Diagnostics and epidemiology of alveolar echinococcosis in slaughtered pigs from large-scale husbandries in Germany

[Zoonoses in endemic, free-ranging mammals]

BACKGROUND

Zoonoses are diseases and infections that can be transmitted naturally between animals and humans. Direct and indirect contact of humans with wildlife occur during hunting activities, when diseased wildlife is found and treated, and in shared fields, forests, parks, gardens, and homes. Zoonoses can only be understood and controlled when ecosystems, animals, and humans are considered holistically.

OBJECTIVE

This paper presents important zoonotic pathogens that are currently present in wild mammals as reservoirs in Germany.

MATERIAL AND METHODS

The literature was searched to determine the prevalence of zoonotic pathogens currently occurring in wild mammals.

RESULTS

Viral zoonotic agents currently present in free-ranging, mammalian animals in Germany as reservoirs of natural origin are bornaviruses, lyssaviruses, hepatitis E virus genotype 3, and Puumala orthohantavirus. Bacterial zoonotic agents beyond typical wound and foodborne pathogens include Brucella suis Biovar 2, Francisella tularensis ssp. holarctica, Leptospira interrogans sensu latu, Mycobacterium caprae, and Yersinia pseudotuberculosis. In particular, parasitic zoonotic agents common in wildlife are Alaria alata, Baylisascaris procyonis, Echinococcus multilocularis, Sacoptes scabei, and Trichinella spp.

CONCLUSION

The presence of zoonotic infectious agents of risk groups 2 and 3 has to be regularly expected in numerous endemic wildlife species, especially canines, small bears, rodents, insectivores, and bats. Animal caretakers, hunters, veterinarians, and human health professionals should be aware of this risk and take protective measures appropriate to the situation.

First report of infection with metacestode stages of Echinococcus multilocularis in a kulan (Equus hemionus kulan) from Slovakia

While the principle definitive host of the zoonotic cestode Echinococcus multilocularis in Europe is the red fox, several rodent species act as main intermediate hosts. Among others, e.g., humans, dogs, and pigs, also horses have been described to act as aberrant hosts in highly endemic regions. Here, a case of an E. multilocularis infection in a kulan (Equus hemionus kulan) is described. The five years old kulan from a zoo in Slovakia was transported to an animal park in Germany. The animal had to be euthanized within a few weeks after the import due to its poor general state of health. The pathological examination revealed a nodular mass in the liver as an incidental finding. By histological examination of the mass, a pyogranulomatous and necrotizing inflammation and intralesional fragments of amorphous eosinophil layers were detected. The suspected diagnosis of E. multilocularis infection was confirmed by PCR addressing parts of the genes 12S rRNA and the NADH dehydrogenase subunit 2, showing very high identities with isolates from France, Slovakia and the USA.

[Alveolar echinococcosis in fattening pigs in a conventional housing system]

In a conventional fattening farm in southern Germany, up to 100 % of the livers of individual slaughter groups were condemned due to parasitic lesions during 2022. Intensification of antiparasitic metaphylaxis with fenbendazole to control Ascaris suum in the herd was unsuccessful. A pathomorphologic examination of 6 livers from two slaughter groups revealed oligofocal fibrotic inflammation. Histologically, chronic granulomatous hepatitis with massive involvement of eosinophilic granulocytes and central parasitic structures of a helminth were detected. Examination of the liver lesions by PCR revealed evidence of Echinococcus (E.) multilocularis. To determine the source of introduction into the herd, fecal samples were collected from semi-feral domestic cats near the feed mixer and in the corridor of the barn. Parasitologically, cestode eggs were detected in the fecal samples. Genome fragments of E. multilocularis could not be amplified by PCR. In the present case, domestic cats were suspected as the most likely source of entry into the herd. Control measures were aimed at preventing parasite entry by therapy of the domestic cats with antiparasitics. Differentially, no other possible pathogens could be detected by PCR and bacteriological examination.

Echinococcus multilocularis genetic diversity based on isolates from pigs confirmed the characteristic haplotype distribution and the presence of the Asian-like haplotype in Central Europe

Introduction

The aim of the study was to determine the genetic diversity of Echinococcus multilocularis in pigs in highly endemic areas in Poland, as well as to attempt to confirm the occurrence and geographical distribution of haplotypes characteristic for these areas, which were previously described on the basis of examination of adult tapeworms isolated from foxes.

Material and Methods

Twenty samples of E. multilocularis larval forms were obtained from pigs' livers in four provinces of Poland. Genetic analyses were conducted on sequences of two mitochondrial genes: cox1 and nad2.

