An updated checklist of leeches and oligochaetes (Annelida: Clitellata) that parasitize or prey upon wild North American amphibians and reptiles is presented: A total of 25 species grouped in 6 genera, 5 families, and 2 orders, are registered; these infect a total of 39 species of reptiles and 39 species of amphibians in the region. An illustrated identification key for the families and genera listed is proposed. Finally, a new record is made for Mexico: the leech Placobdella parasitica (Say, 1824) (Glossiphoniidae) parasitizing the Mesoamerican slider Trachemys venusta (Gray, 1856) (Emydidae) in the state of Tamaulipas.

Hedruris has a worldwide distribution, parasitizing lampreys, fishes, frogs, and lizards. In South America, 4 species have been reported on frogs (Hedruris heyeri, Hedruris juninensis, Hedruris moniezi, and Hedruris mucronifer), 3 on fishes (Hedruris basilichtensis, Hedruris orestiae, and Hedruris suttonae), and 1 on turtles (Hedruris dratini). We examined a frog (Pseudis minuta) found dead in the Pescado stream, Argentina, searching for parasites. A Hedruris sp. was found and subsequently subjected to integrative analyses. The 18S rDNA was sequenced, and specimens were examined using electron and optical microscopy. Genetic analysis grouped this nematode with H. dratini. Its morphology was similar to that species but differed in having bifid derid in frogs, compared to a simple deirid in turtles. This difference could result from various causes, such as host-parasite interaction or a teratological feature, or it could indicate high morphological variability. To resolve this, molecular analysis of all described Hedruris species is necessary, in addition to morphological studies. According to the prevalence and intensity of infection reported in the literature, the definitive host of H. dratini is likely the turtle. However, the nematode may use different hosts, or the frog may have ingested an amphipod harboring the parasite's intermediate stage. This is the first Hedruris parasite of frogs to be sequenced and represents, after H. mucronifer, the second report of the genus in anurans from Argentina.

Turtle acanthocephalans in the genus Neoechinorhynchus have complex life cycles and are thought to involve an ostracod intermediate host and a turtle definitive host. For Neoechinorhynchus emydis, an additional snail paratenic host is part of its life cycle. However, how snails become infected and whether other species of Neoechinorhynchus can be found in snails remains unclear. This study was conducted to understand the survival, development, and host use of 4 species of turtle acanthocephalans (Neoechinorhynchus chrysemydis, N. emydis, Neoechinorhynchus emyditoides, and Neoechinorhynchus pseudemydis) in their intermediate, paratenic, and definitive hosts. Using eggs recovered from adult acanthocephalans from naturally infected turtle hosts in Oklahoma, experimental infections were conducted in 2 species of ostracods and 1 species of freshwater snail. Ionomes also were generated for these acanthocephalans and their turtle definitive hosts to better understand resource competition. Upon ingestion by ostracods, eggs of all 4 species of acanthocephalans hatched in both ostracod species. However, no further acanthocephalan development occurred in Cypridopsis sp. ostracods, whereas all 4 acanthocephalan species grew and developed into infective juveniles over 28–32 days in Physocypria sp. ostracods. Of the 4 species of acanthocephalans, N. emydis grew faster early in ostracods and was the only species to survive and establish in snail hosts. This finding was supported by the observation of proboscis remnants in the feces of snails that ingested ostracods infected with N. chrysemydis, N. emyditoides, and N. pseudemydis. In contrast, when snails were exposed to eggs of all 4 acanthocephalan species, eggs were passed in the feces, resulting in no infections. The overall ionomic composition of adult acanthocephalans and their turtle hosts suggested that the hosts and parasites share host resources. However, specific elemental differences indicated that turtle acanthocephalans can accumulate heavy metals at concentrations higher than those in their hosts. Results of this study support previous field observations and hypotheses that (1) Physocypria sp. ostracods serve as intermediate hosts for N. chrysemydis, N. emydis, N. emyditoides, and N. pseudemydis; (2) N. emydis uses snail paratenic hosts, but snails are a non-viable route of transmission to turtles for N. chrysemydis, N. emyditoides, and N. pseudemydis; and (3) as adults, these 4 acanthocephalan species utilize their turtle definitive hosts similarly in terms of ionomic composition. This work challenges the traditional view of the acanthocephalan life cycle and sets the stage for future hypotheses.

