Abstract

BackgroundSpirometra erinaceieuropaei is a diphylobothriid tapeworm with a complex life-cycle including definitive, intermediate and paratenic (transport) hosts. Multiple routes of parasite transmission often make it impossible to determine what type of host a specific infected animal is considered to be. Spargana larvae cause sparganosis, a severe food- and water-borne disease mainly found in Asia. In Poland, Spirometra sp. was reported in large carnivores in Białowieża Primeval Forest for the first time in the 1940s and was recently confirmed as S. erinaceieuropaei in several mammals and snakes using molecular methods.MethodsIn total, 583 carcasses of 9 carnivore species were necropsied between 2013 and 2019 in north-eastern (NE) Poland. The larvae of S. erinaceieuropaei (spargana) were isolated from subcutaneous tissue, counted, and preserved for genetic analyses. We calculated the prevalence and intensity of infection. To assess spatial variation in S. erinaceieuropaei infection probability in NE Poland, we applied a generalized additive model (GAM) with binomial error distribution. To confirm the species affiliation of isolated larvae, we amplified a partial fragment of the 18S rRNA gene (240 bp in length).ResultsSpirometra larvae were found in the subcutaneous tissue of 172 animals of 7 species and confirmed genetically as S. erinaceieuropaei. The overall prevalence in all studied hosts was 29.5% with a mean infection intensity of 14.1 ± 33.8 larvae per individual. Native European badgers and invasive raccoon dogs were characterized by the highest prevalence. An analysis of parasite spread showed a spatially diversified probability of infection with the highest values occurring in the biodiversity hot spot, Białowieża Primeval Forest.ConclusionsOur study revealed that various mammal species (both native and non-native) can serve as S. erinaceieuropaei reservoirs. The frequency and level of infection may differ between selected hosts and likely depend on host diversity and habitat structure in a given area. Further studies are needed to assess the distribution of the parasite throughout Europe and the environmental and biological factors influencing infection severity in wild mammals.

Highlights

  • Spirometra erinaceieuropaei is a diphylobothriid tapeworm with a complex life-cycle including defini‐ tive, intermediate and paratenic hosts

  • The highest overall prevalence was estimated for European badgers (36.4%) and raccoon dogs (30.9%)

  • All 25 newly generated 18S rRNA sequences of larvae isolated from autopsied animals of 7 different species showed 99% identity with the 3 sequences for S. erinaceieuropaei deposited on GenBank (Additional file 2: Figure S1, Additional file 3: Figure S2)

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Summary

Introduction

Spirometra erinaceieuropaei is a diphylobothriid tapeworm with a complex life-cycle including defini‐ tive, intermediate and paratenic (transport) hosts. Multiple routes of parasite transmission often make it impossible to determine what type of host a specific infected animal is considered to be. For most of helminth parasites, host specificity appears less defined at the intermediate host stage than at the definitive host stage, with non-adult intermediate (larval) stages able to infect different organs and tissues of diverse intermediate hosts. Several parasites use paratenic (transport) hosts, where parasite larvae show no development [5]. The role of paratenic hosts is important; they facilitate contact between parasite larvae and the definitive host, contributing to an increase of prevalence in a specific host population [6]

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