Results

Seven haplotypes were found for the cox1 gene (OQ874673-OQ874679) and four haplotypes for nad2 (OQ884981-OQ884984). They corresponded to the haplotypes described earlier in foxes in Poland (some of them differing only in one nucleotide). The analysis showed the presence of the Asian-like haplotype in both the cox1 and nad2 genes. The remaining haplotypes were grouped in the European clade. The geographical distribution of haplotypes identified in the pig samples was noticed to bear a similarity to the distribution of haplotypes previously isolated from foxes in the same regions.

Conclusion

The characteristic geographical distribution of E. multilocularis haplotypes in Central Europe (including the presence of the Asian-like haplotype) previously described in the population of definitive hosts (foxes) has now been confirmed by the analysis of samples from non-specific intermediate hosts (pigs).

Membrane Technology for Rapid Point-of-Care Diagnostics for Parasitic Neglected Tropical Diseases

Parasitic neglected tropical diseases (NTDs) affect over one billion people worldwide, with individuals from communities in low-socioeconomic areas being most at risk and suffering the most. Disease management programs are hindered by the lack of infrastructure and resources for clinical sample collection, storage, and transport and a dearth of sensitive diagnostic methods that are inexpensive as well as accurate. Many diagnostic tests and tools have been developed for the parasitic NTDs, but the collection and storage of clinical samples for molecular and immunological diagnosis can be expensive due to storage, transport, and reagent costs, making these procedures untenable in most areas of endemicity. The application of membrane technology, which involves the use of specific membranes for either sample collection and storage or diagnostic procedures, can streamline this process, allowing for long-term sample storage at room temperature. Membrane technology can be used in serology-based diagnostic assays and for nucleic acid purification prior to molecular analysis. This facilitates the development of relatively simple and rapid procedures, although some of these methods, mainly due to costs, lack accessibility in low-socioeconomic regions of endemicity. New immunological procedures and nucleic acid storage, purification, and diagnostics protocols that are simple, rapid, accurate, and cost-effective must be developed as countries progress control efforts toward the elimination of the parasitic NTDs.

Echinococcus multilocularis genetic diversity in Swiss domestic pigs assessed by EmsB microsatellite analyzes

Assessing the genetic diversity of the parasite Echinococcus multilocularis provides key information about the temporal and spatial strain flow in a given area. Previous studies indicated that a historical endemic area conventionally presents a relatively high genetic diversity, whereas peripheral or newly endemic areas exhibit a more restricted variability of the parasite. The Swiss plateau region is part of the European historically endemic area, and the genetic diversity has already been investigated by assessing either human metacestode isolates or adult worms from foxes. To date, there have been no studies covering the whole geographical area affected by the parasite. The aim of the present study was to make use of the domestic pig to investigate the genetic diversity of E. multilocularis in relation to spatial distribution. A total of 55 E. multilocularis-induced hepatic lesions from slaughtered pigs from Switzerland were studied using EmsB microsatellite analyzes, and findings were compared to already published data (originating from human, primate, foxes, and rodent samples). A total of 12 EmsB profiles were described among the domestic pigs, some of them presenting a clear spatial organization in the Swiss plateau, with three of the main profiles geographically separated. One of the 12 EmsB profiles has been newly identified for Switzerland in this study, while the other 11 profiles had been previously described in other Swiss E. multilocularis isolates from other hosts. Overall, a total of 18 EmsB profiles have so far been described within the Swiss endemic area. Six profiles appeared only among human, primate, rodent, and fox samples. Based on a richness and diversity accumulation analysis, the sampling efficiency for the whole studied area has now been improved considerably by compilation of 178 E. multilocularis specimens obtained from four different intermediate and one definitive host species in Switzerland.

Echinococcus multilocularis infection in horses in Poland

A cross-sectional survey was performed to obtain first information on the prevalence of Echinococcus multilocularis infection in slaughter horses from central, eastern and southern Poland, a country with a highly endemic occurrence of this tapeworm in red foxes. White tough nodular lesions being 3-10 mm in size, sharply demarcated and spherically or irregularly shaped were found in 54 of 365 livers examined. Histologically, focal granulomatous necrotizing inflammations and sometimes PAS-positive acellular lamellar structures being characteristic of the E. multilocularis metacestode stage were visible; protoscoleces were not found. E. multilocularis DNA was detected in six of 19 hepatic lesions examined by nested PCR. Our results from molecular and morphological diagnostics suggest an overall prevalence of alveolar echinococcosis between 4.7% and 14.8% in the horse population studied. Horses as dead-end hosts do not play any role in the life cycle of E. multilocularis but may serve as additional sentinel animals in monitoring the environmental contamination with tapeworm eggs.

Combined cross-sectional and case-control study on Echinococcus multilocularis infection in pigs in Switzerland

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Minimal prevalence for Echinococcus multilocularis infection in Swiss domestic pigs was established.