The range of hosts a parasite can successfully occupy is partially determined by the niche breadth, that is, the set of environmental conditions necessary to maintain a stable population. Niche breadth is often quantified using host specificity, which encompasses the number of host species a parasite can exploit and the parasite's distribution among its hosts. Parasites with a wider niche breadth can potentially occupy more host species and are often more evenly distributed among hosts than parasites with a narrower niche breadth. However, parasites interact with potential hosts within the context of a geographic locality and the set of environmental characteristics associated with it. The extent to which environmental filters associated with host individuals and the geographic context explain variation in occupancy of parasites, and the extent to which variation in occupancy is associated with host range and specificity, is poorly understood. Using data from small mammals and ectoparasites in Vermont, I used a multiscale, multispecies occupancy model (MSOM) to (1) estimate ectoparasite occupancy at 10 geographic sites and on individual hosts within each site, (2) quantify the variation in occupancy explained by the site and host levels of the model using Bayesian R², and (3) evaluate associations between explained variation and host range of ectoparasites. For ectoparasites collected from at least 4 different host species, I calculated structural specificity to determine the distribution of these parasites across the hosts, and β-specificity to evaluate changes in host use across habitats. Host range was significantly associated with host-level Bayesian R²: generalist parasites had more variation in occupancy explained by host-level covariates than specialist parasites. This result may be explained by differences in structural specificity: many generalists disproportionally occurred on a single-host species, suggesting that host characteristics act as habitat filters for these parasites. There were no significant associations between site-level Bayesian R² and host specificity. However, some generalists demonstrated high β-specificity, suggesting these parasites may “switch” hosts, depending on host availability. These results highlight that the terms specialist and generalist are context dependent and may not accurately describe the niche breadth of parasite taxa. Understanding variation in host specificity as it pertains to potential habitat filters may be important for predicting which parasites can bypass host filters and “jump” to a novel host, which has implications for the surveillance and management of vector-borne diseases.

The Cyathocotylidae Mühling, 1896 is a small but broadly distributed family of digeneans parasitic in a wide range of vertebrate definitive hosts, from fish to mammals. Despite existing taxonomic questions, only a few studies have generated DNA sequence data from cyathocotylids, and only a single publication included sequence data from a cyathocotylid parasitic in snakes. Four genera are known to infect snakes: Gogatea Lutz, 1935, Szidatia Dubois, 1938, Mesostephanoides Dubois, 1951, and Serpentostephanus Sudarikov, 1961. Members of these genera were known from only Asia and Africa. In the present study, we describe 2 new species of Gogatea from snakes in Australia and 1 from Vietnam. The new species from Vietnam described herein is the first member of the genus that lacks a ventral sucker. We used partial sequences of the nuclear large ribosomal subunit (28S) and mitochondrial cytochrome c oxidase subunit I (COI) genes to explore phylogenetic relationships among cyathocotylids and species differentiation. In addition, this is the first report of a cyathocotylid from snakes in Australia, thus posing interesting questions regarding the dispersal and historical biogeography of these parasites. Cyathocotylid genera from snakes have a long, convoluted taxonomic history. The genera Gogatea, Mesostephanoides, and Szidatia were distinguished from each other based on very small morphological differences. Therefore, the validity of Szidatia and Mesostephanoides was often questioned in the literature. Based on the detailed morphological analysis of our freshly collected high-quality specimens and comparison with published information, we synonymize Mesostephanoides and Szidatia with Gogatea.

