Nematodes constitute one of the most diverse and ecologically significant parasite groups in fishes, yet their diversity and host associations remain poorly documented in tropical freshwater systems. In this study, a community-wide survey of 10 fish species from La Mojana wetland was conducted to assess nematode diversity and host associations. The highest infection indices were recorded in Pseudoplatystoma magdaleniatum (Pimelodidae), Sorubim cuspicaudus (Sciaenidae) and Sternopygus macrurus (Sternopygidae). Morphological examination revealed 2 distinct nematode morphotypes corresponding to larval Contracaecum (Anisakidae) and adult camallanids. Molecular analyses based on ITS2, 18S rRNA, 28S rRNA and mitochondrial rrnS markers resolved well-supported lineages corresponding to Contracaecum jorgei Sardella, Mancini, Salinas, Simões & Luque, 2020 and Spirocamallanus sp. The multilocus approach demonstrated the coexistence of phylogenetically distinct nematode groups within the same fish community. Patterns of parasite association revealed a broader host distribution for Contracaecum, whereas Spirocamallanus showed more restricted occurrence. Coinfections reflected the structural complexity of parasite communities in this tropical system. Because fish represent a primary protein source for local communities in La Mojana, the detection of anisakids raises considerations for food safety and public health. This study provides the first multilocus characterization of nematode diversity and host associations in the region, contributing to the understanding of parasite ecology in tropical freshwater ecosystems.
Abstract Six freshly dead adult great cormorant Phalacrocorax carbo sinensis (Blumenbach, 1798) were collected during the winter season of 2025 from the coast of Canneviè lagoon (Northern Adriatic Sea, Italy). All 6 P. carbo sinensis (prevalence 100%) were infected with nematodes of the genus Contracaecum Raillet and Henry, 1912, with the intensity of infection ranging from 39 to 550 worms per host (212.8 ± 80.7; mean ± s.e. ). From the same lagoon, 41 European seabass, Dicentrarchus labrax (L.), were examined for helminths and in 27 specimens (65%) L3 larvae of C. rudolphii were encountered in extraintestinal sites of the seabass. In this study, 40 adults and 30 larvae of C. rudolphii from cormorants and 40 nematode larvae from seabass were characterized at species level using the diagnostic key based on the Restriction Fragment Length Polymorphism of 2 ribosomal regions, the nuclear ITS and the mitochondrial rrnS (12S). Adult nematodes from cormorants were identified as Contracaecum rudolphii B 83.8% (31/37) and the remaining 16.2% (6/37) were C. rudolphii A . Of the 30 larvae recovered from bird stomach 84.2% (16/19) appeared to be C. rudolphii B and 15.7% (3/19) were C. rudolphii A and all parasites from the seabass were third stage larvae of C. rudolphii A . Histological sections of cormorant alimentary canal showed that the nematodes went into the depth of the gastric folds and induced detachment of epithelial cells and secretion of excessive mucus. Furthermore, near the worm site of attachment, different types of innate immune cells were documented.
Abstract This study describes Vairimorpha rumexii sp. nov., a newly identified microsporidian parasite infecting Gastrophysa viridula , the green dock leaf beetle, in northeastern Türkiye. Microscopic examination revealed 2 distinct spore types, with light microscopy and Giemsa staining confirming both disporoblastic and octosporoblastic sporulation cycles characteristic of the genus Vairimorpha . Transmission electron microscopy provided detailed insights into spore ultrastructure, including polar tube configuration, spore wall stratification and nuclear arrangement. Molecular characterization using partial small subunit ribosomal RNA (SSU rRNA) and RNA polymerase II gene sequences, combined with phylogenetic analyses (maximum likelihood and Bayesian inference), placed V. rumexii sp. nov. in a distinct clade, closely related to but genetically separate from Vairimorpha gastrophysae . Notably, pairwise comparison of SSU rRNA sequences revealed a genetic distance of 0.0608 between the 2 species, supported by 72 nucleotide substitutions and 32 deletions, clearly indicating molecular divergence. The integration of morphological, ultrastructural and multilocus molecular data robustly supports its taxonomic distinctiveness as a novel species. This discovery expands the known diversity of microsporidia associated with Chrysomelidae, highlights the value of integrative taxonomy in resolving cryptic species and contributes to the understanding of Türkiye’s microsporidian fauna, potentially informing future biological control strategies.
