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The Pacific thread herring, Opisthonema libertate, is a fishery resource in the eastern tropical Pacific, yet its population dynamics are poorly understood. The aims of this work were to document the metazoan parasite species in O. libertate from the Gulf of California in Mexico, determine latitudinal changes in their infection levels, and assess their potential as biological tags. Six parasitic species were identified: Myosaccium ecaude and Parahemiurus merus digeneans, Cribromazocraes cf. travassosi and Mazocraeoides georgei monogeneans, Pseudoterranova sp. nematodes, and Lepeophtheirus sp. copepods. The monogenean and copepod species are reported for the first time in O. libertate. Many fish were infected with digeneans, and there was a rare occurrence of other parasites. While the prevalence and median intensity of M. ecaude and P. merus significantly varied among sampling localities, a multivariate analysis revealed a distinct separation between some localities; these results suggest that individual fish form several discrete populations. However, the utility of these parasites as biological tags will be further probed because they cannot satisfy all requirements for good biological tags. The present results might be helpful in complementing other techniques to determine the movement and stock structure of O. libertate, albeit with certain limitations. [ABSTRACT FROM AUTHOR]

Nematodes are among the most common parasites in aquatic mammals. Because of their cuticular covering, these worms are frequently collected from the examination of feces or stranded hosts. This work provides new records of three nematode taxa infecting three different aquatic mammal species (Lontra longicaudis annectens, Trichechus manatus, and Zalophus californianus) in Mexico. Additionally, it brings together all available published records about this country's nematode fauna parasitizing aquatic mammals. The aim is to describe the current state of the art, which sets the basis for the strategic design of future research. Given the diversity of printed sources recording nematode fauna, we gathered literature, including theses and articles in journals profiled in the Journal Citation Reports or similar academic databases. The compiled information shows that 24 nominal nematode taxa have been reported from 11 species of aquatic mammals in Mexico. Our study exhibits irregular patterns of geographic distribution and host spectrum, existing entire marine ecoregions, and numerous host species lacking records. [ABSTRACT FROM AUTHOR]

Two new species of Viannaia from the intestine of the North American opossums, Didelphis virginiana (Virginia opossum), and Philander opossum (gray four-eyed opossum), are described based on morphological and molecular data, through an integrative taxonomic approach. Maximum likelihood and Bayesian inference analyses for each dataset and the concatenated dataset were performed using a mitochondrial cytochrome c oxidase subunit 1 (COI) gene, and the nuclear ribosomal internal transcribed spacer region (ITS1–5.8S–ITS2). The phylogenetic analyses revealed 2 new species that occur in Mexico, one from the western state of Colima and another from the southern state of Chiapas. Our phylogenetic trees for both molecular markers and concatenated datasets yielded similar topologies with high bootstrap values and posterior probabilities. Viannaia is recovered as a monophyletic group, but the family Viannaiidae appears as non-monophyletic, due to the position of Travassostrongylus scheibelorum, similar to previous studies. Finally, the morphology of Viannaia and Hoineffia is discussed. [ABSTRACT FROM AUTHOR]

Sixty-eight lizards representing 4 species (Aspidoscelis mexicanus, Sceloporus horridus, Sceloporus ochoterenae, and Urosaurus bicarinatus) collected from the locality of Santiago Tamazola in the Mixteca Region of Oaxaca, Mexico were examined for gastrointestinal helminths. One species of Cestoda, Mesocestoides sp. (tetrathyridium larvae), and 2 species of Nematoda, Physaloptera retusa and Spauligodon garciaprietoi were found. Physaloptera retusa had the highest prevalence (85%) in S. horridus and was found parasitizing all 4 lizard species, and S. garciaprietoi had the most numerous helminth (n = 626) in A. mexicanus. The helminths are generalist and have indirect life cycles with the exception of S. garciaprietoi. We provided new host and distribution records for the 3 helminth species (Mesocestoides sp., P. retusa, and S. garciaprietoi) and present the first helminth reports for S. horridus, S. ochoterenae, and U. bicarinatus. Further, Mesocestoides sp. tetrathyridia is reported for the first time in Oaxaca State. This work contributes to the helminth fauna associated with lizards from Mexico. [ABSTRACT FROM AUTHOR]

An inventory of parasites infecting the jaguar (Panthera onca) across its distribution range is relevant for the conservation of this threatened big cat. In this study, we report the occurrence of helminths in a jaguar from Mexico using morphological techniques (cleared and stained mounts and scanning electron microscopy) and partial sequences of the 28S ribosomal RNA (28S rRNA) gene and the cytochrome c oxidase 1 mitochondrial (COI) gene. We also provide an updated list of helminth species reported in jaguars in the Americas. Three helminth taxa are identified in the jaguar examined from Mexico: Toxocara cati, Physaloptera sp., and Taenia sp. The new 28S rRNA sequences of To. cati, Physaloptera sp., and Taenia sp. and the COI sequence of Taenia sp. corroborate the identity of the helminths isolated from this host. One hundred and twenty-nine records of helminths parasitizing jaguars from 49 studies up to May 2023 were identified in the Americas. In most of these studies (73.6%), helminths were identified using coproparasitological techniques. Sixteen helminths (7 nematodes, 5 cestodes, 3 acanthocephalans, and 1 trematode) were identified at the species level in free-ranging and captive jaguars. The study demonstrates the value of an integrative taxonomy approach to increase the accuracy of parasite identification in wildlife, especially when helminth specimens are scarce or poorly fixed., (© American Society of Parasitologists 2024.)

