Morphologic development of unidentified Sarcocystis sp. schizonts associated with encephalitis in a 9-wk-old gray fox (Urocyon cinereoargenteus) from Texas is described. Sarcocystis schizonts were confined to lesions. They were sparsely distributed and their staining affinity for hematoxylin and eosin varied with developmental stages; immature schizonts were deeply stained compared with mature schizonts. Most parasites were extravascular and the host cell was not identified for those that were intracellular. The parasite divided by endopolygeny, in which the nucleus became lobulated but lobes remained connected. Schizonts were up to 30 μm long and contained up to 32 merozoites/nucleus. The merozoites were slender and unlike any known species of Sarcocystis. The schizonts were distinct from Sarcocystis neurona schizonts, which cause encephalitis in many species of animals.

Host specificity is essential to understanding the ecology and evolution of parasites, and it is often complicated to estimate because of the presence of morphologically similar but genetically distinct species. Morphological identification of larval trematodes is often challenging because of the lack of diagnostic characteristics that only appear in the sexually mature adult stage. The difficulty in accurate species identification may obscure their compatibility with the host species. We investigate the parasites infecting 2 Asian mud snail species, Batillaria multiformis and Batillaria attramentaria, at 1 site where the 2 host snails co-occur to identify the level of their host specificity. We found that the morphospecies Cercaria batillariae was the most common trematode species in B. attramentaria and B. multiformis. We conducted polymerase chain reaction (PCR) -based restriction fragment-length polymorphism (RFLP) analyses of 77 C. batillariae infections in B. attramentaria and 150 in B. multiformis. We further sequenced the representative RFLP patterns to evaluate their phylogenetic relationship. We observed 6 genetically distinct species infecting 2 host species. Of those, 2 parasite species exclusively infected B. attramentaria, and 1 was found only in B. multiformis. Although 3 parasite species infected both hosts, 2 of them showed highly biased infections to either host species. Our study suggests that trematodes in the Batillaria snails can be host specific and highlighted the usefulness of molecular genetics for assessing host specificity.

Swimmer's itch is caused by the accidental penetration of human skin by various species of avian schistosomes that naturally cycle in bird and snail hosts. Little is known about the ontogeny of avian schistosomes in their vertebrate hosts, especially in wild birds. Taking advantage of the abundance of common merganser (Mergus merganser) broods on northern Lower Peninsula lakes in Michigan, we obtained fecal samples from 97 common mergansers, focusing on ducklings (n = 75) of 13 different ages but also including birds that were 1 yr and older. Miracidia hatching from fecal samples were quantified per gram of feces to determine the timeline and reproductive output of naturally acquired schistosome infections. All ducklings 18 days or younger were negative. Beginning at 21 days old, some ducklings were passing a small number of eggs, with the percentage of ducklings passing eggs increasing with age. The number of eggs passed by ducklings remained low until approximately 7 wk of age. At 52 days and older, all ducklings were passing eggs and the number of miracidia produced was frequently many times higher, strongly consistent with published mitigation studies that duckling relocation severely reduces snail infections and case reports of swimmer's itch. Surprisingly, second-year common mergansers also passed high numbers of schistosome eggs but may contribute less to successful transmission to snails based on the published success of mitigation by duckling relocation. All brooding hens sampled were positive but passed low numbers of eggs. This is the first study of the development patterns of any avian schistosome in wild young-of-the-year birds, and the patterns are compared with the few known laboratory studies on worm development.