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Minimal prevalence was 0.008% for fattening pigs and 0.11% for breeding pigs, respectively.

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All but one metacestode were degenerated; no protoscoleces were detected in histopathology.

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Main risk factors were foxes or other animals in the barns, no hygiene barrier, outdoor feeding and grass feeding.

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No geographical clusters of higher infection with E. multilocularis were evident.

The canid tapeworm Echinococcus multilocularis causes alveolar echinococcosis (AE) in humans and other intermediate hosts. Depending on the permissiveness of the intermediate host, the larval form of E. multilocularis (metacestode) may be either fertile, e.g. in rodents, and thus supporting the life cycle of the parasite, or infertile, e.g. in pigs, and thus interrupting the life cycle. Pigs have been shown to act as aberrant hosts for the metacestode and consequently develop liver lesions but represent a dead-end for the parasite. Routine liver inspection at slaughter provided the basis for a large-scale surveillance study on E. multilocularis infection in pigs. The aim of this combined cross-sectional and case-control study was to estimate the minimal prevalence of E. multilocularis in pigs in Switzerland, to find factors associated with infection, and to assess potential regional clusters of infection.

During the 12-month-study period, approximately 85% of all pigs slaughtered in Switzerland were assessed. In total, 450 pig livers with macroscopic lesions suggestive of E. multilocularis infection were analysed. Of those, 200 samples were positive by E. multilocularis-PCR. Thus, the overall minimal prevalence detected by molecular means was 0.009% in all slaughter pigs (200 of 2'143'996), 0.008% in finishing pigs (177 of 2'123'542), and 0.11% in breeding pigs (22 of 20'454). Histology revealed the unique presence of a laminated layer in 105 cases, and an additional germinal layer detected in a single case. Protoscoleces could not be observed in any of the lesions. Factors positively associated with infection were "foxes seen in the pig shed", "foxes on premises", "presence of other animals in the shed", "absence of a hygiene barrier", "outdoor feeding", "feeding grass", "lack of rodent control", "not having own dogs on the farm" and "infrequent deworming of sows". Infection was present in all regions sampled and was representative of the important pig rearing areas of Switzerland, without evidence of any obvious geographical cluster.

Conclusively, our study provided further evidence of widespread environmental contamination with E. multilocularis eggs in Switzerland. Furthermore, the absence of protoscoleces in any of the lesions supported the concept that pigs act only as a dead-end host and thus do not contribute to the life cycle of the parasite. Factors associated with E. multilocularis infection were in-line with parasite biology, and many can be addressed by increasing hygiene and management standards.

Clinical, pathological and parasitological examinations of a German spaniel with alveolar echinococcosis, Germany, 2018

Alveolar echinococcosis (AE) is a parasitic zoonosis occurring in most European countries and also emerging in parts of Asia and North America. AE is caused by the larval stage of Echinococcus multilocularis in intermediate and also in accidental hosts. The principal definitive host is the red fox, but domestic dogs and cats are also potential definitive hosts. Several species of rodents serve as intermediate hosts of this parasite. However, there are also some species acting as accidental intermediate hosts, among them dogs. Since the late 1980s cases of canine AE have been diagnosed. Here, we present a case of canine AE in a two-year old female intact German spaniel from Thuringia, Central Germany. The dog was used as a hunting dog and presented to a small animal clinic for subacute lethargy and inappetence. Abdominal ultrasound and contrast computed tomography (CT) scan were performed and revealed intrahepatic lesions. Multinodular changes of the liver and the greater omentum were demonstrated by exploratory laparotomy. After euthanasia, a necropsy was performed and histological sections of representative tissue samples were prepared. PCR followed by sequencing was conducted with DNA extracted from tissue samples of the liver, hepatic lymph nodes and greater omentum. The sequence herein obtained showed very high similarity with other partial nad2 sequences of E. multilocularis from the GenBank database by BLASTn analysis and was analysed using the maximum likelihood method. The presented case combines the clinical presentation and pathological, parasitological and phylogenetic analyses.

