Helminths Of Fish Research Articles

Sclerocollum saudii Al-Jahdali, 2010 (Acanthocephala: Cavisomidae) as a sentinel for heavy-metal pollution in the Red Sea.

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

Accentuated Molecular Detection Technique to Segregate and Identify Helminths of Fish through High Resolution Melting (HRM) Analysis

Real-time PCR coupled with high-resolution molecular (HRM) analysis was conducted to target the second internal transcribed spacer (ITS-2) of nuclear ribosomal DNA. The latter acted as a genetic marker to identify and distinguish two anisakid and one cucullanid species parasitizing marine and freshwater fish. Unique and distinct characteristics of HRM patterns were produced for each of the three roundworms investigated. The melt profiles and threshold of the cycles (Ct values), at which amplification commenced, for Anisakis simplex (Rudolphi), Contrcaecum osculatum (Rudolphi) Dujardin, Contrcaecum sp. and Dacnitoides cotylophora (Ward and Magath) were diagnostic for species. The molecular analyses by sequencing and comparing the internal transcribed spacer (ITS) of the ribosomal DNA of Dacnitoides, Anisakis and Contrcaecum assays established their distinct identity. The present investigation propagates molecular-phylogenetic and morpho-molecular analysis to characterize diagnostic constituents of cucullanid and anisakid roundworms.

Protective responses of intestinal mucous cells in a range of fish-helminth systems.

Histopathological, immunofluorescence and ultrastructural studies were conducted on the intestines of four fish species infected with different taxa of enteric helminths. Brown trout (Salmo trutta trutta), eel (Anguilla anguilla) and tench (Tinca tinca) obtained from Lake Piediluco (central Italy) were examined. Brown trout and eel were infected with two species of acanthocephalans, and tench was parasitized with a tapeworm species. In addition to the above site, specimens of chub (Squalius cephalus) and brown trout infected with an acanthocephalan were examined from the River Brenta (north Italy). Moreover, eels were examined from a brackish water, Comacchio lagoons (north Italy), where one digenean species was the predominant enteric worm. All the helminths species induced a similar response, the hyperplasia of the intestinal mucous cells, particularly of those secreting acid mucins. Local endocrine signals seemed to affect the production and secretion of mucus in the parasitized fish, as worms often were surrounded by an adherent mucus layer or blanket. This is the first quantitative report of enteric worm effects on the density of various mucous cell types and on the mucus composition in intestine of infected/uninfected conspecifics. We provide a global comparison between the several fish-helminth systems examined.

Parasites of freshwater fishes and the Great American Biotic Interchange: a bridge too far?

We examine the extent to which adult helminths of freshwater fishes have been part of the Great American Biotic Interchange (GABI), by integrating information in published studies and new data from Panama with fish biogeography and Earth history of Middle America. The review illustrates the following: (1) the helminth fauna south of the Trans-Mexican Volcanic Belt, and especially south of the Isthmus of Tehuantepec, shows strong Neotropical affinities; (2) host-parasite associations follow principles of the 'biogeographic core fauna' in which host-lineage specificity is pronounced; (3) phylogenetic analysis of the widespread freshwater trematode family Allocreadiidae reveals a complex history of host-shifting and co-diversification involving mainly cyprinodontiforms and characids; (4) allocreadiids, monogeneans and spiruridan nematodes of Middle American cyprinodontiforms may provide clues to the evolutionary history of their hosts; and (5) phylogenetic analyses of cryptogonimid trematodes may reveal whether or how cichlids interacted with marine or brackish-water environments during their colonization history. The review shows that 'interchange' is limited and asymmetrical, but simple narratives of northward isthmian dispersal will likely prove inadequate to explain the historical biogeography of many host-parasite associations in tropical Middle America, particularly those involving poeciliids. Finally, our study highlights the urgent need for targeted survey work across Middle America, focused sampling in river drainages of Colombia and Venezuela, and deeper strategic sampling in other parts of South America, in order to develop and test robust hypotheses about fish-parasite associations in Middle America.