The knowledge of the long-distance dispersal mechanisms of meiofauna is still limited. Rafting is considered as the main mechanism of dispersal of the meiofauna. The recent events of the Sargassum spp. arrival in the Caribbean provides the opportunity to explore long distance mechanisms. Four samples of floating Sargassum spp. were collected from the water column in Xcalak, Quintana Roo, which arrived at the Reef lagoon and Mangrove fringe. A total of 425 organisms were present, 388 nematodes, 36 tardigrades, and a single acarus. Tardigrades were represented by three species, whereas nematodes were represented by 16 morphotypes. The population of both tardigrades and nematodes was composed of mature and juvenile specimens. One tardigrade was collected during their ecdysis process. Our results suggest that not only the nematodes, but also tardigrades and acari can reach the floating Sargassum spp., maintaining in the algae, growing, and reproducing, while they are transported in the sea. We can conclude that in the Caribbean Sea, the floating Sargassum spp. floating is a dispersal mechanism of nematodes and tardigrades., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hosts provide the main environmental traits parasites have to deal with, resulting in covariation between both associates at both micro‐ and macro‐evolutionary scales; phylogenetic analyses of highly host‐specific parasites have shown that parasite and host phylogeny might be highly congruent, and adaptation of a host species to new environments may lead to concordant changes of their parasites. Procamallanus (Spirocamallanus) neocaballeroi is a highly host‐specific parasitic nematode of the Neotropical freshwater fish genus Astyanax in Mexico. One of the host species of the nematode is the emblematic Mexican tetra, A. mexicanus, which exhibits two contrasting phenotypes, a cave‐dwelling morph (with troglomorphic features), and the surface‐dwelling morph; other congeneric species inhabit rivers and lakes, and some of them occur in sympatry, displaying trophic specializations. Here, we explored the hypothesis that contrasting environments (surface rivers vs cave rivers), and host morphological divergence (sympatric ecomorphs in a lacustrine environment) might result in the divergence of their parasites, even though the hosts maintain a cohesive genetic structure as the same species. To test the hypothesis, several populations of Astyanax spp. were sampled to search for P. (S.) neocaballeroi. The nematode was found in 10 of the 52 sampled sites; two localities corresponded to cave populations. The phylogenetic analysis based on COI sequences yielded three major lineages for P. (S.) neocaballeroi. We found no concordance between the three lineages and the habitat where they occur in Astyanax mexicanus, even considering those living in drastic environmental conditions (caves), or between these lineages and lacustrine ecomorphs of Astyanax aeneus and A. caballeroi occurring in sympatry. Instead, genetic lineages of the nematode exhibit a clearer pattern of host species association and geographical distribution; our results showed that P. (S.) neocaballeroi is experiencing an incipient divergence although the morphological study of lineages shows no conspicuous differences. [ABSTRACT FROM AUTHOR]

Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae) is described from the lung of the nauyaca viper Bothrops asper in Puebla State, central Mexico. This new species is the fifth of the genus described having onchia. Among the species included in this group, the new species is morphologically closest to S. viperidicus and S. atroxi. However, it differs from both species mainly by having only one excretory gland (compared to two present in S. viperidicus and S. atroxi). In addition, S. mexicanus n. sp. can be separated of S. viperidicus by tail length, shape of vulval lips, geographic distribution and host species and from S. atroxi by body length, number of papillae in the cephalic region, as well as the host species and geographic distribution. In the present study, we propose the new species based on morphological, host spectrum and genetic evidence. Phylogenetic analysis indicated Serpentirhabdias as a monophyletic group, with two subgroups that are congruent with the presence/absence of onchia in the esophagostome, host association and other relevant morphological characters., (© 2024. The Author(s).)

Specimens of Foleyellides were collected from the body cavity of frogs in different regions of Mexico; Lithobates brownorum from Yucatán, Quintana Roo and Campeche; L. megapoda from Jalisco and Rhinella marina, from Guerrero. Foleyellides calakmulesis n. sp. is described based on specimens found parasitizing L. brownorum. The new species is distinguished from the other members of the genus by the combination of the following male characters: four pairs of caudal papillae different in size and the presence of a preanal plaque. Partial DNA sequences of the mitochondrial Cytochrome Oxidase C, subunit I of the four known Mexican species of Foleyellides and two potentially new species collected in this study were generated and compared, validating the erection of the new species., (© 2023. The Author(s).)

Introduction: Defoliation and light competition are ubiquitous stressors that can strongly limit plant performance. Tolerance to defoliation is often associated with compensatory growth, which could be positively or negatively related to plant growth. Genetic variation in growth, tolerance and compensation, in turn, plays an important role in the evolutionary adaptation of plants to changing disturbance regimes but this issue has been poorly investigated for long-lived woody species. We quantified genetic variation in plant growth and growth parameters, tolerance to defoliation and compensation for a population of the understorey palm Chamaedorea elegans. In addition, we evaluated genetic correlations between growth and tolerance/compensation. Methods: We performed a greenhouse experiment with 711 seedlings from 43 families with twelve or more individuals of C. elegans. Seeds were collected in southeast Mexico within a 0.7 ha natural forest area. A two-third defoliation treatment (repeated every two months) was applied to half of the individuals to simulate leaf loss. Compensatory responses in specific leaf area, biomass allocation to leaves and growth per unit leaf area were quantified using iterative growth models. Results: We found that growth rate was highly heritable and that plants compensated strongly for leaf loss. However, genetic variation in tolerance, compensation, and the individual compensatory responses was low. We found strong correlations between family mean growth rates in control and defoliation treatments. We did not find indications for growth-tolerance/compensation trade-offs: genetic correlation between tolerance/compensation and growth rate were not significant. Implications: The high genetic variation in growth rate, but low genetic variation in tolerance and compensation observed here suggest high ability to adapt to changes in environment that require different growth rates, but a low potential for evolutionary adaptation to changes in damage or herbivory. The strong correlations between family mean growth rates in control and defoliation treatments suggest that performance differences among families are also maintained under stress of disturbance. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The chigger species Acomatacarus coahuilensis n. sp. (Acariformes: Trombidiformes: Leeuwenhoekiidae) inhabiting the neck scales of the wary spiny lizard Sceloporus cautus Smith, 1938 (Squamata: Iguania: Phrynosomatidae), from Chihuahuan Desert Province, Coahuila, Mexico, is described herein. The new mite species is assigned to the genus AcomatacarusEwing, 1942, based on a palptarsus with 6 branched setae plus the tarsala (ω). This new species can be separated from the other species in this genus mainly based on the combination of the following characters: presence of mastisetae (MTa) on tarsus III and tibiala (φ) on tibia III, subterminala (ζ1), parasubterminala (z), and pretarsala (ζ2) on tarsus I, 2 genualae (σ1-2) on genu I, onychotriches and claw-like empodium of legs I-III, and absence of mastisetae on tibia III. In addition to the new species, the gastrointestinal nematode Skrjabinoptera phrynosoma (Ortlepp, 1922) Schulz, 1927 (Physalopteridae), was also found, which represents a new host record in the wary spiny lizard. This study reports the third species of the genus Acomatacarus recorded from Mexico and the first record of chigger mites and helminth parasites associated with Sc. cautus., (© American Society of Parasitologists 2023.)

