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A new genus and species of nematode, Tziminema unachi n. gen., n. sp. is described from the caecum and colon of Baird's tapir Tapirus bairdii (Gill, 1865), found dead in the Reserva de la Biósfera El Triunfo, Chiapas State, in the Neotropical realm of Mexico. Tziminema n. gen. differs from the other nine genera included in the Strongylinae by two main characteristics: having 7–9 posteriorly directed tooth-like structures at the anterior end of the buccal capsule, and the external surface of the buccal capsule being heavily striated. Phylogenetic analyses of the DNA sequences of the mitochondrial cytochrome c oxidase and nuclear DNA, including a partial sequence of the internal transcribed spacer 1, 5.8S and a partial sequence of the internal transcribed spacer 2 of the new taxon, confirmed its inclusion in Strongylinae and its rank as a new genus. [ABSTRACT FROM AUTHOR]

Pterygodermatites (Paucipectines) baiomydis n. sp., an intestinal parasite of the northern pygmy mouse, Baiomys taylori (Cricetidae), collected in La Yerbabuena, Colima, Mexico, is described herein. Specimens were studied using light and scanning electronic microscopy. This is the 19th species of the subgenus Paucipectines described worldwide and the fourth collected in Mexico. It is differentiated from the remaining species in the subgenus by having 25 perioral denticles, arranged in a triangle (seven on each lateroventral margin, and eleven on the dorsal margin), and 10 pairs of caudal papillae.

In the Reserva Ecológica del Pedregal of San Ángel, located in the south of Mexico City, Mexico, free-roaming dogs and cats coexist with 148 bird, 33 of mammal, 23 of reptile and seven amphibian species, that represent a remnant of the original fauna of the Mexican Plateau. The negative impact that dogs and cats have on local fauna is unobjectionable, however, the role that these introduced vertebrates play as potential transmitters of infectious diseases for native fauna and humans, is much less understood. Information about parasitic infections in native and introduced animals in this location is scarce. In order to ameliorate this lack of information, the objective of this study is to characterize the helminth fauna of the free-ranging dogs and cats of the ecological reserve. Between 2018 and 2023, 36 Felis silvestris catus and 7 Canis lupus familiaris were studied from the helminthological perspective. Endoparasites were obtained from the digestive tract and were identified to the species level using morphological and molecular evidence. Hosts were parasitized by eight species of helminths: in cats the cestodes Hydatigera taeniaeformis, Mesocestoides sp., Taenia rileyi and the nematode Toxocara cati were recorded, while in dogs, the cestode Taenia pisiformis and the nematodes Ancylostoma caninum, and Uncinaria stenocephala were found. The only species shared between cats and dogs was the cestode Dipylidium caninum. These free-ranging animals act as definitive hosts of 5 species known to have zoonotic potential; their presence in the area may generate a public and animal health problem if programs of dog and cat population control are not continued., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Camacho-Giles et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Human population is exposed to numerous parasitic ichthyozoonoses. Although Tamaulipas state (northeastern Mexico) is well known for its fishing and aquaculture industry, there are few reports of this type of zoonosis. Therefore, it is imperative to investigate whether the parasites that affect these fish may represent a zoonotic risk for the inhabitants of the area. The objective of this study was to identify molecular and/or morphologically muscle parasites of fish from coastal locations in Tamaulipas, Mexico, and assess the risk of infection for humans. Between 2017 and 2018, 764 individual fish belonging to 28 species were examined for parasites. Collected worms were processed for their identification using morphological characteristics. In addition, partial sequences of the large subunit (28S) ribosomal RNA gene were obtained from some species to corroborate their identity. Prevalence and mean intensity of all registered infections were calculated. A total of seven species of parasites were found: cestodes (Poecilancistrium caryophyllum), trematodes (Clinostomum tataxumui, Clinostomum cichlidorum), nematodes (Eustrongylides sp., Contracaecum sp.) and pentastomids (Sebekia purdieae, Sebekia sp.). Parasites infected 10 species belonging to different fish families (Ariidae, Centrarchidae, Centropomidae, Cichlidae, Eleotridae, Ictaluridae, Mugilidae and Sciaenidae). Congeneric species of parasites or related to those registered in this study have been identified as zoonotic agents in other regions of the world. Despite the low levels of infection (2.6-16.6% prevalence and 1-5.5 parasites per infected host), there is a latent risk of transmission to humans, so it is recommended to avoid eating raw or undercooked fish meat., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Gastrointestinal helminths of migratory waterfowl can cause several lesions that may affect the health and even the survival of their hosts. As part of an ongoing project that aims to inventory the helminth species that infect this group of birds, as well as the histopathologic lesion they cause, a total of 200 digestive tracts of nine species of anatid birds ( Spatula discors, S. cyanoptera, S. clypeata, Mareca strepera, M. americana, Anas crecca, A. acuta, A. platyrhynchos diazi, and Oxyura jamaicensis ) were collected in the Atarasquillo marsh of Lerma, in the State of Mexico. The present work had a twofold goal: to determine the taxonomic identity of the helminth species present in waterfowl as well as their infection levels and to describe the lesions caused by gastrointestinal parasites in migratory and resident anatids in Atarasquillo marsh, State of Mexico. The specimens were examined using routine helminthological and histopathological techniques. A total of 23 helminths were identified: six trematodes ( Zygocotyle lunata, Notocotylus triserialis, Notocotylus seineti , Psilochasmus oxyurus, Australapatemon burti and Cotylurus magniacetabulus ), four cestodes ( Cloacotaenia megalops, Fimbriaria fasciolaris, Gatrotaenia cygni and Diorchis sp.), eleven nematodes ( Echinuria uncinata, Tetrameres sp., Tetrameres fissispina, Hystrichis sp ., Streptocara sp., Amidostomum sp., Epomidiostomum uncinatum, Capillaria sp., Capillaria contorta, Ascaridia sp. and Heterakis sp.) and two acanthocephalans ( Pseudocorynosoma constrictum and Filicollis sp.). At the proventriculus level, Echinuria uncinata caused the most severe lesions; in the gizzard, Amidostomum sp. and E. uncinatum produced hemorrhages and necrosis. Finally, the main lesions found in the intestine (necrosis, heterophilic granulomas and the formation of lumps on the serosa) were caused by the implantation of the acanthocephalans' proboscis. Eleven species of gastrointestinal helminths found are new records for the Lerma marshes, as well as the first record in Mexico of the nematode Capillaria contorta and the acanthocephalan Filicollis sp., Competing Interests: The authors declared that no conflicts of interest exist., (© 2020 The Author(s).)

