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Last modified: 09. May 2024

One Health Working Group analyses the increasing incidence of the potentially fatal parasitic disease.

Across Europe, human alveolar echinococcosis is receiving great attention. Its causative agent is the tapeworm Echinococcus multilocularis. In recent years, the incidence of human cases has steeply elevated. Wild canine predators play a key role in parasite incidence. Research concerning Somogy and Baranya counties revealed that the occurrence of the pathogen is influenced by some climatic and land cover related factors.  

The cestode Echinococcus multilocularis is one of the most threatening parasitic challenges in the European Union. In recent years, official reports revealed that the disease has spread across Europe with an increasing number of cases. At the end of the 1980s, the disease was endemic only in the Alpine regions of France, Germany, Switzerland, and Austria. After 30 years, human alveolar echinococcosis has already been reported in almost all European countries.

The parasite has an indirect life cycle, which requires two hosts. The adult worms can be found in the small intestines of the final hosts (dominantly wild canids, e.g. red fox, golden jackal). Besides the definitive hosts, mainly rodents can serve as intermediate hosts in the life cycle. An adequate intermediate host could ingest the released eggs in the environment. In their liver, the parasite grows like a malignant tumour. After the predation on an infected rodent, the final host (e.g. red fox, golden jackal) could become infected.  

Humans could be infected accidentally after egg ingestion by consumption of unwashed raw plant material (e.g. vegetables, berries). The E. multilocularis infection is asymptomatic for several years. The first symptoms (general malaise, weight loss, abdominal pain) could appear for 5-15 years. Imaging techniques play a central role in the differential diagnosis and clinical management of human cases. Treatment sometimes requires extensive surgery and/or anti-infective prophylaxis. Untreated cases or delayed treatments have a high fatality rate.

Though the parasite occurs mainly in cold and moderate climatic conditions, in recent years, severe human cases have been confirmed in warmer, sub-Mediterranean areas, including southwestern Hungary. Despite the increasingly warm climate, our previous studies confirmed continuously elevated infection rates in Somogy County.

To clarify possible explanatory causes, researchers of the One Health Working Group conducted a surveillance study between 2021-2022 with examination of 197 foxes and 194 golden jackals to confirm the presence of tapeworms. Seventy-one infected animals were found, of which 41 were jackals. A novel statistical approach was used for habitat analyses, which has not been applied previously in parasitology, yet. The investigation allowed a simultaneous global and local assessment of the most relevant environmental factors of infection risk.

Based on the results, the researchers found that wetlands, annual precipitation, and precipitation seasonality play a role in the worm's distribution. Based on the localization of infected animals, three high-risk areas could be determined: the Drava Plain, Zselic south of Kaposvár, and the southern shore of Lake Balaton.

The results obtained may help understand the ecological demands of tapeworms and contribution to the mapping of high-risk areas for human infection and planning prevention strategies.