Hepatozoon sp. stages were detected in histological sections of the muscles of 11 of 25 bobcats (Lynx rufus). Parasites were detected from the myocardium of 11, tongues of 4, and limb muscles of 5 of these animals, which had been hunted in Mississippi in 2017. The intensity of infection was highest in the heart. Only asexual stages (meronts) were detected. Three types of meronts (types 1, 2, and 3) were detected, based on structure and mode of division. Additionally, individual zoites were found in leukocytes in the blood vessels of the myocardium, but the stage was not identified. Based on genomic DNA characterized from paraffin-embedded myocardium sections from 1 bobcat using 18S rRNA gene, the Hepatozoon species from the bobcat was related to but distinct from other Hepatozoon spp. of felids. This is the first description of the development of Hepatozoon in the muscles of bobcats. A new name, Hepatozoon rufi, is proposed for this parasite in bobcats.

Nine species of Hemirhamphiculus Bychowsky and Nagibina, 1969 (Dactylogyridae) were recorded from 6 beloniform fishes during a survey of the monogenoids infecting these fishes in the Gulf of Mexico off Florida from September 2017 through December 2020. Five new species were collected, illustrated, and described: Hemirhamphiculus acarips n. sp., Hemirhamphiculus longiclathra n. sp., and Hemirhamphiculus lucernula n. sp. all from Strongylura notata (Poey) and Hemirhamphiculus bilobatus n. sp. and Hemirhamphiculus litus n. sp. both from Strongylura timucu (Walbaum). Four previously described species were transferred to Hemirhamphiculus: Hemirhamphiculus tylosuri (MacCallum, 1917) n. comb. [formerly Ancyrocephalus tylosuri (MacCallum, 1917) Johnston and Tiegs, 1922]; Hemirhamphiculus parvus (Linton, 1940) n. comb. (formerly Ancyrocephalus parvus Linton, 1940); Hemirhamphiculus cornutus (Williams and Rogers, 1972) n. comb. (formerly Ancyrocephalus cornutus Williams and Rogers, 1972); and Hemirhamphiculus trullae (Williams, 1980) n. comb. (formerly Ancyrocephalus trullae Williams, 1980). The occurrence of He. trullae on Hyporhamphus meeki represents a new host record for the parasite. Three Indo-Pacific species of Dactylogyridae were transferred to Hemirhamphiculus: Pseudohaliotrematoides recurvatus Yamaguti, 1968, as Hemirhamphiculus recurvatus (Yamaguti, 1968) n. comb.; Tylosuricola haikouensis Zhang, 2001, as Hemirhamphiculus haikouensis (Zhang, 2001) n. comb.; and Xenentocleidus xenentodoni (Jain, 1961) Tripathi, Agrawal, and Pandey, 2007, as Hemirhamphiculus xenentodoni (Jain, 1959) n. comb. Xenentocleidus Tripathi, Agrawal, and Pandey, 2007, was synonymized with Hemirhamphiculus as its junior subjective synonym. Bychowskymonogenea Caballero and Bravo Hollis, 1972, and Bychowskymonogenea sogandaresi Caballero and Bravo Hollis, 1972, were placed as junior subjective synonyms of Hemirhamphiculus and He. tylosuri, respectively, and the Bychowskymonogeninae Caballero and Bravo Hollis, 1972, was rejected as a valid subfamily of the Dactylogyridae.

During August 2021 and again in July 2022 and July 2023, 4 freckled madtoms, Noturus nocturnus, were collected from a creek in Columbia County, Arkansas (Ouachita River drainage), and their gills, gallbladder, fins, integument, musculature, and other major organs were examined for myxozoans. The gallbladder of 1 (25%) was infected with apparently novel myxozoans. Qualitative and quantitative morphological data were from preserved formalin-fixed myxospores. Molecular data include 2,059 bp (for a Myxidium sp.) and 951 bp (for an unobserved Myxozoa sp.) sequences of the partial small subunit (SSU) ribosomal RNA gene. Phylogenetic analysis placed the Myxidium sp. among a clade of myxozoans that infect fish from the southern portion of North America. These represent the first myxozoans reported from the gallbladder of madtoms.

