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As training in helminthology has declined in the medical microbiology curriculum, many rare species of zoonotic cestodes have fallen into obscurity. Even among specialist practitioners, knowledge of human intestinal cestode infections is often limited to three genera, Taenia , Hymenolepis and Dibothriocephalus . However, five genera of uncommonly encountered zoonotic Cyclophyllidea ( Bertiella , Dipylidium , Raillietina , Inermicapsifer and Mesocestoides ) may also cause patent intestinal infections in humans worldwide. Due to the limited availability of summarized and taxonomically accurate data, such cases may present a diagnostic dilemma to clinicians and laboratories alike. In this review, historical literature on these cestodes is synthesized and knowledge gaps are highlighted. Clinically relevant taxonomy, nomenclature, life cycles, morphology of human-infecting species are discussed and clarified, along with the clinical presentation, diagnostic features and molecular advances, where available. Due to the limited awareness of these agents and identifying features, it is difficult to assess the true incidence of these ‘forgotten’ cestodiases as clinical misidentifications are likely to occur. Also, the taxonomic status of many of the human-infecting species of these tapeworms is unclear, hampering accurate species identification. Further studies combining molecular data and morphological observations are necessary to resolve these long-standing taxonomic issues and to elucidate other unknown aspects of transmission and ecology.

Background Dipilidiosis is a parasitic disease caused by the tapeworm Dipylidium caninum . Fleas and, less frequently, lice act as an intermediate host, and their ingestion is required for infection to occur. While the disease mainly affects domestic and wild carnivores, it is also considered a zoonotic disease, with most human cases reported in children. Dipylidium caninum is considered to be the most common tapeworm infesting companion animals, but dipilidosis in humans is rare. The aims of this review were to improve current understanding of the epidemiology of this parasitosis and its management by the medical and veterinary community. Methods A comprehensive review of the published literature during the last 21 years (2000–2021) on the epidemiology, clinical features, diagnosis, treatment and prevention measures of D. caninum infection and dipilidiosis in companion animals and humans was conducted. Results Using predefined eligibility criteria for a search of the published literature, we retrieved and screened 280 publications. Of these, 161 (141 epidemiological studies, 20 case reports [16 human cases]) were considered for inclusion in this review. This parasitosis is present worldwide; however, despite being the most frequent cestode infection in animals, it is often underdiagnosed using common coprological techniques. Its diagnosis in humans has also proved challenging, being frequently confused with pinworm infection, leading to inappropriate treatment and to the persistence of the disease over time. Prevention measures include control of ectoparasites in animals and the environment, as well as regular deworming of animals, most commonly with praziquantel. Conclusions The diagnosis of dipilidiosis remains challenging in both animals and humans, primarily due to the low sensitivity of the diagnostic methods currently available and a lack of knowledge of the morphological characteristics of the parasite. Although treatment with the appropriate anti-cestode compounds is well tolerated and results in resolution of the infection, indiscriminate use of these compounds may predispose to an increase in resistance. Given the worldwide distribution of this parasite, it is essential to act on several fronts, with a focus on health education for children and animal owners and the control of intermediate hosts, both in animals and in the surrounding environment. Graphical Abstract

Background The cestode Dipylidium caninum is known to infect dogs via the ingestion of an intermediate flea host, typically Ctenocephalides felis . Simparica Trio ® is an oral combination drug product for dogs effective in the treatment and prevention of fleas, including C. felis . Here, we report two laboratory studies evaluating the efficacy of a single administration of Simparica Trio at the minimum label dosage of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, and 5 mg/kg pyrantel (as pamoate salt) in preventing D. caninum infection in dogs for 1 month through killing of C. felis . Methods A total of 20 dogs ( n  = 10 per group) proven to be suitable hosts for C. felis were used in each of the two studies. Treatment occurred on day 0, with each dog given either the placebo or Simparica Trio. On days 0 (after treatment), 7, 14, 21, and 30, dogs were infested using 200 (± 5) unfed D. caninum -infected C. felis . Live flea counts were conducted on day 33 (72 ± 2 h after day 30 infestation). All dogs were euthanized on day 58, and each dog was necropsied for the recovery of D. caninum scolexes from the gastrointestinal tract. Results Placebo-treated dogs had adequate flea infestations and cestode infections in both studies. Simparica-Trio-treated dogs were free of fleas on day 33 (100% efficacy) and had significantly lower mean flea counts compared with placebo-treated dogs ( P  ≤ 0.0007). Scolex counts in Simparica-Trio-treated dogs were also significantly decreased compared with placebo-treated dogs in both studies. The efficacy of Simparica Trio against D. caninum based on least squares mean scolex counts was 100% ( P  < 0.0001) in study 1 and 92.1% ( P  = 0.0033) in study 2. Conclusions The efficacy provided by Simparica Trio against C. felis at the minimum dosage of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, and 5 mg/kg pyrantel (as pamoate salt) prevented D. caninum infection in dogs for 1 month. Graphical Abstract

