In a range of trematode species, specific members of the parthenitae colony infecting the molluscan first intermediate host appear specialized for defence against co-infecting species. The evolution of such division of labour requires that co-infection entails fitness costs. Yet, this premise has very rarely been tested in species showing division of labour. Using Himasthla elongata (Himasthlidae) and Renicola roscovita (Renicolidae) infecting periwinkles Littorina littorea as study system, we show that the size of emerged cercariae is markedly reduced in both parasite species when competing over host resources. Cercarial longevity, on the other hand, is negatively influenced by competition only in R. roscovita. Season, which may impact the nutritional state of the host, also affects cercarial size, but only in H. elongata. Hence, our study underlines that cercarial quality is, indeed, compromised by competition, not only in the inferior R. roscovita (no division of labour) but also in the competitively superior H. elongata (division of labour).

Neglected tropical diseases (NTDs) share certain traits: they are parasitic infections, prevailing in tropical environments and affecting marginalized sectors of the population. Six NTDs – ascariasis, cysticercosis, echinococcosis, hookworm infection, onchocerciasis and trichuriasis – all of them endemic in Latin America and the Caribbean (LAC), are analysed in this work. This review aims to discuss key information on the function of excretory/secretory (E/S) proteins from these parasites in their infectivity, pathogeny and diagnosis. The modulation of the host immune system to favour the permanence and survival of the parasite is also discussed. An updated knowledge on the function of E/S molecules in endemic parasitoses in LAC may lead to new approaches for the clinical management and diagnosis of these diseases. In turn, this could allow us to optimize their treatment and make it more affordable – a relevant goal given the economic constraints that the region is facing.

An annotated checklist of the cestode parasites of Argentinean wild birds is presented, as the result of a compilation of parasitological papers published between 1900 and April 2021. This review provides data on hosts, geographical distribution, sites of infection, location of material deposited in helminthological collections, references and taxonomic comments. A host/parasite list is also provided. During this period, 38 papers were published that gather information about 34 cestode nominal species and 11 taxa identified at generic level, belonging to three orders, ten families and 35 genera. The highest number of cestode taxa was recorded in the family Hymenolepididae, with 12 nominal species and two taxa identified at generic level, followed by Dilepididae, with eight nominal species and three taxa identified at generic level. Of the 1042 species of birds reported in Argentina, only 29 (2.8%) were reported as hosts of adult cestodes. The families of birds with the highest number of reported taxa were Laridae and Anatidae, with 20 and 14 taxa, respectively.

In the paper “Acuariid, capillariid and hymenolcpidid parasites of the dasyurid marsupial Antechimis stuartii Macleay, 1841, from southeastern Australia” by I. Beveridge and I. K. Barker, which appeared in part no. 4 (December) of volume 49, 1975, the descriptions of spiruroid larvae and of Capillaria rickardi sp.n. on page 223 should have appeared before that of Hymenolepis aklei sp.n. on page 220.

Gyrodactylus sprostonae Ling, 1962 is a highly invasive parasite reported across freshwater environments of the northern hemisphere. The taxon was originally described from Carassius auratus (Linnaeus, 1758) and Cyprinus carpio Linnaeus, 1758 in China. This parasite has never been reported in Africa or the southern hemisphere. Recently, this taxon was collected from an indigenous yellowfish, Labeobarbus aeneus (Burchell, 1822), in the Vaal River, South Africa. The present study includes the conclusive identification of the gyrodactylid parasites collected from L. aeneus, including additional taxonomic data, using microscopy and molecular techniques. Microscopy included light microscopy (LM) of whole worms and scanning electron microscopy (SEM) of isolated haptoral sclerites. Additionally, morphometric data were obtained from SEM and compared to that generated using LM. For molecular analysis, the internal transcribed spacer (ITS) region of rDNA was amplified and phylogenetic topologies constructed. The specimens were morphometrically and genetically highly similar to other data for G. sprostonae. Additional point-to-point measurements and ITS rDNA sequences were generated for the taxon, contributing to the morphometric and molecular data for G. sprostonae. The study also includes the first study of the isolated haptoral sclerites of the taxon using SEM, with similar morphometric results to LM. This is the first record of G. sprostonae in the southern hemisphere and from a new, indigenous African host, L. aeneus, indicating host switching to smallmouth yellowfish. Furthermore, these results expand on the knowledge of the distribution of invasive parasites in South Africa, as well as Gyrodactylus species diversity in Africa.