Cospeciation has been observed multiple times between parasites and their hosts. Here we compare the phylogeny of 2 different groups of chewing lice (Phthiraptera), one known for being host specific (Amblycera: Myrsidea) and one known for including many generalist species (Ischnocera: Brueelia-complex, specifically Guimaraesiella and Priceiella) with that of their songbird hosts (Passeriformes), which are participants in mixed-species feeding flocks in South China. Using event- (Jane) and distance-based (ParaFit) analyses we found that both groups of lice have phylogenies that are more similar than by chance to those of their hosts. However, more cospeciation and host-switching events were inferred for the Myrsidea data set, whereas more duplication events and losses were inferred for the Brueelia-complex data set. Even though these louse groups are found on roughly the same host species, the differences in sorting events may be linked to the different modes of dispersal. Whereas both groups transfer by direct contact, phoresy is recorded only in lice belonging to the Brueelia-complex.

During a survey for Sarcocystis infections in Pennsylvania in wild canids, muscles from the tongue and limb were examined microscopically for sarcocysts. Between 9 February 2024 and 11 February 2024, muscle samples were collected from 76 coyotes, 46 gray foxes, and 21 red foxes from Pennsylvania hunter harvested animals. Around 5 g of muscle was examined microscopically by compression between a glass slide and coverslip. Trichinella murrelli larvae were detected in 1 of 76 coyotes (Canis latrans), 1 of 46 gray foxes (Urocyon cinereoargenteus), and in 7 of 21 red foxes (Vulpes vulpes) muscles. Diet and individual host susceptibility probably contributed to the differences in prevalence of T. murrelli in these hosts. This is the first report of Trichinella infection in coyotes from Pennsylvania. The reasons for differences in Trichinella species could be due to inherent susceptibility or the area sampled.

Although harvest of Octopus maya (Mexican four-eyed octopus) is one of the most important fisheries in the Yucatan Peninsula, little is known about the parasites of these cephalopods and how they affect host physiological processes. We analyzed the spatio-temporal variation of infection of O. maya by the cestode larva Prochristianella sp. (found in the anterior salivary glands) and its relationship with the gonad development stages (GDSs) of the host. From August 2009 to May 2010, 439 specimens of O. maya were caught in 2 localities on the northern coast of the Yucatán Peninsula: Dzilam de Bravo (n = 239) and Ria Lagartos (n = 200). The mantle length, eviscerated body weight, reproductive complex weight, and gonad weight were recorded in each specimen. Portions of each gonad were used to identify the GDS based on histology for each individual to determine the periodicity of the reproductive cycle and the monthly variation in the reproductive complex weight. Temporal variation in the monthly mean abundance of cestodes but not in prevalence was evident. A permutational multivariate analysis of variance indicated that variation in the mean abundance of Prochristianella sp. was affected by host GDS, month of sampling, host sex, and sampling locality; however, the first-order interactions indicated that the most were important variables were GDS, month, and host sex. General linear model analyses also indicated that the size, reproductive status, and sex of the hosts were significantly related to the abundance of cestodes. Temporal variation was evident in the monthly mean abundance of Prochristianella sp. but not in its prevalence; the number of parasites increased in octopuses from September to December. Regarding the GDS, the mean abundance of the parasite increased as gonads developed, and gonad development was related to water temperature and time, which are linked to season and the upwelling that occurs in spring and summer. In the oral cavity of octopuses, variations in cestode abundance related to host sex, size, and reproductive status can have major implications for the production of saliva, an essential secretion for food acquisition and defense in this host, and could affect octopus reproduction and recruitment of this food resource so important for the Yucatán Peninsula.

As predators of a wide variety of livestock and wildlife species, wolves (Canis lupus) could serve as definitive hosts for species of Sarcocystis parasites infecting many intermediate hosts. Sarcocystis sporocysts have been observed in the feces of wolves fed infected beef before, but genetic tools have not yet definitively identified which species of parasites they harbor, impairing understanding of their contribution to infections in wild and domesticated intermediate hosts. Therefore, we genetically characterized sporocysts derived from a small sample of naturally infected wolves in Minnesota. Doing so established evidence that wolves may excrete sporocysts and therefore transmit Sarcocystis cruzi to cattle (Bos taurus), Sarcocystis mehlhorni to black-tailed deer (Odocoileus hemionus columbianus), and Sarcocystis wenzeli to chickens (Gallus domesticus). Given their wide host range and appetite, wolves may serve as a source of infection for cattle, deer, and chickens.

