A parasitic tapeworm, known scientifically as Echinococcus multilocularis and commonly referred to as the "fox tapeworm," has been detected for the first time in wildlife along the West Coast. University of Washington researchers found the parasite in 37 out of 100 coyotes sampled in the vicinity of Puget Sound in Washington State. The findings were published earlier this year in the journal PLOS Neglected Tropical Diseases.
The presence of the parasite in wildlife does not indicate a common occurrence of human infections, and the risk to the general public is considered low, according to the researchers.
Parasite's Spread and Variant
Genetic analysis of the coyotes revealed they carried a European variant of the tapeworm. This strain has become the predominant type in the United States and Canada. Prior to the 2010s, the parasitic tapeworm was infrequent in North America, with most cases confined to remote areas of Alaska. However, over the past 15 years, the parasite has expanded its range, leading to an increase in dog and human infections across the Midwestern U.S. and Canada. Cases in coyotes have been observed spreading westward from the upper Midwest for several years, with infected animals now found on the West Coast.
Human Infection and Symptoms
The tapeworm cycle typically involves canids, such as foxes, and rodents. Humans can become infected by accidentally ingesting tapeworm eggs. This can occur after handling contaminated soil, consuming contaminated food, or by touching their mouth after handling an infected pet. The infection can lead to a condition called echinococcosis, which is described as one of the most lethal human parasitic diseases.
The development of cysts, which contain immature tapeworms, is a hallmark of the infection. These cysts commonly form in the liver but can spread to other organs. The infection often remains undetected for years or even decades due to the slow growth rate of the cysts. Symptoms, which may not appear until cysts grow large enough to impinge on healthy organs and tissues, can include abdominal pain and increased belly size if the liver is affected, or coughing and shortness of breath if the lungs are involved.
A more dangerous form, alveolar echinococcosis, is rarer and more lethal. It manifests as a tumor-like mass that invades and destroys surrounding tissue, primarily in the liver, but it can also spread to the brain. In severe instances, this can result in liver failure and death. Symptoms of liver failure include fatigue, yellowing of the skin and eyes, and abdominal pain. Experts note that this form can mimic cancer, underscoring the importance of seeking medical attention if symptoms arise.
Prevention Measures
While the overall risk of infection remains low, basic precautions can help reduce exposure. Maintaining good hand hygiene, particularly washing hands before eating and after being outdoors or handling soil in areas where the tapeworm is endemic, is recommended. Dog owners are advised to prevent their pets from consuming wild rodents and to ensure regular veterinary care for their animals. The Centers for Disease Control and Prevention also suggests avoiding direct contact with wild animals known to carry the tapeworm, such as foxes and coyotes.