In this work, we document for the first time four species of Ichthyostraca in Mexico, one Branchiura: Argulus foliaceus (fish parasite), and three Pentastomida: Porocephalus clavatus (reptile parasite), Raillietiella hebitihamata (reptile parasite) and Raillietiella orientalis (frog parasite). In addition, a total of 11 new host records and 16 new localities are presented for Ichthyostraca in Mexico. Based on the compilation of published information and on specimens deposited in scientific collections, the first checklist of Ichthyostraca from North America (Canada, United States of America and Mexico) is compiled. To March 2019, records of Ichthyostraca from North America include 64 species and 8 undetermined taxa, parasitizing 293 host species (64 of them identified only to a supra-specific level) in 77 provinces and states (8 from Canada, 47 from the USA, and 22 from Mexico). The subclass Branchiura is represented by 1 order, 1 family, 1 genus, 35 species and 1 undetermined taxa; the subclass Pentastomida includes records of 4 orders, 9 families, 14 genera, 29 species and 7 undetermined taxa. Ten species reported in this work are thought to be introduced into North America with only a few records of them parasitizing native hosts. This checklist summarizes the available records of this class of crustaceans in North America and represents a base line for future studies.

Some Onchocercidae nematodes such as Pelecitus are parasites of medical and veterinary importance. The adult stage of Pelecitus has been reported infecting birds, and the microfilaria has been associated to human blindness. However, in some of these cases, the nematode was incompletely identified at the species level due to the scarcity of morphological taxonomic keys and, also, to the lack of molecular diagnostic analysis. Here, we report a new Pelecitus species in a crested caracara (Caracara cheriway) producing a severe tenosynovitis and microfilarial dermatitis. It is also the first record of Pelecitus in an American bird of prey. Clinical and histopathological features are described, contributing towards our understanding of the pathogenesis of Pelecitus and the health and conservation of wild bird populations. Our study also provides new information on the molecular diagnosis of this parasite and highlights the potential role of wild birds as Pelecitus reservoirs, and health risk for humans and wildlife.

