Taxonomic and ecological aspects of the helminths found in the assemblage of sigmodontine rodents (Cricetidae-Muroidea) of the Atlantic Forest in Argentina are studied in this paper. The following species Akodon montensis, Brucepattersonius sp. and Thaptomys nigrita (Tribe Akodontini), as well as, Euryoryzomys russatus, Nectomys squamipes, Oligoryzomys nigripes, and Sooretamys angouya (Tribe Oryzomyini) are analyzed. A complete taxonomic list with a total of 25 species of helminths, including Digenea (Dicrocoeliidae), Cestoda (Hymenolepididae) and Nematoda (Trichuridae, Capillariidae, Cooperidae, Helligmonellidae, Oxyuridae, and Onchocercidae) is provided. Twenty new host and locality records for Misiones, Argentina, are reported and the results of the ecological descriptors of component communities are given. The highest value of richness was observed for A. montensis (S=8) and E. russatus (S=7). The diversity index (H´) reached values between 1.03 and 1.39 in all rodents, with the exception of N. squamipes that reached 0.75. The equitability indeces with highest value were observed for T. nigrita and E. russatus. The Berger-Parker index of dominance was similar for all host species. The highest prevalence, mean abundance and mean intensity values corresponded to Nippostrongylinae, followed by Syphacinii. This survey constitutes the report with the most diverse parasitic assemblage of rodents described for the Atlantic Forest ecoregion and for Argentina.

The acuarioid nematode Echinuria skrjabiniensis Efimov in Skryabin, Sobolev et Ivashkin, 1965 was found in Calidris bairdii and C. fuscicollis (Aves, Scolopacidae) examined from several locations from Patagonia, Argentina. These constitute new host records as well as the first record of this parasite species in South America. Using both light and scanning electron microscopies, new morphological details are provided, including the description of the left spicule and the number and the arrangement of male caudal papillae. The taxonomic history of the species is summarized, corroborating its correct spelling and valid name.

Inglisera cirrohamata (Linstow, 1888) (Nematoda: Acuariidae) is redescribed based on specimens collected from the type host, Phalacrocorax verrucosus (Aves: Phalacrocoracidae), and the type locality, Kerguelen Island, in the southern Indian Ocean. Three new hosts and 2 new localities were recorded, i.e., Phalacrocorax [atriceps] albiventer and P. brasilianus from Puerto Madryn, Argentina and P. magellanicus from Puerto Williams, Chile. The structure of the cephalic ornamentations was observed and fully described. The presence of 6 pairs of postcloacal papillae is confirmed, a description of the tip of left spicule is given, and the presence of post-deirids is reported for the first time. This constitutes the first record of this nematode in South America and provides the first study of the genus by scanning electron microscopy.

Objectives Our previous research in Mbyá‐guaraní communities of central Misiones showed high levels of growth stunting and intestinal parasites in children, as well as associations between these variables and deficient sanitary conditions. New studies were necessary to update the present health status of the previously studied Mbyá populations after around two decades. Therefore, we evaluated the current nutritional status, intestinal parasites, and socio‐environmental conditions among Mbyá‐guaraní children from these communities. Methods Body weight and height of 102 individuals (aged 2–14) were measured and nutritional status was estimated according to the World Health Organization criteria. Serial fecal samples and anal swabs were analyzed from 75 children (aged 1–14). Socio‐environmental data were obtained from questionnaires. Results The prevalence of undernutrition was 31.4% and excess of weight was 10.8%. The prevalence of stunting and of overweight reached 30.4% and 8.8%, respectively. About 85% of the children were infected with at least one of the 14 species identified, and around 44% had multiple parasite infections. The most prevalent species were Enterobius vermicularis and hookworms. Among undernourished children, 88.2% were parasitized by at least one of the potentially pathogenic species detected. Most of the families lived in overcrowded conditions in precarious houses, defecated in latrines, and consumed well water. A higher risk of parasitosis was associated with the source of drinking water. Conclusions Although the prevalence of undernutrition and intestinal parasites decreased compared with our previous studies, we still observed the coexistence of stunting, excess weight, and parasitic infections, in a context of socio‐environmental vulnerability.

A new species of Heligmonellidae (Trichostrongylina, Heligmosomoidea), Stilestrongylus kaaguyporai n. sp. is described from the small intestine of Euryoryzomys russatus (Rodentia, Cricetidae, Sigmodontinae) from the Argentine Atlantic Forest, in the Misiones province. The new species was found at Campo Anexo Manuel Belgrano, Reserva de Vida Silvestre Urugua-í and Parque Provincial Urugua-í, with a prevalence of 73% in 15 hosts examined. Stilestrongylus includes 24 Neotropical species, all parasitic in rodents, mostly Sigmodontinae. Stilestrongylus kaaguyporai n. sp. can be differentiated from its congeners by the following characters: caudal bursa dissymmetrical with right lobe larger and pattern of type1-4 in both lobes, rays 6 not forming a lateral trident with rays 4 and 5, rays 8 with dissymmetrical pathway, genital cone hypertrophied with a conspicuous hood-like projection and females with a marked dorso-ventral torsion of the posterior end. This report is the second record of a Stilestrongylus species in E. russatus, increasing to nine the number of parasitic species known from this host.