Accurate detection of schistosome infections in snails is vital for epidemiologic and laboratory studies. Traditional microscopy methods to detect schistosomes in snails are hindered by long prepatent periods and snail survivorship, leading to inaccurate assessment of infections. A rapid, multiplexed PCR assay targeting Biomphalaria sudanica or Biomphalaria glabrata (internal control) and Schistosoma mansoni DNA is described. The method takes less than 90 min starting from extracted snail DNA and is successful at amplifying schistosome DNA in snail tissue as soon as 30 min following exposure. Accurate measures of schistosome infection success in snails (compatibility) are possible by 4–7 days postexposure.

Parasitism is ubiquitous, yet little is known about the evolutionary mechanisms that lead to a parasitic lifestyle. Facultative parasites can switch between free-living and parasitic lifestyles, which may provide an opportunity for researchers to study the genetic mechanisms underlying a transition to parasitism. The oligochaete Dero (Allodero) hylae is a facultative parasite commonly found within the ureter of various anuran species, such as the Cuban tree frog (Osteopilus septentrionalis). The Dero hylae worm passes into the frog's cloaca, where it then infects the ureter. In the ureter, the worm loses its free-living characteristics such as hair setae, dorsal setae, a digestive tract, and fossa with gills as it transitions to a parasitic lifestyle. The parasite may be expelled from its host during urination, and when this occurs the worm will reacquire its free-living characteristics. The focus of this study was to compare the differential gene expression profiles observed when this rapid morphological change takes place. Specimens of D. hylae were extracted from wild Cuban tree frogs and either flash-frozen to capture the parasitic RNA gene expression profile or cultured for 2 wk and allowed to metamorphose to their free-living stage and then flash-frozen. The extracted RNA was used for de novo transcriptome assembly, and we conducted a differential gene expression analysis using an RNA Tag-Seq approach for both the free-living and parasitic life forms. Based on these results, we identified 213 differentially expressed transcripts between the 2 developmental forms, with 190 of these up-regulated in the free-living life form. Although over half of the differential genes recovered did not result in any significant BLAST hits, many of these genes did provide insight into which molecular signals are potentially used after the parasite transforms into the free-living form. This analysis provides significant insight into differentially expressed transcripts associated with the drastic morphological changes observed in this rare case of oligochaete parasitism by D. hylae encompassing both free-living and parasitic forms.

Echinococcus is a genus of cestode parasites of paramount veterinary and medical importance globally. Two species, Echinococcus granulosus sensu lato and Echinococcus multilocularis, are endemic to North America and are the etiologic agents of cystic echinococcosis and alveolar echinococcosis, respectively. North America is currently experiencing an epidemiological shift in the state of transmission, distribution, and prevalence of E. multilocularis, following the introduction of the European variant of the parasite. The rapid expansion of the parasite into the northeastern United States has resulted in novel detections of spillover to humans, indicating the need for active surveillance to direct public health education and disease control measures. Our surveillance of the parasite in definitive hosts in New York State from 2019 to 2023 yielded 8 detections of the parasite, for a sample prevalence of 8.3% (8/96). Phylogenetic analysis of mitochondrial markers confirmed that all New York isolates belong to the European lineage and group in a well-supported clade with E. multilocularis isolates described from Slovakia and Poland. Investigation of the highly polymorphic EmsB microsatellite marker revealed several E. multilocularis genotypes circulating in New York, including 1 that is distinct from European isolates detected in western North America. These data are consistent with 1 or more unique introductions from Europe rather than a spread from western regions of Canada and the United States, where other European variants are found. Echinococcus multilocularis appears to have a complex epidemiology in North America that warrants further detailed surveillance to evaluate the risks for zoonotic transmission.