Fine structure and cellular responses at the host–parasite interface in a range of fish–helminth systems

A series of ultrastructural-based studies were conducted on the interface region in different fish–helminth systems: (a) an intestinal infection of the cestode Monobothrium wageneri in tench, Tinca tinca; (b) an extensive intestinal submucosa and mucosal infection in tench by metacercariae of an unidentified digenean trematode; (c) an intestinal infection in brown trout, Salmo trutta, by the acanthocephalan Dentitruncus truttae; (d) an extraintestinal infection by larvae of the acanthocephalan, Pomphorhynchus laevis in three-spined sticklebacks, Gasterosteus aculeatus; and (e) an infection in the livers of Eurasian minnow, Phoxinus phoxinus, by larvae of the nematode Raphidascaris acus. Endoparasitic helminths frequently cause inflammation of the digestive tract and associated organs, inducing the recruitment of various immune cells to the site of infection. In each of the fish–helminth systems that were studied, a massive hyperplastic granulocyte response involving mast cells (MCs) and neutrophils in close proximity to the helminths was documented. The current study presents data on the interface region in each fish–helminth system and documents the penetration of mast cells granules within the tegument of P. laevis larvae. No extracellular vesicles containing tegumental secretions from any of the four different taxa of endoparasitic helminths species at the host–parasite interface region were seen.

An Updated Checklist Of Parasitic Helminths Of Marine Fish From Turkey

Abstract An updated checklist carried out indicated the occurrence of 161 helminth species from wild marine fish species in Turkey, which includes 49 monogeneans, 63 digeneans, 18 cestodes, 17 nematodes, 11 acanthocephalans and three annelids, from 88 different fish (86 native, two migratory) species. Since the publication of the checklist of helminth parasites of marine fishes in Turkey over nine years ago (Öktener, 2005), there have been a number of new records. This update includes these additional records and has allowed the correction of those errors and omissions that were present in the previous version. The parasite species list is arranged by phylum and class, providing parasite species name, host fish, location of host fish capture and author, and date of published record. The host list consists of all parasite species listed by host species. All parasites and their hosts are confirmed with the recent systematic accounts and full taxonomic account.

Revision of Parasitic Helminths Reported in Freshwater Fish From Turkey with New Records

Abstract This new checklist is an update of helminths of freshwater fish from Turkey. The last publication of a checklist of helminth parasites of freshwater fish in Turkey was over 11 years ago (Öktener, 2003), and there have been a number of new records. This update includes additional records and allows for the correction of errors and omissions that were present in the preceding version. The revision literature indicated the occurrence of 123 parasite species which included 60 monogeneans, 20 digeneans, 20 cestodes, 11 nematodes, seven acanthocephalans, five annelids from 71 different wild fish (64 native, four transitional, three introduced fish) species from freshwater in Turkey. Parasites not identified to species level are listed separately, and not included in the resulting comments, because of reporting different host species. Cyprinidae, with 50 species, is the dominant family among the examined fish with regard to species diversity

New host and locality records of freshwater fish helminth parasites in river basins north of the Transmexican Volcanic Belt: another look at biogeographical patterns

Freshwater fish helminths have been studied for more that 80 years in Mexico, and currently the inventory of this parasite fauna is nearing completion. Between 1999 and 2006, we studied 958 freshwater fishes belonging to 34 species in 36 localities distributed along 9 states of the Mexican Republic, north of the Transmexican Volcanic Belt. In total, 25 helminth taxa were found, including 9 digeneans, 6 nematodes, 4 monogeneans, 5 cestodes, and 1 acanthocephalan. Of the 25 species of helminths, 12 were found as larval stages while 13 were found as adults. A large number of hosts (582, i.e., 60.7%) were uninfected with helminth parasites. The data we present here is then used in combination with other recently published parasite surveys conducted in northern Mexico to revise our understanding of the biogeographical patterns of the freshwater fish parasite fauna in an area inhabited predominantly by Nearctic freshwater fishes.