Abstract Micromammals are abundant in nature and have a significant role as reservoirs for various parasites and pathogens. Very little is currently known about Sarcocystis prevalence and species richness in wild micromammals from Mediterranean Spain. In the present study, a pool of heart, lungs, and brain of 371 individuals representing three species, Algerian mouse ( Mus spretus ), wood mouse ( Apodemus sylvaticus ), and white-toothed shrew ( Crocidura russula ), was screened for Sarcocystis using molecular methods. Animals were sampled across 4 seasons in both natural and agricultural habitats. Prevalence in white-toothed shrew (28%) was significantly higher than in wood and Algerian mouse (17% and 18%, respectively). The lowest prevalence occurred in autumn, whereas no significant differences were detected between habitats. Analysis of 28S rRNA sequences revealed 11 Sarcocystis lineages, with the highest lineage diversity observed in the Algerian mouse. Based on comparative sequence and phylogenetic analysis, most of these lineages are suspected to use snakes as definitive hosts (DHs), three are associated with birds, and the DHs for two lineages are likely mammals. Notably, cox1 sequences could not be used to confidently identify all lineages. Our results reveal substantial diversity of Sarcocystis in Mediterranean micromammals and provide new insights into their transmission cycles.
Udonellids are monopisthocotylan flatworms that occupy a unique epibiotic niche, attaching to parasitic copepods while parasitizing the fish host's epithelial surface. Despite their broad distribution, species diversity within the genus Udonella Johnston, 1835 remains underexplored, particularly in South African marine environments, where new species discoveries are essential for refining its phylogeny. This study presents the integrative description of Udonella umgibeli n. sp., a new epibiotic monopisthocotylan collected from Caligus tetrodontis Barnard, 1948, parasitizing the evileye blaasop, Amblyrhynchote honckenii (Bloch), off the coast of South Africa. Twelve specimens were recovered from 3 copepods infecting a single fish host. Morphological analyses revealed distinct diagnostic features, including body proportions, haptor size, gonad arrangement and caudal gland configuration, separating the new species from all known congeners. Molecular characterization based on partial 18S and 28S rDNA sequences supported species delimitation, with U. umgibeli n. sp. most closely related to U. australis Carvajal & Sep & uacute;lveda, 2002. Although 18S rDNA divergence was low, this is consistent with the marker's highly conserved nature. This study provides the first molecular characterization of an Udonella species from the southwestern Indian Ocean and the first COI mtDNA sequence for the genus, underscoring the importance of integrative taxonomy for resolving species boundaries in morphologically conservative parasites.
We discuss some of the major cerebral parasites responsible for neglected diseases affecting humanity, especially in low-income countries. The World Health Organization states that cerebral malaria caused by Plasmodium falciparum is responsible for over 20% of deaths, especially in paediatric age. In addition to microscopy and molecular techniques, diagnosis can also be made with fundus magnetic resonance imaging and retinal fluorescein angiography, which have recently proven useful for assessing and understanding the clinical status of brain malaria. Currently, the best available treatment is combination therapy with artemisinin derivatives. Experimental drugs that prevent the development of malaria and blood-brain barrier dysfunction will be discussed. Neurocysticercosis is the most common helminthic infection of the central nervous system and a major cause of acquired epilepsy in resource-limited countries. Imported cases are increasing in Europe. Neuroimaging supported by immunodiagnostic tests with purified parasite antigens is the most important diagnostic test. Clinical management includes antiparasitic treatment, antiepileptic drugs, anti-inflammatories and surgery for obstructive hydrocephalus. In cerebral hydatidosis, brain involvement occurs primarily in childhood. Diagnosis is usually made through clinical, laboratory and imaging tests. The opportunistic toxoplasmic encephalitis is due to reactivation and can still be observed in AIDS patients with low access to antiretroviral therapy. Less common cerebral parasitic diseases include schistosomiasis, toxocariasis and amoebiasis, of which primary amoebic meningoencephalitis (Naegleria fowleri) has a very high mortality rate and treatment remains challenging in the absence of new drugs. The modification of existing drugs using nanotechnology offers promising prospects in the development of therapeutic interventions against these parasitic diseases.
