Echinococcus multilocularis in foxes and raccoon dogs: an increasing concern for Baltic countries

Echinococcus species in wildlife

Transmission of Echinococcus spp. in life cycles that involve mainly wildlife is well recognized for those species with small mammals as intermediate hosts (e. g. E. multilocularis), as well as for E. felidis and the 'northern' genotypes of E. canadensis (G8 and G10). In contrast, the remaining taxa of E. granulosus sensu lato are best known for their domestic life cycles, and the numerous wild mammal species (mainly ungulates) that have been recorded with cystic echinococcosis in the past were mainly considered a result of spill-over from the dog-livestock transmission system. This view was challenged with the advent of molecular characterization, allowing discrimination of the metacestodes, although the contribution of wild mammals to various Echinococcus life cycles has remained uncertain for scarcity of wildlife studies. Numerous records of cysts in wild ungulates date back to the 20th century, but cannot with certainty be allocated to the Echinococcus species and genotypes that are recognized today. This means that our current knowledge is largely restricted to studies of the past two decades that kept adding gradually to our concepts of transmission in various geographic regions. In particular, new insights were gathered in the past years on E. granulosus s.l. in wildlife of sub-Saharan Africa, but also on transmission patterns of E. multilocularis in previously neglected regions, e. g. North America. Here, an update is provided on the current state of knowledge on wild mammals as hosts for all Echinococcus species, listing >150 species of wild hosts with references, as well as estimates on their epidemiological impact and our current gaps of knowledge.

Global and local drivers of Echinococcus multilocularis infection in the western Balkan region

The cestode, Echinococcus multilocularis, is one of the most threatening parasitic challenges in the European Union. Despite the warming climate, the parasite intensively spread in Europe's colder and warmer regions. Little is known about the expansion of E. multilocularis in the Balkan region. Ordinary least squares, geographically weighted and multi-scale geographically weighted regressions were used to detect global and local drivers that influenced the prevalence in red foxes and golden jackals in the southwestern part of Hungary. Based on the study of 391 animals, the overall prevalence exceeded 18% (in fox 15.2%, in jackal 21.1%). The regression models revealed that the wetland had a global effect (β = 0.391, p = 0.006). In contrast, on the local scale, the mean annual precipitation (β = 0.285, p = 0.008) and the precipitation seasonality (β = - 0.211, p = 0.014) had statistically significant effects on the infection level. The geospatial models suggested that microclimatic effects might compensate for the disadvantages of a warmer Mediterranean climate. This study calls attention to fine-scale analysis and locally acting environmental factors, which can delay the expected epidemic fade-out. The findings of our study are suggested to consider in surveillance strategies.

Role of invasive carnivores (Procyon lotor and Nyctereutes procyonoides) in epidemiology of vector-borne pathogens: molecular survey from the Czech Republic

BACKGROUND

Vector-borne pathogens (VBPs) are a major threat to humans, livestock and companion animals worldwide. The combined effect of climatic, socioeconomic and host composition changes favours the spread of the vectors, together with the expansion of invasive carnivores contributing to the spread of the pathogens. In Europe, the most widespread invasive species of carnivores are raccoons (Procyon lotor) and raccoon dogs (Nyctereutes procyonoides). This study focused on the detection of four major groups of VBPs namely Babesia, Hepatozoon, Anaplasma phagocytophilum and Bartonella in invasive and native carnivores in the Czech Republic, with the emphasis on the role of invasive carnivores in the eco-epidemiology of said VBPs.

METHODS

Spleen samples of 84 carnivores of eight species (Canis aureus, Canis lupus, Lynx lynx, P. lotor, Martes foina, Lutra lutra, Mustela erminea and N. procyonoides) were screened by combined nested PCR and sequencing for the above-mentioned VBPs targeting 18S rRNA and cytB in hemoprotozoa, groEL in A. phagocytophilum, and using multilocus genotyping in Bartonella spp. The species determination is supported by phylogenetic analysis inferred by the maximum likelihood method.

RESULTS

Out of 84 samples, 44% tested positive for at least one pathogen. Five different species of VBPs were detected in P. lotor, namely Bartonella canis, Hepatozoon canis, Hepatozoon martis, A. phagocytophilum and Bartonella sp. related to Bartonella washoensis. All C. lupus tested positive for H. canis and one for B. canis. Three VBPs (Hepatozoon silvestris, A. phagocytophilum and Bartonella taylorii) were detected in L. lynx for the first time. Babesia vulpes and yet undescribed species of Babesia, not previously detected in Europe, were found in N. procyonoides.