Various sanitation methods to recover helminth eggs are currently in use; however, no international standard exists. Development of such a method first involves testing the effects of all reagents used in current methods on helminth egg viability to determine whether these chemicals affect the test organism. This study was conducted to investigate the effects on viability and development of Ascaris suum eggs when exposed for various periods to wash solutions (water, ammonium bicarbonate, Tween® 20, Tween® 80, Triton® X-100, Sunlight® Liquid, bentonite, and 7X®), flotation solutions (zinc sulfate, magnesium sulfate, sodium nitrate, brine, and sucrose), extraction solutions (10% formalin, acetoacetic buffer, acid-alcohol, ethyl acetate, and diethyl ether), extraction combinations (10% formalin + ethyl acetate, 10% formalin + diethyl ether, acetoacetic buffer + ethyl acetate, acetoacetic buffer + diethyl ether, and acid-alcohol + ethyl acetate), and incubation solutions (water, 0.1 N sulfuric acid, physiological saline, and 0.5%, 2%, and 5% formalin). Ammonium bicarbonate and 7X® performed best as wash solutions (including for overnight soaking), and zinc sulfate is recommended for flotation for up to 30 min of exposure. Individually, all extraction solutions had minimal effects on egg viability, and in combination, acid-alcohol and ethyl acetate did not impact egg viability for up to 15 min of exposure. Postincubation, sulfuric acid allowed optimal egg development and clear samples for microscopy.

Many technical aspects are associated with helminth egg isolation and enumeration that affect how efficiently eggs are recovered from samples. This study investigated Ascaris egg recoverability when samples were washed with or without pressure, and from different sample types (water, effluent, ventilated improved pit latrine [VIP], urine diversion dry toilet [UDDT], dried, fatty, and septic tank sludges, and soil) when processed with water, ammonium bicarbonate, and 7X®. We also looked at egg recovery after flotation with zinc sulfate, magnesium sulfate, and sodium nitrate at specific gravities of 1.18, 1.2, and 1.3, at respective centrifugation speeds and times after washing (1,050 and 1,512 g for 5, 10, and 15 min) and after flotation (672 and 1,050 g for 5, 10, and 15 min). We found that samples should be washed under pressure to ensure full dissociation of eggs from the sample matrix and then centrifuged at 1,512 g for 10 min. For sludge samples (or samples with high-fat content), 7X produced the best egg recovery and clearest samples for microscopic analysis, while soil and soil-containing (UDDT sludge) samples were best processed with ammonium bicarbonate. Flotation was optimal with zinc sulfate at a specific gravity of 1.3 after centrifugation at 672 g for 15 min.

Completing parts of trematode life cycles in the laboratory is a useful way to obtain experimentally infected hosts and identify how specific aspects of parasitism influence host ecology and behavior. However, a lack of knowledge about host specificity and other factors that influence prevalence can hamper those efforts. Echinostoma trivolvis lineage c is a genetically distinct member of the E. trivolvis species complex that is known only from DNA sequences from adult and larval stages recovered from naturally infected muskrats (Ondatra zibethicus) and the marsh pondsnail (Ladislavella elodes), respectively. We determined the effect of host species/morphotype, host size, and miracidial dose on the infection success in potential first intermediate hosts. In the laboratory, we exposed 2 freshwater snail species (L. elodes and Planorbella duryi) and a morphological variant of L. elodes (formerly known as Stagnicola reflexa) to 2 miracidia to determine first intermediate host use. Among these 3 snail groups, we also tested the effect of host size on infection success with 3 size classes (1–5 mm, 5–10 mm, and 10–15 mm). Within 1 host species, L. elodes, we compared the effect of 2 doses (2 and 5 miracidia) and 3 size classes on infection success. At a dose of 2 miracidia, rediae and cercariae developed within 1 host species, L. elodes, as well as the S. reflexa morphotype, although infection success varied according to host size. At a dose of 5 miracidia, infection success increased in small and medium-size L. elodes relative to the low dose group. Our results confirm the first intermediate host species observed in nature but indicate that prevalence is influenced by host species morphotype, host size, and parasite dose. To obtain more infected snails, our experiments suggest exposing small and medium-size L. elodes snails to 5 miracidia. This research encourages further use of E. trivolvis lineage c in the laboratory to explore aspects of host-parasite interactions such as parasite-modified behavior.