During August 2010, a total of 66 cane toad Rhinella marina were collected in Laguna de Coyuca, Guerrero, Mexico and examined for the presence of helminths. Ninety-two percent were parasitized by 1 or more parasite species. A total of 4624 individuals were found, belonging to 8 helminth taxa (1 digenean, 1 cestode and 6 nematodes). Infracommunities harbored by this host species are highly variable (mean Jaccard similarity index 0.31±0.27); mean percent similarity index 0.26±0.32) and depauperate (mean richness 1.91±0.92; mean abundance 64.4±100.34); almost 50% of them were dominated by Rhabdias fuelleborni, a skin-penetrating nematode. Differences related to host gender and size were found, since males registered infracommunities with lower species richness and diversity than females. The reproductive condition of females (collected during the breeding season) might explain the results obtained; during this season, females invest less in resistance to infection in favor of investing resources in reproduction. However, confirmation of this statement can only be made by sampling in the dry season, when the toads do not reach their reproductive peak., (Copyright © 2017 Elsevier B.V. All rights reserved.)

We detected macroscopic Sarcocystis cysts in a Northern Shoveler ( Anas clypeata ) in the Lerma Marshes, State of Mexico, Mexico in February 2014. The 5.0×2.0-mm macrocysts in the breast muscle of the duck were ovoid and yellow. Using an optical microscope, we saw parasitic forms of a Sarcocystis sp. among muscular fibers; the cysts measured 3.5×1.1 mm. The external wall had a smooth surface and the internal wall had a spongy texture. We identified the macrocysts as Sarcocystis rileyi according to sequences of the 18S rRNA gene, 28S rRNA gene, and ITS-1 region. Sarcocystosis should be considered in similar assessments in wild waterfowl in Mexico. Awareness of S. rileyi among anatids in the Lerma Marshes will contribute to more-effective conservation and management actions.

A new nematode species, Foleyellides rhinellae sp. nov. (Onchocercidae), is described from specimens found in the body cavity of the cane toad, Rhinella marina (Linnaeus) (Anura, Bufonidae), in the Laguna de Coyuca, Guerrero, in the Pacific slope of Mexico. The new species differs from the other nine species of Foleyellides by infecting bufonid anurans and by the number and arrangement of caudal papillae. Other distinguishing feature of the new species is the size of the left spicule (0.16-0.23 long), the smallest recorded among the species included in the genus. Foleyellides rhinellae sp. nov. is the second known species of the genus recorded from amphibians of Mexico.

Pathogen cross transmission between wildlife and domestic animals represents an extinction risk for wildlife; however, reliable verification is difficult to perform, and in some cases, it is even considered unlikely to be conducted. The aim of this work was to identify cross transmission of helminths between feral cats and captive wild felids at a zoological park in southeastern Mexico. Feces were collected from jaguars (Panthera onca), cougars (Puma concolor), ocelots (Leopardus pardalis), margays (Leopardus wiedii), and jaguarundis (Puma yagouaroundi). A flotation technique and macroscopic sieving were performed on the feces. Additionally, as part of the noxious fauna control program of the park, feral cats were captured and euthanized. To perform parasitologic studies, helminths from these animals were recovered. Toxocara cati and Trichuris campanula were shared by jaguarundis and feral cats. Ancylostoma sp. was found in jaguar and ocelot and Ancylostoma tubaeforme in feral cats. Additionally, during this study, a couple of jaguarundis died with clinical signs of trichuriasis. This is the first report of T. campanula in jaguarundi. Because feral cats roam freely in the park, transmission could occur from these vertebrates to wild felids. This study shows the risk that parasites represent to wild felids; a similar situation could be found in free-living species, especially in fragmented habitats that favor contact with domestic animals.

Oswaldocruzia lamotheargumedoi n. sp., inhabiting the intestine of the cane toad, Rhinella marina (L.), in Laguna de Coyuca, Guerrero, México, is described here. The new species differs from 10 congeners infecting bufonid hosts because it has a type I bursa. In contrast, 7 of these species have type II bursa and 3 more a type III bursa. The species most similar to the species described herein is Oswaldocruzia pipiens Walton, 1929 . These 2 species share traits such as body size, bursa type, presence of cervical alae, and dorsal ray morphology. Nevertheless, both species can be distinguished based on the number of synlophe ridges at mid-body (54-56 for O. lamotheargumedoi vs. 45-48 for O. pipiens) and by the presence of a chitinous support in the long, and well developed, cervical alae of O. pipiens. In the new species, these structures are short, poorly developed, and lack chitinous support. Previous records of species of Oswaldocruzia in México include Oswaldocruzia subauricularis (Rudolphi, 1819) Travassos, 1917 in the Neotropical Realm and O. pipiens in the Nearctic.

