Trichinellosis, a zoonotic disease caused by nematodes of the genus Trichinella, is still a public health concern in the Arctic. The aims of this study were to investigate the seroprevalence of anti-Trichinella IgG in aboriginal peoples of two settlements in the Chukotka Autonomous Okrug (Russian Federation) on the Arctic coast of the Bering Sea, and to evaluate the survival of Trichinella nativa larvae in local fermented and frozen meat products. A seroprevalence of 24.3% was detected in 259 people tested by an enzyme-linked immunosorbent assay (ELISA). The highest prevalence was detected among people who consumed traditional local foods made from the meat of marine mammals. Trichinella nativa larvae were found to survive for up to 24 months in a fermented and frozen marine mammal meat product called kopalkhen. Since the T. nativa life cycle can be completed in the absence of humans, it can be expected to persist in the environment and therefore remain a cause of morbidity in the human populations living in Arctic regions.

The family Clinostomidae Lühe, 1901 contains 29 species allocated to seven genera, of which Clinostomum Leidy, 1856 is the most diverse, with c. 14 valid species. The diversity of Clinostomum has been assessed, combining morphological and molecular data. The genetic library for species in this genus has increased steadily, although there is little or no information for the other genera included in the family. Molecular phylogenetic relationships among the genera of clinostomids have not been assessed, and their classification is still based on morphological traits. The monotypic Ithyoclinostomum was described from a fish-eating bird in Brazil, and its metacercariae have been found in several locations in South America, parasitizing erythrinid freshwater fishes. We collected unusually large metacercariae from the body cavity of cichlids in several locations across Middle America. These metacercariae exhibited some resemblance to Ithyoclinostomum, although several differences prevent their inclusion in Ithyoclinostomum dimorphum, casting doubt on their taxonomic identification. The main objective of this paper was to characterize the metacercariae collected in cichlids using both morphology and molecular data from three molecular markers, and to assess the molecular phylogenetic relationships among the genera of Clinostomidae to establish the position of the newly generated sequences. We took a conservative position and tentatively placed the metacercariae as belonging to Ithyoclinostomum.

Opecoelid species Pseudopecoelus cf. vulgaris and Anomalotrema koiae Gibson & Bray, 1984 were found in fish collected in the boreal waters of the North Pacific. Pseudopecoelus cf. vulgaris differs from Pseudopecoelus vulgaris (Manter, 1934) in terms of the egg size. This is the first record of A. koiae in the North Pacific, and the second of Pseudopecoelus cf. vulgaris. Previously, A. koiae was recorded only in North Atlantic fish. Partial sequences of 28S rDNA obtained for these two species and six other previously unsequenced representatives of the family Opecoelidae were analysed together with data from GenBank. Phylogenetic analysis supports the allocation of the six clades of opecoelids – Helicometrinae, Opecoelinae, Opistholebetinae, ‘freshwater Plagioporinae’, ‘marine Plagioporinae B’ and ‘marine Plagioporinae C’, and confirms the paraphyly of the group ‘deep-sea Plagioporinae’. Our phylogeny does not support previous hypotheses about the monophyly of opecoelines with a uroproct.

The helminth endoparasites of many European amphibian species are often known exclusively from morphological descriptions. A molecular library of DNA sequence data linked to morphological identifications is still in its infancy. In this paper, we aim to contribute to such a library on the smooth newt Lissotriton vulgaris, the intermediate and definitive host of 31 helminth parasites, according to evidence published so far. Newts (n = 69) were collected at two study sites in western Germany and examined for the presence of helminths. A total of five helminth species were detected in 56 (81%) of the newts, but only one or two species infected a single host. Four out of five helminth species were identified morphologically and based on DNA sequences as Parastrigea robusta (metacercariae), Oswaldocruzia filiformis, Megalobatrachonema terdentatum (adults and larvae) and Cosmocerca longicauda, and the corresponding sequences were provided subsequently. Oswaldocruzia molgeta was confirmed to be a junior synonym of O. filiformis. Molecular data on a fifth species (a cosmocercid nematode) that could not be identified at species level were added to GenBank. These findings increased the molecular library on morphologically identified smooth newt parasites significantly, from 12 to 15 entries.