CONCLUSIONS

Wild carnivores in the Czech Republic are hosts of several VBPs with potential veterinary and public health risks. Among the studied carnivore species, the invasive raccoon is the most competent host. Raccoons are the only species in our study where all the major groups of studied pathogens were detected. None of the detected pathogen species were previously detected in these carnivores in North America, suggesting that raccoons adapted to local VBPs rather than introduced new ones. Babesia vulpes and one new, probably imported species of Babesia, were found in raccoon dogs.

Introduction, spread, and impacts of invasive alien mammal species in Europe

Biological invasions have emerged as one of the main drivers of biodiversity change and decline, and numbers of species classed as alien in parts of their ranges are rapidly rising. The European Union established a dedicated regulation to limit the impacts of invasive alien species (IAS), which is focused on the species on a Union List of IAS of particular concern. However, no previous study has specifically addressed the ecology of invasive alien mammals included on the Union List.We performed a systematic review of published literature on these species. We retrieved 262 publications dealing with 16 species, and we complemented these with the most up-to-date information extracted from global databases on IAS.We show that most of the study species reached Europe as pets and then escaped from captivity or were intentionally released. On average each year in the period 1981-2020, 1.2 species were recorded for the first time as aliens in European countries, and most species are still expanding their alien ranges by colonising neighbouring territories. France is the most invaded nation, followed by Germany, Italy, and the Russian Federation, and the muskrat Ondatra zibethicus, the American mink Neovison vison, and the raccoon dog Nyctereutes procyonoides are the most widespread species, having invaded at least 27 countries each. Invasive mammals of European Union concern are threatening native biodiversity and human well-being: worryingly, 81% of the 16 study species are implicated in the epidemiological cycle of zoonotic pathogens.Containing secondary spread to further countries is of paramount importance to avoid the establishment of new populations of invasive mammals and the related impacts on native communities, ecosystem services, and human health.We present a compendium on the ecology and impacts of invasive mammals of European Union concern. It can be used to assist environmental policies, identify and subsequently fill knowledge gaps, and inform stakeholders.

Infection of Raccoon Dogs (Nyctereutes procyonoides) from Northern Poland with Gastrointestinal Parasites as a Potential Threat to Human Health

The aim of the study was to determinate the prevalence and intensity of infection of raccoon dogs with internal parasites, with a particular emphasis on particular species of helminths known to be dangerous to humans. A total of 96 raccoon dogs were obtained from hunters from September 2018 to October 2021. The digestive tract was taken for examination. The parasitological examination was performed using the dissection methods. The extensity of infection with all internal parasites was 60.3%. The following parasites were found in the tested animals: Echinococcus multilocularis (in 10.42% of animals), Toxocara canis (18.75%), Alaria alata (25.0%), Taenia spp. (19.79%), Uncinaria stenocephala (27.08%), Mesocestoides spp. (54.17%) and Dipylidium caninum (6.25%). The highest mean intensity of infection was demonstrated by A. alata and E. multilocularis then by Mesocestoides spp. This study showed that the raccoon dog from northern Poland is a reservoir host of zoonotic pathogens, such as E. multilocularis, Toxocara canis and Alaria alata. Although the role of the racoon dog as a final host of the life cycle of E. multilocularis is considered of less importance than that of the red fox, this species may increase the risk of echinococcosis in humans, mainly due to its growing population in northern Poland.

Asian Admixture in European Echinococcus multilocularis Populations: New Data From Poland Comparing EmsB Microsatellite Analyses and Mitochondrial Sequencing

The cestode Echinococcus multilocularis is the causative agent of a severe zoonotic disease: alveolar echinococcosis (AE). The parasite is distributed over a vast area in northern Eurasia and North America, but the impact of AE on human health is highly uneven between different regions. One hypothetical reason for this difference in virulence may be the genetic structure of E. multilocularis which—based on mitochondrial sequences and EmsB microsatellite profiles—forms four distinct clades. These clades correspond approximately to their continents of origin: Asia, Europe, and North America, with a fourth clade apparently restricted to Mongolia and neighboring regions, even though this clade has not yet been described by EmsB genotyping. However, there are various records of genetic variants from the “wrong” region, e.g., “European” haplotypes in Western Canada, which may be the result of introduction or natural migration of host animals. One such example, prompting this study, is the recent record of an “Asian” mitochondrial haplotype in worms from foxes in Poland. At the time, this could not be confirmed by EmsB microsatellite analysis, a method that has proven to possess greater discriminatory power with the E. multilocularis nuclear genome than sequencing of mitochondrial markers. Therefore, worms collected from foxes in Poland were examined both by EmsB analysis and sequencing of the full mitochondrial cox1 gene in order to allocate the samples to the European or Asian cluster. Based on EmsB analyses of 349 worms from 97 Polish red foxes, 92% of the worms clearly showed “European-type” EmsB profiles, but 27 worms (8%) from seven foxes showed profiles that clustered with samples of Asian origin. According to cox1 sequences, a total of 18 worms from 8 foxes belonged to the Asian cluster of haplotypes. The two methods did not fully agree: only 13 worms from three foxes belonged to Asian clusters by both EmsB and cox1, whereas 18 worms from nine foxes belonged to different clusters, according to each marker. Cross-fertilization between worms of Asian origin and those from the European Polish population may explain these conflicting results. The presence of clearly Asian elements in the Polish E. multilocularis population could be the result of introduction of E. multilocularis with host animals (e.g., domestic dogs), or the migration of foxes. In the absence of genetic data from eastern European countries, especially those bordering Poland, it cannot be concluded whether this Asian admixture is typical for a larger area toward central/eastern Europe, or the Polish parasite population is the western extreme of a gradient where both European and Asian elements mingle. Further studies are needed on this subject, preferably using both mitochondrial sequencing and EmsB microsatellite analysis.