Many human infections are transmitted through contact with household pets. The purpose of this cross-sectional study was to determine the occurrence of ticks and fleas on pets (dogs and cats) in local veterinary clinics in Statesboro, Georgia. We screened ectoparasites for Rickettsia and Bartonella and assessed owner knowledge and practices related to tick- and flea-borne diseases. Ectoparasites were collected and identified using standard taxonomic keys, and their genomic DNA was extracted. Three TaqMan assays were used to test ectoparasites for flea-borne Rickettsia DNA. Nested PCR targeting riboflavin synthase encoding gene (ribC) was used to detect Bartonella species DNA. Restriction fragment length polymorphism analysis and sequencing were used to identify the microorganisms detected. Upon providing written consent, owners completed a self-administered questionnaire to provide information concerning their knowledge and practices about vector-borne diseases. Data from 27 pets were collected from 2 veterinary clinics during September to December 2014. A total of 58 ectoparasites including fleas (n = 51) and ticks (n = 7) were collected from 19 cats and dogs. The cat flea, Ctenocephalides felis (n = 44), was the predominant flea species followed by Pulex sp. (n = 7). All ticks were Ixodes scapularis. Using PCR, RFLP, and sequencing, it was determined that the majority of cat fleas contained DNA of known human pathogens, including Rickettsia asembonensis (72.5%), Rickettsia felis (5.9%), Bartonella henselae (2%), and Bartonella quintana (7.8%). DNA of B. quintana was also detected in 2 Pulex sp. fleas and 2 ticks. Two animals had ectoparasites co-infected with Rickettsia and Bartonella. Most owners (95.7%) knew that fleas can transmit animal disease agents, but they were less aware that fleas can spread diseases to humans, and only 12.5% of owners knew about cat scratch disease. Our data indicate that there is a risk of flea- and tick-borne zoonotic infections in households owning cats and dogs. Educational materials, vector-control preventive measures, and appropriate personal attitudes and practices are needed to ensure public health safety and wholesome interactions with pets.

Toxoplasma gondii is a coccidian parasite capable of infecting humans and other warm-blooded animals, with approximately 30% of the world's population chronically infected. Workers who handle animals occupationally, such as veterinarians in small-animal practices, are at a higher risk of infection. Common risk factors among these workers include contact with cats and other animals in a clinical setting. For this reason, this study aimed to determine the seroprevalence of anti-T. gondii immunoglobulin (Ig)G and IgM antibodies among small-animal veterinary personnel in Veracruz, Mexico. Blood samples were collected from 133 healthy individuals and examined using an enzyme-linked immunosorbent assay. A detailed survey on work activities was conducted. The findings showed a 2.2% positive rate for specific anti-T. gondii IgG antibodies and a 0% rate for anti-T. gondii IgM antibodies, which underscores the need for further preventive educational programs to reduce exposure to T. gondii infection in this population.

The family Camallanidae Railliet and Henry, 1915 comprises parasitic nematodes found in the digestive tracts of fishes, amphibians, and reptiles. In this family, the taxonomic status of several genera is still under debate. Zeylanema Yeh, 1960, is a genus of uncertain status that was segregated from CamallanusRailliet and Henry, 1915. Some researchers have argued that Zeylanema is either a subgenus or junior synonym of Camallanus based on morphological characteristics. No genetic information for Zeylanema has been reported to date, and therefore the molecular phylogenetic relationships of the genus have not been investigated. In this study, nucleotide sequences for 18S and 28S ribosomal DNA and mitochondrial cytochrome c oxidase subunit I of Zeylanema worms were analyzed, and these data were combined with detailed morphological observations. Molecular phylogenetic trees based on 18S and 28S sequences were constructed. The sequences for the Zeylanema worms were included in a single Camallanus clade. This result supported the previous opinion that Zeylanema is a subgenus or junior synonym of Camallanus. These results should prompt further studies to evaluate the taxonomic status and relationships of other genera within the Camallanidae.