Next generation sequencing technologies have facilitated a shift from a few targeted loci in population genetic studies to whole genome approaches. Here, we review the types of questions and inferences regarding the population biology and evolution of parasitic helminths being addressed within the field of population genomics. Topics include parabiome, hybridization, population structure, loci under selection and linkage mapping. We highlight various advances, and note the current trends in the field, particularly a focus on human-related parasites despite the inherent biodiversity of helminth species. We conclude by advocating for a broader application of population genomics to reflect the taxonomic and life history breadth displayed by helminth parasites. As such, our basic knowledge about helminth population biology and evolution would be enhanced while the diversity of helminths in itself would facilitate population genomic comparative studies to address broader ecological and evolutionary concepts.

Calodium hepaticum is a zoonotic nematode with a worldwide distribution. Although the host range of C. hepaticum includes a wide spectrum of mammals (including humans), this parasite is predominantly associated with the families Muridae and Cricetidae. Several Sigmodontinae species from Argentina were found to be infected by C. hepaticum, with a high prevalence in Akodon azarae. The present study focuses on C. hepaticum eggs from natural infection of three species of sigmodontine rodents from Argentina. Eggs were genetically characterized (intergenic 18S rRNA region). The objectives of this work are: (i) to propose a new analytical methodology; and (ii) to morphologically characterize C. hepaticum eggs, from three Sigmodontinae species (A. azarae, Calomys callidus and Oligoryzomys flavescens). Analyses were made by the Computer Image Analysis System based on the new standardized measurements and geometric morphometric tools. The resulting factor maps clearly illustrate global size differences in the parasite eggs from the three Sigmodontinae species analysed. The degree of similarity between egg populations was assessed through pairwise Mahalanobis distances, showing that the largest distances were detected between parasite eggs from C. callidus and O. flavescens. Herein, the phenotypical plasticity of C. hepaticum eggs is shown. Significant positive correlations were obtained between each egg parasite principal component 1 and rodent corporal characteristics: weight; liver weight; rodent length; and rodent body condition. The usefulness of the geometric morphometric analysis in studies of the relationship between C. hepaticum and its host must be highlighted. The high prevalence observed in A. azarae, associated with the wide size range of the parasite eggs evidenced by principal component analysis, suggests A. azarae to be the Sigmodontinae host species that plays the most important role as reservoir host for C. hepaticum in the New World.

Ocular lesions have been reported in patients with schistosomiasis; however, the problem with studying schistosomal infection of the human eye is that biopsies are almost impossible to take, and histopathological examination of suspicious lesions can only be undertaken post-mortem or after enucleation. This work aimed to study the possible effects and pathogenesis of schistosomiasis on the eye. This study involved 55 hamsters; five hamsters remained non-infected and the remaining 50 hamsters were infected with Schistosoma mansoni cercariae. Infected hamsters were sacrificed on weeks 8, 12, 16 and 20 post-infection (pi). Eye sections were prepared and stained for histopathological and immunohistochemical studies. Histopathological changes detected in hamsters infected after 16 and 20 weeks included looseness and oedema of the innermost retinal layers together with hyperplastic polypoid growth. Neither eggs nor granulomata were detected in eye sections throughout the experimental period. Deposition of S. mansoni antigen was revealed in 35% of infected hamsters. Later, on weeks 16 and 20 pi, moderate subepithelial conjuctival deposits and marked subchoroidal and scleral deposition were detected. In conclusion, the deposition of schistosomal antigen and immune complexes may play a pivotal role in the ocular changes that occur in schistosomiasis, even in the absence of detectable Schistosoma eggs. Schistosomiasis should be suspected in cases with unexplained ophthalmological findings, especially in endemic areas.

