Fasciolosis caused by Fasciola hepatica severely affects the efficiency of livestock production systems worldwide. In addition to the economic impact inflicted on livestock farmers, fasciolosis is an emergent zoonosis. This review emphasizes different aspects of the disease in South America. Available data on epidemiology in bovines and ovines in different countries, as well as a growing body of information on other domestic and wildlife definitive hosts, are summarized. The issue of drug resistance that compromises the long-term sustainability of current pharmacological strategies is examined from a regional perspective. Finally, efforts to develop a single-antigen recombinant vaccine in ruminants are reviewed, focusing on the cases of leucine aminopeptidase or thioredoxin glutathione reductase.

Latin America has tripled production by aquaculture up to 78 million tonnes in the past 20 years. However, one of the problems that aquaculture is facing is the presence of helminth parasites and the diseases caused by them in the region. In this review we have collected all the available information on helminths affecting commercial aquaculture in Latin America and the Caribbean (LAC), emphasizing those causing serious economic losses. Monogeneans are by far the most common and aggressive parasites affecting farmed fish in LAC. They have been recognized as serious pathogens in intensive fish culture because they reach high levels of infection rapidly, and can infect other phylogenetically related fish species. The next most important group comprises the larval stages of digeneans (metacercariae) such as Diplostomum sp. and Centrocestus formosanus, which cause serious damage to farmed fish. Since LAC aquaculture has been based mainly on exotic species (tilapia, salmon, trout and carp), most of their parasites have been brought into the region together with the fish for aquaculture. Recently, one of us (A.I.P.-T.) has suggested that monogeneans, which have generally been considered to be harmless, can produce serious effects on the growth of cultured Nile tilapia. Therefore, the introduction of fish together with their ‘harmless’ parasites into new sites, regions or countries in LAC should be considered a breakdown of biosecurity in those countries involved. Therefore, the application of quarantine procedures and preventive therapeutic treatments should be considered before allowing these introductions into a country.

Helminths in aquatic invertebrate hosts have been overlooked in comparison with vertebrate hosts. Therefore, the known diversity, ecology and distribution of these host–parasite systems are very limited in terms of their taxonomic diversity, habitat and geographic regions. In this study we examined the published literature on helminth parasites of aquatic invertebrates from Latin America and the Caribbean (LAC) to identify the state of the knowledge in the region and to identify patterns of helminth diversity. Results showed that 67% of the literature is from Argentina, Mexico and Brazil. We found records for 772 host–parasite associations. Most records relate to medically or economically important hosts. Molluscs were the most studied host group with 377 helminth records (80% trematodes). The lymnaeids and planorbids were the most studied molluscs across LAC. Arthropods were the second most studied host group with 78 helminth records (trematodes 38%, cestodes 24% and nematodes 20%), with shrimps and crabs being the most studied hosts. Host species with the largest number of helminth taxa were those with a larger sampling effort through time, usually in a small country region. No large geographical-scale studies were identified. In general, the knowledge is still too scarce to allow any zoogeographical or helminth diversity generalization, as most hosts have been studied locally and the studies on invertebrate hosts in LAC are substantially uneven among countries.

The South American subcontinent supports one of the world's most diverse and commercially very important ichthyofauna. In this context, the study of South American fish parasites is of increased relevance in understanding their key roles in ecosystems, regulating the abundance or density of host populations, stabilizing food webs and structuring host communities. It is hard to estimate the number of fish parasites in South America. The number of fish species studied for parasites is still low (less than 10%), although the total number of host–parasite associations (HPAs) found in the present study was 3971. Monogeneans, with 835 species (1123 HPAs, 28.5%), and trematodes, with 662 species (1127 HPAs, 30.9%), are the more diverse groups. Data gathered from the literature are useful to roughly estimate species richness of helminths from South American fish, even though there are some associated problems: the reliability of information depends on accurate species identification; the lack of knowledge about life cycles; the increasing number of discoveries of cryptic species and the geographically biased number of studies. Therefore, the closest true estimations of species diversity and distribution will rely on further studies combining both molecular and morphological approaches with ecological data such as host specificity, geographical distribution and life-cycle data. Research on biodiversity of fish parasites in South America is influenced by problems such as funding, taxonomic impediments and dispersion of research groups. Increasing collaboration, interchange and research networks in the context of globalization will enable a promising future for fish parasitology in South America.