Taxonomic composition and endemism of the helminth fauna of freshwater fishes of Mexico

We examine the taxonomic composition and endemism of adult helminth parasites of freshwater fishes of Mexico, with regard to the main hydrological basins of the country. A presence-absence matrix, including every species of adult helminth parasites of freshwater fishes from 23 Mexican hydrological basins was compiled and examined in this paper. The helminth fauna of freshwater fishes of Mexico consists of a large group of Central American Neotropical species (S = 119) and another set, less rich of Nearctic species (S = 48), which are distributed along with the families of its fish hosts; insufficient data preclude the assignation of three species. This fauna is composed predominantly by nematodes, trematodes, and monogeneans, which together contributed 86% of the total species recorded; cestodes and acanthocephalans being the taxa with the least species recorded. Current data suggests a 22% (37/170) endemism amongst helminths of freshwater fishes of Mexico. Data suggests that the isolation of bodies of water in the Mexican territory, mostly in the Neotropical areas of southeastern Mexico and in the central Altiplano Mexicano (Mexican Highland Plateau), with well delimited basins separated by orographic features, provided peculiar conditions that have been conducive to the diversification of a unique helminth fauna.

The influence of host ecology and biogeography on the helminth species richness of freshwater fishes in Mexico

Freshwater fish helminths, the most well known Mexican vertebrate parasites, include approximately 260 species (platyhelminthes, acanthocephalans, nematodes, and hirudineans). The distribution patterns of adult helminth diversity (throughout parasite and host groups and hydrological regions) are described and the effects of host traits and environmental and geographical factors on diversity are evaluated. Adult helminths include 160 species, parasitizing 149 fish species of 23 families distributed in 21 regions. Nematoda was the most species-rich (>50 species). Cichlidae harboured rich helminth assemblages, with widespread parasites. By contrast, Atherinopsidae and Goodeidae showed relatively poor helminth assemblages, including specific parasites with narrow distribution. Helminth richness in southeastern Mexico was higher than northern or central regions. Non-parametric richness estimators were used to avoid confusion in comparisons with unequal sampling efforts. Bootstrap values, the method with the best performance, indicated that estimated richness shows the same distribution pattern that observed richness. Non-phylogenetic and phylogenetic analyses were used to determine the role of different factors in the parasite diversification. The distribution range was the most important richness predictor (widespread fishes harbour richer parasite assemblages), although interactions between this variable and others such as trophic level, latitude, habitat temperature and precipitation are also important. Likewise, biogeographical factors can also affect parasite diversity.

Helminths of freshwater fishes in the reservoir of the Hydroelectric Power Station of Itaipu, Paraná, Brazil

This study presents results from several expeditions in 1985, 1991-1995 and 2003 to the Medium Paraná River in the section that begins below the Itaipu Dam and ends at the trinational border of Brazil, Argentina and Paraguay, in the lotic and lentic zones of the reservoir of the Hydroelectric Power Station of “Itaipu Binacional” (localities Foz do Iguaçu, Santa Helena and Guaira). Ninety-eight species of freshwater fishes belonging to 22 families were examined for helminths. A host-parasite list based on Acanthocephala, Cestoda, Digenea, Monogenea and Nematoda collected from the region in question is provided. New host records are presented for Digenea and Nematoda. The Monogenea and Acanthocephala are being studied and will be published in a later paper, but are referred in the host-parasite list, in order to demonstrate the parasitism in the fishes of the reservoir. The results are compared with those presented by other authors from the Upper Paraná River.