We describe Baccigeroides currani n. sp. (Digenea: Gymnophalloidea) infecting the intestinal mucosa of the Gulf menhaden, Brevoortia patronus Goode, 1878 (Clupeiformes: Alosidae) from the Gulf of Mexico. The new species differs from its congeners by the combination of having an oral sucker that is more narrow than (vs. equal to or larger than) the ventral sucker, ceca that extend posteriad to the middle of the post-testicular space (vs. to the level of the testes), a cirrus sac that extends posteriad to the middle of or beyond the posterior margin of the ventral sucker (vs. wholly confined to the forebody or slightly overlapping the anterior margin of the ventral sucker), a bipartite (vs. unipartite) seminal vesicle, and a post-testicular (vs. pre-testicular) ovary. We emend Baccigeroides Dutta, 1995 to include features of the new species and its congeners: ceca that extend posteriad to the middle of the post-testicular space, a cirrus sac that extends posteriad to the middle of or beyond the posterior margin of the ventral sucker, a bipartite seminal vesicle, a median genital pore, a post-testicular ovary, a dorsal Laurer's canal pore opening near the posterior body end, and an excretory system with arms merging anteriorly at the level of the pharynx. The ITS2 and 28S sequences of the new species were most similar to those of Bacciger bacciger (Rudolphi, 1819) Nicoll, 1914 (type species) and Pseudobacciger cheneyae Sun, Bray, Yong, Cutmore, and Cribb, 2014. Phylogenetic analyses of the 28S and ITS2 sequences each recovered species of Bacciger Nicoll, 1914, Baccigeroides, and Pseudobacciger Nahhas and Cable, 1964 as closely related taxa and sister to the gymnophalloids of Tandanicolidae Johnston, 1927. Bacciger was polyphyletic (B. currani, Cercaria rangiae Wardle, 1983, and P. cheneyae nested in the clade of Bacciger spp.) and requires revision. We reject the synonymy of Baccigeroides opisthonemae (Nahhas and Cable, 1964) n. comb. and Baccigeroides ovatus (Price, 1934) Cutmore, Bray, and Cribb, 2018 because they are morphologically distinct; however, both species require redescription based on the types and new specimens collected from the type host and type locality. The present study comprises the first phylogenetic analysis that includes a sequence of Baccigeroides and the first report of species of Baccigeroides infecting an alosid from the northern Gulf of Mexico.

Sucking lice are obligate parasites of eutherian mammals and are generally considered to be host-specific parasites. Molecular investigations have found that some current louse taxonomy is incorrect and does not reflect the relationships among families and species. Western chipmunks (23 species of Tamias) and the eastern chipmunk (Tamias striatus) are infested by 2 different species of Hoplopleura sucking lice, Hoplopleura arboricola and Hoplopleura erratica. Hoplopleura arboricola has been found on 19 of 23 western chipmunk species, and H. erratica has only been recorded as a parasite of T. striatus. We investigated the relationships between these chipmunk lice and louse systematic status by supplementing published sequence data with additional sequences and morphological examinations. We estimated phylogenetic relationships using 1,107 coding loci in a maximum-likelihood framework and a species tree approach. In addition to the phylogeny, we calculated raw pairwise distances of the cytochrome oxidase subunit 1 gene (COI) between clades. Both phylogenetic approaches recovered 2 well-supported clades of H. arboricola, 1 of which included H. erratica, suggesting that the 2 louse species are not distinct. Further, examination of louse specimens found no morphological traits that distinguish lice from any of the lineages, including differentiating H. erratica from H. arboricola. The average pairwise distance of COI sequences between the 2 major H. arboricola clades exceeded that of the distances between H. erratica and either of the H. arboricola clades. Based on the genetic similarities and phylogenetic relationships of the lice, it appears that an ancestral louse was associated with western chipmunks and then transferred to the eastern chipmunk. Using the phylogenetic and morphological evidence presented here, Hoplopleura arboricolaKellogg and Ferris, 1915 is relegated to a junior subjective synonym of Hoplopleura erratica (Osborn, 1896). A holotype from the type series is designated for H. erratica. These results suggest a history of chipmunk host species interactions that enabled ectoparasites to disperse between chipmunk species and illustrate the importance of phylogenomic analyses to study species interactions and the history of interspecific associations.

