The $1.6 Billion Bio-Threat: Why Feral Hogs are the Ultimate Disease “Super-Spreaders”

It’s no secret that feral hogs are not good news for the ecosystems of America. But now they present an additional threat. Two new and devastating diseases can potentially be spread by these hogs, and the consequences could be very costly for U.S. agriculture. We have researched the threat that both diseases would present to U.S. agriculture if they entered the wild pig population, and what is being done to prevent that from happening. This is what we discovered.

Wild Pigs Are Damaging Ecosystems

Wild pigs (Sus scrofa) were brought to the U.S. in the 1500s by European settlers. More were introduced during the 1900s for sport hunting. They soon interbred with escaped domestic pigs, so today’s wild pigs are actually a mix of domestic pigs, wild boar, and hybrids of both. Right now, there are around 6.9 million of them in at least 35 states.

They reproduce rapidly, live in large groups, and will eat almost anything, including food crops. This makes them very unpopular with farmers and results in at least $1.5 billion in damage each year. Feral pigs also eat roots, nuts, birds’ eggs, and small carrion. They destroy the habitats of other animals by uprooting plants and displacing soil. There have always been concerns about them spreading disease to wildlife, domestic animals, and even humans. However, two diseases called African swine fever and New World screwworm are causing huge concern right now.

African Swine Fever and Feral Hogs

As the name suggests, African swine fever has its origins in the sub-Saharan region of Africa. It is caused by a virus and probably originated in warthogs, who can carry it without suffering any symptoms. The disease can also infect domestic pigs, where it is both highly contagious and deadly.

It was introduced to the Eurasian continent in 2007 and has since infected both domestic swine and Eurasian wild boar populations. It has not yet been identified in the United States (it is considered a foreign animal disease), but it is inching closer. In 2021, it was found in the Dominican Republic and Haiti. The United States Department of Agriculture is alert for signs in both domestic and feral pig populations.

A Threat to the Domestic Swine Industry

Meanwhile, the domestic swine industry is concerned about the feral hog population acting as a potential vector should the disease enter the country. The virus spreads through exposure to bodily fluids from an infected pig. It can also be transmitted via contaminated feed, garbage feeding (eating discarded pork meat), and contact with infected carcasses in the environment. People can inadvertently carry the virus to domestic pigs on their footwear, clothing, or through infected meat products. Currently, there is no vaccination and no treatment.

Should the disease enter the feral pig population, it would be extremely difficult to eradicate and would threaten domestic pigs. They would suffer from horrible symptoms, including decreased appetite, blotchy red skin, weakness, diarrhea, vomiting, coughing, and difficulty breathing. Most cases are fatal. Infections among domestic pigs in the U.S. would lead to pork shortages, trade disruptions, and significant economic impacts. Thankfully, humans cannot get the disease, so there is no direct threat to public health.

What is New World Screwworm?

The New World screwworm (Cochliomyia hominivorax) is a type of parasitic fly. Their average life cycle lasts 10–30 days and begins when the adults mate. The female then lays her eggs at the edge of an open wound or exposed tissue of a warm-blooded host. This could be a human, a pet animal, livestock, or wildlife. The fly gets its name from the way the larvae ‘screw’ into the flesh using their sharp mouth hooks. The larvae hatch and burrow into the wound, feeding on living tissue. After about a week, mature larvae drop to the ground and pupate in the soil. Pupation occurs more quickly in warmer temperatures, and the adult fly then emerges to repeat the cycle.

Screwworm causes a problem for livestock because of the damage the larvae cause. The flies are attracted to cuts, scratches, surgical sites, eyes, ears, noses, and soft tissue around the navel and genital areas. The damage they cause is termed myiasis and attracts more flies to lay additional eggs as well as infections. If left untreated, the infestation can be fatal.

This parasite was once present in the U.S. but was eradicated in 1966 by an innovative sterile fly program developed by the USDA. Currently, there is no New World screwworm in the U.S., but it is present in South America. There was one outbreak among the Key deer population in the Florida Keys, but it never spread to the mainland.

National Swine Health Strategy

The National Swine Health Strategy is being developed by the National Pork Producers Council (NPPC) and state pork associations. It is a producer-driven effort designed to protect and improve the health of the U.S. swine herd. The looming threat of foreign animal diseases, such as African swine fever and New World screwworm, has driven the momentum for the strategy. One of the aims is to keep foreign and emerging diseases out using prevention and preparedness methods. Another function is the monitoring and early detection of emerging diseases. Ongoing vigilance will be necessary to prevent wild hogs from causing even greater economic damage in the future.