African Swine Fever: A primer

Photo by Marcus Platt on Unsplash.

By Yvette Tan

African Swine Fever (ASF), also called African Swine Flu, is a highly contagious viral disease that affects wild and domesticated pigs. It cannot be passed on to humans, but is nonetheless an illness that should be contained and eradicated because of its leathat effect on hogs.

According to Dr. Deo Alcantara, Assistant Professor at UP College of Veterinary Medicine in the University of the Philippines Los Baños, the first incident of ASF was reported in 1921. It has spread through several continents, including Europe, Eastern Europe, and South America. It also spread through Spain, where it first appeared in the 1960 and was finally eradicated 1995 through the thorough and widespread implementation of preventative and curative measures. It is commonly believed that the virus entered China through Russia in 2018, and from there, it spread to the Philippines.

ASF in the Philippines

“The first incidents [in the Philippines] were reported in Rizal. That particular outbreak was associated with the very common swill feeding of their backyard farms and apparently, the swill they were feeding had contaminated meat,” Dr. Alcantara says. “The speculation [is that the contaminated meat] came directly from smuggled pork from China, which at this point was already highly infected and the virus was basically ravaging the whole swine industry of China already.”

He adds, “The speculation was apparently in Rizal, swill feeding was a very common practice. You were hearing that these backyard farms were buying their swill at a very cheap price-P115 per sack. At the end of the day, if you’re raising pigs, that’s a very [cheap] feed for your animals.”

Aware of the ASF outbreak in China, the Bureau of Animal Industry (BAI) had issued a ban on the importation of meat products from affected countries like China. However, tainted meat was still making its way to Philippine shores. It is speculated that the disease was first observed in Rizal in June 2019, but wasn’t officially reported until August, after its presence was properly confirmed.

Alarming spread

After the announcement, BAI instituted protocols to contain the disease but by this time, infections had already cropped up in Quezon City, also due to swill feeding.

“Controls were not that effective. A lot of the pigs that were being raised that were apparently infected were subsequently were not prevented from entering slaughterhouses in Bulacan, thus the start of the outbreak and incidences in Bulacan on top of the problems that we saw on the news that with dead pigs that they started throwing their dead carcasses in the estuaries and riverbanks. Those were very complicated situations as to why the situation blew up,” Dr. Alcantara says.

“And now, as it’s spreading throughout the country, we’re seeing its mostly a man-driven or infection is through carriers like persons. People are the ones actually causing the main spread of the disease now,” he adds.

The veterinarian explains that in the wild, ASF is spread through infected wild boars. In the Philippines´case, however, since it hasn’t surfaced in the wild pig population, the prevailing theory is that it reached local hogs through human activity.

“It’s a virus that could really survive outside of the environment,” Dr. Alcantara says.

“Swill feeding was probably the cause of the initial entry, but ultimately, the pigs were somehow able to go into the slaughterhouses in Bulacan and from there, it could have had direct… some people with their vehicles going to several farms and ultimately, it now spread via biyahero (middleman). I mean, your middlemen don’t normally practice biosecurity when they go in and out of your slaughterhouses. Hence, their vehicles and their personnel just go to the farm and select the animals they want to buy, among other modes of transmitting the disease to other farms.”

ASF symptoms

The public has largely swept ASf under the rug because it isn’t infectious to humans. This is dangerous, as the disease is highly communicable among swine, and whether humans can get a disease or not, eating tainted meat is unhealthy and unsanitary.

What are the symptoms of ASF? Dr. Alcantara enumerates:

“You see high fever as a sign that the pigs are in discomfort and have had a fever. The reddening, blotches of red discoloration on the animal on the ears, on the belly, on its extremities. Animals would have bloody diarrhea. You’ll also see respiratory signs–sneezing, coughing, you’ll see death on affected animals,” he says.

“Reddenings on the skin are actually indications that it’s undergoing internal hemorrhage. These would be your lesions on the skin. Even your eyes could be bloodshot red, but when you open up the animal, you’ll see that the muscles and the organs would also be bleeding internally. It may be comparable to hemorrhagic fever or ebola in humans.”

He concludes by saying, “The virus is that virulent. It’s a very invasive and lethal virus that most… before the pig could establish an immune response. That’s why ultimately, the mortality is very high.”

