Pigs, like humans, evolved as omnivores. They’ll gobble up meat, roots, grains and whatever else their probing snouts discover, including the waste from people’s kitchens. The ability of pigs to turn garbage into meat has long made them a crucial resource for the world’s poor.

Now those indiscriminate eating habits have become a liability. The African swine fever epidemic is killing millions of the animals in Asia, having already wiped out a quarter of the global pig population. It has been spread, in part, by pigs eating virus-laden pork scraps.

We can’t blame the pigs — it’s in their nature. In their efforts to combat the disease, governments are banning the use of garbage as feed. The costs — to the lives of pigs and the livelihoods of farmers — will be enormous.

The swine fever virus has never been found in the United States, but it has killed pigs in the Caribbean, Europe and Russia. No outbreak, however, has been as devastating as the current one in Asia.

The disease was first reported in Asia in 2018; it began in northeastern China in August, then swept across the country, crossed borders into Vietnam and other countries, and jumped oceans to infect the Philippines and Indonesia.

Harmless to humans, the virus kills nearly every pig it infects, and there’s no vaccine. To stop it, governments kill sick pigs, bury them and quarantine the area. China has more than 400 million pigs and may lose half of those to swine fever. Pork prices have climbed to record highs, prompting authorities to release meat from the national strategic pork reserves (the very existence of which indicates pork’s importance in China, where it accounts for 60 percent of meat consumption).

The virus can spread directly from pig to pig or hitch a ride on a truck’s tires or a farmworker’s shoes. And it can survive for months in frozen or cured pork, infecting pigs that eat it.

That’s a problem in China, where 40 percent of pork production happens at “backyard” operations. Rather than feeding pigs the corn-soy rations typical of giant farms in the United States and China, some small farms fatten pigs on whatever is cheapest. Of 68 outbreaks studied in China, more than a third were caused by feeding pigs virus-tainted garbage.

Garbage is the most traditional type of pig feed. Thousands of years ago, Eurasian wild boars started lurking around the first human settlements to eat garbage, gradually evolving into domestic pigs. Farmers everywhere were quick to recognize the value of these creatures that reproduce rapidly and produce meat that preserves well with salt and smoke.

The upper classes have often looked askance at the dubious dietary habits of pigs, but most people couldn’t afford to be picky. The ability of pigs to survive without pasture, eating foods of no monetary value, made them indispensable to poor villagers from Southeast Asia to England and, after 1492, in the Americas as well.

As late as the 1960s, Secaucus, N.J., was known as “the pig capital of the East,” for its giant herds fattened on Manhattan’s food waste. (In E.B. White’s “Charlotte’s Web,” Wilbur lunches on “apple parings, meat gravy, carrot scrapings, meat scraps, stale hominy, and the wrapper off a package of cheese.”) Garbage feeding is still practiced in the United States today, but it’s less common and is tightly regulated to prevent disease transmission.

The rest of the world is moving in the same direction. Even the Food and Agriculture Organization of the United Nations has called for prohibitions on garbage feeding.

Such policies may help stop the epidemic, but the costs are high. After an outbreak of African swine fever in Spain and Portugal in the 1960s, regulations led to the consolidation of the industry by big farms. In Russia, small-scale pork production plunged in the wake of a more recent swine fever epidemic.

The same process is now at work in China, which has banned raw swill and is shutting down small farms and promoting well-funded players who can afford to implement biosecurity measures and fatten pigs on soy meal purchased on global commodity markets.

Backyard farmers are being left behind, in China and elsewhere in Asia. Cambodian farmer Bun Kim Long got her start by raising a few pigs inside her house alongside her children, eventually building a herd of 80. Then one pig fell sick and all were killed under government order. Kim Long now finds herself deep in debt.

“I worked so hard to get where I am now,” she told Nikkei Asian Review. “I want to cry.”

Such scenes of small-scale devastation are playing out all across Asia. China has offered compensation for culled pigs, but the rates are low and the money isn’t making it to those who need it most. Most other countries offer no reimbursement at all.

Governments, though, might find it in their best interests to do more to help the millions of struggling farmers.

If they find themselves without other options, they’ll do what poor farmers have always done: buy a young pig, keep it in the backyard and feed it scraps scavenged from the dump — thereby creating a reservoir of African swine fever virus, primed to start the next epidemic.