Background Revolution ® Plus is a topical combination drug product containing selamectin and sarolaner that has been proven effective against the cat flea Ctenocephalides felis , the intermediate host of the cestode Dipylidium caninum . Here, we report two studies evaluating the efficacy of a single administration of Revolution Plus in preventing D. caninum infection in cats for 1 month through killing of the flea intermediate host. Methods Two studies (study 1 and 2) with the same design were conducted. In both studies, 2 treatment groups of ten cats each were enrolled. On Day 0, the cats in group 1 were treated with a placebo, and the cats in group 2 were treated with Revolution Plus at the minimum recommended dose of 6.0 mg/kg selamectin and 1.0 mg/kg sarolaner. After treatment on Day 0, as well as on Days 7, 14, 21, and 30, the cats in both treatment groups were infested with 100 (± 5) unfed, D. caninum -infected fleas. Live flea counts were conducted on Day 33 (72 ± 2 h after Day 30 infestation). All cats were euthanized on Day 58, and necropsies were performed to enumerate D. caninum scolices in the gastrointestinal tract. Results In both study 1 and 2, all placebo-treated cats were infested with two or more D. caninum scolices at necropsy. Significantly lower mean flea counts were recorded for the Revolution Plus-treated cats compared with placebo-treated cats ( P  ≤ 0.0001), and efficacy based on least squares mean flea counts on Day 33 was 100% (in study 1) and 94.3% (in study 2). Scolex counts were also significantly decreased in Revolution Plus-treated cats compared with placebo-treated cats, with a 97.1% efficacy in study 1 and a 99.3% efficacy in study 2. Conclusions One topical administration of Revolution Plus at the minimum dosage of 6.0 mg/kg selamectin and 1.0 mg/kg sarolaner provided high efficacy in the prevention of D. caninum infection through the killing of its vector, C. felis , for an entire month. Graphical Abstract

The members of genus Moniezia are the common parasites of livestock in tropical areas. The tapeworm, Moniezia expansa is commonly found in the gastrointestinal tract of the small and large ruminants. The present study focused on reporting the prevalence of M . expansa in small ruminants of southern Punjab: sheep and goats, in relation with epidemiological factors like age and gender. An overall prevalence of 27.2% was estimated for the small ruminants with higher infection rates in males (29.8%) and younger age group (<1 year; 32.9%). Moreover, the molecular characterization and phylogenetic analysis of the isolates based on partial cox1 gene indicated the placement of these sequences in the M . expansa cluster. Two distinct haplotypes, without any host tropism, were identified within the Pakistani isolates. A meta-analysis for M . expansa was run for all available global reports exhibiting an overall pooled prevalence of 21.3% (CI 95%: 13.5–29.0). Additionally, a global dataset encompassing 59 partial cox1 sequences submitted from different geographical locations was also assessed. Moderate haplotype diversity (0.760 ± 0.051) and significantly negative deviations from neutrality were estimated. The median joining haplotype network for these sequences revealed an interesting population structure indicating highly divergent sequences from China and Iraq compared to Pakistan, India, Vietnam, Senegal and Ethiopia. Given inconsistencies in genetic data there is a dire need to carry out molecular studies across the entire distributional range of M . expansa to delineate genetic diversity and population structure of the species. This will also be crucial in reevaluating the taxonomy of genus Moniezia .

Dipylidium caninum is a common tapeworm of dogs. Two cases of praziquantel resistance have been described in D. caninum in the United States. No further reports have been published to the authors’ knowledge. Here, the case of a dog imported to Switzerland from Spain with a history of chronic excretion of tapeworm proglottids and unresponsiveness to praziquantel treatments is reported. Clinical signs were mild (restlessness, tenesmus, anal pruritus, squashy feces) and flea infestation could be ruled out. Infection with D. caninum was confirmed through morphological and genetic parasite identification. Different subsequently applied anthelmintic compounds and protocols, including epsiprantel, did not confer the desired effects. Proglottid shedding only stopped after oral mebendazole administration of 86.2 mg kg−1 body weight for 5 consecutive days. Clinical signs resolved and the dog remained coproscopically negative during a follow-up period of 10 months after the last treatment. This case represents the first reported apparent praziquantel and epsiprantel resistance in D. caninum in Europe. Treatment was extremely challenging especially due to the limited availability of efficacious alternative compounds.

Abstract The objective of this study was to document the infection by cestodes Crepidobothrium sp. in Bothrops atrox, which are from the Tapajós National Forest, located in the western part of Pará state, Brazil. Thirty-six specimens of B. atrox were examined, of which 13 individuals (36%) were infected by Crepidobothrium sp. and a total of 147 parasites were collected from these hosts. The mean abundance of these endoparasites was 4.1 and the mean infection intensity was 11.3. In relation to parasitic infection sites, 88.4% of these cestodes were found in the small intestine, 9.52% in the large intestine and 2% in the stomach of the hosts. This was the first report of Crepidobothrium sp. in B. atrox in the Brazilian Amazon. Resumo O objetivo deste estudo foi registrar infecção por cestoides Crepidobothrium sp. em Bothrops atrox, as quais são provenientes da floresta Nacional do Tapajós, localizada no oeste do estado do Pará, Brasil. Foram examinados 36 espécimes de B. atrox, dos quais 13 indivíduos (36%) estavam infectados por Crepidobothrium sp. e um total de 147 parasitos foram coletados desses hospedeiros. A abundância média desses endoparasitos foi de 4,1 e intensidade média de infecção de 11,3. Em relação aos sítios de infecção parasitária, 88,4% destes cestoides foram encontrados no intestino delgado, 9,52% no intestino grosso e 2% no estômago dos hospedeiros. Este foi o primeiro relato de Crepidobothrium sp. em B. atrox na Amazônia brasileira.