In order to better understand how patterns of parasitism in howler monkeys are affected by forest fragmentation, we carried out a 1 year survey of gastrointestinal parasites in fecal samples from three groups of Mexican howler monkeys inhabiting different forest fragments in the Los Tuxtlas Biosphere Reserve, Mexico. The study groups were chosen because the conditions in which they lived suggested a potentially negative gradient for parasite richness and a positive gradient for levels of parasitism. We report for the first time the presence of Entamoeba coli in Alouatta palliata mexicana and of hookworms (Family Ancylostomidae) in A. palliata. A reduction in home range size and an increase in disturbance was associated with a loss of parasite richness, which in general was high. Parasite prevalence and the proportion of contaminated samples in which each parasite taxon was present was also high in general and there were no differences between groups. A factor related to the generally high levels of parasitism in our study groups could be the high humidity in the study area, because this favors the survival of parasitic free forms and increases the chances of infection. This would also account for the tendency towards higher levels of parasitism observed in the rainy season. Finally we did not find a pattern relating sex and parasitism.

A new species of nematode, Cucullanus costaricensis n. sp., is described from the Red Sea catfish Bagre pinnimaculatus from Río Tempisque, Costa Rica. The new species is characterized by the following traits: spicules and gubernaculum length (0.48 +/- 0.02 [0.45-0.50] and 0.20 +/- 0.02 [0.18-0.21], respectively); a protruding cloacal region in males, and the arrangement of caudal papillae (1 medial unpaired precloacal papilla and 10 pairs of papillae: 3 precloacals [first pair subventral and anterior to ventral sucker; second and third pairs posterior to ventral sucker; second pair asymmetric and subventral; third pair slightly subventral and closer to cloacal opening], 3 subventral adcloacal pairs [pairs 4-6], and 4 pairs of postcloacal papillae [seventh pair lateral, eighth pair subdorsal, ninth and tenth pairs subventral]); and lateral phasmids between the seventh and eighth pairs of postcloacal papillae. This finding represents the first record for a species of Cucullanus in Central America.

Thirty-four adult cane toads Bufo marinus L. (12 males and 22 females) collected from 2 localities in Mexico (Cerro de Oro and Temascal Dams, Oaxaca) in September 2003 were examined for helminth parasites. In total, 14,749 helminths belonging to 14 taxa were collected. Included were 2 adult digeneans (Choledocystus hepaticus, Mesocoelium monas); 1 larval cestode (an unidentified pseudophyllidean); and 11 nematodes, including 3 species of larvae (Contracaecum sp., Physaloptera sp., Physocephalus sexalatus) and 8 species of adults (Aplectana itzocanensis, Cosmocerca sp., Cruzia morleyi, Ochoterenella digiticauda, Oswaldocruzia sp., Raillietnema sp., Rhabdias americanus, and Rhabdiasfuelleborni). Higher species richness was recorded in B. marinus from Cerro de Oro (12 taxa versus 9 in those from Temascal); hosts from both localities shared 7 taxa. There were 25 new locality records, and 2 taxa were registered in Mexico for the first time. To date, 112 helminth species have been recorded parasitizing B. marinus along its native and introduced range of distribution, with 40.5% of them reported from Mexico.

We analyzed 19 samples of Baird's tapir feces from La Sepultura Biosphere Reserve, collected between March and July 1999. We also took samples directly from a male tapir captured at the Montes Azules Biosphere Reserve. Both reserves are in Chiapas, Mexico. We used five techniques: flotation, MacMaster, micrometric, Ritchie's sedimentation and Ferreira's quantitative. In addition, we collected ectoparasites from animals captured in both reserves and from a captive couple from Tuxtla Gutierrez, Chiapas. These nematodes and protozoans were found: Agriostomun sp., Lacandoria sp., Neomurshidia sp., Trichostrongylus sp., Strongylus sp., Brachylumus sp, and an unidentified species of ancilostomaide. We also found Eimeria sp. and Balantidium coli, as well as the mites Dermacentor halli, Dermacentor latus, Amblyomma cajannense, Amblyomma coelebs, Amblyomma ovale, Anocentor nitens and Ixodes bicornis.

Gnathostoma lamothei n. sp., inhabiting the stomach of Procyon lotor hernandezii Wagler, 1831, in Tlacotalpan, Veracruz State, and Rio Sapo, Oaxaca, Mexico, is described. This new species differs from all other congeners by having the posterior half of the body surface covered by rows of tiny round bosses instead of spines, or lacking ornamentations. Sequences of the ITS2 of the ribosomal DNA of G. lamothei n. sp. are compared with sequences of other species of the genus recorded in Mexico; they show a wide divergence (<50%) with Gnathostoma binucleatum Almeyda-Artigas, 1991, and Gnathostoma turgidum Stossich, 1902, and high similarity with Gnathostoma sp. I sequence (99.2%). On the basis of morphometric traits and sequences, previous records of Gnathostoma sp. I (=Gnathostoma procyonis of Almeyda-Artigas et al., 1994, not Chandler, 1942, and Gnathostoma neoprocyonis nomen nudem) in Mexico are referred to as the new species.

