Molecular identification of Taenia specimens after long-term preservation in formalin

Comprehensive Diagnosis, Treatment, and Outcome of Taenia crassiceps Cysticercosis in a Ring-Tailed Lemur (Lemur catta) from a Croatian Zoo: No Longer Unusual?

Taenia crassiceps is a zoonotic tapeworm of the genus Taenia that is distributed throughout the Northern Hemisphere. Wild and domestic carnivores are final hosts, while rodents and rabbits are primarily intermediate hosts, although many other mammals may harbour the larval stage, Cysticercus longicollis. This case report aims to describe C. longicollis infection in a lemur and molecularly characterise the isolated parasite. The excised lesion was subjected to morphological and histopathological examination, which revealed cysticerci of the tapeworm. Formalin-fixed and paraffin-embedded block (FFPEB), as well as the cysticerci fixed with formalin stored for one year, were subjected to molecular analysis, which aimed at detecting the partial mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of Taenia sp. Based on the morphological characteristics, the parasite was identified as a metacestode of T. crassiceps. The presence of the cox1 gene was detected using polymerase chain reaction (PCR) in all samples. A randomly selected PCR product was sequenced and compared with other sequences from the GenBank database, confirming that the detected parasite was T. crassiceps. This article reports the first case of T. crassiceps cysticercosis in a lemur (Lemur catta) in Croatia and emphasises the potential risk of transmission from wild carnivores.

SNP data reveals the complex and diverse evolutionary history of the blue-ringed octopus genus (Octopodidae: Hapalochlaena) in the Asia-Pacific

The blue-ringed octopus species complex (Hapalochlaena spp.), known to occur from Southern Australia to Japan, currently contains four formally described species (Hapalochlaena maculosa, Hapalochlaena fasciata, Hapalochlaena lunulata and Hapalochlaena nierstraszi). These species are distinguished based on morphological characters (iridescent blue rings and/or lines) along with reproductive strategies. However, the observation of greater morphological diversity than previously captured by the current taxonomic framework indicates that a revision is required. To examine species boundaries within the genus we used mitochondrial (12S rRNA, 16S rRNA, cytochrome c oxidase subunit 1 [COI], cytochrome c oxidase subunit 3 [COIII] and cytochrome b [Cytb]) and genome-wide SNP data (DaRT seq) from specimens collected across its geographic range including variations in depth from 3m to >100m. This investigation indicates substantially greater species diversity present within the genus Hapalochlaena than is currently described. We identified 10,346 SNPs across all locations, which when analysed support a minimum of 11 distinct clades. Bayesian phylogenetic analysis of the mitochondrial COI gene on a more limited sample set dates the diversification of the genus to ∼30mya and corroborates eight of the lineages indicated by the SNP analyses. Furthermore, we demonstrate that the diagnostic lined patterning of H. fasciata found in North Pacific waters and NSW, Australia is polyphyletic and therefore likely the result of convergent evolution. Several "deep water" (> 100m) lineages were also identified in this study with genetic convergence likely to be driven by external selective pressures. Examination of morphological traits, currently being undertaken in a parallel morphological study, is required to describe additional species within the complex.

Case Report: Molecular and Pathological Investigations of Zoonotic Anatrichosoma Spp.-Induced Ulcerative Pododermatitis in a Domestic Cat in Thailand

Anatrichosoma spp. is a group of trichuroid nematodes that mainly infect non-human primates and domestic cats. The lifecycle of these nematodes remains unclear. In non-human primates, Anatrichosoma spp. were found in the nasal cavity. However, ulcerative dermatitis has been reported in infected cats. An adult, intact, female domestic short-haired cat was presented with ulcerative pododermatitis of all limbs. Punch biopsy was performed at the edge of the ulcerative wound for histopathological investigation and showed necrosis and infiltration of inflammatory cells around the nematode-like lesion. Eggs with Capillaria-like characteristics were present. Tissue sections were subjected to DNA extraction and PCR targeting 18S rRNA, using primers designed from Anatrichosoma 18S rRNA. The phylogenetic tree revealed that DNA obtained from the lesion of the domestic cat was grouped with Anatrichosoma spp. from the olive glass mouse (Abothirx olivacea), Capillaria plica and Eucoleus aerophilus, both from the red fox (Vulpes Vulpes). The study is the first report of feline anatrichosomiasis in Thailand, and we present both pathological findings and molecular evidence. The cat was successfully treated with emodepsine/praziquantel. The skin lesion recovered within 3 days after anthelmintic treatment. Because Anatrichosoma spp. have been reported in humans, the zoonotic potential of this parasite should be considered.