Unregulated economic growth in Latin America has resulted in environmental degradation, including the release of toxic compounds into the environment. One strategy to understand and prevent the outcomes of this harmful environmental degradation is the use of bioindicators. These are free-living or parasite species that respond to habitat alterations with changes in their numbers, physiology or chemical composition. The aim of this review was to determine whether there is evidence of a significant parasite response to environmental damage in Latin America. We collected 26 papers published between 2003 and 2015 and conducted a meta-analysis to test the null hypothesis that there is no significant overall effect of environmental insults on parasites. The meta-analysis showed a low but still significant negative mean overall effect (Hedges’ g = −0.221; 95% CI: −0.241 to −0.200; P < 0.0001). However, the magnitudes and directions of the significant effects varied widely. These results suggest that different groups of parasites have distinct responses to various environmental insults and that the groups should be separately analysed after the accumulation of a sufficient number of studies. For future studies on this topic in Latin America, we suggest: (1) using field and experimental approaches to determine the response of parasites to environmental degradation; (2) using an interdisciplinary approach, including different types of biomarkers in both parasites and individual hosts to generate long-term datasets in polluted and reference areas; (3) conducting studies on parasites as accumulation bioindicators.

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.

Three species of genus Bychowskyella Akhmerov (1952), i.e. B. fossilisi Majumdar & Agarwal, 1989, B. tchangi Gusev, 1976 and B. wallagonia (Jain, 1959a) Gusev, 1961, were found to parasitize the gill filaments of siluriform fish in India. This redescription based on light microscopic examination of B. fossilisi, B. tchangi and B. wallagonia provides detailed taxonomic data for these species. We also amplified the 18S ribosomal RNA gene to evaluate the phylogenetic relationships of these three species. The morphological and genetic profiles confirmed the validation and taxonomical relationships of the above-mentioned species belonging to the genus Bychowskyella.

Two partial regions of ribosomal DNA (28S and 18S) were used to evaluate genetic variations among the species of Cornudiscoides, viz. C. proximus, C. geminus and C. agarwali, all parasites of Mystus vittatus (Bagridae) from River Gomati, Ganges River basin, India. Our findings demonstrated that both the large and small ribosomal subunits are useful for species identification and genetic characterization of parasites, leading to resolution of inter/intra-relationships at generic and specific levels. The secondary structures of all three species for 28S and 18S rRNA genes contained exact pattern matches (EMPs) displaying the high degree of similarity among them. The phylogenetic analyses within the members of Dactylogyridae demonstrated that species of Cornudiscoides cluster together for 28S rRNA and 18S rRNA genes.

Seizures, headache, depression and neurological deficits are the signs and symptoms most frequently reported in human neurocysticercosis. However, the cause of the associated learning and memory deficits is unknown. Here, we used Taenia crassiceps infection in mice as a model of human cysticercosis. The effects of T. crassiceps metacestode infection or T. crassiceps metacestode factor (MF) treatment on mouse hippocampal cells were studied; control mice were included. At 45 days after infection or treatment of the mice with MF, all mice were anaesthetized and perfused transcardially with saline followed by phosphate-buffered 10% formalin. Then the brains were carefully removed. Coronal sections stained using several techniques were analysed. Extensive and significant apoptosis was found in the experimental animals, mainly in the dentate gyrus, CA1, CA2, CA3 and neighbouring regions, in comparison with the apparently intact cells from control mice (P < 0.01). These results suggest that neurological deficits, especially the learning and memory deficits, may be generated by extensive apoptosis of hippocampal cells.

A new entomopathogenic nematode species of Heterorhabditis, described as H. pakistanense n. sp., was isolated from soil samples around the roots of grass at Malir, Karachi, Sindh, Pakistan. The new species is characterized morphologically by features of males: body size 819 μm (720–1013 μm), D% ((distance from anterior end to excretory pore divided by pharynx length) × 100) 119 (110–126), SW% ((spicule length divided by anal body diameter) × 100) 156 (144–191), GS% ((gubernaculum length divided by spicule length) × 100) 58 (48–65) and variations in the number of bursal papillae of the terminal group: 8th and 9th papillae sometimes absent on both sides, sometimes eight papillae present on the right side whereas six papillae present on the left side. On the right side the arrangement of papillae is 1 + 2 + 3 + 2 whereas on the left side it is 1 + 2 + 3. The hermaphrodite has a prominent post-anal swelling and a conoid tail 82 μm (64–95 μm) long with a pointed terminus. Hermaphrodites of H. pakistanense n. sp. can be distinguished from all species of Heterorhabditis except H. downesi by having a mucronate tail. Infective juveniles have a medium-sized body (581 μm (558–624 μm)), long pharynx (117 μm (113–125 μm)), ensheathed tail (99 μm (95–110 μm)) and E% ((distance from anterior end to excretory pore divided by tail length) × 100) 100 (95–107). The new species can be distinguished from all species of Heterorhabditis by the absence of the 7th, 8th and 9th bursal papillae. Heterorhabditis pakistanense is further characterized by the internal transcribed spacer (ITS) and the D2D3 region of the 28S rDNA gene. The closest species H. indica, H. gerrardi, H. amazonensis and H. noenieputensis being separated by 9, 7, 66 and 15 bp, respectively, in the ITS region. Molecular phylogenetic trees based on sequences of ITS rDNA, D2D3 regions and the mitochondrial 12S rRNA gene support the description of H. pakistanense as a new species.