The disease is incurable and is so deadly that once a farm has it, there is rarely any recourse but to cull the whole stock and start over.

“If a farm is infected, basically, the farm can’t do anything anymore. It’s a virus [that has] no cure, and it’s a very lethal disease, so ultimately, whether the farmer likes it or not, he’s going to lose his stock in a couple of weeks. That’s why the only mode is to control the spread,” Dr. Alcantara says.


The numbers 1-7-14 protocol refer to the radius with regards to the farm affected. Every piggery within a one kilometer range of the affected farm should be put under quarantine and all stock culled. Every farm within a seven kilometer of the affected farm should be intensely monitored for the disease, and there should be a buffer zone of 14 kilometers.

Unfortunately, this wasn’t implemented strictly enough, as the disease has spread to provinces such as Pampanga, Tarlac, Kalinga, Camarines Sur, and even Davao.

Dr. Alcantara says that there are two prevailing theories on how ASF reached Davao: one is that it came from Luzon, the other is that it came from Indonesia. “That’s still open for speculation,” he says.

Preventing and controlling ASF

As ASF has no cure, the only way to keep it from spreading is to “control pig movement.” “Meaning it should have been effective if we were able to prevent the disease from spreading. You eradicate any animals in the perimeter of [any farm with positive cases],” Dr. Alcantara says. “Well, it failed.”

Part of why this was successful in other countries that have eradicated the disease is because there were incentives for farmers to cull their infected herds. It’s believed that a lot of farms hid the presence of the disease from authorities, resulting in the spread within the country.

After ridding farms of infected herds, the disease can be prevented by practicing strict biosecurity protocol.

“The essence of biosecurity is isolating your farm, basically segregating your farm from possible infections. That’s why on the backyard level, that’s something that’s close to impossible to do,” Dr. Alcantara says.

“For one, most backyard farms don’t really have a perimeter fence to keep possible sources of infections out of their farm. …dogs carrying carcasses, wild birds, and farms that are close to their operations—these are all highly likely to be the ones to contaminate your farm. That most backyard farms can’t even secure their own perimeter is basically a biosecurity measure can’t be implemented properly.”

This is easier for commercial farms because they will at least have walls and a gate to keep outsiders from entering the compound, the entirety of which should be a clean site.

The basic rule in what farms are doing now is trying everything to prevent all possible sources of contamination from entering their premises. They’re beefing up their perimeter biosecurity…. They don’t allow visitors. They don’t even allow most of their middlemen or biyaheros… to [enter] the farm. Sales transactions might be done away from the farm just so that the biyahero ([which] for most farms, [are] known to be the number one spreader of the disease) [is kept as far away from the] herds as possible.

Of course, no farm can stay locked down forever. Farm workers and feed and supply delivery vehicles need to enter, and trucks carrying the livestock to slaughterhouses need to be able to come and go.

“This is where your proper disinfection and sanitation of those vehicle trucks fall,” Dr. Alcantara says. “That is something most backyards cannot really perform. They don’t have a perimeter fence to keep possible sources of contaminants out, meaning their perimeter is so porous they cannot really monitor what’s coming in and out of their facilities. They might not have a proper disinfection area so that vehicles that are coming from the slaughterhouse and any other areas could be a source of infection. They cannot implement proper disinfection protocols.”

There is no other way to control and prevent the spread of ASF. “The word is biosecurity,” Dr. Alcantara reiterates. “Big or small, if you could isolate, lock down your farm, prevent entry of unnecessary or most important, contaminated items, that’s the only way to control the disease now.”

The future of the Philippine hog industry

With ASF’s presence in the country, what does this mean for the local hog industry? “What’s the prediction?” Dr. Alcantara asks, “All you have to do is look at where China is now.”

After the disease was initially reported in the Philippines, sales of pork went down. “A lot of farms, even if they were not being hit by ASF, suffered from low prices because of the low demand, and the pigs, if they did not die of ASF, they were dying of other diseases because the farms became just too congested. The capacities became overloaded,” Dr. Alcantara narrates. “On the economic side, the farms lost money, couldn’t pay their bills, and one way or another, that’s the scenario because the demand for pork suddenly dropped. You’ll hear of farms who could sell a thousand pigs a month suddenly the demand dropped to 300 a month. Where will you put the additional 700 that were supposed to be sold? Basically, you see farms that were overstocked and had nowhere to bring their pigs.”