Parasite Inventories and DNA-based Taxonomy: Lessons from Helminths of Freshwater Fishes in a Megadiverse Country

Freshwater fish helminth parasites are undoubtedly the most well-known group among vertebrate parasites in Mexico; these parasites include 37 adult and 43 larval (metacercariae) species of trematodes, 62 monogeneans, 15 adult and 18 larval (metacestode) cestodes, 6 adult and 4 larval (cystacanth) acanthocephalans, and 54 adult and 15 larval nematodes (L3). Here, we evaluate the extent of the freshwater fish helminth inventory of Mexico using species accumulation curves and discuss the implications of DNA-based taxonomic methods in our understanding of the helminth biodiversity in freshwater fishes. Future directions for the study of the helminth parasites of freshwater fishes are proposed, particularly the role of DNA-based species delimitation criteria in recognizing parasite species, but also in discovering cryptic species. Species accumulation curves indicate that even though the asymptote has not been reached, a tendency toward stabilization is observed in all taxonomic groups except monogeneans. We suggest, therefore, that the inventory, as conventionally understood, is nearing completion for most groups. We suggest that future survey work aimed at enhancing the biodiversity inventory should be strategic, i.e., it should combine the need to target missing components of the host spectrum with the choice of appropriate drainages based on biogeographic, faunistic, and hydrologic data. We also posit that the future belongs to DNA-based taxonomic approaches that aim to uncover previously unrecognized biodiversity.

Report on some monogenean and clinostomid infestations of freshwater fish and waterbird hosts in Middle Letaba Dam, Limpopo Province, South Africa

This report deals with the results of a parasitological study done as part of a post-impoundment ecological study of Middle Letaba Dam, Limpopo Province, South Africa. It involved a seasonal survey protocol with particular attention to the diversity and prevalence of the parasitic fauna of the indigenous fish community of the dam and the role of selected fish-eating birds in the life cycle and distribution of fish helminths. The potential species composition of fish of the dam is provided. Monogenean and clinostomatid parasites encountered are listed and infestation statistics of fish and fish-eating bird hosts are presented. The results of this study also provide information on new distribution and host records of the encountered monogeneans.

Communities of gastrointestinal helminths of fish in historically connected habitats: habitat fragmentation effect in a carnivorous catfish Pelteobagrus fulvidraco from seven lakes in flood plain of the Yangtze River, China

BackgroundHabitat fragmentation may result in the reduction of diversity of parasite communities by affecting population size and dispersal pattern of species. In the flood plain of the Yangtze River in China, many lakes, which were once connected with the river, have become isolated since the 1950s from the river by the construction of dams and sluices, with many larger lakes subdivided into smaller ones by road embankments. These artificial barriers have inevitably obstructed the migration of fish between the river and lakes and also among lakes. In this study, the gastrointestinal helminth communities were investigated in a carnivorous fish, the yellowhead catfish Pelteobagrus fulvidraco, from two connected and five isolated lakes in the flood plain in order to detect the effect of lake fragmentation on the parasite communities.ResultsA total of 11 species of helminths were recorded in the stomach and intestine of P. fulvidraco from seven lakes, including two lakes connected with the Yangtze River, i.e. Poyang and Dongting lakes, and five isolated lakes, i.e. Honghu, Liangzi, Tangxun, Niushan and Baoan lakes. Mean helminth individuals and diversity of helminth communities in Honghu and Dongting lakes was lower than in the other five lakes. The nematode Procamallanus fulvidraconis was the dominant species of communities in all the seven lakes. No significant difference in the Shannon-Wiener index was detected between connected lakes (0.48) and isolated lakes (0.50). The similarity of helminth communities between Niushan and Baoan lakes was the highest (0.6708), and the lowest was between Tangxun and Dongting lakes (0.1807). The similarity was low between Dongting and the other lakes, and the similarity decreased with the geographic distance among these lakes. The helminth community in one connected lake, Poyang Lake was clustered with isolated lakes, but the community in Dongting Lake was separated in the tree.ConclusionThe similarity in the helminth communities of this fish in the flood-plain lakes may be attributed to the historical connection of these habitats and to the completion of the life-cycles of this fish as well as the helminth species within the investigated habitats. The diversity and the digenean majority in the helminth communities can be related to the diet of this fish, and to the lacustrine and macrophytic characters of the habitats. The lake isolation from the river had little detectable effect on the helminth communities of the catfish in flood-plain lakes of the Yangtze River. The low similarities in helminth communities between the Dongting Lake and others may just be a reflection of its unique water environment and anthropogenic alterations or fragmentation in this lake.