Morphological analysis of lungworms collected among Caprinae from Uzbekistan resulted in the identification of four species of Protostrongylidae: Protostrongylus rufescens, Protostrongylus hobmaieri, Spiculocaulus leuckarti and Cystocaulus ocreatus. The following species were recorded as definitive hosts: Ovis aries, Ovis ammon, Ovis vignei, Capra hircus, Capra falconeri and Capra sibirica. The prevalence of P. rufescens reached 45.3%, followed by S. leuckarti and C. ocreatus with 31.7% and P. hobmaieri with 16.9%. The sex ratio ranged between 1:3.1 and 1:6.2, with P. hobmaieri showing the strongest predominance of females over males. The prevalence of infection of small ruminants with protostrongylid nematodes increased with the age of the hosts. Protostrongyles use terrestrial gastropods as intermediate hosts, and infective larvae were found in the species Vallonia costata, Gibbulinopsis signata, Pupilla muscorum, Pseudonapaeus albiplicata, Pseudonapaeus sogdiana, Leucozonella ferghanica, Xeropicta candacharica, Candaharia levanderi and Macrochlamys sogdiana. Xeropicta candacharica was the most abundant gastropod and had the highest prevalence of infection with protostrongylids. Adult X. candacharica had a significantly higher infection intensity than juveniles. The epidemiology of protostrongylid infections is dynamic and subject to considerable changes. Further characterization of the interaction of protostrongylid parasites with their terrestrial gastropods as intermediate hosts and Caprinae as definitive hosts is required to understand these processes and to monitor the effects of changing ecological contexts.

The family Deletrocephalidae consists of three species, from two genera: Deletrocephalus dimidiatus, D. cesarpintoi and Paradeletrocephalus minor, which differ from one another in terms of the buccal capsule structure, the dorsal ray from the male copulatory bursa and the length of the vagina in the female. All these species are parasites of the gastrointestinal tract of the rhea, Rhea americana. Only D. dimidiatus was reported to be a parasite of the other rhea species, Darwin's rhea, R. pennata. Currently, there are no studies on the ultrastructure and biology of these parasites or their pathogenicity in these birds. Thus, the present study aimed to examine the ultrastructure and add more details of the morphology of D. dimidiatus from R. americana. Four adult rheas were necropsied, and the gastrointestinal tract was collected and examined for the presence of parasites. Nematodes were analysed by optical and scanning electron microscopy (SEM). All birds were parasitized by D. dimidiatus. Some morphological and morphometric characters were observed that differ from reports of other studies of this species by other authors. In addition, new details were added, well described by SEM, and a key to the species of the subfamily Deletrocephalinae is given.

Orthocoelium streptocoelium is a common paramphistome species parasitizing the rumen and/or reticulum of small ruminants, leading to significant losses. This study first determined the complete mitochondrial (mt) genome of O. streptocoelium. The complete mt genome of O. streptocoelium was amplified, sequenced, assembled, analysed and then compared with those of other digeneans. The entire mt genome of O. streptocoelium is 13,800 bp in length, which is smaller than those of other digeneans except for Opisthorchis viverrini. This mt genome contains 12 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and two non-coding regions. The arrangement of the O. streptocoelium mt genome is the same as those of other digeneans except for Schistosoma haematobium and Schistosoma spindale. Phylogenetic analyses based on concatenated amino acid sequences of the 12 protein-coding genes representing 16 digeneans were conducted to assess the relationship of O. streptocoelium with other digeneans. The result indicated that O. streptocoelium is closely related to Paramphistomum cervi and Fischoederius elongates, which is in accordance with their relationships by taxonomy. This complete mt genome of O. streptocoelium enriched the mitochondrial genome data of paramphistomes and provided important molecular markers for diagnostics and studies of population variation, epidemiology, ecology and evolution of O. streptocoelium and other digeneans.

The United States of America (USA) has the largest international population of any nation in the world. Immigrants from Latin American countries, where intestinal parasites are endemic, comprise more than half of this population. This study aims to determine the prevalence of strongyloidiasis, a potentially deadly parasitic infection, in foreign-born individuals. We conducted a cross-sectional study in Washington, DC, to determine the seroprevalence of Strongyloides stercoralis infection using an NIE-ELISA IgG antibody assay. Multi-parallel quantitative real-time polymerase chain reaction (qPCR) was performed in stool samples of NIE-ELISA-positive patients to investigate possible polyparasitism. The NIE-ELISA assay detected an S. stercoralis prevalence of 4.2% in a group of 119 volunteers. Combining NIE-ELISA and qPCR detected a parasite prevalence of 5.0%. Our results underscore the relevance of systematic testing for gastrointestinal parasites in individuals from endemic regions. It also makes a case for a survey in the USA to identify immigrants' risk for strongyloidiasis and other gastrointestinal parasitic infections.