Copyright of Therya is the property of Asociacion Mexicana de Mastozoologia, A. C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective was to evaluate the effect of the resistance of ewes to gastrointestinal nematodes (GIN) on the parasitologic and productive performance of their lambs during preweaning and postweaning periods. Offspring from 44 Pelibuey ewes classified as resistant or susceptible to GIN were evaluated. During the preweaning period, birth weight (BW), live weight (LW) at 35 and 70 days of age, and live weight changes (LWC) were determined in 73 lambs. During the postweaning period, 20 lambs to susceptible or resistant ewes were evaluated. The lambs were challenged under natural GIN infections and artificial infection with L3 of Haemonchus contortus. The fecal egg count (FEC), hematocrit (HT), peripheral eosinophil count, plasma protein, LW, and LWC were determined. There were no differences among parameters evaluated during preweaning (P > 0.05). The type of lambing (single or multiple) affected the BW, LW, and LWC (P < 0.01). The sex (male) of the lamb had a positive effect on BW at 35 and 70 days of age (P < 0.05). After weaning, lambs of susceptible ewes showed higher FEC than resistant ewes (P < 0.05). The HT of lambs to resistant ewes was higher than those the susceptible group (P < 0.01). In conclusion, offspring of resistant ewes show low FEC compared with those susceptible during the postweaning stage., (© American Society of Parasitologists 2023.)

Two species of pinworms, Trypanoxyuris atelis and Trypanoxyuris atelophora were collected from the black-handed spider monkey ( Ateles geoffroyi ) in several localities across southeastern Mexico, representing the first record for both species in Mexican primates. Identification of pinworm species was based on morphological and molecular data. These pinworms are distinguished from other congeners, and from each other, by the buccal structure, the lateral alae, and the morphology of the oesophagus. Phylogenetic analyses based on sequences of the mitochondrial cytochrome c oxidase subunit 1 gene placed T. atelis as the sister species of Trypanoxyuris minutus, a parasite of the howler monkey Alouatta palliata , and T. atelophora as the sister species of T. microon , a parasite of the night monkey, Aotus azarae . These relationships were supported with high posterior probability values by Bayesian inference. Comparisons of additional pinworm taxa from Neotropical primates are needed to assess oxyurid diversity, and to better understand the evolutionary relationships among these nematodes and their primate hosts. [ABSTRACT FROM AUTHOR]

Most of the available knowledge in the literature on Mexican fishes and their parasites refers to information within political divisions and/or hydrological basins in the country. Indeed, only a few studies have analyzed the helminth fauna of these vertebrates as a biological group distributed nation-wide. This lack of available knowledge prevents the study of several basic and applied aspects involving fish-parasite interactions at different spatial and temporal scales. In this dataset, we compiled all the available geographic information on fish-helminth parasite interactions involving native and exotic fish species recorded in continental waters throughout the Mexican territory. After an exhaustive filtering and the curation of information, our data set contains 5999 records of 361 freshwater fish species (roughly 70% of known freshwater fish species occurring in Mexico) and 483 endo- and ectoparasitic helminths collected over an 85-year period (from 1936-2021) in 1070 localities distributed throughout Mexico. These records are mainly concentrated in only a few states located to the south and east of the country; although all states have been sampled and all major basins in Mexico are represented. The fish order with the highest number of records was Perciformes (n = 2325, 38.75%) while the fish family with the highest number of records was Cichlidae (n = 1741, 29.02%). Native species of fishes corresponded to 92.14% of the records (n = 5528) and fish-associated parasites were found in 41 habitat types in/on their host bodies. Regarding fish parasites, we found that most of the records are from the phylum Platyhelminthes (n = 4495, 74.92%). At the class level, we observed that Trematoda reached the highest number of records (n = 2965, 49.42%). Moreover, we found that Diplostomidae (n = 917, 15.25%) were the family of trematodes with the highest number of records. Most parasites were registered in their adult stage (n = 3730, 62.17%), followed by larval stages (n = 2267, 37.78%). We hope that the fish-parasite interactions data set will encourage researchers worldwide to explore different ecological and coevolutionary aspects of fishes and their helminth parasites, as well as provide useful information for the better implementation of conservation initiatives. There are no copyright restrictions; please cite this data paper when using its data in publications or teaching events., (© 2022 The Ecological Society of America.)

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. [Display omitted] • Fish species for human consumption in Tamaulipas are infected with larval parasites. • Species of platyhelminthes, nematodes and pentastomids were identified taxonomically. • Parasites were related to species known as etiological agents of human parasitosis. • Infection levels were low, but there is a latent risk of human infections. [ABSTRACT FROM AUTHOR]

Parasites cause losses in animal production. Parasite infection in ruminants has been estimated to be a major problem causing more than 3 billion USD per year, from which 60% corresponds to the sheep industry. Treatment is based on the use of synthetic anthelmintics; however, repeated application or under dosage have resulted in the selection of nematodes resistant to anthelmintics. The objective of the present work was to perform a diagnosis of gastrointestinal parasites in sheep kept under different zootechnical management. Ninety female sheep were used, most of them pregnant. Sampling was performed monthly from December 2015 to June 2016 (flock 5 until April). Fecal samples were collected from the rectum; the McMaster technique was performed, morphological characteristics were observed, oocysts and eggs were counted per gram of feces (opg and epg), frequency and intensity were obtained. Faecal culture was performed for feces that had a positive result, infective larvae were obtained and taxonomically identified. At the end of the study, a dewormer (fenbendazole) was administered and its effect was measured. The frequency of gastrointestinal parasites was 100%. The highest opg was 3,600 (flock 3, March, 2016), the epg for cestodes was 2800 (flock 1, January, 2016) and for gastrointestinal nematodes (GIN) was 25,000 (flock 1, May, 2016); the intensity was variable and it was increased by peripartum. Protists (Eimeria spp), cestodes (Moniezia) and nematodes (Haemonchus, Trichostrongylus, Cooperia, Chabertia ovina. Teladorsagia, Oesophagostomum, Nematodirus and Trichuris ovis) were identified. No previous diagnosis is performed in flocks, and sometimes dewormers are administered, even though resistance to ivermectin and benzimidazole is suspected. Flock management, its feeding system and its conditions were determinant for the observed results; therefore, it is necessary to count with a diagnosis that provides information about the parasitic population and its dynamic, in order to carry out a selective and comprehensive control that has an impact on the animal, human and environmental health., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new species of Rhabdochona is described as a parasite of two endemic species of catfishes ( Ictalurus dugesii and Ictalurus pricei) from two river basins in central and northern Mexico (Río Ameca and Río Tunal). Rhabdochona ictaluri sp. nov. is characterized by a combination of morphological traits that include the presence of basal teeth, bifurcated deirids, absence of a dorsal barb in left spicule and length ratio between spicules. The combination of these traits readily distinguishes the new species from all its congeners, including those species possessing 14 teeth in the prostom. The new species appears to be specific to freshwater ictalurids. [ABSTRACT FROM AUTHOR]