1. Salting of pasture was explored as a means of controlling stomach worm infestation of grazing sheep.

2. Infestation with Haemonchus contortus was significantly decreased, but that with Ostertagia spp. and Trichostrongylus axei was not significantly affected.

The identity and status of the nematode described by van Breda de Haan (1902) from the roots of diseased rice plants in the Dutch East Indies under the name of Tylenchus oryzae have remained more or less conjectural owing to the inadequacy of the original description and the absence of any drawings showing its appearance and structure. The present writer was so doubtful of its validity as a species that in his monograph on the genus Anguillulina (1932) he listed it under “species inquirendae.” In April 1934, Dr. J. van der Vecht of the Institute of Plant Diseases, Buitenzorg, Java, visited this Institute and in the course of conversation informed the writer that in his opinion the species was a valid and distinct one. He kindly promised that on his return to Buitenzorg he would collect specimens of the parasite and forward them for examination. In due course a good number of adult specimens, preserved in 5% formalin, were received and on these it has been possible to base the observations embodied in the following pages. The writer desires to express his thanks to Dr. P. van der Goot, Director of the Institute of Plant Diseases, Buitenzorg and to Dr. van der Vecht for their kindness in making this interesting material available for investigation.

Two new species of Diaphorocleidus and one new species of Rhinoxenoides n. gen. are described from the gills of Acestrorhynchus falcatus (Bloch) from rivers of north-eastern Pará, Brazil. Diaphorocleidus jaymedeloyolai n. sp. is characterized by a male copulatory organ (MCO) possessing three counterclockwise coils; similar anchors with subtriangular superficial roots; a ventral bar with posteromedial projection; and hooks of pairs 1, 4 and 7 approximately three times longer than hook pair 5. Diaphorocleidus sclerocolpus n. sp. differs from its congeners by a dual-branched accessory piece articulated with the MCO and a sclerotized tubular vagina with a bottle-shaped vestibule. Rhinoxenoides n. gen. is proposed and is characterized by possessing: MCO sclerotized with clockwise coils; an accessory piece articulated to the base of MCO; a sinistroventral vaginal aperture; ventral anchor with conspicuous roots; dorsal anchor with superficial root five times longer than deep root; and absence of dorsal bar. The proposal of Rhinoxenoides n. gen. is also supported by its phylogenetic relationship with Protorhinoxenus prochilodi and species of Rhinoxenus, using 16 morphological characters, which resulted in the following hypothesis of sister-group relationships: Rhinoxenoides n. gen. [Protorhinoxenus (Rhinoxenus curimatae (R. nyttus (R. bulbovaginatus (R. guianensis, R. piranhus, R. euryxenus (R. arietinus, R. anaclaudiae)))))].

A new species of the genus Diomedenema, a spiruromorph nematode, collected from the lung of Spheniscus magellanicus (Sphenisciformes) found on the southern coast of the state of Rio Grande do Sul, Brazil, is described. The new species is differentiated from the only previously described species of the genus, D. diomedeae Johston & Mawson, 1952, by males possessing a set of caudal papillae with three pairs of precloacal, two pairs of adcloacal and one pair of postcloacal papillae; precloacal papillae with the papillae of the first two pairs being closer to each other than those of the third pair; a longer and pointed tail in males; and females with the vulva at mid-body. This is the first report of a nematode infecting the lung of a sphenisciforme host.