Trichinella species are widely distributed on all continents with the exception of Antarctica, although the full spectrum of Trichinella species found in sub-Saharan African countries, and their hosts, has not been fully documented. This study was conducted to determine the prevalence of Trichinella in wildlife from the Greater Kruger National Park (GKNP) and adjacent areas located in the Limpopo and Mpumalanga provinces of South Africa, and to identify the species and/or genotypes of Trichinella larvae isolated from muscle tissues, using molecular techniques. A review of Trichinella spp. and their wildlife hosts reported during 1964–2011 was also conducted and the results were compared with our current study. Ninety samples representing 15 mammalian, two bird and three reptile species were screened for Trichinella infection during 2012–2016, using artificial digestion. Isolates detected were identified using a multiplex polymerase chain reaction (PCR) amplification of the internal transcriber spacers ITS1 and ITS2, and expansion segment V (ESV) regions of ribosomal DNA, followed by molecular analysis of the sequences. Twenty samples from seven wildlife species were positive for Trichinella spp. larvae, with an overall prevalence of 21.1% (20/90). The prevalence was higher in carnivores (18.9%, 18/90) than in omnivores (2.2%, 2/90). Analysis of sequences showed that eight of the isolates – two from spotted hyaena (Crocuta crocuta) (2/8), three from lion (Panthera leo) (3/13), one from leopard (Panthera pardus) (1/6), one from small spotted genet (Genetta genetta) (1/2) and one Nile monitor lizard (Varanus niloticus) (1/2) – conformed to Trichinella zimbabwensis. One isolate from a hyaena was grouped under the encapsulated species clade comprising T. nelsoni and genotype Trichinella T8 reported to be present in South Africa. This is the first report confirming natural infection by T. zimbabwensis in hyaena, leopard, genet and Nile monitor lizard, adding to the body of knowledge on the epidemiology of Trichinella infections in the Greater Kruger National Park of South Africa. Ten Trichinella-like larval isolates recovered after digestion from four wildlife species in this study (2012–2016) revealed inconclusive results due to DNA degradation resulting from poor storage or too few larvae for analysis, in comparison to 20 unidentified isolates from five wildlife species during the 1964–2011 period.

One hundred and sixty-one northern bobwhites (Colinus virginianus; hereafter ‘bobwhite’) were examined from the Rolling Plains ecoregion of Texas and western Oklahoma from 2011 to 2013. Complete necropsies yielded 13 species, of which two are new host (Gongylonema phasianella) and region (Eucoleus contortus) records and three (Dispharynx nasuta, Tetrameres pattersoni and Oxyspirura petrowi) are known to cause morbidity and mortality. Of the species found, Aulonocephalus pennula commonly occurred, Oxyspirura petrowi was intermediate in prevalence, and the remaining species were rare. Species richness was similar compared to studies from the southeastern U.S., but higher than studies from the same region. In addition, 12 of the 13 species were heteroxenous helminths, supporting the theory that heteroxenous helminths in semi-arid regions are more successful than monoxenous helminths. Prevalence and abundance of A. pennula and O. petrowi were higher in adult bobwhites than in juveniles. Abundance of A. pennula and O. petrowi was higher at southern locations compared to northern locations in the study area. Our study is the first to provide a current assessment of the bobwhite helminth community across the Rolling Plains ecoregion of the U.S.

Currently, fish helminth parasites, especially cestodes and acanthocephalans, are regarded as sentinel organisms to elucidate metal pollution in aquatic ecosystems. Here, 34 specimens of the fish Siganus rivulatus were collected in the Red Sea, from a seriously polluted, small lagoon named Sharm-Elmaya Bay, at Sharm El-Sheikh, South Sinai, Egypt; 22 (64.7%) were infected by Sclerocollum saudii (Acanthocephala: Cavisomidae). Thus, 22 natural infrapopulations (26–245 individuals) of this parasite were collected from infected fish. Samples of water and sediments from the bay, samples of muscle, intestine and liver from each fish, and samples from the parasite were taken for analysis of heavy metals (cadmium (Cd) and lead (Pb)). Both Cd and Pb concentrations in sediments were higher than those in water. The concentration of these metals were significantly higher in tissues (intestine, liver and muscle) of non-infected fish than those in infected fish, with Pb concentrations consistently higher than those of Cd, and both were drastically decreased in the order: liver > intestine > muscle. Metal concentrations in this acanthocephalan were much higher than those in its fish host. There were strong negative relationships between metal concentrations in tissues (intestine, liver and muscle) of infected fish and infrapopulation size, and between metal concentrations in the acanthocephalan and its infrapopulation size. These relationships strongly suggest competition for these metals between the fish host and its acanthocephalan parasite, and intraspecific competition among acanthocephalan individuals for available metals in the fish intestine. Bioconcentration factors were relatively high, since the mean Cd concentration in S. saudii was 239, 68 and 329 times higher than those in intestine, liver and muscle tissues, respectively, of its fish host. Also, mean Pb concentration was 55, 13 and 289 times higher than those in these tissues, respectively. The host–parasite system described here seems to be promising for biomonitoring of metal pollution in the Red Sea.