Taenia asiatica: Historical overview of taeniasis and cysticercosis with molecular characterization

Asian Taenia is a human-infecting Taenia tapeworm known as Taenia asiatica following morphological examination of adult and larval stages of the tapeworm by Eom and Rim (1993). The life cycle of T. asiatica differs from that of T. saginata in its intermediate host (pigs versus cattle) as well as in the infected organs (liver versus muscle). T. asiatica can be differentiated from T. solium and T. saginata by examination of morphological characteristics such as the scolex, mature and gravid proglottids in the adult stage, and the scolex and bladder surface in the larval stage. T. asiatica has been identified in Korea, Taiwan, the Philippines, China, Thailand, Indonesia, Vietnam, Japan, Lao PDR, Nepal and India. The molecular tools employed for T. asiatica identification have been developed to differentiate T. asiatica from other human-infecting Taenia tapeworms based on genetic information such as nucleotide sequence of mitochondrial genes, nuclear ribosomal genes and nuclear genes that lead to development of the subsequent molecular techniques, such as PCR-RFLP, PCR-RAPD, BESST-base, LAMP and qPCR. Investigation of the phylogenetic relationships among human Taenia species revealed that T. asiatica is a sister species with T. saginata, which is genetically more similar than other Taenia species in terms of the nucleotide sequences of cox1, nad1 and 28S rDNA. The mitochondrial genomes of human Taenia tapeworms comprise 13,703bp (T. asiatica), 13,670bp (T. saginata) and 13,709bp (T. solium), and contain 36 genes including 12 protein-coding genes, 2 ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). Sequence differences in the full genome of T. asiatica and T. saginata mitochondria is 4.6%, while T. solium differs by 11%. Hox gene orthology in T. asiatica was established by comparative analysis with Platyhelminthes Hox genes. T. asiatica Hox revealed six Hox orthologs including two lab/Hox1, two Hox3, one Dfd/Hox4 and one Lox/Lox4. Hybridization between T. asiatica and T. saginata was definitely observed in these species which are sympatrically endemic in the regions of Korea, Thailand, China and Lao PDR. Comparative analyses of T. asiatica, T. saginata and T. solium genomes were also reported with genome features. Taenia asiaticus nomen novum was proposed for T. asiaticaEom and Rim, 1993 which is a homonym of T. asiatica Linstow, 1901 (Davaineidae).

A co-infection case report of Taenia saginata in a patient with subclinical clonorchiasis confirmed by the combination of diagnostic tools

Background

Clonorchiasis is the common parasitic infection in the general population of the Republic of Korea, however, taeniasis is scarcely reported recently. Here, we describe a case of co-infection with the cestode T. saginata in a patient with subclinical clonorchiasis diagnosed by a combination of diagnostic tools in Korea.

Case presentation

A 56-year-old man visited the hospital having passed proglottids in his stool for the past two months and brought a stool sample with segments to our hospital. He had no abdominal symptoms, such as nausea, vomiting, abdominal pain, diarrhea, or constipation. He used to consume raw beef and fish frequently. We could not find evidence of gravid proglottids which contain fully developed uteri filled with ova or branched uterine structures, within the submitted sample. To identify the tapeworm species, we carried out molecular analyses on the proglottids. The cox1 and ef1a sequences had a 100% match with those of T. saginata and differed from the sequences of the other Taenia species. Upon examination of stool samples fixed by formalin-ether concentration method, no Taenia species ova were observed in 10 slides. Instead, C. sinensis ova were observed, despite the level of IgG specific to C. sinensis being within the normal range. The patient was treated with praziquantel (25 mg/kg, three times a day) for 3 days, and subsequently C. sinensis ova were not found in his stool.