The helminths of Freshwatere fishes caught from waters of rural areas of Kirkuke governorate, Iraq

Six freshwater species of fishes have been subjected to parasitological investigation, which were collected from water in different urban area of Al-tamim governorate. The results revealed the presence of four species of helminthes; include one species of cestoda(Bothriocephalus gowokensis) collected from Cyprinus carpio and Aspiux vorax( with the rate 2.9 %and 25% respectively); one species of nematoda (Cucullanus cyprini) collected from the carp; two species of acanthocephalans namely Neoechinorhynchus rutili collected from Cyprinus carpio, Barbus luteus, Chondrostoma regius and Varicorhinus trutta. The incidence of infection in Cyprinus carpio(4.2% in males and 8.3 % in females); in Barbus luteus(2.5%); in Chondrostoma regius(8% in males and 9.9% in females) and in Varicorhinus . trutta(50%).The other species of acanthocephala is Neoechinorhynchus iraqinensis which has been revealed from Liza abu( 15.7% in males and 35% in females). From the result of the present study, it can be concluded, that, all four helminthic parasites are the first record in fishes caught from Kirkuk province.

Three species of parasites emerging on the gills of mulloway, Argyrosomus japonicus (Temminck and Schlegel, 1843), cultured in Australia

Mulloway is an Indo‐West Pacific sciaenid fish with a short history of commercial culture in Australia. In January 2005, a harvest sample of these fish cultured off South Australia was observed macroscopically with large numbers of a blood‐feeding polyopisthocotylean. Epizootics of this parasite may pose a threat to the economics of farming this species, since it appears to be associated with anemia, as indicated by pale gills. Based on morphological characters, we identify the monogenean as Sciaenacotyle sciaenicola [Murray, F.V., 1932. Correction: note on a microcotylid from Sciaena antarctica. Parasitology 24, 448.] Mamaev [Mamaev, Yu.L., 1989. On species composition and morphological features of the Microcotyle genus (Microcotylidae, Monogenoidea). In: Lebedev, B.I. (Ed.), Investigations in Parasitology . Collection of Papers. DBNTs AN SSSR: Vladivostok, pp. 32–38 [In Russian].]. Maximum likelihood analysis of ITS2 rDNA confirms that the genus Sciaenacotyle is not closely related to two other microcotylid genera also known from sciaenid fishes: Diplostamenides (represented by D. sciaenae (Goto, 1894) Mamaev [Mamaev, Yu.L., 1989. On species composition and morphological features of the Microcotyle genus (Microcotylidae, Monogenoidea). In: Lebedev, B.I. (Ed.), Investigations in Parasitology . Collection of Papers. DBNTs AN SSSR: Vladivostok, pp. 32–38 [In Russian].] from white croaker, Pennahia argentata, in Japan) and Anchoromicrocotyle (represented by A. guaymensis [Bravo‐Hollis, M., 1981. Helminths of fish of the Mexican Pacific. XXXVI. A new genus and subfamily of the family Microcotylidae Taschenberg, 1879 emended. An. Inst. Cienc. Mar Limnol. Univ. Nac. Auton. Mex. 8, 305–313.] from white seabass, Atractoscion nobilis, in California). In more intensive sampling of gills, we detected two other species of metazoan parasites, the monopisthocotylean Calceostoma glandulosum Johnston et Tiegs, 1922; and a copepod we identify as Caligus cf. elongatus, a sea louse very similar to C. elongatus Nordmann (1832), which affects farmed salmonids in the North Atlantic. Praziquantel bath treatment at an initial concentration that removed S. sciaenicola from mulloway gills did not remove C. glandulosum.

