New research uncovers concerning threat lurking in suburban backyards: 'Can have severe consequences'

Raccoons may look harmless wandering city streets or forests, but they carry a hidden threat: a parasitic roundworm that can infect humans and wildlife. Since the animals first arrived in Europe from North America in the early 20th century, they've brought along Baylisascaris procyonis, a parasite that's quietly spreading across the continent.

What's happening?

After escaping or being released from fur farms, raccoons have spread across much of Central Europe — and so have the parasites they carry. Germany is now considered the main distribution area for both.

A study led by professors Sven Klimpel and Anne Steinhoff of Goethe University Frankfurt looked to map the spread of the roundworm in Europe and identify areas where more research is needed, according to a news release. To do this, Klimpel and Steinhoff examined 146 raccoons from Germany via necropsy and combined their findings with a review of existing data from across Europe.

Infection rates were high: 77.4% of raccoons in Hesse carried the parasite, along with 52.9% in North Rhine-Westphalia and 51.1% in Thuringia, where such data was recorded for the first time. 

"The results show both an expansion of the roundworm's distribution area and stable infection occurrence at high levels in German raccoon populations," Klimpel said.

Looking beyond Germany, the analysis found that wild raccoons in nine mostly Central European countries are infected, and in some areas infection rates are very high. In three additional countries, cases appeared in captive raccoons or other animals.

Why is this spread concerning?

Human infections, known as baylisascariasis, are rare but serious. "If the larvae enter the central nervous system, the disease can have severe consequences. Due to frequent hand-to-mouth contact, young children are primarily affected," Steinhoff explained.

In North America, where raccoons and the roundworm are native, infections have often resulted in permanent neurological damage or death. European cases, though rare, have led to lasting visual impairment.

The parasite's spread is closely tied to the raccoon population, which is growing and increasingly urban. As raccoons adapt to city life, the likelihood of human exposure rises. "The actual distribution of the roundworm is likely significantly underestimated due to insufficient or absent data collection," Klimpel added.

What's being done to reduce the parasite's spread?

Researchers stress that monitoring raccoon populations and studying Baylisascaris procyonis in Europe is urgent. Preventing human infection starts with awareness: Keeping children away from raccoon latrines, washing hands after outdoor activities, and reducing raccoon access to urban spaces can help limit exposure.

In a broader sense, studying invasive raccoons and their parasites also supports conservation efforts. Understanding how raccoons outcompete native species helps protect local ecosystems, preserve natural food chains, and limit opportunities for diseases to spread.

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