Conclusion

Our case indicates that a combination of morphological, serological, and molecular diagnostic tools should be used for the accurate diagnosis of subclinical parasitic infections.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3758-0) contains supplementary material, which is available to authorized users.

Diagnosis of human taeniasis

Taenia solium, T. saginata and T. asiatica are taeniid tapeworms that cause taeniasis in humans and cysticercosis in intermediate host animals. T. solium can also cause cysticercosis in humans. A number of diagnostic methods have been developed to diagnose Taenia species that infect humans. This article is aimed at providing an overview of currently available diagnostic methods for human taeniasis.

Human Infections with Spirometra decipiens Plerocercoids Identified by Morphologic and Genetic Analyses in Korea

Tapeworms of the genus Spirometra are pseudophyllidean cestodes endemic in Korea. At present, it is unclear which Spirometra species are responsible for causing human infections, and little information is available on the epidemiological profiles of Spirometra species infecting humans in Korea. Between 1979 and 2009, a total of 50 spargana from human patients and 2 adult specimens obtained from experimentally infected carnivorous animals were analyzed according to genetic and taxonomic criteria and classified as Spirometra erinaceieuropaei or Spirometra decipiens depending on the morphology. Morphologically, S. erinaceieuropaei and S. decipiens are different in that the spirally coiled uterus in S. erinaceieuropaei has 5-7 complete coils, while in S. decipiens it has only 4.5 coils. In addition, there is a 9.3% (146/1,566) sequence different between S. erinaceieuropaei and S. decipiens in the cox1 gene. Partial cox1 sequences (390 bp) from 35 Korean isolates showed 99.4% (388/390) similarity with the reference sequence of S. erinaceieuropaei from Korea (G1724; GenBank KJ599680) and an additional 15 Korean isolates revealed 99.2% (387/390) similarity with the reference sequences of S. decipiens from Korea (G1657; GenBank KJ599679). Based on morphologic and molecular databases, the estimated population ratio of S. erinaceieuropaei to S. decipiens was 35: 15. Our results indicate that both S. erinaceieuropaei and S. decipiens found in Korea infect humans, with S. erinaceieuropaei being 2 times more prevalent than S. decipiens. This study is the first to report human sparganosis caused by S. decipiens in humans in Korea.

Four cases of Taenia saginata infection with an analysis of COX1 gene

Human taeniases had been not uncommon in the Republic of Korea (=Korea) until the 1980s. The prevalence decreased and a national survey in 2004 revealed no Taenia egg positive cases. However, a subsequent national survey in 2012 showed 0.04% (10 cases) prevalence of Taenia spp. eggs suggesting its resurgence in Korea. We recently encountered 4 cases of Taenia saginata infection who had symptoms of taeniasis that included discharge of proglottids. We obtained several proglottids from each case. Because the morphological features of T. saginata are almost indistinguishable from those of Taenia asiatica, molecular analyses using the PCR-RFLP and DNA sequencing of the cytochrome c oxidase subunit 1 (cox1) were performed to identify the species. The PCR-RFLP patterns of all of the 4 specimens were consistent with T. saginata, and the cox1 gene sequence showed 99.8-100% identity with that of T. saginata reported previously from Korea, Japan, China, and Cambodia. All of the 4 patients had the history of travel abroad but its relation with contracting taeniasis was unclear. Our findings may suggest resurgence of T. saginata infection among people in Korea.