Among the Brazilian marsupials, the species of the genus Didelphis are the most parasitized by helminths. This study aimed to describe the species composition and to analyse the helminth communities of the Atlantic Forest common opossum Didelphis aurita at infracommunity and component community levels using the Elements of Metacommunity Structure Analysis, considering peri-urban, sylvatic and rural environments in the state of Rio de Janeiro, Brazil. Seventy-three specimens of D. aurita were captured during the study. Fourteen species of helminths were collected: nine of the phylum Nematoda (Trichuris minuta, Trichuris didelphis, Globocephalus marsupialis, Heterostrongylus heterostrongylus, Travassostrongylus orloffi, Viannaia hamata, Aspidodera raillieti, Cruzia tentaculata and Turgida turgida); four of the phylum Platyhelminthes (three species of Trematoda, Duboisiella proloba, Brachylaima advena and Rhopalias coronatus, and one species of the class Cestoda); and one species of the phylum Acanthocephala (Oligacanthorhynchus microcephalus). More than 95% of the animals were infected with parasites. The most abundant parasite species were V. hamata, T. turgida, C. tentaculata and T. orloffi. The nematodes T. turgida, C. tentaculata and A. raillieti were the most dominant species in the three environments. The analysis of the metacommunity structure indicated a structured pattern as a function of the environmental gradient, but only when all localities were considered together. At the infracommunity and component community levels, quasi-nested and nested structures with stochastic species loss were observed, respectively. The results indicate that the settlement of helminth species in the opossums can be attributed to the heterogeneity among individual hosts in relation to their exposure to parasites and to extrinsic factors, which vary among habitats, considering a regional scale. On a local scale, the characteristics of this host species may promote homogenization among individual hosts in terms of their exposure to the helminths. This study constitutes a new host record for the species G. marsupialis and T. didelphis and represents a pioneering investigation of the helminth metacommunity of a Neotropical marsupial.

In the Pampa region of Argentina, farming activities have been performed since the beginning of the 20th century, but in the 1990s, land-use patterns rapidly changed towards intensive agriculture and poultry breeding. This study compares the helminth community of Akodon azarae (Rodentia) among three habitats with different land use in pampean agroecosystems: poultry farms, mono-cultivated fields and abandoned fields (not used for 35 years), under the prediction that there will be greater helminth richness and diversity in mice from abandoned fields compared to those from the other habitats. Nevertheless, the highest abundance of A. azarae occurred on poultry farms, the habitat most disturbed by human activity, while cultivated fields showed the lowest. Helminth richness and diversity were significantly higher on poultry farms than in the other habitats, due to the presence of Trichuris laevitestis, Protospirura numidica criceticola and cysts of Taenia taeniaeformis. We suggest that the helminth fauna of A. azarae can survive on poultry farms despite disturbance from farming activities, because rodents can move and get shelter within farm perimeter fences, where dense and high vegetation grows. This farm area could offer good conditions for geohelminth development, while chicken sheds could attract insects that are intermediate hosts of helminths with indirect life cycles. On the contrary, agrochemicals applied in cultivated fields would negatively influence helminth diversity and composition, by decreasing host populations (arthropods and rodents) and affecting free larval stages of geohelminths.

