance of implementing strict biosecurity as well as maintaining a high level of disease awareness among all actors involved in the value chain.
ASF: Constant vigilance
In the EU, Poland and Germany both just reported new outbreaks in domestic pigs. Only the year before, Europe noted the highest outbreak numbers in domestic pigs since 2019, and cases in wild boar increased five times compared to the previous year. A vaccine is still not commercially available, there is no single reliable treatment and effective control measures are not in place everywhere. As long as that situation persists, the virus will continue to spread and new outbreaks in wild and domestic pigs will be reported regularly. It is therefore imperative that we exhaust all measures to contain the virus and use all the means at our disposal to fight it.
Know thy enemy
African swine fever (ASF) is a contagious viral disease of domestic and feral pigs. It has serious consequences for the animal population concerned and for the profitability of livestock farming, as it disrupts the movement of consignments of these animals and their products within the EU and exports to third countries. No wonder it has become one of the biggest threats to the global pig industry in recent years.
The virus is shed in the faeces, saliva and urine and can easily transmitted by direct contact from pig to pig via the nasal/oral route, or by indirect contact with contaminated objects or feed (fig. 1). Clothing, transport vehicles and equipment may also be a source of infection.
Taking stock of the armoury
Since the path of transmission cannot always be determined with certainty, comprehensive biosecurity measures are still the most important tool to ensure that there is no gap through which the virus can enter the farm. Biosecurity comprises, among others, the restriction of people movement, quarantine protocols for incoming animals, pest control and the implementation and observance of cleaning and disinfection regimens. But what about feed? While the role of feed, water and bedding in the transmission of African swine fever is still controversial and more research is needed (Blome et al., 2020), it has been shown before that the risk cannot be completely excluded. The African swine fever virus can survive humid conditions and high temperatures and the infectious dose is low. Some feed ingredients can even prolong the life of the virus. Feed and water experimentally contaminated with ASFV at the minimum infectious dose of 104 and 100 TCD50 respectively was able to cause infection in pigs when consumed naturally (Niederwerder et al., 2019). Hazard analysis and risk-based preventive controls in the feed supply chain should therefore include securing raw materials and feed by removing the virus to prevent the spread of the disease.
Target the feed
Feed additives used as mitigants to reduce viral load in feed need to be non-toxic and fast acting. Chemical disinfectants like formaldehyde can be problematic because of their carcinogenicity which means that their use is limited.
More natural and sustainable solutions need to be developed to protect animals, workers, and the environment. These include plant metabolites, which have long been studied for their antimicrobial, anti-inflammatory and immunomodulatory effects. Because ASFV is a hulled virus, it is vulnerable to molecules that disrupt its lipid-envelope structure. Clinical studies suggest that botanical formulations may have antiviral properties by targeting viral cell entry and viral replication (Wang et al., 2015). Dr Eckel’s powerful proprietary botanical formulation, Anta®Shield, uses these bioactive compounds that can destabilise cell membranes to offer a 100 % natural tool to reduce the risk of spreading the ASF virus from feed to animals.
Total destruction
During the development process, one of the goals was finding and exploiting possible synergies between the different plant extracts. In an in-vitro feed model test, commercial swine feed was infected with African swine fever virus and plant extracts selected for their anti-viral potential were screened at different dosages. When plant extracts (i) and (ii) were used at a low dose, they reduced viral load in the feed within 24 hours compared to infected feed without any additives. As assessed by HAD50 cell culture test, the reduction was 1.34 and 1.74 logs, respectively. This corresponds to a pathogen reduction of 92.6 and 95.8 %. Using the components at a higher dosage increased this effect. Interestingly, when the plant extracts were combined at the low dosages in the final formulation Anta®Shield, the resulting titer was 2.54 log – a reduction of 99.7 % – lower than the positive control and below the minimum infectious level (fig. 2). This observed effect was greater than the sum of the individual effects, demonstrating clear synergy between plant extracts and making Anta®Shield especially effective already at low dosages.
A PCR study with different doses of organic acids and Anta®Shield clearly showed that the phytogenic feed mitigant was not only more effective at lower doses than the organic acids but that it also worked faster. After three days, no viral DNA could be detected with 400 g Anta®Shield, while it took seven days in the organic acid groups when applied at lower doses than 1.0 % (fig. 3).
It has been shown before that the AFS virus stays viable in certain pig feed and feed components for several days. Also, in our study the viral load was still high enough to potentially cause an infection in pigs after seven days. It is therefore imperative to prevent ASF from entering farms via the feed. We could show that mitigating additives can reduce viral load and infectivity in feed and that it is possible to achieve a fast and effective virus reduction by natural means. In fact, the plant-based feed formulation Anta®Shield was the most effective in terms of dosage and either regarding dosage or speed of decontamination.
Fill up your armoury – with Anta®Shield
We must accept that the question of the role of feed in transmission of African Swine Fever virus will remain unanswered, perhaps for much longer. In the meantime, we cannot afford to stand idle and lose precious time. Anta®Shield has been developed to incorporate natural feed mitigation strategies into existing biosecurity measures. This 100 % natural solution is based on powerful plant extracts and is neither harmful for workers nor corrosive for equipment. Close the gap in your biosecurity plan and get your ally in the ASF fight.