Multispecies reservoir of Spirometra erinaceieuropaei (Cestoda: Diphyllobothridae) in carnivore communities in north-eastern Poland

Background

Spirometra 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.

Methods

In 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).

Results

Spirometra 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.

Conclusions

Our 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.

Parasites in the changing world - Ten timely examples from the Nordic-Baltic region

The world is changing, and parasites adapt. The Nordic-Baltic region in northern Europe - including the Nordic countries Denmark, Finland, Iceland, Norway and Sweden, and the Baltic States Estonia, Latvia and Lithuania - is facing new parasitological challenges due to changes in populations of parasites and their hosts and the spread of new parasites to the region due to climate change. Some changes can also be ascribed to increased awareness and detection. In this paper, we review and discuss a convenience selection of ten timely examples of recent observations that exemplify trends and challenges from different fields of parasitology, with particular focus on climate change and potential changes in epidemiology of pathogens in northern Europe. The examples illustrate how addressing parasitological challenges often requires both intersectoral and international collaboration, and how using both historical baseline data and modern methodologies are needed.

Seroprevalence of Echinococcus spp. and Toxocara spp. in Invasive Non-native American Mink

Invasive non-native species can become reservoirs of zoonotic pathogens and cause their spread during colonization, increasing the risk of zoonoses transmission to both wild hosts and humans. American mink (Neovison vison) are considered an important invasive mammal species responsible for carrying endoparasites. The aim of our study was to evaluate the role of feral American mink as a possible transmission vector of Echinococcus spp. and Toxocara spp. in wildlife. We analysed the frequency of American mink exposure to both parasites, the spatial distribution in Poland, and the variability over time on the basis of specific antibody presence using ELISA and Western blot. Alimentary tract analyses revealed that American mink do not serve as definitive hosts for these parasites. Altogether, 1100 American mink were examined. The average seropositivity for American mink was 14.2% for echinococcosis and 21.7% for toxocarosis; dual-seropositivity was detected in only 6.0%. Seroprevalence of both parasites differed between study sites and significantly increased over time in Toxocara spp. Thus, our study revealed that free-living American mink are exposed to parasites and likely to be involved in the maintenance of both Echinococcus spp. and Toxocara spp. in the wild as paratenic hosts.

Echinococcus multilocularis and Echinococcus granulosus in canines in North-Khorasan Province, northeastern Iran, identified using morphology and genetic characterization of mitochondrial DNA

Background

Canids are definitive hosts of Echinococcus multilocularis and Echinococcus granulosus. This study aimed to survey these two Echinococcus species in canids of North-Khorasan Province, northeastern Iran, using morphological criteria and genetic characterization of mitochondrial DNA.

Methods

The carcasses of 106 canids, namely 61 jackals (Canis aureus), 23 foxes (Vulpes vulpes), 19 dogs (Canis familiaris) and three wolves (Canis lupus) were collected from the study area in 2013–2014 and examined for Echinococcus species. Morphological features were assessed by microscopy of adult worms. For molecular characterization, DNA was extracted, mostly from the adult worms but also from eggs. DNA fragments of the cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) mitochondrial genes were amplified and sequenced. Sequences were aligned and compared with reference sequences. Intraspecific and interspecific diversity were calculated and phylogenetic analysis was performed.

Results

Overall, 9.4% of the canids (eight jackals and two foxes) were found infected with E. multilocularis by molecular methods, of which seven cases were also confirmed using morphological description of the adult worms. Echinococcus granulosus was found in 6.6% of the canines (four dogs, two jackals and one wolf) as determined by both molecular methods and adult cestode morphology. All E. granulosus isolates were identified as the G1 genotype. Comparative sequence analysis indicated 0–0.7% and 0% intraspecific divergence within E. granulosus isolates and 0% and 0–0.2% within E. multilocularis isolates for cox1 and nad1, respectively.