Helminths of Antarctic fishes: Life cycle biology, specificity and geographical distribution

AbstractBony fishes (Teleostei) play an important role in the completion of life cycles of helminth parasites in the Antarctica. These fishes may be definitive, second intermediate or paratenic hosts of the helminths. The most species-rich taxon is Digenea. Virtually all of these digeneans use teleosts as definitive hosts. Only one species, Otodistomum cestoides, occurs as the adult stage in skates (Chondrichthyes), with teleosts as its second intermediate host. Among 14 cestode species maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni, whereas the others are parasites of Chondrichthyes (cartilaginous fishes). Antarctic Chondrichthyes are not infected with nematode and acanthocephalan species. Specificity to the intermediate and/or paratenic hosts of the majority of Antarctic helminths is wide, whereas that for definitive hosts is often narrower, restricted to one order or sometimes even to one or two host species. Almost all of 73 helminth species maturing in Antarctic fishes are endemics. Only 4 digenean and one nematode species are cosmopolitan or bipolar.

Helminths of Freshwater Fishes from the Metztitlán Canyon Reserve of the Biosphere, Hidalgo, Mexico

The occurrence of 6 species of helminth parasites (Clinostomum complanatum, Diplostomidae gen. sp., Posthodiplostomum minimum, Bothriocephalus acheilognathi, Glossocercus sp., Contracaecum sp.) is reported from 7 species of freshwater fishes (Chirostoma jordani, Astyanax mexicanus, Herichthys labridens, Oreochromis niloticus niloticus, Abramis brama, Cyprinus carpio carpio, and Poeciliopsis gracilis) in Metztitlan Lake (Laguna de Metztitlan), Reserva de la Biosfera Barranca de Metztitlan, Hidalgo, Mexico. Fish were collected between July 2002 and June 2003. The helminth fauna of H. labridens, an endangered species of Cichlidae, is described for the first time. Migratory birds of the families Ardeidae and Phalacrocoracidae appear to play an important role in the helminth species composition of fishes from Metztitlan Lake. All helminth species represent new records for this federally protected area of Hidalgo.

Helminth Parasites of Freshwater Fishes of the Pánuco River Basin, East Central Mexico

This study presents results from a survey of helminth parasites of fishes in the Panuco River basin, in the states of San Luis Potosi, Hidalgo, Queretaro and Guanajuato, all in east central Mexico. Seventeen freshwater fish species (n = 1,019) were examined for helminths between May 1997 and September 1998. Thirty-one helminth species were collected: 11 allogenic species, mostly Nearctic in origin, and 20 autogenic species. Two anthropogenically introduced species were recorded. The most prevalent and widespread helminth taxon was Posthodiplostomum minimum (metacercariae). The helminth fauna of fishes of the Panuco River is dominated by trematodes (12 species) and nematodes (11 species) accompanied by a few monogenean (4 species), cestode (3 species), and acanthocephalan (1 species) taxa. Most of the helminth taxa reported have been reported from other regions of Mexico. Thus, the helminth parasite fauna of fishes of the Panuco River basin are not exclusive, including a primordially autogenic Neotropical species component mixed with a mainly allogenic, globally distributed Nearctic species component. The regional freshwater fish helminth fauna is associated with the ichthyofaunanal composition of the basin. The nematode family Rhabdochonidae displays high species richness in this hydrological basin of Mexico.

Helminth Parasites of Freshwater Fishes of the Ayuquila River, Sierra de Manantlán Biosphere Reserve, West Central Mexico

This study presents results from the first survey of the helminth parasites of fishes in the Ayuquila River, Sierra de Manantlan Biosphere Reserve, in the states of Jalisco and Colima, west central Mexico. Twenty-eight helminth species were collected from 14 freshwater fish species in July 2000 and February 2001. No helminth species collected is exclusive to the Ayuquila River: 11 are allogenic species, mostly Nearctic in origin, and 17 are autogenics. Three introduced species were recovered. Saccocoelioides sogandaresi (Trematoda) was the most prevalent and widespread helminth recovered. The fish helminth fauna of the Ayuquila River is dominated by trematode and nematode species with only a few monogenean and acanthocephalan species. The fauna exhibits considerable overlap with that reported for other freshwater basins in Mexico, and all helminths recovered have been reported previously from Mexico.