Abstract: A cross sectional survey was performed to identify gastrointestinal helminths and protozoans in naturally infected horses from the biosphere reserve known as “La Sierra Madre de Chiapas”, Mexico (El Triunfo and La Sepultura). During a three-year survey, fecal samples from 90 horses and parasites from 2 necropsied animals were collected. Five families from the Nematoda class: Ascaridae, Kathlanidae, Oxyuridae, Strongylidae and Trichostrongylidae were found, whereas, only one family from the class Cestoda, was observed: Anoplocephalidae. One family from the class Insecta, was observed: Gasterophiilidae. The number of species of parasites ranged from 13 to 18 with an average of 15 per animal. Adult parasites were recovered from the large intestine luminal contents at necropsy. Species recovered included: Strongylus vulgaris, S. equinus, S. edentatus, Oxyuris equi, Parascaris equorum, Coronocyclus coronatum, C. labiatus, C. labratus, Cyathostomum tetracanthum, Cylicocyclus insigne, C. leptostomus, Cylicodontophorus bicoronatus, Cylicostephanus asymetricus, C. bidentatus, C. minutus, C. longibursatus, Petrovinema poculatum, Poteriostomum imparidentatum, Cylicostephanus goldi, Tridentoinfundibulum gobi, Triodontophorus serratus and T. tenuicollis. One species of Diptera were recovered from stomach and identified: Gasterophilus intestinalis. Furthermore, different species of protozoa were recovered from fresh horse-dung and identified in four classes: Sporozoa, Litostomatea, Ciliasida and Suctoria. Nine families: Cryptosporidiidae, Eimeriidae, Balantidiidae, Buetschliidae, Blepharocorythidae, Cycloposthiidae, Spirodiniididae, Ditoxidae, Acinetidae; and 31 ciliates species were recorded: Allantosoma dicorniger, A. intestinalis, Alloiozona trizona, Blepharosphaera intestinalis, Blepharoprosthium pireum, Blepharoconus benbrooki, Bundleia postciliata, Didesmis ovalis, D. quadrata, Sulcoarcus pellucidulus, Blepharocorys angusta, B. cardionucleata, B. curvigula, B. juvata, B. uncinata, B. valvata, Cycloposthium bipalmatum, C. edentatum, C. scutigerum, Charonina equi, Ditoxum funinucleum, Spirodinium equi, Tetratoxum unifasciculatum, Triadinium caudatum, T. galea, T. minimum and Tripalmaria dogieli. Other ciliate observed and recorded was Ochoterenaia appendiculata. This study describes the biodiversity and distribution of common and new helminths and protozoas found in the gastrointestinal tract from horses in the biosphere reserve “Sierra Madre de Chiapas” in Mexico. [Copyright &y& Elsevier]

The article discusses research on the nematode species Cucullanus oaxaquensis recovered from the intestine of freshwater fish Thorichthys helleri from the Río Modelo, Los Chimalapas, Oaxaca, Mexico. An electro-fishing machine was used to collect the yellow cichlid. The head end and oral opening of the nematodes are described as rounded and dorsoventrally elongate, respectively. The prevalence and range of intensity of nematodes in 10 fishes examined is 40%. The length of spicules and gubernaculum differentiates C. oaxaquensis from C. oceaniensis.

This is a first record of Probstmayria tapiri in Mexico found in 60(41.09%) fecal samples from Baird's tapir (Tapirus bairdii) in the Biosphera Reserves "La Sepultura" and "El Triunfo" in the Sierra Madre de Chiapas, Mexico. Morphological characteristics of small nematode spindle-shaped forms truncated anteriorly and with a long, gradually attenuated, acutely pointed tail. Mouth with tree lips, pharynx elongated, aesophagus with tree portions: Anterior portion, long and slender, posterior portion, shorter, and pyriform portion, with a bulb. The excretory pore is situated near oesophagi bulb and ventral surface of the body. Vulva of female at about the middle of the body. Spicules asymmetrical and curved. On the ventral surface of the tail there are nine small postanal papillae. These results allow us to extend their geographic distribution of nematode to Central America and another species of Tapir's (T. bairdii). Finally we emphasized that the environmental conditions of La Sierra Madre de Chiapas, are optimal for the biological development of this nematode from tapirs of Central and South America [ABSTRACT FROM AUTHOR]

Distribution records of 152 adult helminth taxa parasites of freshwater fishes in Mexico were analysed to determine areas of high richness and endemism. Distribution maps were prepared for each taxon and overlaid onto a map of Mexico divided into 1 × 1 degree grid-cells. Richness was determined by counting recorded helminth species in each grid-cell. A corrected weighted endemism index was calculated for each grid-cell, and the relationship between richness and endemicity was analysed with an Olmstead–Tukey corner test of association. Five areas of high richness and endemism were identified: (1) Los Tuxtlas and the Papaloapan river basin, on the Gulf of Mexico; (2) the Grijalva-Usumacinta basin near the Gulf of Mexico coastal plain; (3) the Yucatan Peninsula; (4) the Sierra de Manantlán Biosphere Reserve in western Mexico; and (5) the Pátzcuaro lake, in central Mexico. The distribution of richness and endemism of helminth parasites of freshwater fishes in Mexico is congruent with distributional patterns described for other freshwater taxa in Mexico. Patterns of richness and/or endemism in the studied areas can be explained by the ichthyological composition of their bodies of water. The present study establishes an objective way of analysing the relationship between richness and endemicity, and suggests that helminths can make valuable contributions to regionalization of geographical areas and for identification of rich and biologically complex areas with potential for conservation of aquatic systems. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 435–444. [ABSTRACT FROM AUTHOR]

This study aimed to describe the shedding pattern of gastrointestinal parasite eggs by a wild population of desert bighorn sheep (DBS; Ovis canadensis) in northern Mexico. Seventy-five fresh faecal samples were collected from the ground in each season within an hour after being expelled by these animals. The generalized linear mixed model showed that eggs per gram of faeces were highest in winter (577 ± 399) and lowest in summer (260 ± 198). Generalized linear models revealed that Strongyloides spp. predominated during most seasons with a peak in summer (85% of faecal samples analysed) and the absence of this helminth in winter. Nematodirus spp. was another helminth present in three seasons, with the presence of this nematode in 35% of the faecal samples in spring and 0% in summer. Other parasites in DBS faeces included Bunostomun spp., Trichostrongylus spp., Cooperia spp., Mecistocirrus digitatus, Haemonchus contortus, Chabertia ovina and Eimeria ovinoidalis. There were differences among seasons in the percentage of these helminths and coccidia in faecal samples for all these parasites. It was concluded that helminths egg output in DBS in a semi-arid rangeland is lowest in summer and spring and highest in autumn and winter. Furthermore, it was shown that DBS in the study site do not suffer from severe parasite burden. Therefore, this nematode parasite burden is compatible with the conservation and well-being of this particular population.