A new species of the genus Lyperosomum Looss, 1899, from the intestine of the golden-fronted woodpecker (Melanerpes aurifrons) from northern Mexico is described. Lyperosomum cuauhxinqui sp. n. is morphologically distinguished from other congeneric species from the Americas by a higher oral/ventral sucker ratio and its body length and width. The sequences of domains D1–D3 of the large subunit (LSU) of nuclear ribosomal DNA and cytochrome c oxidase subunit 1 (cox 1) from the mitochondrial DNA of the new species were obtained and compared with available sequences from GenBank. The genetic divergence estimated between the new species and other congeneric species ranged from 2 to 6% and 13.4 to 17.3% for LSU and cox 1, respectively. Phylogenetic analyses based on the two (LSU and cox 1) molecular markers consistently showed that L. cuauhxinqui sp. n. was nested within the genus Lyperosomum, with strong bootstrap support (100%) and Bayesian posterior probabilities (1.0). In particular, the LSU tree indicated that the sequence of the new species is closely related to sequences from Zonorchis alveyi, Zonorchis delectans and Zonorchis sp. from Central America, suggesting that these sequences should be transferred to the genus Lyperosomum. The new species represents the first record from Mexico and the fifth species identified in the Americas. Our study also revealed that the taxonomy of the genus Lyperosomum should be re-examined by combining molecular, morphological and ecological characteristics.

Papaya latex has been demonstrated to be an efficacious anthelmintic against murine, porcine, ovine and canine nematode parasites, and even those infecting poultry, and it has some efficacy against rodent cestodes. The active ingredients of papaya latex are known to be cysteine proteinases (CPs). The experiments described in this paper indicate that CPs in papaya latex, and also those in pineapples, are highly efficacious against the equine cestode Anoplocephala perfoliatain vitro, by causing a significant reduction in motility leading to death of the worms. The susceptibility of A. perfoliata to damage by CPs was considerably greater than that of the rodent cestodes Hymenolepis diminuta and H. microstoma. Our results are the first to report anthelmintic efficacy of CPs against an economically important equine helminth. Moreover, they provide further evidence that the spectrum of activity of CPs is not restricted to nematodes and support the idea that these plant-derived enzymes can be developed into useful broad-spectrum anthelmintics.

Androgens have been shown to exert a cysticidal effect upon Taenia crassiceps, an experimental model of cysticercosis. To further inquire into this matter, the Taenia crassiceps model was used to evaluate the expression of several proteins after testosterone (T4) and dihydrotestosterone (DHT) in vitro treatment. Under 2-D proteomic maps, parasite extracts were resolved into approximately 130 proteins distributed in a molecular weight range of 10–250 kDa and isoelectrical point range of 3–10. The resultant proteomic pattern was analysed, and significant changes were observed in response to T4 and DHT. Based on our experience with electrophoretic patterns and proteomic maps of cytoskeletal proteins, alteration in the expression of isoforms of actin, tubulin and paramyosin and of other proteins was assessed. Considering that androgens may exert their biological activity in taeniids through the non-specific progesterone receptor membrane component (PGRMC), we harnessed bioinformatics to propose the identity of androgen-regulated proteins and establish their hypothetical physiological role in the parasites. These analyses yield a possible explanation of how androgens exert their cysticidal effects through changes in the expression of proteins involved in cytoskeletal rearrangement, dynamic vesicular traffic and transduction of intracellular signals.

Largemouth bass, Micropterus salmoides, is a native fish species with special importance for sport fishing competitions in Nuevo León, Mexico. However, no study has investigated the parasitic fauna of M. salmoides, and no reports are available on monogenean parasites in this fish species. Therefore, we described the monogenean parasites of M. salmoides and the effects of season and fish condition factor in five reservoirs: La Boca (LB), El Cuchillo–Solidaridad (CS), Sombreretillo (S), Laguna Salinillas (LS) and Cerro Prieto (CP). The monogeneans infecting M. salmoides were Clavunculus unguis and Acolpenteron ureteroecetes (collected in all localities), as well as Syncleithrium fusiformis, Haplocleidus furcatus, Clavunculus bifurcatus and Urocleidus principalis (CS). Clavunculus unguis had the highest prevalence in fish from all reservoirs. The abundance of monogeneans was generally greater in late spring to autumn than in winter. Although season was not correlated with abundance (rs = 0.0934, P <  0.0154), the months of highest temperature (from May to September) were positively correlated with parasite abundance. A significant association was observed between fish condition factor and the presence of monogeneans (P <  0.05), except for A. ureteroecetes. Our findings include five new geographic records for C. unguis, S. fusiformis, H. furcatus and C. bifurcatus.