In this study, we analysed and compared the whole parasite community from the fish Notothenia rossii and Notothenia coriiceps collected from Fildes Bay at King George Island, Antarctica, during January–February 2017 in a field campaign supported by the Chilean Antarctic Institute. The fish samples collected were 45 specimens of N. rossii and 22 of N. coriiceps, with total lengths averaging 29.7 ± 5.3 cm and 32.5 ± 3.2 cm, respectively. Fish were dissected to collect their internal and external parasites. All the fish were parasitized; 13 taxa were found in N. rossii and 12 taxa in N. coriiceps. Acanthocephalans, mainly Metacanthocephalus johnstoni and Aspersentis megarhynchus, were the most abundant and prevalent parasites in both fish species. The abundance and richness of the parasite infracommunity increased with the host body length only in N. rossii. Twelve parasitic taxa were shared by both notothen species. Abundance and prevalence of parasitic taxa, as well as the average richness and abundance of the parasite infracommunities were mostly similar between the two fish species. Parasite compositions of N. coriiceps reported in published studies from King George Island were relatively comparable to our sample. We concluded that the two congeneric and sympatric fish species had highly similar parasite communities, which indicates that they use resources in a similar way, thus allowing them to become parasitized with the same parasitic species and in the same abundances. All parasites recorded in this study have been found in several other fish species; therefore, parasites from notothens are considered to be generalists.

There is a paucity of information on the diversity and occurrence of freshwater fish parasites in Australia. This study investigates the distribution and occurrence of a parasitic nematode of the genus Contracaecum in freshwater fish from south-eastern Australia. Fish (n = 508) belonging to nine species and eight families were collected from eight wetlands associated with the Murrumbidgee River floodplain in the southern Murray–Darling Basin and subjected to laboratory examination. Third-stage nematode larvae were found in eight of the nine fish species. The exception was the fly-specked hardeyhead (Craterocephalus stercusmuscarum), although only one specimen of this species was examined. Nematode larvae were identified as Contracaecum bancrofti using a combined morphological and molecular approach. The parasite was most prevalent in weather loach (Misgurnus anguillicaudatus; 34.8%) and Australian smelt (Retropinna semoni; 21.4%), followed by carp (Cyprinus carpio; 9.5%), of which the former and latter are non-native species. Contracaecum prevalence differed between locations, with Two Bridges having the highest number of infected fish. This may be due to the higher number of suitable host species collected at these localities. Contracaecum spp. are parasites with low host specificity that have also been reported in Australian marine fish, humans and piscivorous birds. The high parasite prevalence in the two abundant non-native fish species in the region suggests that they act as a suitable host for this endemic parasite, resulting in the increase in the parasite population. It would be interesting to study host–parasite interactions in this area, especially if introduced fish populations declined dramatically in the attempt to eradicate them or control their population.

The toxicity of water–ethanol extracts of garlic (Allium sativum), ginger (Zingiber officinale), basil (Ocimum basilicum), bitter chaparro (Castela tortuousa), onion (Allium cepa) and papaya (Carica papaya) against adults, eggs and oncomiracidia of Neobenedenia spp. parasites was examined. Parasites were exposed to continuous immersion and treated as follows: extracts were tested at three dilutions: 1:10, 1:50 and 1:100 made with filtered seawater (35 g l–1); ethanol (70%) was evaluated at the same dilutions of 1:10 (7% ethanol), 1:50 (1.4% ethanol) and 1:100 (0.07% ethanol) and a seawater (35 g l–1) control. The antiparasitic effect was measured on: (1) adult survival, egg production and time to detachment from the culture vessel; (2) egg development and cumulative egg hatching; and (3) oncomiracidia survival. All three dilutions of ginger and dilutions 1:100 and 1:50 of basil extract reduced adult survival in vitro, time to detachment from the surface of the culture vessel, egg production and oncomiracidia survival. Bitter chaparro extract reduced adult egg production and oncomiracidia survival. Hatching success was significantly reduced (P < 0.05) in basil extract (1:100) to 86.6% compared to the seawater control (100%). Dilutions 1:10 of ginger and basil exhibited the highest impact on the biological parameters of Neobenedenia sp. Our study demonstrates that water–ethanol extracts of ginger, basil and bitter chaparro are toxic against Neobenedenia sp. life stages.

