Verónica Flores

Diplostomidae includes ecologically important digenean parasites with complex life cycles involving freshwater snails and vertebrate hosts. We present the first comprehensive synthesis of freshwater Diplostomidae in Argentina, based on 118 studies published between 1951 and 2026, to assess patterns of occurrence, host use, sampling effort, and knowledge gaps. Records were classified by life-cycle stage, host group, geographic region, molecular information, and host–parasite association. A total of 580 occurrence records were compiled, representing 13 genera. Metacercariae accounted for 78.4% of all records, whereas cercariae (10.2%), mesocercariae (0.5%), and adults (10.9%) were comparatively scarce. Of the total records, 70.9% were registered in Patagonia, while northeastern Argentina exhibited the highest genus richness. Records were strongly concentrated in Patagonia, the Pampeana region, and northeastern Argentina, while northwestern and central-western Argentina remained poorly studied. The documented host–parasite interactions remain incompletely sampled, with marked differences among regions and life-cycle stages. Molecular information is available for relatively few taxa, and complete life cycles have been confirmed for only two species. Integrative taxonomy and systematic surveys are essential for determining the true diversity and distribution of diplostomids in Argentina.

This study describes two new species of Neodiplostomum (Trematoda: Diplostomidae) and reports a new lineage parasitising birds in Northwestern Patagonia, Argentina, based on morphological and molecular evidence. Specimens were recovered from the intestines of Falco sparverius , Caracara plancus , Accipiter bicolor , and Strix rufipes between 2001 and 2025. Morphological analyses revealed that the new taxa, herein named Neodiplostomum sparverius n. sp., and Neodiplostomum caracara n. sp., and the unnamed species Neodiplostomum sp. 1 show differences mainly in body segment ratio, sucker size, and vitelline gland distribution. This work contributes 14 new sequences to this genus. Phylogenetic analyses of nuclear (28S rDNA) and mitochondrial ( cox1 ) sequences placed N. sparverius n. sp. within a clade comprising Neodiplostomum banghami and Neodiplostomum americanum ; Neodiplostomum sp. 1 clustered with Neodiplostomum microcotyle and Neodiplostomum vaucheri , among others, confirming the existence of two well-supported Neodiplostomum lineages: the first is restricted to avian hosts, whereas the second includes birds and mammals. These results provide the first record of species of the genus Neodiplostomum in Patagonia, and the first molecular sequences for species of this genus in Argentina, thus expanding the known diversity and distribution of the genus in South America. The integrative approach supports the need for taxonomic revision of the genus Neodiplostomum.

Avian schistosomatids are blood flukes parasitizing a wide spectrum of aquatic birds. However, its research in the Neotropics is ongoing with several putative new taxa pending description. Although waterfowl represent the most important avian hosts for these flukes, only a small proportion of these birds have been assessed for schistosomatids. This study aimed to describe avian schistosomatids from two native ducks from the Southern Cone of South America. A total of 24 Chiloe wigeon ( Mareca sibilatrix ) and three Cinnamon teals ( Spatula cyanoptera ) from different localities in Chile and Argentina were dissected to retrieve schistosomatids. The retrieved worms were described through an integrative approach considering morphology (staining and SEM) and molecular tools (PCR: COI , 28S rRNA genes). The new schistosomatid: Trichobilharzia kulfu sp. nov. was recovered from the viscera of Chiloe wigeon. It was closely related to other undescribed Trichobilharzia taxa from the United States, also from Mareca ducks. The new species was morphologically and molecularly different from other Trichobilharzia species, and it was included in the clade Q. In addition, SEM imaging proved to be an important tool to describe unnoticed traits on the tegument of worms. This new species represents the second Trichobilharzia taxon from the Neotropics described through an integrative approach. Furthermore, the Cinnamon teals harboured Trichobilharzia querquedulae. Considering there are several avian schistosomatids described only through morphological or molecular tools, there is a clear need to include a comprehensive approach in the description of avian schistosomatids, considering the remarkable richness of schistosomatids in Neotropics.