Dispharynx nasuta is a widespread nematode parasite located in the proventriculus. This parasite may cause mortality in free-living birds or in captivity. However, reports of this parasite in psittacines are scarce. In a private aviary, in Zamora, Michoacan, Mexico six red-rumped parrots (Psephotus haematonotus) died in one month, from mid-August to mid-September 2016, and one more specimen died during the examination. Prior to death, the birds presented depression, ruffled feathers, crop atony, and regurgitation. Upon necropsy, ulcers in the proventriculus, and hemorrhagic content associated with the presence of round worms was observed. At histopathology examination, the parasites were identified as Spirurida nematodes, located in the proventricular and ventricular mucosa. Specimens were submitted to the parasitology laboratory of the College of Veterinary Medicine and Husbandry, National Autonomous University of Mexico (UNAM), where the parasites were identified as D. nasuta. This is the first report of D. nasuta in P. haematonotus and the first report of D. nasuta in Mexico., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Gut bacteria may coexist with other groups of organisms, such as nematode parasites, that inhabit the gastrointestinal tract of primates; however, the possible effects of endoparasites on bacterial communities are frequently overlooked. Here we explored whether infection with Trypanoxyuris, an oxyurid gastrointestinal parasite, is associated with changes in the gut bacterial community of wild black howler monkeys (Alouatta pigra), by comparing gut bacterial communities of consistently infected individuals and individuals that never tested positive for Trypanoxyuris throughout different months across the year. We additionally controlled for other sources of variation reported to influence the primate microbiome including individual identity, social group, and seasonality. Trypanoxyuris infection was not related to differences in gut bacterial alpha diversity, but was weakly associated with differences in gut bacterial community structure. In contrast, among the covariates considered, both individual identity and social group were more strongly associated with variation in the howler gut bacterial community. Our results suggest that gastrointestinal parasites may be associated, to some extent, with shifts in the gut bacterial communities hosted by free-ranging primates, although a causal link still needs to be established. Further studies of wild primate hosts infected with parasite species with different pathogenicity are needed to better elucidate health-related consequences from the parasite-microbiome interplay., (© 2021 Wiley Periodicals LLC.)

Surveys on parasites of bats from the Americas have been conducted, but information on helminths is still scarce, especially in the Neotropical region. In Mexico, there are species of bats that lack of a record for helminth species, such as members of the family Noctilionidae. The present study describes for the first time the helminths of Noctilio leporinus in Campeche, Mexico. In 2017, six specimens of N. leporinus were studied for helminths. The species identification of helminths was based on morphological studies and molecular analysis of fragments of the 28S rDNA. All bat specimens were infected for at least one helminth species. Three helminth taxa were identified: the trematode Pygidiopsis macrostomum , and the nematodes Tricholeiperia cf. proencai , and Heligmonellidae gen. sp. The morphological identification of P. macrostomum was confirmed by sequence analysis of 28S rDNA gene. The phylogeny of P. macrostomum grouped our sequence with other sequences of the same species collected in Brazil. The phylogenetic tree of Heligmonellidae gen. sp. indicated that the helminth belongs to clade formed by the species Odilia bainae , Nippostrongylus magnus and Nippostrongylus brasiliensis of the family Heligmonellidae. The phylogenetic analysis of the 28S sequences of T. cf. proencai did not show any similarity or close affinity with nematodes from which that gene has been sequenced to date. The findings of the present study increase the number of helminth species parasitizing bats in Mexico. [Display omitted] • Helminths were collected from the bat Noctilio leporinus in Mexico. • Morphological characterization and molecular data of helminths were provided. • One species of trematode and two of nematodes were reported. [ABSTRACT FROM AUTHOR]

The present study explored the frequency of hair-sheep farms with gastrointestinal nematodes (GIN) resistant to albendazole sulfoxide (AS), ivermectin (IVM) and levamisole (LEV) in the Yucatán peninsula, México, using the faecal egg count reduction test (FECRT), and compared the frequency of farms diagnosed with resistance using three different formulae. The survey included farms from the states of Campeche (9) and Yucatán (14) (2016-2019). Collaborating farms had >100 grazing ewes. Animals in the FECRT were > 12 months old, received no anthelmintic for >8 weeks and had ≥150 GIN eggs per gramme of faeces (EPG). Animals were distributed to respective groups: untreated controls, AS (5 mg/kg BW), IVM (0.2 mg/kg BW), and LEV (7.5 mg/kg BW). Due to low EPG, some farms only included one or two AH groups. Second faecal samples were obtained on day 14 post-treatment to estimate the percentage reduction (%R) and 95% confidence interval (95%CI). Criteria to declare resistance were those proposed by the World Association for the Advancement of Veterinary Parasitology. Three formulae were used to estimate resistance frequency: The RESO© and eggCounts-T:C, which considered treated and control EPG means post-treatment, but differed in their 95%CI estimation, while the eggCounts-T:T only considered pre- and post-treatment EPG means with 95%CI. The RESO© and eggCounts-T:C formulae resulted in the same frequency of IVM resistant farms for Campeche (100%; 9/9) and Yucatán (92.9%; 13/14), while, the eggCount-T:T formula resulted in a frequency of 85.7% (12/14) IVM resistance in Yucatán. The three formulae estimated the same frequency of AS resistant farms in Campeche (100%; 9/9) and Yucatán (87.5%; 7/8). The RESO© and the eggCounts-T:C formulae resulted in the same frequency of LEV resistant farms for Campeche (44.4%; 4/9), and Yucatán (60.0%; 6/10), but the eggCounts-T:T formula resulted in a frequency of 40.0% (4/10) LEV resistance in Yucatán. The FECRT using RESO© or eggCounts-T:C formulae are stricter than the eggCounts-T:T as the latter cannot identify what proportion of the %R cannot be attributed to the AH. The untreated control group helped adjusting the %R calculation and seemed more adequate considering the propensity of hair-sheep to reduce their EPG on their own. ., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Three new species of the genus Longior Travassos Kloss, 1958 are described and illustrated, namely L. surieli n. sp. in Antillanax dominicanus (Doesburg, 1953) from the Dominican Republic, L. lamothei n. sp. in Passalus punctiger Le Peletier Serville, 1825 from Mexico and Colombia and L. zumpimito n. sp. in P. punctatostriatus Percheron, 1835 from Mexico. These constitute the first records of the genus Longior for the aforementioned countries, rising to nine species in the genus. The new species can be differentiated mainly by the length of their body, oesophagus and tail in both sexes, the extension of the lateral alae in the females and the morphology of the cephalic and posterior end in the males. The molecular phylogeny of the new taxa is inferred by the 28S and 18S rDNA and they form a monophyletic clade with other Longior species. The phylogeny of Longior and that of their passalid hosts reveal coevolutionary relationships. These patterns suggest that the phylogeny of Longior species is probably strongly influenced by the evolutionary trajectories of their passalid hosts.