Larval trematodes are the main parasites of snails, and they play a crucial role because they usually castrate their snail hosts and can thus alter their population and community dynamics. This study involved a survey of seven gastropod species (Crepipatella dilatata, Fissurella radiosa, Nacella magellanica, Pareuthria fuscata, Siphonaria lessonii, S. lateralis and Trophon geversianus) parasitized by 12 trematode species (one hemiurid, one gymnophallid, two lepocreadiids, two microphallids, one notocotylid, two renicolids, one philophtalmid, one schistosomatid and one zoogonid) from southern Patagonia (47°S, 65°W), Argentina. Only F. radiosa was free of parasites. The study included the description of five new larvae, based on morphological and molecular information, and a comparison of the parasite diversity with that of a northern locality (42°S, 64°W), characterized by a lower mollusc diversity. Species richness and diversity of parasites were higher in the southern site. This suggests a correlation between the level of parasitism and the diversity of molluscs (first intermediate hosts), which is higher at the high-latitude site and seems to attract shorebirds, which disperse the digenean eggs and facilitate the completion of their life cycles. These results support the notion that parasitism is influenced by large-scale factors such as biogeographical patterns, and small-scale factors such as diversity or abundance of intermediate and definitive hosts.

The phylogenetic relationships of 42 species of cloacinine nematodes belonging to three tribes (Coronostrongylinea, Macropostrongylinea and Zoniolaiminea) were examined based on sequence data of the first and second internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA. All nematodes examined are parasites of Australian macropodid marsupials. None of the three nematode tribes was monophyletic. Paraphyly was also encountered in three genera: Papillostrongylus, Monilonema and Wallabinema. Species within the genus Thallostonema were limited to a single host genus (i.e. Thylogale), whereas species within the five principal genera (Coronostrongylus, Macropostrongylus, Popovastrongylus, Wallabinema and Zoniolaimus) were found to occur in multiple host genera. Potential modes of evolution among these nematodes are discussed.

The cestode Hymenolepis erinacei is regarded as a widely distributed parasite in European hedgehogs of the genus Erinaceus, although the taxonomic position of this hymenolepidid has been debated for a considerable period of time. We present the first molecular data for this cestode, including partial DNA sequences of mitochondrial 16S and nuclear 28S ribosomal genes. Molecular phylogenetic analysis clusters H. erinacei in one clade together with representatives of the genus Hymenolepis from rodents. Characteristic morphological features, including the oval embryophore without filaments and shape of the embryonic hooks of H. erinacei are described. Features of these cestode eggs are proposed as a basis for non-invasive detection of parasitic infections in small mammal populations. The present study explores phylogenetic relationships within the genus Hymenolepis and the host switching related to H. erinacei. Cases of host switching in other genera of the family Hymenolepididae are reviewed. A short critical review of cestodes parasitizing hedgehogs in the Palaearctic is presented.

Vertebrate hosts commonly harbour concurrent infections of different helminth species which may interact with each other in a synergistic, antagonistic or negligible manner. Direct interactions between helminths that share a common site in the host have been regularly reported, but indirect interactions between species that occur in different sites are rarely described, especially in fish hosts. Plerocercoids of Ligula intestinalis are common infections of the peritoneal (body) cavity of roach (Rutilus rutilus) in freshwater habitats. These larval cestodes can cause extensive systemic pathologies to the fish host, which in turn may alter its susceptibility as a target host for other helminth species. The present study, using an existing dataset, investigates the influence of L. intestinalis (ligulosis) on frequently occurring eyefluke infections in roach sampled from a lake in south-east England. The occurrence of two species of eyefluke (Diplostomum sp. and Tylodelphys sp.) in the roach population demonstrated no significant levels of interaction with each other. The prevalence but not mean intensity or abundance of Diplostomum sp. was significantly increased in ligulosed roach, while the incidence of Tylodelphys sp. remained unchanged. Analyses of bilateral asymmetry in the occurrence of eyeflukes in left and right eyes of infected fish demonstrate that Tylodelphys sp. shows significant asymmetry in non-ligulosed roach, which is not replicated in ligulosed individuals. In contrast, Diplostomum sp. shows no evidence of asymmetry in either ligulosed or non-ligulosed fish.