Relative to the numerous studies focused on mammalian schistosomes, fewer include avian schistosomatids particularly in the southern hemisphere. This is changing and current research emerging from the Neotropics shows a remarkable diversity of endemic taxa. To contribute to this effort, nine ducks (Spatula cyanoptera, S.versicolor, Netta peposaca), 12 swans (Cygnus melancoryphus) and 1,400 Physa spp. snails from Chile and Argentina were collected for adults and larval schistosomatids, respectively. Isolated schistosomatids were preserved for morphological and molecular analyses (28S and COI genes). Four different schistosomatid taxa were retrieved from birds: Trichobilharzia sp. in N. peposaca and S. cyanoptera that formed a clade; S.cyanoptera and S. versicolor hosted Trichobilharzia querquedulae; Cygnus melancoryphus hosted the nasal schistosomatid, Nasusbilharzia melancorhypha; and one visceral, Schistosomatidae gen. sp., which formed a clade with furcocercariae from Argentina and Chile from previous work. Of the physid snails, only one from Argentina had schistosomatid furcocercariae that based on molecular analyses grouped with T. querquedulae. This study represents the first description of adult schistosomatids from Chile as well as the elucidation of the life cycles of N.melancorhypha and T. querquedulae in Chile and Neotropics, respectively. Without well-preserved adults, the putative new genus Schistosomatidae gen. sp. could not be described, but its life cycle involves Chilina spp. and C. melancoryphus. Scanning electron microscopy of T. querquedulae revealed additional, undescribed morphological traits, highlighting its diagnostic importance. Authors stress the need for additional surveys of avian schistosomatids from the Neotropics to better understand their evolutionary history.

Summary Human and dog health are inextricably linked, and although our relationship with dogs brings numerous benefits for our well-being , it is known that they can transmit disease. Bariloche is a Patagonian tourist city with heterogeneous social composition. This study evaluates the population of free-roaming dogs and their intestinal parasites in relation to the socioeconomic level of the city’s human population. Census areas were used as survey units, stratified in three levels according to socioeconomic status. The free-roaming dog population was estimated by walking around each census area. Eight fresh feces per census count area were collected and analyzed using coproparasitological flotation tests, and CoproELISA was used to detect Echinococcus sp. A total of 858 free-roaming dogs were registered along 40.9 km, with significant differences between socioeconomic strata: the highest numbers were found in the lowest income strata. Of the feces collected, 39.2% tested positive for parasites, those associated with a lower socioeconomic level having higher percentages of positive feces and a greater number of species. Eight species of helminths were found, some of which were zoonotic, such as Echinococcus sp., Toxocara canis , and Dibothriocephalus latus . The presence of parasites can be explained by dog size and the number of free-roaming dogs per block. The free-roaming dogs generally have owners, and their parasitic infection is strongly associated with the socioeconomic level of the population. The main problem is irresponsible pet care, which generates bad conditions for both dogs and humans. Thus, both dogs and humans deserve effective and ethical public policies.

The current conservation status of Percichthys trucha (Creole perch) is Least Concern, although the population trend is considered to be decreasing. We conducted an extensive survey of parasite fauna in this species over two decades in its distribution range in Argentina. Fish were collected using gill and trawl nets. Parasites were collected, identified, and counted to calculate prevalence and mean intensity. The present work reports the parasite species infecting P. trucha, using data from our own survey and from previously published records. This information enables us to evaluate infection and distribution patterns, assess the role of P. trucha as host, determine the specificity of the parasites, and evaluate the threat represented by introduced, invasive parasites. The data set consists of a total of 453 host-parasite-locality records, of which only 15 are exclusively bibliographic. We found 44 parasite taxa: 19 digeneans, 4 monogeneans, 5 cestodes, 8 nematodes, 4 acanthocephalans, 3 crustaceans, and 1 mollusk. The most represented families were Diplostomidae, Heterophyidae, and Dactylogyridae. This study increases the number of parasite species known from 25 to 44. It can be concluded that this parasite fauna is characterized by high diversity, particularly of digeneans, and most of the parasites reproduce within this host, a pattern which is related to the top position of this fish species in the trophic webs. Six parasite species (Allocreadium patagonicum, Homalometron papilliferum, Acanthostomoides apophalliformis, Duplaccessorius andinus, Pseudodelphys limnicola, and Hysterothylacium patagonense) exhibit high host specificity (only matures in Creole perches) and are widely distributed, which could now be considered as “biogeographical core helminth fauna.” Some P. trucha populations are affected by the invasion of alien fishes like Cyprinus carpio and pathogenic parasites like Lernaea cyprinacea and Schizocotyle acheilognathi. Our findings emphasize the need for further research.