Salamanders of the tribe Bolitoglossini Hallowell are a highly diversified group of amphibians, and their helminth parasite fauna has been scarcely studied. Some species of plethodontid salamanders distributed along the Trans-Mexican Volcanic Belt, in central Mexico, were sampled, and their helminth parasites were recovered for taxonomic identification. Specimens of a pharyngodonid nematode from 2 species of bolitoglossines of the genus Pseudoeurycea Taylor were morphologically identified as Batracholandros salamandrae (Schad, 1960) Petter and Quentin, 1976. These specimens were studied in further detail through light and scanning electron microscopy and were sequenced for 2 ribosomal genes and 1 mitochondrial gene to test the hypothesis of whether B. salamandrae is a species widely distributed in salamanders across the Nearctic biogeographic region, or if it represents a cryptic species complex. Our molecular results revealed that these specimens consisted of 2 genetic lineages in concordance with host species, although with slight morphological differences among specimens in each of them. A thorough study, including the generation of molecular data from individuals from other areas of North America, and the examination of type specimens, is required to test the reliability of these morphological differences and to corroborate the species identity of the 2 genetic lineages., (© American Society of Parasitologists 2020.)

Wild and domestic populations of waterfowl garner economic benefits, as they are hunted for human consumption or as a recreational activity. Waterfowl migrate to their wintering grounds in Mexican wetlands where habitat conditions are more favourable. In this study, we present a list of helminth species sampled from the gastrointestinal tract of 59 wild birds belonging to the family Anatidae in three localities of Mexico, and a checklist of the helminth parasite fauna of the members of the family in the whole country, built from literature records. After helminthological examination, 25 taxa were identified: eight trematodes; four cestodes; 12 nematodes; and one acanthocephalan. Obtained records dated from 1943 to 2019. Our literature search yielded 563 records corresponding to 95 parasite taxa: 38 trematodes, 24 cestodes, 23 nematodes and ten acanthocephalans. In Mexico, 17 anatid species have been studied for helminths. Records correspond to 55 locations from 20 Mexican states. An insight gained from the collated literature and recent records was that trematodes represent the most diverse parasite group in anatids in Mexico. We briefly discuss that the information about helminths parasitizing waterfowl will be useful for understanding the effect of habitat loss and pollution of wetlands where migratory birds spend the breeding season, for addressing ecological programs aimed to guarantee the health and conservation of North American migratory birds or the effect of bird migration in the composition of the helminth parasite communities, and for freshwater biologists interested in the understanding of freshwater ecosystem health.

The genus Rhabdochona Railliet, 1916 is one of the most speciose group of nematodes, parasites of freshwater fishes, with approximately 103 species described worldwide. Twenty-two species have been recorded in the Americas, 14 of them in Mexico. In this paper we describe a new species of Rhabdochona on the basis of light and scanning electron microscopy and molecular tools. Rhabdochona adentata n. sp. was recovered from the gallbladder of the freshwater Oaxaca killifish, Profundulus oaxacae (Meek, 1902) (Profundulidae) captured in the Río Grande, State of Oaxaca, Mexico. Rhabdochona adentata n. sp. differs markedly from its congeners by possessing an unusual prostom lacking anterior teeth, small simple deirids, and the location of the excretory pore at the level of the union of the muscular and glandular esophagus. Sequences of cytochrome c oxidase subunit I (COI) from mitochondrial deoxyribonucleic acid and the D2 + D3 domains of the large ribosomal subunit (28S) were obtained from 3 specimens and were analyzed using maximum likelihood and Bayesian inference analyses. Phylogenetic analyses using COI and 28S genes recovered 1 new lineage of Rhabdochona. The new species is described on the basis of a detailed morphological study. This parasite represents the first species of Rhabdochona without prostomal teeth and with a different site of infection, the gallbladder., (© American Society of Parasitologists 2020.)

A new species of the nematode Triumphalisnema Kloss, 1962 (Oxyuridomorpha), is described from the wood beetle Proculejus hirtus Truqui from the mountain mesophilic forest in Hidalgo State, Mexico. Triumphalisnema zuuei n. sp. is distinguished from the other 4 congeners species by the presence of an expanded cervical ring, well-developed lateral alae, an obtuse cauda with a short and bifurcated caudal appendage, series of cuticular folds at ventral and dorsal body surface from excretory pore level to anal region, and ellipsoidal eggs ornamented with numerous small mushroom-like structures over the surface. The phylogenetic position of the new species is inferred based on a Maximum Likelihood and Bayesian Inference analysis of partial sequences of 18S SSU rRNA . The phylogenetic analysis showed that Triumphalisnema zuuei n. sp., the only representative of the Traklosiidae in our study, is closely related to Coynema poeyi and species of Longior, Hystrignathus, and Lepidonema, all of them members of Hystrignathidae. These relationships are supported by high support values. The present study increases to 5 the number of species assigned to Triumphalisnema, all of them parasites of Passalidae. Additionally, a taxonomic key to the species of the genus is provided.