Antechiniella septentrionalis n. sp. (Spirurida: Acuariidae) is described from the duodenum of a tundra vole, Microtus oeconomus (Pallas), collected in the Magadan region in the north-east part of Russia. It differs from A. suffodiax (Beveridge & Barker, 1975) and A. sertatum Smales, 1991 mainly in having a larger number of postcloacal papillae (5–6 pairs vs 4 pairs), a differently shaped left spicule, the disposition of precloacal papillae in two rows vs one, and oblong vs oval eggs. Other differences include the different disposition of ovaries in A. septentrionalis n. sp and A. suffodiax and the different structure of deirids in A. septentrionalis n. sp. and A. sertatum. The new species was characterized molecularly (partial sequences for 18S rRNA, 28S rRNA and cox1 mtDNA). The phylogenetic analyses performed showed the affinity of the new species to the members of the Acuariidae and other spirurid nematodes.

An understanding of the mechanisms that determine host and parasite relationships is a central aim in parasitology. Association of a parasite species with a host species may be influenced primarily by phylogenetic constraints that cause parasite species to co-speciate with their host species, or predominantly by ecological parameters that influence all other co-evolutionary scenarios. This study aimed to investigate the role of co-speciation as well as other co-evolutionary scenarios in influencing the assemblages of tapeworm parasites (marine cestodes) in skate hosts (Rajiformes) using a modification of the PACo (Procrustean Approach to Cophylogeny) method. The study found that phylogeny and host ecology are both significant predictors of skate–tapeworm relationships, implying that co-speciation as well as other co-evolutionary scenarios are shaping these associations. The study also investigated the key ecological parameters influencing host-switching and found that host diet, distribution depth, average body size and geographical location have a combined effect. Given the importance of parasites in ensuring healthy and stable marine ecosystems, the findings of this study have implications for conservation management worldwide.

A new species of Nippostrongylinae (Nematoda: Heligmonellidae), Stilestrongylus rolandoi n. sp., is described from specimens collected from the small intestine of the rodent Euryoryzomys russatus in the Atlantic Forest (Santo Amaro da Imperatriz, Santa Catarina state, southern Brazil). The genus Stilestrongylus includes 23 species, which parasitize rodents occurring in the Neotropical region. Stilestrongylus aureus (Durette-Desset & Sutton, 1985) from Argentina, S. azarai (Durette-Desset & Sutton, 1985) from Argentina, S. flavescens (Sutton & Durette-Desset, 1991) from Uruguay, S. franciscanus (Digiani & Durette-Desset, 2002) from Argentina, S. gracielae (Digiani & Durette-Desset, 2006) from Argentina, and S. oryzomysi (Sutton & Durette-Desset, 1991) from Argentina are closely related to Stilestrongylus rolandoi n. sp., all having caudal bursa patterns of types 1–4 in one of the lobes. Stilestrongylus rolandoi n. sp. is distinguished from the aforementioned species by its ray 6 being short in relation to rays 4 and 5, which are long and robust, and by having caudal bursa patterns of types 1–4 in both lobes. The new species has 27 ridges in the mid-body in males, and 24 in females, and has one of the highest ratios of spicule length to body length (21−33%) in this genus.

We describe the larval developmental stages and life cycle of the dracunculid nematode Mexiconema cichlasomae in both the intermediate, Argulus yucatanus (Crustacea: Branchiura), and definitive hosts, Cichlasoma urophthalmus (Perciformes: Cichlidae), from the Celestun tropical coastal lagoon, Yucatan, Mexico. The morphological analyses showed significant differences between the total length of L1 found in M. cichlasomae gravid female and L2–L3 in A. yucatanus. This result indicates that the M. cichlasomae larval development occurs in the intermediate host. We obtained sequences from the small subunit (SSU) ribosomal marker from larval stages of M. cichlasomae in A. yucatanus and adult nematodes in C. urophthalmus. Our morphological and molecular results support conspecificity between M. cichlasomae larvae in A. yucatanus and the adult stages in C. urophthalmus. We briefly discuss the phylogenetic position of M. cichlasomae among the Daniconematidae, and provide evidence of the monophyly of the daniconematids associated with branchiurid intermediate hosts. Based on the phylogenetic results, we support the transfer of the Mexiconema genus to the family Skrjabillanidae and do not support the lowering of family Daniconematidae to subfamily.