Hysterothylacium perezi n. sp. is described from the intestine of the "cuatete" Ariopsis guatemalensis Günther, 1864 (Osteichthyes: Ariidae), in Tres Palos, a coastal lagoon located in the Mexican Pacific basin. The new species differs from all other species of Hysterothylacium Ward and Magath, 1917, in possessing a spinous postcloacal pad. In addition, H. perezi is readily distinguished from the 21 species described in fishes from America and Hawaii by having the greatest number of caudal papillae (47 to 51 pairs + 1 single, precloacal papillae). This species is the third described from hosts inhabiting estuarine environments in America and the fourth reported in Mexico.

Gnathostomiasis is an emerging zoonosis in Mexico. However, for most endemic zones, the source of human infection has not been established. During 2000-2003, we investigated 2168 vertebrates (2047 fish, 31 amphibians, 4 reptiles, 19 birds and 67 mammals) from 39 localities distributed in nine states. We registered 7 vertebrate species as new hosts for Gnathostoma, and 22 new locality records for this nematode.

The goal of this study was to provide further information about helminth parasites of Virginia opossum Didelphis virginiana Kerr, 1792 from Mexico. During routine faunal investigations between 1958 and 2001, 101 opossum were necropsied. Nineteen taxa of helminths were collected, representing 13 genera from hosts in 27 localities from Mexico. There are 58 new locality records, with 6 species recorded in Mexico for the first time: Brachylaima virginiana Dickerson, 1930; Cruzia americana Mapleston, 1930; Didelphonema longispiculata (Hill, 1939); Didelphostrongylus hayesi Prestwood, 1976; Viannaia didelphis Travassos, 1914; and Viannaia viannai Travassos, 1914. This increases the number of helminth taxa previously known for this host in Mexico to 28.

In order to clarify the specific identity of the etiological agent of human gnathostomosis in Nayarit State, Mexico, morphological and molecular studies were conducted on advanced third stage larvae obtained from human and fish tissue. Cathorops fuerthii from Agua Brava lagoons complex, was the only fish species found to be infected among four species surveyed. Morphological variability does not allow specific identification of the larvae. Internal transcribed spacer 2 of the ribosomal DNA was sequenced for six larvae (five from fish, one from human tissue). Low divergence in the sequences of Nayarit larvae and Gnathostoma binucleatum (0.24% or less) indicate that the larvae examined belong to this species.

Re-examination of capillariid specimens collected from the freshwater fish Chirostoma estor Jordan from Lake Pátzcuaro in 1985-1986 and deposited as paratypes of Capillaria patzcuarensis Osorio-Sarabia, Pérez-Ponce de León & Salgado-Maldonado, 1986 showed that their morphology was in contradiction with the description of this species and, in fact, they could be identified as the species originally described as C. appendiculata Freitas, 1933 from cormorants Phalacrocorax brasilianus (Gm.) in Brazil; conspecific capillariid specimens were later recorded from Chirostoma estor and Cyprinus carpio L. from the same locality. This species and two others are transferred to Ornithocapillaria Barus & Sergeeva, 1990 as O. appendiculata (Freitas, 1933) n. comb., O. carbonis (Dubinin & Dubinina, 1940) n. comb., and O. phalacrocoraxi (Borgarenko, 1975) n. comb. This is the first record of O. appendiculata in Mexico. Its occurrence in fishes suggests that these nematodes may be acquired by their fish hosts accidentally while feeding on cormorant excrement containing mature nematodes. A female capillariid collected from one of 110 Chirostoma estor examined from this locality in April, 1998 was identified as Capillaria patzcuarensis. Both capillariid species are briefly described and illustrated.

Juveniles of Contracaecum multipapillatum infected the Mayan cichlid (Cichlasoma urophthalmus) and adults infected the olivaceous cormorant (Phalacrocorax olivaceus) and the great egret (Casmerodius albus) in the coastal lagoon at Celestun, State of Yucatan, Mexico. All are new host records, and, even though the geographic locality record of Mexico for the species has not been published, unidentified but presumably conspecific specimens have been reported from there. When juveniles of C. multipapillatum were fed to a kitten, but not rats, ducks, or chickens, they developed into adults. Measurements and morphological data are provided on the specimens from the kitten. Development of an avian ascaridoid in the intestine of a mammal increases the potential of this widespread species to infect other mammals, including humans.