Snappers from the southern Gulf of Mexico (SGM) and Mexican Caribbean (CAR) were examined for parasitic nematodes to determine their richness, composition, and infection parameters (prevalence and mean intensity). From February 2016 to March 2018, 431 individuals of 8 snapper species were collected in 6 localities. In all, these fishes were parasitized by 2,275 individual nematodes belonging to 13 taxa: Terranova sp. was found in 7 of 8 host species and showed the highest prevalence (23%), while the rest had lower values (<10%). Lutjanus griseus (Linnaeus) harbored the highest species richness (10 species), followed by Lutjanus apodus (Walbaum) (8 species). Most localities were similar in terms of species richness but differed in the specific composition. Eight nematode taxa represent new host records for the family Lutjanidae (Gill), thus increasing to 22 the nematode taxa in the SGM and CAR. There is a potential risk to public health due to the presence of nematodes with zoonotic potential (as Anisakis sp.) and the habit in the region of eating raw fish (cebiche).

A new species of nematode, Ascarophis morronei n. sp. (Cystidicolidae), is described from the stomach wall of the woolly sculpin Clinocottus analis (Cottidae) collected in the rocky intertidal from northwestern Baja California, Mexico. Collected nematodes were studied using both light and scanning electron microscopy. Sequence fragments for 18S rDNA molecular markers were obtained from the new nematode species, in order to test its position within the family Cystidicolidae under a phylogenetic context. Main characters distinguishing this new species include the reduced labia and the morphology of the eggs, distances of nerve ring and excretory pore from the anterior end, and left spicule of males. The new species described here is the second for the genus Ascarophis reported as adult in the Southern California Bight, and the first one recorded for the fish genus Clinocottus .

Plant metabolites have been used for many years to control pests in animals and to protect crops. Here, we reviewed the available literature, looking for the species of Mexican flora for which extracts and metabolites have shown activity against pest insects and parasitic nematodes of agricultural importance, as well as against nematodes that parasitize domestic cattle. From 1996 to 2018, the search for novel and eco-friendly biopesticides has resulted in the identification of 114 species belonging to 36 botanical families of Mexican plants with reported biological effects on 20 insect species and seven nematode species. Most plant species with detected pesticide properties belong to the families Asteraceae, Fabaceae, and Lamiaceae. Eighty-six metabolites have been identified as pesticidal active principles, and most have been terpenoids. Therefore, the continuation and intensification of this area of research is very important to contribute to the generation of new products that will provide alternatives to conventional pesticide agents. In addition, future studies will contribute to the recognition and dissemination of the importance of propagating plant species for their conservation and sustainable use.

The objective of the study was to evaluate phenotypic resistance against gastrointestinal nematodes in Blackbelly, Pelibuey and Katahdin ewes before pregnancy in the humid tropics of Mexico. Individual faecal and blood samples were taken in 59 Pelibuey, 69 Blackbelly and 73 Katahdin ewes. The egg count per gram of faeces (EPG) of gastrointestinal nematodes (GINs) was determined. The percentage of packed cell volume (PCV) and body condition score (BCS) of each animal were also recorded. The ewes were segregated as susceptible, intermediate or resistant based on the EPG using the quartile method. The data were analysed using the general linear method, and the means between breeds were compared by Tukey's test. The relationships between the EPG, PCV and BCS were evaluated by Spearman correlation. The Katahdin ewes showed the highest EPG counts (3613.6 ± 5649) compared to the Blackbelly and Pelibuey ewes (576.1 ± 1009 and 56.8 ± 187, respectively, P < 0.01). The PCV values between breeds were similar (P > 0.05). The susceptible ewes had the highest EPG counts and the lowest PCV percentage (5069 ± 6404 and 22.8% ± 8.1% respectively) compared to the resistant ewes (P < 0.01). A higher percentage of Katahdin ewes were susceptible compared to the other breeds (P < 0.05). The main GIN species were Haemonchus contortus, Trichostrongylus colubriformis and Cooperia curticei. In conclusion, Katahdin ewes showed susceptibility to GIN compared to Blackbelly and Pelibuey ewes before the pregnancy period in the humid tropics of Mexico.

The genus Rhabdochona includes more than 100 species infecting freshwater fishes in all zoogeographical regions of the world. In Mexico, 12 nominal species of Rhabdochona have been recorded. Of these, Rhabdochona ictaluri was originally described as a parasite of endemic catfishes of the family Ictaluridae; however, the species was later considered on morphological grounds as a junior synonym of Rhabdochona kidderi. In this study, newly sampled specimens of R. ictaluri were obtained from the type host and type locality and were used to perform a detailed morphological analysis and molecular phylogenetic inferences through one mitochondrial and two nuclear genes; data were used in an integrative taxonomy context to test the taxonomic status of R. ictaluri. This approach proved to be very useful to confirm the validity of this species, and robust species limits were established between these two putative species considering morphology, molecular data, host association, and biogeography.

Six new species of Geomonhystera (Nematoda, Monhysterida: Monhysteridae) Andrássy, 1981, are described and illustrated, five from México and one from Ecuador. The new species have many features in common and in common with at least several other species of the genus. Consequently, those features individually are not very useful for species-level diagnosis. They include the cuticular striation which, under light microscopy, ranges from fine to apparently smooth; however, scanning electron micrographs reveal very fine cuticular striation on all the new species. All the new species have a few body setae scattered along the length of the body and the vulval lips of females are slightly protruding. As for other species of the genus, there is considerable overlap in the ranges of standard morphometric characters so a combination of standard and additional morphometrics, as well as qualitative characters, is necessary for species separation. Geomonhystera mexiquense sp. n., collected from moss on a rock and on the trunk of Quercus crassipes in Juchitepec, México State, México, has outer labial setae that are unsegmented and 44-67% of the head width, the cephalic setae are thin, unsegmented and 31-50% of the head width; the vulval lips protrude slightly. Geomonhystera michoacana sp. n., collected from moss on a rock in Tzararacua National Park, Uruapan, Michoacan State, México, has a very finely-striated cuticle which appears almost smooth and bears rare cervical and caudal setae; the tail is long, 15-17% of the body length, and the rectum also is long, 23-32 (27±2.0) µm. Geomonhystera longispiculata sp. n., collected from an epiphytic plant in the botanical garden of the Ecology Institute in Jalapa, Veracruz State, México, is distinguished from all the species of the genus by the long, slender spicules, 55-85 (75±3.0) µm. The cuticle has conspicuous fine striation and there are somatic setae scattered along the body. Geomonhystera ecuatoriana sp. n., collected from moss on the trunk of Scalesia pedunculata growing on the twin volcanoes of Isla Santa Cruz, Galapagos, Ecuador, has fine cuticular striation and a few small body setae; the unsegmented outer labial setae are 42-54% of the head width and the cephalic setae are thin, unsegmented and 33-45% of the head width; the vulval lips protrude slightly and the vulva-anus distance is 37-48 µm or 2.1-2.5 times anal body diameter. Males of G. ecuatoriana have slightly arcuate spicules, 35 µm long. Geomonhystera galindoi sp. n., collected from moss on the trunk of Quercus peduncularis in San Pablo Ixzayo, Texcoco, México State, México, has fine cuticlar striation and a few fine body setae, the vulval lips are slightly protruding; the vulva-anus distance is 35-50 (41±0.9) µm, 1.5-2.2 (1.9±0.2) times anal body diameter. Males of G. galindoi are slightly ventrally curved with the posterior end strongly curved, giving the body a hook-shaped appearance. Geomonhystera chiautzingoensis sp. n., collected from moss on the trunk of Crataegus mexicana in Chiautzingo, Puebla State, México, has exceedingly fine striation of the cuticle and outer labial and cephalic setae that are less than 50% of the head width. Additionally, G. dubia Siddiqi Shahina, 2004 was sollected in soil samples around a plum tree (Prunus sp.) in the garden of Montecillo Campus, Colegio de Postgraduados, Texcoco, México State, México This species has a small body with fine cuticular striation and a few sparsely-distributed body setae; the outer labial and cephalic setae are unsegmented, 5-8 and 3-5 µm long, 56-80% and 33-50% of the head width, respectively; the vulval lips protrude slightly but are sometimes flush with the body contour.