Epidemiology and genetic diversity of Taenia asiatica: a systematic review

Taenia asiatica has made a remarkable journey through the scientific literature of the past 50 years, starting with the paradoxical observation of high prevalences of T. saginata-like tapeworms in non-beef consuming populations, to the full description of its mitochondrial genome. Experimental studies conducted in the 1980s and 1990s have made it clear that the life cycle of T. asiatica is comparable to that of T. saginata, except for pigs being the preferential intermediate host and liver the preferential location of the cysts. Whether or not T. asiatica can cause human cysticercosis, as is the case for Taenia solium, remains unclear. Given the specific conditions needed to complete its life cycle, in particular the consumption of raw or poorly cooked pig liver, the transmission of T. asiatica shows an important ethno-geographical association. So far, T. asiatica has been identified in Taiwan, South Korea, Indonesia, the Philippines, Thailand, south-central China, Vietnam, Japan and Nepal. Especially this last observation indicates that its distribution is not restricted to South-East-Asia, as was thought so far. Indeed, the molecular tools developed over the last 20 years have made it increasingly possible to differentiate T. asiatica from other taeniids. Such tools also indicated that T. asiatica is related more closely to T. saginata than to T. solium, feeding the debate on its taxonomic status as a separate species versus a subspecies of T. saginata. Furthermore, the genetic diversity within T. asiatica appears to be very minimal, indicating that this parasite may be on the verge of extinction. However, recent studies have identified potential hybrids between T. asiatica and T. saginata, reopening the debate on the genetic diversity of T. asiatica and its status as a separate species.

Advances in diagnosis and spatial analysis of cysticercosis and taeniasis

Human cysticercosis, caused by accidental ingestion of eggs of Taenia solium, is one of the most pathogenic helminthiases and is listed among the 17 WHO Neglected Tropical Diseases. Controlling the life-cycle of T. solium between humans and pigs is essential for eradication of cysticercosis. One difficulty for the accurate detection and identification of T. solium species is the possible co-existence of two other human Taenia tapeworms (T. saginata and T. asiatica, which do not cause cysticercosis in humans). Several key issues for taeniasis/cysticercosis (T/C) evidence-based epidemiology and control are reviewed: (1) advances in immunological and molecular tools for screening of human and animals hosts and identification of Taenia species, with a focus on real-time detection of taeniasis carriers and infected animals in field community screenings, and (2) spatial ecological approaches that have been used to detect geospatial patterns of case distributions and to monitor pig activity and behaviour. Most recent eco-epidemiological studies undertaken in Sichuan province, China, are introduced and reviewed.

Bayesian modelling to estimate the test characteristics of coprology, coproantigen ELISA and a novel real-time PCR for the diagnosis of taeniasis

OBJECTIVE

To estimate and compare the performances of coprology, copro-Ag ELISA and real-time polymerase chain reaction assay (copro-PCR) for detection of Taenia solium tapeworm carriers.

METHODS

The three diagnostic tests were applied on 817 stool samples collected in two Zambian communities where taeniasis is endemic. A Bayesian approach was used to allow estimation of the test characteristics. Two (0.2%; 95% Confidence Interval (CI): 0-0.8), 67 (8.2%; 95% CI: 6.4-10.3) and 10 (1.2%; 95% CI: 0.5-2.2) samples were positive using coprology, copro-Ag ELISA and copro-PCR, respectively.

RESULTS

Specificities of 99.9%, 92.0% and 99.0% were determined for coprology, copro-Ag ELISA and copro-PCR, respectively. Sensitivities of 52.5%, 84.5% and 82.7% were determined for coprology, copro-Ag ELISA and copro-PCR, respectively.

CONCLUSIONS

We urge for additional studies exploring possible cross-reactions of the copro-Ag ELISA and for the use of more sensitive tests, such as copro-PCR, for the detection of tapeworm carriers, which is a key factor in controlling the parasite in endemic areas.