Fischoederius elongatus (Poirier, 1883) is a common rumen fluke found in Asia and Africa. Nucleotide sequence data for F. elongatus have been reported but are limited to certain ribosomal and mitochondrial DNA regions. High diversity in the nucleotide sequences of the mitochondrial cytochrome c oxidase subunit 1 (COI) haplotypes has been reported in some Asian countries. Some researchers have advocated the possibility of cryptic species within F. elongatus based on the high genetic diversity within the species as well as the genetic distance within and between sister species. However, the number of examined parasites, hosts, and geographic regions was limited in these studies, and the intraspecific variation of the species remains unclear. Therefore, additional studies are required to provide more insight into the genetic variation of F. elongatus. This study characterized F. elongatus in the rumen of Cambodian cattle and documented its genetic information and intraspecific variation. The flukes were morphologically identified, and the molecular structure of the 28S and COI regions was analyzed. The partial sequences of 28S from the 45 specimens yielded 2 genotypes, and the 28S sequences of F. elongatus seem to be highly conserved in Cambodia. In contrast, partial sequences of COI from 44 specimens exhibited 29 distinct haplotypes, and the similarity among the haplotypes was 92.9-99.7%, indicating high diversity of the COI sequence in the Cambodian F. elongatus population. In both 28S and COI phylogenetic trees, the present sequences formed a single clade with Gastrothylacidae species; however, the 4 genera within the family did not form genus-specific clades. These results suggest that complete species identification of Gastrothylacidae is difficult to perform based solely on the 28S and COI sequences. The molecular population genetics of F. elongatus in Cambodia were found to be highly diverse in COI sequences, and a star-like haplogroup was also detected. In addition, some haplotypes were identical to those from neighboring countries, such as India and Thailand, and no distinct country-specific haplogroups were found. Therefore, ancient domestication, artificial migration, and the contemporary import of host cattle may have involved genetic populations in these countries. Highly diverse COI haplotypes were found with few or no differences in morphology, and the diverse haplotypes found in the current and previous studies were unlikely to originate from cryptic species.

We herein describe a new species of Cathariotrematinae Bullard, 2021 (Monogenoidea: Monocotylidae Taschenberg, 1879) and propose a new genus to accommodate it. Nasigulper itsgotatao n. gen., n. sp. infects the olfactory lamellae (nose) of the deepwater gulper shark, Centrophorus granulosus (Bloch and Schneider, 1801) (Squaliformes: Centrophoridae) from the north-central Gulf of Mexico outer continental shelf. The new species was assigned to Cathariotrematinae by having a 3-part attachment organ (TAO) and by lacking open loculi that symmetrically encircle a cluster of >2 loculi in the center of the haptor. The proposal of a new genus is warranted because the new species is the only known monocotylid that has a TAO comprising 3 closed loculi with 2 relatively small hamuli flanking the posteriormost loculus. The most morphologically similar cathariotrematine genus is represented by a single species (Squalotrema llewellyni Kearn and Greene, 1983) that infects the spiny dogfish, Squalus acanthias (Squaliformes: Squalidae) in the North Sea. Nasigulper itsgotatao differs from Squalotrema llewellyni by having a TAO comprising 3 closed loculi, relatively small hamuli flanking the posteriormost loculus, and a relatively short, sinous ovovitelline duct and by lacking depressions associated with the central loculus. Squalotrema llewellyni has a TAO comprising 3 supraloculi, hamuli that are equal to the length of the posteriormost loculus, a central loculus having a central depression flanked by 2 pear-shaped depressions anterolaterally, and an extensive ovovitelline duct that is sinuous sinistral to the proximal ovary. A phylogenetic analysis of all acceptable monocotylid 28S sequences recovered the new species sister to isolates of Cathariotrema selachii (MacCallum, 1916) Johnston and Tiegs, 1922 from the Gulf of Mexico (no sequence of a species of Squalotrema exists). The new genus and species are the sixth and eighth, respectively, added to Cathariotrematinae.

In a parasitological survey of the least killifish, Heterandria formosa (Girard), from Ward Creek in Louisiana, we encountered a myxozoan parasite in the gallbladders of this host bearing myxospores consistent with a Myxidium species. Prevalence was 72.2% in 18 hosts examined, with infection characterized by the presence of sheetlike to discoid plasmodia, approximately 1-2 mm across, floating freely in the gallbladder. Myxospores were observed in the plasmodia and found floating freely in the bile and were elliptoid and fusiform in valvular and sutural views respectively. The myxospore poles were slightly pointed away from the midline of the sutural plane of the myxospore. The myxospore valve surface had 9-12 striations. Mean myxospore dimensions (range, μm) were 13.7 (13.0-14.2) long, 6.5 (5.4-7.2) wide, and 6.4 (6.1-6.7) thick. Two equal-sized polar capsules were broadly ovoid to spherical, oriented to opposite extremes of the myxospore, and contained a tubule with 4-6 coils. Mean polar capsule dimensions (and range) were 4.3 (3.6-4.9) long and 3.6 (3.2-4.4) wide. Morphologically, the myxospores of this species were distinct from those of most other Myxidium species, and for the few species where dimensions overlapped, the average dimensions were different, and host and locality were also distinct. As such, we described this as Myxidium fonti n. sp. in honor of William F. Font. Phylogenetically, M. fonti is sister to Myxidium phyllium from another poeciliid host, and these species fall into a larger biliary tract lineage of myxosporeans. The relationships support previous work that suggests that tissue specificity, with some exceptions, is important in the phylogeny of myxosporeans.