Acetylcholine is the major endogenous classical neurotransmitter in the central and peripheral nervous system of trematodes and mammals. This study investigates the effects of cholinergic drugs on muscle activity in the amphistome, Gastrothylax crumenifer. In the present investigation, acetylcholine (10− 7–10− 3 m) did not produce any marked effect, whereas carbachol (10− 7–10− 3 m) elicited a concentration-dependent decrease in amplitude, baseline tension and frequency of contractions as compared to the control. Nicotine (10− 7–10− 3 m) produced a significant decrease in the amplitude and frequency of spontaneous muscular activity in a concentration-dependent manner, as compared to control amplitude (0.5 ± 0.01 g) and frequency (58.5 ± 3.45 per 5 min). However, the baseline tension was also reduced significantly by 10− 3 m nicotine. Atropine (10− 7–10− 3 m) elicited a concentration-dependent increase in amplitude and baseline tension, whereas there was no significant effect on the frequency of the spontaneous contractions of rumen flukes. These observations indicate that G. crumenifer has an inhibitory cholinergic system and that the inhibitory activity of nicotine is more pronounced than that of carbachol or acetylcholine.

Cystacanths of the acanthocephalan, Bolbosoma vasculosum Rudolphi 1819, were found to be encapsulated in the connective tissues of the viscera of the black scabbard fish, Aphanopus carbo and oceanic horse mackerel, Trachurus picturatusfrom Madeira, Atlantic Ocean. Juvenile worms were obtained from the intestine of a stranded common dolphin, Delphinus delphis, also from Madeira. Cystacanths were 11–15 mm long, with a proboscis of 18–19 longitudinal rows, eight hooks per row, and two sets of trunk spines. Overall, the morphology and dimensions of the proboscis, neck and trunk corresponded to previous descriptions. Scanning electron microscopy of the proboscis structures and trunk spines is provided for the first time. The prevalence of B. vasculosum in A. carbo increased with fish length. There were no statistical differences in the prevalence and intensity of infection between seasons. The intensity of infection was similar for male and female fishes, but there were significant differences in relation to length, longer fishes having heavier infections. Aphanopus carbo from Madeira represents a new host record and a new geographic location for B. vasculosum.

A 30 kDa antigen was characterized as a hydrophobic polypeptide containing 16 amino acids and evaluated as a potential candidate vaccine against infection by Schistosoma mansoni. CD1 albino mice immunized at 0, 14, and 21 days with 25 or 50 μg of the 30 kDa antigen per mouse with and without alum developed high levels of IgG antibodies (predominantly IgG2a and IgG2b isotypes). When immunized mice were infected with 200 S. mansoni cercariae, the highest protection levels (61% and 65% reduction in worm burden in two separate experiments) were obtained using the 50-μg antigen without alum adjuvant. The granuloma size decreased to 10%, a non-significant level in mice immunized using alum adjuvant. The results demonstrate the ability of the 30 kDa antigen with and without alum adjuvant to protect mice against S. mansoni infection.

The phylogenetic relationships of 42 species of cloacinine nematodes belonging to three tribes (Coronostrongylinea, Macropostrongylinea and Zoniolaiminea) were examined based on sequence data of the first and second internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA. All nematodes examined are parasites of Australian macropodid marsupials. None of the three nematode tribes was monophyletic. Paraphyly was also encountered in three genera: Papillostrongylus, Monilonema and Wallabinema. Species within the genus Thallostonema were limited to a single host genus (i.e. Thylogale), whereas species within the five principal genera (Coronostrongylus, Macropostrongylus, Popovastrongylus, Wallabinema and Zoniolaimus) were found to occur in multiple host genera. Potential modes of evolution among these nematodes are discussed.