When African swine fever (ASF) strikes a pig herd, why do some animals survive while others die?
Could the difference be explained by their level of exposure to the virus, their health status, or perhaps something in their genetic makeup?
A research team led by Associate Professor Do Duc Luc at the Vietnam National University of Agriculture, in collaboration with the University of Liège in Belgium, investigated whether genetic differences could help explain why some pigs survive ASF outbreaks in Vietnam.
The study was presented at the 21st Asian-Australasian Animal Production Congress (AAAP 2026), held in Hanoi in late October.
Looking for genetic differences between survivors and fatalities
The researchers collected data from 528 pigs on farms affected by natural ASF outbreaks. Of these, 320 survived and 208 died.
After excluding samples that did not meet quality requirements, the final analysis included 488 pigs: 300 survivors and 188 fatalities.
The team examined 51,139 positions across the pigs’ genomes, looking for genetic differences associated with survival.
These positions are known as single nucleotide polymorphisms (SNPs), points in the DNA where individual animals may carry different genetic variants.
In practical terms, the researchers wanted to determine whether certain genetic variants were associated with a higher likelihood of death among pigs in ASF-affected herds.
They used a statistical model that accounted for sex, population genetic structure and genetic relationships between animals, helping to reduce the possibility that differences between groups would be mistaken for genetic effects.
Three genetic signals worth investigating
The analysis identified three positions on chromosomes 1, 2 and 18 showing preliminary statistical associations with mortality.
The most notable signal was found on chromosome 2, near a gene called RELA.
RELA plays a role in regulating immune and inflammatory responses. It is not specific to ASF but is involved in how the body responds to various disease-causing agents.
At this location, one genetic variant was associated with 4.25 times higher odds of death compared with the reference variant in the study’s statistical model. This does not mean that the probability of death was 4.25 times higher, nor does it establish that the variant directly caused mortality.
Interestingly, a study published in 2024 involving pigs in Uganda also reported a genetic association in the region near RELA while investigating survival following ASF.
The other two signals were located near ERRFI1 and ZMYND11 on chromosome 1, and LDLR and PCSK9 on chromosome 18. These genes are involved in biological processes that could influence how the body responds to viral infection.
However, all three signals require further investigation and validation.
A research direction, not yet a breeding solution
Although the researchers identified three potentially relevant genetic positions, none met the stringent statistical significance threshold used when examining tens of thousands of positions across the genome.
According to the authors, the relatively limited sample size reduced the study’s statistical power and prevented the findings from reaching this higher level of significance.
The results therefore point to genetic regions worth investigating further. They do not establish that any particular gene enables pigs to survive ASF.
It is also important to distinguish between disease resistance and disease tolerance. A pig with greater tolerance may still become infected but suffer less severe consequences. This differs from resistance, which involves limiting or preventing infection.
If future studies confirm that particular genetic characteristics contribute to improved ASF tolerance, the findings could eventually open another avenue for pig breeding research.
For now, however, the three genetic signals identified in this study cannot be used as validated markers for selecting pigs with a better chance of surviving ASF.
For Vietnam’s pig industry, where ASF remains a major challenge, the research provides preliminary evidence that may help scientists better understand why some pigs survive outbreaks that kill others.
This is not yet the answer to ASF, but it is one step towards finding that answer.
Source: Do Duc Luc, Nguyen Thai Anh, Nguyen Hoang Thinh, Vu Dinh Ton and Frederic Farnir. Identification of Single Nucleotide Polymorphisms Associated with Tolerance to African Swine Fever in Pigs using a Generalized Mixed Model. Proceedings of AAAP 2026, Volume 1, page 2.
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