Molecular approaches to Taenia asiatica

Taenia solium, T. saginata, and T. asiatica are taeniid tapeworms that cause taeniasis in humans and cysticercosis in intermediate host animals. Taeniases remain an important public health concerns in the world. Molecular diagnostic methods using PCR assays have been developed for rapid and accurate detection of human infecting taeniid tapeworms, including the use of sequence-specific DNA probes, PCR-RFLP, and multiplex PCR. More recently, DNA diagnosis using PCR based on histopathological specimens such as 10% formalin-fixed paraffin-embedded and stained sections mounted on slides has been applied to cestode infections. The mitochondrial gene sequence is believed to be a very useful molecular marker for not only studying evolutionary relationships among distantly related taxa, but also for investigating the phylo-biogeography of closely related species. The complete sequence of the human Taenia tapeworms mitochondrial genomes were determined, and its organization and structure were compared to other human-tropic Taenia tapeworms for which complete mitochondrial sequence data were available. The multiplex PCR assay with the Ta4978F, Ts5058F, Tso7421F, and Rev7915 primers will be useful for differential diagnosis, molecular characterization, and epidemiological surveys of human Taenia tapeworms.

Molecular evidence of host influences on the evolution and spread of human tapeworms

The taeniasis/cysticercosis complex is included in the list of neglected zoonotic diseases by the World Health Organization due to its significant impact on public health in tropical areas. Cysticercosis is still endemic in many regions of Asia, Africa and Latin America. Long absent in Europe and in other developed countries, cysticercosis has recently re-emerged in the United States and Canada, due to immigration, travel and local transmission. This has encouraged the use of molecular data to understand better the influence of animal and human hosts on the emergence and spread of Taenia species. The increasing number of mitochondrial sequences now available from human tapeworms and recent advances in computational tools has enabled reconstruction of the biogeography and evolutionary history of these organisms. New molecular data have provided insights into the biogeography of T. solium, T. asiatica and T. saginata. A Bayesian statistical framework using variable evolutionary rates from lineage to lineage has allowed an improved timescale analysis of human tapeworms. The dates of divergence obtained were compared to the timing of evolutionary events in the history of their hosts, based on the hypothesis that Taenia spp. and their hosts share a common history. Herein, we review changes in the definitive and secondary hosts and human interactions that underlie the differentiation and evolution of tapeworms. Species diversification of Taenia seems to be closely linked with the evolution of intermediate hosts in response to climatic events during the Pleistocene. Different genotypes of T. solium emerged when European and Asian wild boar Sus spp. populations diverged. Taenia saginata emerged when wild cattle Bos primigenius evolved and when zebu Bos indicus and taurine Bos taurus ancestors separated. Humans through migrations and later with the development of farming and animal husbandry may have had a significant impact on the spread and diversification of tapeworms. Migrations of Homo erectus from Africa to Asia and later of Homo sapiens facilitated the diversification and dispersal of T. solium and T. saginata populations. The development of animal husbandry, making Sus scrofa and Bos taurus preferential intermediate hosts, led to the worldwide distribution of parasites. New molecular data combined with an innovative dating method allow us to explain the ways in which ancient human migrations promoted the emergence and spread of taeniasis and cysticercosis around the world. Another intriguing phenomenon explained better by our approach is the influence of human settlement on the spread of these parasites in recently inhabited areas. The diverse nature of T. solium currently observed in Madagascar may correspond to multiple imports of the parasite during Austronesian migrations, while in Mexico a recent influence of humans during the colonial period is more likely. Human activities, especially food preparation and husbandry methods, remain responsible for the transmission and persistence of these parasites.

Taeniasis and cysticercosis due to Taenia solium in Japan

Taenia solium is a zoonotic cestode that causes taeniasis and cysticercosis in humans. The parasite is traditionally found in developing countries where undercooked pork is consumed under poor sanitary conditions and/or as part of traditional food cultures. However, the recent increase in international tourism and immigration is spreading the disease into non-endemic developed countries such as the United States. Although there has been concern that the number of cysticercosis cases is increasing in Japan, the current situation is not clear. This is largely because taeniasis and cysticercosis are not notifiable conditions in Japan and because there have been no comprehensive reviews of T. solium infections in Japan conducted in the last 15 years. Herein, we provide an overview of the status of T. solium infection in Japan over the past 35 years and point out the potential risks to Japanese society.