Conclusions

This study revealed the presence of E. multilocularis and E. granulosus in canids of North-Khorasan Province of Iran. Jackals were found infected with both E. multilocularis and E. granulosus, but infection with the former species was higher.

Echinococcosis: Advances in the 21st Century

Echinococcosis is a zoonosis caused by cestodes of the genus Echinococcus (family Taeniidae). This serious and near-cosmopolitan disease continues to be a significant public health issue, with western China being the area of highest endemicity for both the cystic (CE) and alveolar (AE) forms of echinococcosis. Considerable advances have been made in the 21st century on the genetics, genomics, and molecular epidemiology of the causative parasites, on diagnostic tools, and on treatment techniques and control strategies, including the development and deployment of vaccines. In terms of surgery, new procedures have superseded traditional techniques, and total cystectomy in CE, ex vivo resection with autotransplantation in AE, and percutaneous and perendoscopic procedures in both diseases have improved treatment efficacy and the quality of life of patients. In this review, we summarize recent progress on the biology, epidemiology, diagnosis, management, control, and prevention of CE and AE. Currently there is no alternative drug to albendazole to treat echinococcosis, and new compounds are required urgently. Recently acquired genomic and proteomic information can provide a platform for improving diagnosis and for finding new drug and vaccine targets, with direct impact in the future on the control of echinococcosis, which continues to be a global challenge.

Echinococcus multilocularis in Denmark 2012-2015: high local prevalence in red foxes

In Western Europe, the Echinococcus multilocularis lifecycle is predominantly sylvatic, typically involving red foxes (Vulpes vulpes) as the main definitive hosts with Microtus spp. and Arvicola spp. as intermediate hosts. During a 4-year surveillance study (2012-2015), Danish red foxes and raccoon dogs (n = 1345) were examined for E. multilocularis. Moreover, 134 insectivores and rodents collected in South Jutland during spring and summer 2016 were examined for the presence of metacestodes. The sedimentation and counting technique and molecular typing were used to identify E. multilocularis infections in the carnivores, while the rodent livers were examined macro- and microscopically for parasite lesions. Following morphological identification of E. multilocularis adult worms, the identity was verified by sequence analysis of the 12S rRNA gene in most cases (n = 13). Echinococcus multilocularis infection was demonstrated in 19 red foxes (Vulpes vulpes) originating from only two specific areas of South Jutland, namely Højer and Grindsted, and in two raccoon dogs (Nyctereutes procyonoides), originating from Højer. In Højer, 28.5% (CI 95% 11.7-45.3) of the examined red foxes were E. multilocularis positive per year. Moreover, positive red foxes were identified each year from 2012 to 2015, while E. multilocularis positive red foxes were only identified in Grindsted in 2013 (4.0%) and 2014 (6.4%). In contrast, all collected rodents were negative for E. multilocularis. We conclude that E. multilocularis is locally endemic in South Jutland with a high local prevalence in Højer.

Prevalence of and risk factors for cystic echinococcosis among herding families in five provinces in western China: a cross-sectional study

Echinococcosis is a severe zoonosis that endangers the health of herdsmen in China’s western provinces. This study aimed to examine the prevalence of this disease and identify potential factors associated with human echinococcosis among herding families.

A cross-sectional study was conducted in five provinces in western China from May 1, 2016 to November 30, 2016, and 1500 herding families participated in the study. A total of 1211 completed questionnaires were analyzed. The prevalence of Cystic echinococcosis (CE) among surveyed herding families was 1.55%. The results of multivariate analysis revealed that the sheep immunization (OR=0.35, 95%CI 0.21-0.58), being concerned about family members echinococcosis (OR=0.49, 95%CI 0.28-0.84) were protective factors, while allowing dogs to roam free (OR=3.17, 95%CI 1.89-5.31), feeding dogs with viscera (OR=3.04, 95%CI 1.83, 5.03), slaughter at home (OR=3.53, 95%CI 2.04-6.12), drinking non-boiled water (OR=2.15, 95%CI 1.28-3.63), eating raw vegetables (OR=1.87, 95%CI 1.13-3.10), not washing hands before meals (OR=3.08, 95%CI 1.68-5.65), and often seeing stray dogs (OR=2.60 95%CI 1.38-4.91) and wild animals (OR=1.92, 95%CI 1.17-3.14) near habitations were more associated with increased risk of infection.

Immunizing sheep, appropriately managing domestic and stray dogs, and improving living environments and behavioral factors may help to reduce the risk of human echinococcosis in western China.