The Zygocotylidae Ward, 1917 is a compact family of amphistome digeneans that until now comprised 2 genera, each represented by a single species: Zygocotyle lunata (Diesing, 1836) Stunkard, 1916 and Wardius zibethicus Barker and East, 1915 in Barker 1915. Despite highly similar morphology, these genera are separated based on the presence (Zygocotyle) or absence (Wardius) of posterolateral projections (=lappets) on the ventral sucker and esophageal bulb. In the present study, we generated partial large ribosomal subunit (28S), internal transcribed spacer 2 (ITS2) rDNA, and cytochrome c oxidase subunit 1 (COI) sequences of Z. lunata from several hosts (12 avian and 1 rodent species) throughout North and South America as well as 28S and COI sequences of W. zibethicus from muskrat in North America. The newly generated 28S sequences were used for sequence comparison and phylogenetic analysis. The COI sequences were used for species-level comparisons. Our analysis revealed a close relationship and high sequence similarity between Z. lunata and W. zibethicus. Considering the low morphological and genetic differences, we synonymize ZygocotyleStunkard, 1916 with Wardius Barker and East, 1915 in Barker 1915 and transfer Z. lunata to Wardius as Wardius lunatus (Diesing, 1836) n. comb.

Toxoplasma gondiii recognized as one of the most successful zoonotic parasites globally, infecting a wide range of hosts including camelids. This infection can lead to serious outcomes such as abortion, neonatal death, or fetal abnormalities. Camels play a crucial role in the economic, ecological, and social landscapes of various regions, particularly in the Middle East, highlighting the importance of close health monitoring and disease screening. Hence in this study, sera from 409 dromedary camels (39 males and 370 females) were examined for T. gondii IgG antibodies using the Modified Agglutination Test (MAT). Both univariable and multivariable statistical analyses were performed using SPSS to identify the risk factors. A seroprevalence of 32% was found with 74% of the reactive specimens exhibiting a MAT titer ≤ 80. Univariate analysis ruled out sex and season as significant risk factors. Multivariable analysis confirmed age and area as statistically significant factors (P value < 0.05) associated with T. gondii seropositivity in camels. Overall, the finding of the present study confirms that T. gondii is prevalent and widely distributed in camels in suburban areas of Qatar. Given the veterinary and economic implications, there is an urgent need for further investigations into the infection's risk factors and its zoonotic impact.

This paper provides correct amended names for adeleid coccidia formerly in the genus Adelina Hesse, 1911, that now belong to the genus Obvallatus Özdikmen, 2009, and their new endings if necessary to satisfy the International Code of Zoological Nomenclature Formation and Treatment of Names (Chapter 7, Article 31.2). The morphometric and host data of Adelina castana Ghosh, Choudhury, and Misra, 2000, indicate that it is a junior synonym of Obvallatus (Adelina) tribolii Bhatia, 1937, and has been synonymized. The taxonomic status of an adeleorinid coccidium, "Adelina bambarooniae," from which sequence data (nuclear 18S rDNA-AF494058, AF494059) have been used widely in molecular phylogenetic studies of adeleorinid coccidia and wider apicomplexan taxa has been corrected. A promised species description listed in the GenBank accession associated with this Adelina sp. was never published; consequently, this species name does not satisfy the Criteria of Publication (Chapter 3, Article 8.1) expected by the International Code of Zoological Nomenclature and is a nomen nudum. The scientific community should refer to the GenBank entries AF494058 and AF494059 as an unnamed Obvallatus sp. (ex. Dermolepida albohirtum) until a formal species description of the parasite has been published.

Twenty-seven Pachycrocuta brevirostris coprolites from Taurida Cave (Early Pleistocene) were studied. Eggs of parasitic worms were found in 6 of them (22.2%). Eggs of Trematoda species were identified among them, as were eggs of Taenia, Toxocara, and Capillaria. Toxocara eggs were the most common; they were found in 15% of the coprolites. This is the earliest evidence of P. brevirostris infection by these groups of helminths.