Comparison of different commercial DNA extraction kits and PCR protocols for the detection of Echinococcus multilocularis eggs in faecal samples from foxes

Effective and sensitive methods for the molecular detection of Echinococcus multilocularis in faecal samples of final hosts are crucial for the prevention and control of human alveolar echinococcosis and for studies on the epidemiology of the parasite. Little is known about the suitability of commercial test kits for isolating DNA of E. multilocularis from fox faeces and the performance of standard Polymerase Chain Reaction (PCR) protocols in relation to the quality of DNA extracted by these kits. We compared four different kits: ZR Faecal DNA MiniPrep™ (Zymo Research), FastDNA^® SPIN Kit for Soil (MP Biomedicals), QIAamp^® Fast DNA Stool Mini Kit (QIAGEN) and NucleoSpin^® Soil Kit (Macherey-Nagel) for the extraction of DNA from E. multilocularis eggs present in faeces of foxes. Negative faecal samples were spiked with 600, 300, 150, 75, 37, 18, 9, 5 or 2 E. multilocularis eggs, and each egg concentration was tested 10 times with each of the DNA extraction kits. Each extracted DNA sample was amplified using three PCR protocols: i. conventional PCR (cPCR, Platinum^®Taq, Invitrogen), ii. qPCR with the iQ™ Supermix (Bio-Rad) and iii. qPCR with the QuantiTect^® Multiplex-Master Mix (QIAGEN). The highest analytical sensitivities for molecular detection of E. multilocularis eggs in spiked fox faeces were observed when combining either the QIAamp^® Fast DNA Stool Mini Kit or the ZR Faecal DNA MiniPrep™ kit with the qPCR using the QuantiTect^® Multiplex-Master Mix (Sensitivities 97% and 94%, respectively). Combinations including the remaining test kits (NucleoSpin^® Soil Kit and FastDNA^® SPIN Kit for Soil) showed a markedly lower analytical sensitivity for PCR examinations. The results of the present study indicate that it is of utmost importance to select suitable DNA extraction kits in combination with robust PCR methods or reagents to achieve acceptable analytical sensitivity in the molecular detection of E. multilocularis eggs in fox faecal samples.

Global Distribution of Alveolar and Cystic Echinococcosis

Alveolar echinococcosis (AE) and cystic echinococcosis (CE) are severe helminthic zoonoses. Echinococcus multilocularis (causative agent of AE) is widely distributed in the northern hemisphere where it is typically maintained in a wild animal cycle including canids as definitive hosts and rodents as intermediate hosts. The species Echinococcus granulosus, Echinococcus ortleppi, Echinococcus canadensis and Echinococcus intermedius are the causative agents of CE with a worldwide distribution and a highly variable human disease burden in the different endemic areas depending upon human behavioural risk factors, the diversity and ecology of animal host assemblages and the genetic diversity within Echinococcus species which differ in their zoonotic potential and pathogenicity. Both AE and CE are regarded as neglected zoonoses, with a higher overall burden of disease for CE due to its global distribution and high regional prevalence, but a higher pathogenicity and case fatality rate for AE, especially in Asia. Over the past two decades, numerous studies have addressed the epidemiology and distribution of these Echinococcus species worldwide, resulting in better-defined boundaries of the endemic areas. This chapter presents the global distribution of Echinococcus species and human AE and CE in maps and summarizes the global data on host assemblages, transmission, prevalence in animal definitive hosts, incidence in people and molecular epidemiology.

Parasitic diseases of the central nervous system: lessons for clinicians and policy makers

Parasitic diseases of the central nervous system are associated with high mortality and morbidity, especially in resource-limited settings. The burden of these diseases is amplified as survivors are often left with neurologic sequelae affecting mobility, sensory organs, and cognitive functions, as well as seizures/epilepsy. These diseases inflict suffering by causing lifelong disabilities, reducing economic productivity, and causing social stigma. The complexity of parasitic life cycles and geographic specificities, as well as overlapping clinical manifestations in the host reflecting the diverse pathogenesis of parasites, can present diagnostic challenges. We herein provide an overview of these parasitic diseases and summarize clinical aspects, diagnosis, therapeutic strategies and recent milestones, and aspects related to prevention and control.

Chemotherapy in alveolar echinococcosis of multi-organs: what's the role?

The aim of this study was to investigate the clinical efficiency of chemotherapy for the treatment of human alveolar echinococcosis (AE). Twenty-four patients who suffered from late-stage AE were enrolled in this study. The classification of the disease stages was performed according to the PNM (parasite lesion, neighboring organ invasion, metastases) classification system established by the World Health Organization Informal Working Group on Echinococcosis and classification standards. Radical surgery (n = 3), palliative surgery plus chemotherapy (n = 11), and sole chemotherapy (n = 10) were given, respectively. For those with AE metastasis with spleen and kidney, radical surgery was effective for the treatment. However, the treatment efficiency for those with AE metastasis to bone tissues was unfavorable. Significant improvement was noted in those with cerebral lesions after chemotherapy. Stable health conditions were observed in those with pulmonary lesions after chemotherapy. For those with liver lesion, long stable health conditions were noted after chemotherapy. However, surgical interventions were needed as the occurrence of bile duct complications. With regards to the other lesions, radical surgeries were recommended. Satisfactory treatment outcomes were obtained in those with AE after chemotherapy.