First Europe-wide analysis shows widespread raccoon roundworm infection

First Europe-wide analysis shows widespread raccoon roundworm infection

The raccoon roundworm Baylisascaris procyonis can cause serious illness and even fatal brain damage in humans. A team of researchers from the ZOWIAC joint project at Goethe University Frankfurt has now presented the first comprehensive analysis for Europe: The parasite is already established in nine countries and is continuing to spread. The study combines new studies on 146 raccoons from Germany with a comprehensive evaluation of all available European data and was published in the journal Parasitology Research.

While the spread of the raccoon in Europe is often discussed, its companion usually remains unnoticed: the raccoon roundwormBaylisascaris procyoniscame to Europe with the first raccoons from North America at the beginning of the 20th century. Since their release or escape from fur farms, raccoons have spread uncontrollably across large parts of Central Europe - and with them their parasite. Germany is now considered the main distribution area for both species in Europe.

Dangerous companion of the raccoon

This parasite can also infect humans and cause so-called diseasesLarva migransin which migratory larvae damage tissue and organs.

Prof. Dr. Sven Klimpel from the Goethe University Frankfurt and the Senckenberg Biodiversity and Climate Research Center

People become infected by accidentally swallowing infectious eggs found in soil, water, or on objects contaminated with raccoon feces.

A research team from the joint research project ZOWIAC (Zoonotic and Wildlife Ecological Impacts of Invasive Carnivores) has now investigated how far the parasite has already spread in Europe.

Insidious life cycle

The parasite's life cycle is complex: adult roundworms live in the small intestines of raccoons. Females produce up to 180,000 eggs every day, which are released into the environment through their feces. The resistant eggs collect in so-called raccoon latrines – favorite defecation places. In the environment, under appropriate temperature and humidity conditions, they develop into infective larvae within two weeks and can survive for several years.

Children are particularly at risk

Infection of humans with the raccoon roundworm is called an infectionBaylisascariasis. Anne Steinhoff from the Goethe University Frankfurt and lead author of the study explains: "If the larvae get into the central nervous system, the disease can have serious consequences. Small children are particularly affected due to frequent hand-to-mouth contact." Most known cases occur in North America, the natural range of the raccoon and the roundworm. In most documented cases there, the disease led to permanent neurological damage or even death.

“In addition, it is assumed that many cases remain undetected or are misdiagnosed due to non-specific symptoms,” adds Klimpel. “In Europe, diagnosis in humans is made even more difficult by the lack of specific diagnostic testing options.” A definitive diagnosis is currently only possibleCenters for Disease Control and Prevention(CDC) in the USA and Canada.

First comprehensive Europe-wide analysis

The aim of the study was to provide a current overview of the spread of the parasite in Europe and to identify research needs. To do this, the team led by Klimpel and Steinhoff examined raccoons from Germany via autopsy and supplemented this new data with a comprehensive analysis of available scientific studies and infection data from Europe.

Of the 146 raccoons examined, 66.4 percent were infectedBaylisascaris procyonis: 77.4 percent in Hesse, 51.1 percent in Thuringia and 52.9 percent in North Rhine-Westphalia. The study provided prevalence data for Thuringia for the first time. “The results show both an expansion of the distribution area of ​​the roundworm and a stable infection rate at a high level in German raccoon populations,” explains Klimpel. The analysis showed that the roundworm occurs in wild raccoons in nine European countries, primarily in Central Europe - sometimes with extremely high infection rates. Infections in raccoons or other captive species have been detected in three other countries.

Spread linked to raccoon populations

"The studies show a constant expansion of the distribution area in Europe. The spread of the roundworm is linked to the constant spread of its final host, the raccoon, which now occurs throughout Europe," continued Klimpel. “The true prevalence of roundworm is likely to be significantly underestimated due to insufficient or no data collection.”

Of particular concern: Urbanization of raccoon populations increases the likelihood of human contact with contaminated areas. Three documented cases ofBaylisascariasisare known in Europe - all of them resulted in permanent visual impairment.

“The results of this study make it clear that further research on the raccoon roundworm is urgently needed in Europe – especially given growing raccoon populations and their increasing adaptation to urban habitats,” concludes Klimpel.

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