As part of an ongoing inventory of the helminth parasites of freshwater fishes in Mexico, 570 individual fish were collected between Apr 2008 and Oct 2011 in 26 localities along the Cuatro Ciénegas region in Coahuila State, northern Mexico. Seventeen species of hosts, mostly corresponding to Nearctic freshwater elements, were studied. A total of 8324 individual worms were collected during this survey, representing 25 species of helminths, of which 9 were digeneans, 3 monogeneans, 3 acanthocephalans, 9 nematodes and 1 cestode. Most of the records in this checklist represent new host or locality records. The information provided in this checklist may be helpful for our understanding of the biodiversity and historical biogeography of this host-parasite system, because in the Cuatro Ciénegas region occur a Nearctic freshwater fish fauna, along with Neotropical and endemic elements, and from a biogeographical point of view, this may represent a transitional area., (© 2013 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.)

The gray fox (Urocyon cinereoargenteus Schreber, 1775) is the most abundant and opportunistic wild canid in Mexico. However, the parasites of this canid in Mexico are poorly known, and an intensive parasite survey is lacking. A survey of gray fox parasitological feces was conducted in El Cimatario National Park, a protected area representative of the seasonally dry, tropical highlands of Mexico. Feces were collected in six 1-km-length transects during the summer of 2003 and spring of 2004. The coproparasitoscopical survey registered nine species of nematodes, typical of wild and domestic canids such as Strongyloides stercoralis, Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, Dioctophyme renale, Trichuris vulpis, Trichuris sp., and Capillaria sp. Ecological factors such as temperature and humidity appear to play a more important role in the establishment of these species of parasites in this protected area than the presence of domestic dogs.

The diversity of parasites found on Nyctiphanes simplex and Nematoscelis difficilis (Order Euphausiacea) was compared during 10 oceanographic cruises made off both coasts of the Baja California peninsula, Mexico. We tested the hypothesis that N. simplex has a more diverse parasitic assemblage than N. difficilis because it is a neritic species, has larger population abundance, and tends to form denser and more compact swarms than N. difficilis. These biological and behavioral features may enhance parasite transmission within swarms. We detected 6 types of ectoparasites: (1) epibiotic diatoms Licmophora sp.; (2) Ephelotidae suctorian ciliates; (3) Foettingeriidae exuviotrophic apostome ciliates; (4) an unidentified epicaridean cryptoniscus larvae (isopoda); and 2 castrators: (5) the ectoparasitic Dajidae isopod Notophryxus lateralis and (6) the ellobiopsid mesoparasite Thalassomyces fagei. We also detected 7 types of endoparasites: (1) an undescribed Collinia ciliate (Apostomatida); 3 types of Cestoda: (2) a Tetrarhynchobothruium sp. (Trypanorhyncha), (3) Echinobothrium sp. (Diphyllidea: Echinobothyriidae), and (4) unidentified metacestode; (5) a Trematoda Paronatrema-like metacercaria (Syncoeliidae); (6) the nematode Anisakis simplex (L3); and (7) Polymorphidae acantocephalan larvae (acanthor, acanthella, and cystacanth larval stages). N. simplex is affected by all types of parasites, except the isopod N. lateralis, having a considerably larger parasitic diversity and prevalence rates than N. difficilis, which is only infested with 3 types of ectoparasites and T. fagei. Euphausiid swarming is an adaptive behavior for reproduction, protection against predators, and increased efficiency in food searching, but has a negative effect due to parasitism. Although the advantages of aggregation must overcome the reduction of population and individual fitness induced by parasites, we demonstrated that all types of parasites can affect approximately 14% of N. simplex individuals. Collinia spp. endoparasitoids must occasionally have a significant influence on population mortality with potential epizootic events.

Five strains of entomogenous nematodes, Steinernema carpocapsae strains DD, Mexican, SR, and Heterorhabditis bacteriophora strains 1S5 and HP88, were tested for their pathogenicity to various developmental stages of five African tick species namely; Rhipicephalus appendiculatus, R. evertsi, Amblyomma variegatum, A. gemma, and Boophilus decoloratus. In engorged female R. appendiculatus, all nematodes at a concentration of 1,000 infective juveniles (IJ)/dish, except S. carpocapsae Mexican strain, induced high mortalities (56-100%), whereas in engorged female R. evertsi, only S. carpocapsae DD and H. bacteriophora HP88 induced high mortalities (78% and 56%, respectively). In engorged B. decoloratus, S. carpocapsae DD, Mexican, SR and H. bacteriophora HP88 (100 IJ/dish) induced mortalities of 85%, 65%, 80%, and 100%, respectively. In all cases, except for S. carpocapsae Mexican strain, a higher concentration (5,000 IJ/dish) did not result in higher mortality than occurred with 1,000 IJ/dish. Unfed females and immature stages of ticks were found to be generally resistant to the nematodes. The feasibility of using entomogenous nematodes for biological control of African tick species are briefly discussed.