Despite the public’s initial reaction, the veterinarian remains optimistic. “Filipinos are really pork eaters so after the scare, ultimately, the demand… should be going back up to normal.”

The veterinarian once again cites China as an example. “Did you know that before ASF, China had an estimated population of 400 million pigs? They’re estimating that the pig population in China, mostly because of ASF, is down 50%. From news clips I hear, before ASF, Chinese were buying their pork for a dollar per kilo. Now you hear that prices of pork are reaching six dollars per kilo. From two dollars to six dollars, so you’re seeing retail prices of pork from a hundred pesos to three hundred pesos basically per kilo because of ASF and the depopulation of their populations, the law of supply and demand, you’re seeing meat to be very expensive.”

As of the time of the interview, ASF was still spreading in China.

Dr. Alcantara thinks that the same scenario will play out locally. According to the Philippine Statistics Authority, the lowest farmgate average for pork in the fourth quarter of 2019 was at P97.08/kg liveweight, recorded in November of that year. In the same time period of the year before, the highest farmgate average was recorded in October at P115.34/ kg liveweight.

“So obviously now, the demand is still low, but once that demand starts to go back to normal, and if we follow the trend of China and Vietnam where [they]basically have no pork available… we’re going to have an imbalance of supply and demand because prices will basically skyrocket. That’s the end result that you’re expecting. A shortfall in supply,” Dr. Alcantara predicts.

What happens now?

As of this writing, in the middle of the COVID-19 crisis, ASF still hasn’t been contained, with around 300,000 hogs culled since August 2019. “The disease is still spreading. And how it ravaged Vietnam and China, we are expecting a massive reduction in our pig population,” Dr. Alcantara says.

“The disease is spreading and it’s more lethal than most diseases. It’s a disease that we expect to linger. Even in the next 3-5 years, I doubt it will be eradicated in the Philippines that time soon because there’s no vaccine to control it properly.”

The veterinarian adds that framing the disease as something that humans cannot get may have contributed to the decline in the demand for pork. “I think it was the wrong message from the start, because pigs get sick. Other than ASF, there are so many other diseases…. The message should have been reassurances that NMIC (National Meat Inspection Service) and BAI are assuring the public that meat going to the markets is safe,” he says, adding that this is to prevent the public from suspecting that the pork they are buying is“double dead,” the local terms for already dead livestock that are cut up and sold as meat.

He further says that that the public should not be fearful because “if you go to a slaughterhouse now, magka-insect bite lang yung baboy (if the hog has just one insect bite)… the NMIC does not even want [it] to enter the slaughter line because they’re really now trying to protect the consumer.”

And while it is imperative that the agencies involved strictly implement protocols aimed at containing and eradicating ASF, it is also important to assure the public that there are systems in place to make it safe for them to buy pork.

“No matter what’s the disease going on… there are a lot of famers still producing good quality pigs and those ultimately are the pigs that reach the market. Especially now, when things are very strict, they do not allow sick, diseased pigs to enter their slaughter lines and most especially the marketplace. Those are the reassurances that the NMIC should be giving to the consumer,” Dr. Alcantara says.

That said, he does acknowledge that it is still possible for disreputable resources to sell infected meat, so buying only from certified safe sources is important. He clarifies: “I say it’s safe to buy meat in the palengke (market), but obviously there’s hot meat (unsafe meat sold as safe to eat), so somehow, it’s better to discourage buyers from buying pork that’s not certified by NMIC.”

The BAI has a portal dedicated to ASF. For more information, visit or call or text the DA–BAI Hotline at 0995-1329339 or 0920-8543119.

This appeared in Agriculture Monthly’s September to October 2020 issue. 

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Yvette Tan
Yvette Tan is Agriculture magazine's managing editor’s web editor. She is an award-winning writer who likes to eat, travel, and listen to stories about the strange and supernatural. She is dedicated to encouraging people to push for sustainable food sources and is an advocate of food security, food sovereignty, and the preservation of community foodways.

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