The present work includes the description of Gyrinicola pilyolcatzin n. sp. (Nematoda: Oxyurida) collected from the large intestine of tadpoles of the Montezuma frog, Rana montezumae. Nuclear DNA and mitochondrial DNA generated via a combination of Sanger and Next Generation shotgun sequencing were used to reconstruct the species in a phylogenetic context, by including the other 4 recognized species in the genus present in North America, namely, Gyrinicola batrachiensis, Gyrinicola armatus, Gyrinicola gulabrevioris, and Gyrinicola moohsia. The distinctiveness of the species was supported by an analysis of branching patterns using Bayesian Poisson tree processes. We used morphometric evidence to enumerate the diagnostic characters that define members of this unique clade within the genus. The species shares a common ancestor with G. gulabrevioris and G. moohsia; yet it is meristically similar to G. armatus. This is the first species of the genus described in Mexico and the fifth species described in the Nearctic, as it is present in the Transvolcanic Axis of Mexico, which acts as a transition zone between the Nearctic and the Neotropics. A dichotomous key to the species in the Nearctic is offered.

Cysto-biliary fistulas are commonly diagnosed, either before or after surgical intervention, in patients with enlarged or advanced-stage hydatid cysts (HCs). Analysis of cystic contents in these patients shows that diminished scolex vitality is more common in patients with cysto-biliary fistulas. This study aims to demonstrate the scolicidal effects of bile on Echinococcus granulosus (EG) scolices at various bile concentrations and over specific periods. The time- and concentration-based scolicidal potency was analyzed in EG scolex samples obtained from HC patients. The integrity of the cyst wall and the scolicidal effect of the contents were evaluated using a vital staining technique with 0.1% eosin. Bile samples were collected from patients with cholelithiasis who were scheduled for surgery. Scolicidal efficacy of 100% was observed in all samples at the 1/4 bile concentration after 10 min and at the 1/8 concentration after 60 min. At a 1/16 concentration, scolicidal efficacy was 66% at 1 min, 89% at 10 min, 93% at 30 min, and 98% at 60 min. At a 1/32 bile concentration, scolicidal efficacy was 59% at 1 min, 68% at 10 min, 89% at 30 min, and 95% t 60 min. At a 1/64 concentration, the scolicidal efficacy was 53% at 1 min, 58% at 10 min, 77% at 30 min, and 93% at 60 min. After 1 hr, reasonable scolicidal efficacy was determined up to a 1/64 concentration; however, significant decreases in scolicidal efficacy were observed at 1/128 and 1/256 bile concentrations. Theoretically, bile, which is an endogenous secretion, can be used as a suitable and potent scolicidal agent. This study lays the groundwork for future in vivo clinical trials utilizing synthetic bile acids for scolicidal purposes or for studies evaluating the scolicidal effects of bile in patients who develop cysto-biliary fistulas.

Species of Placobdella have been the frequent subject of revisionary and alpha-taxonomy in the past 2 decades. Recent molecular analyses introduced uncertainty about the taxonomic status of several broadly distributed and morphologically variable Placobdella species, including Placobdella picta (Verrill 1872), compounded by incomplete original descriptions reliant upon characters that are no longer unique in comparison to modern congeners. We assessed specimens of P. picta to identify any distinct phylogenetic entities that align with our morphological observations of the type series and novel topotype specimens. Using mitochondrial COI and ND1 and nuclear 18S rDNA with Maximum Likelihood and Bayesian Inference, we evaluated species boundaries using species delimitation analyses (ABGD, mPTP, bPTP, and GMYC) and molecular phylogenetics. Our analyses revealed 2 species entities equivalent to 2 non-reciprocal monophyletic clades. Morphological examinations revealed the lectotype was determined to be Placobdella ornata (Verrill 1872), and paralectotypes are other leech species or were poorly preserved and unidentifiable. Due to the problems with the type series, P. picta is now considered a junior synonym of P. ornata. Based on our results, we describe 2 new species: Placobdella unimaculata n. sp. from Connecticut and Placobdella desseri n. sp. from Algonquin Provincial Park, Ontario, Canada.

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.

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.