In this first report of endoparasites from endemic land-mammals of the Galápagos Islands, we describe a new species of cestode of the genus Raillietina (Cyclophyllidea: Davaineidae) from a species of Nesoryzomys and summarize the extent of helminth parasitism in both oryzomyine endemics and introduced species of Rattus. Up to the current time, no helminth parasites have been reported from rodents of the Galápagos, and little work has yet been done describing and synthesizing Galápagos parasite diversity. In historical times, several species of autochthonous rodents have occupied the islands including: Nesoryzomys narboroughi Heller 1904, N. fernandinae Hutterer and Hirsch 1979, N. swarthi Orr, 1938, and Aegialomys galapagoensis (Waterhouse, 1839). Colonization of the islands by humans brought 3 known species of synanthropic rodents: Rattus rattus, R. norvegicus, and Mus musculus which are suspected to have caused the extinction of at least 3 other oryzomyines in historical times.

Taenia multiceps is a taeniid cestode that inhabits the small intestines of both wild and domestic carnivores. The larval stage, Coenurus cerebralis , is typically found in the central nervous system (CNS) of a wide range of livestock and, to a lesser extent, in the extra-cerebral tissues of sheep and goats. This review covers all aspects of the life cycle of T. multiceps and its epidemiology, molecular characterization, pathogenesis, diagnosis, therapy, control and zoonotic potential. Coenurosis caused by the larval stage of T. multiceps has a worldwide distribution and is often fatal in intermediate hosts, which can result in substantial economic losses in livestock farming. Molecular characterization using the mitochondrial genes cytochrome c oxidase subunit 1 and nicotinamide adenine dinucleotide dehydrogenase subunit 1 of different T. multiceps populations has revealed significant genetic variation and the presence of three major haplotypes. The disease mostly affects young sheep and is referred to as either acute or chronic coenurosis. Acute coenurosis occurs as a result of oncospheres migrating through the CNS, while chronic coenurosis occurs as a consequence of the coenurus maturing, which causes displacement and pressure atrophy of brain tissue. Non-cerebral coenurosis has been most commonly reported in goats. The best diagnostic method for cerebral coenurosis involves the interpretation of clinical signs with accurate localization of the cyst using diagnostic imaging techniques. A vaccine based on recombinant oncosphere antigens has proved to be an effective tool against T. multiceps infection in sheep. Additionally, use of anthelmintics during the parasite’s migration stages reduces the development of cysts in the sheep brain. Surgery is considered the most effective method for the treatment of cerebral coenurosis in small ruminants, but is often not carried out because of the limited finances of many sheep and goat breeders. However, coenurosis can also be controlled effectively through preventative measures, such as anthelmintic treatment of dogs and the proper disposal of intermediate host carcasses. The parasite is also zoonotic, and cases of coenurosis have been reported in humans with coenuri located in the brain, spinal cord and eyes. Graphical abstract

Helminth infections are cryptic and can be difficult to study in wildlife species. Helminth research in wildlife hosts has historically required invasive animal handling and necropsy, while results from noninvasive parasite research, like scat analysis, may not be possible at the helminth species or individual host levels. To increase the utility of noninvasive sampling, individual hosts can be identified by applying molecular methods. This allows for longitudinal sampling of known hosts and can be paired with individual-level covariates. Here we evaluate a combination of methods and existing long-term monitoring data to identify patterns of cestode infections in gray wolves in Yellowstone National Park. Our goals were: (1) Identify the species and apparent prevalence of cestodes infecting Yellowstone wolves; (2) Assess the relationships between wolf biological and social characteristics and cestode infections; (3) Examine how wolf samples were affected by environmental conditions with respect to the success of individual genotyping. We collected over 200 wolf scats from 2018–2020 and conducted laboratory analyses including individual wolf genotyping, sex identification, cestode identification, and fecal glucocorticoid measurements. Wolf genotyping success rate was 45%, which was higher in the winter but decreased with higher precipitation and as more time elapsed between scat deposit and collection. One cestode species was detected in 28% of all fecal samples, and 38% of known individuals. The most common infection was Echinococcus granulosus sensu lato (primarily E . canadensis ). Adult wolves had 4x greater odds of having a cestode infection than pups, as well as wolves sampled in the winter. Our methods provide an alternative approach to estimate cestode prevalence and to linking parasites to known individuals in a wild host system, but may be most useful when employed in existing study systems and when field collections are designed to minimize the time between fecal deposition and collection.