An annotated checklist of the nematodes parasites of Argentinian freshwater fishes is presented. This review includes information for 42 taxa of parasitic nematodes from 56 species of freshwater fish hosts. Fourty nematode species have been reported as adults and two as larvae. Camallanidae was the nematode family with the highest number of taxa (12 species), followed by Cucullanidae (4 species) and Raphidascarididae (4 species and 1 at genus level). The larval nematode Contracaecum sp. was the parasite with the widest range of host species, follow by Spirocamallanus hilarii, Spirocamallanus inopinatus, and Camallanus corderoi. Of the 570 species of freshwater fishes reported in Argentina, only 65 (11.4 %) were recorded as hosts of nematodes. Most records were in Characiformes, Siluriformes and Galaxiiformes, which may reflects sampling effort, since its abundance and widely distributions across differents ichthyogeographic provinces of Argentina. Most sampling were done in Great River and Patagonian ichthyogeographic provinces. The small number of examined fish hosts and geographically biased studies may not reflect the real richness and distribution of these parasites. Other obstacles that also contributes to the lack of completeness of this checklist are the problems in the taxonomic validity of some nematode species, doubtful host identification, and poor taxonomic resolution for larval stages of nematodes. Therefore, it is strongly recommended to deposit voucher specimens, including also of the hosts in reference collection, as well as performing integrative studies to elucidate the real taxonomic identity of nematode larvae. This is the first compilation on the nematode parasites of freshwater fishes from Argentina, including three nematode taxa recorded for new host records and four from new localities. Despite this study is exhaustive, the knowledge about parasitic nematodes from Argentinian freshwater fishes is far from complete, since some hydrological basin mainly in Pampean and Andean Cuyan regions and some host families remain unexplored in terms of nematode parasite detection.

BACKGROUND Hymenolepiasis is a globally prevalent zoonosis of the monoxenic cycle. Humans acquire the disease through fecal-oral transmission by ingesting food or water with infective eggs from infected rodents. This report presents 3 cases of hymenolepiasis in children, due to zoonotic transmission from rodents and presumably associated with the consumption of powdered milk contaminated with infective eggs of Hymenolepis nana, and shows that awareness and early diagnosis contributed to timely treatment of the disease. CASE REPORT Three children, aged 9, 12, and 13 years, living in a marginal urban area of Guayaquil, Guayas province, Ecuador, presented symptoms of diarrhea, low body weight, abdominal discomfort, anorexia, paleness, and anal itching. Subsequently, their fecal samples were analyzed by direct coproparasitic methods, flotation and sedimentation with centrifugation using saline solution; the presence of H. nana eggs was determined. Blood biometry was performed. Further, 10 rodents were captured and necropsied to obtain intestinal contents. The powdered milk consumed by the children was analyzed, the same powder that contained rodent feces. Subsequently, these were studied with the above-mentioned coproparasitic methods. H. nana eggs were identified in the 6 trapped rodents, the powdered milk, and the feces of rodents found in the milk powder. CONCLUSIONS Hymenolepiasis can affect populations of endemic areas. In this case, the disease was identified in 3 children, who were diagnosed with eosinophilia and anemia. Additionally, the presence of H. nana eggs in captured rodents and in powdered milk was determined, indicating that the community was exposed to this zoonotic disease.

Ecoepidemiology of Ancylostoma spp. in Urban-Marginal and Rural Sectors of the Ecuadorian Coast and Prevalence of Cutaneous Larvae Migrans - Article abstract #943931

Helminthological examination of viscera of six freshwater fish species, collected from Mision la Paz, Pilcomayo River, Province of Salta, Argentina, revealed the presence of five species of parasitic nematodes belonging to the Camallanidae, Cystidicolidae, Cucullanidae and Anisakidae The material also contained one unknown species, Procamallanus (Spirocamallanus) tomsici sp. nov. collected from Pimelodus albicans, Pygocentrus nattereri and Hoplias misionera. This species is distinguished from its congeners all over de world by possessing six pores distinctly surrounding the mouth aperture, a buccal capsule with 3-4 spiral thickenings complete, females possessing a lateral cuticular ornamentation along the body, and two pairs of preanal and three pairs of postanal papillae in males. The findings represent new hosts and geographical records.

Intestinal parasites are a global public health concern, affecting both humans and animals, particularly in neglected and underserved communities. These parasites can lead to severe health complications and have zoonotic potential, especially in areas with close human–animal interactions and poor sanitation. This study investigates the ecoepidemiology and zoonotic relationship of intestinal parasites in humans and their domestic dogs in marginalized urban and rural sectors of the Ecuadorian coast. A total of 500 domestic dogs and 160 human participants from four neglected areas of Guayas province were studied between April and October 2024. Fecal samples were collected and analyzed using coproparasitic techniques (direct, flotation, sedimentation, and modified Baermann), followed by morphometric confirmation. Sociodemographic surveys, environmental assessments, and epidemiological indicators were also collected. Statistical analyses, including chi-square tests and logistic regression models, were used to identify associations between parasite prevalence and socioenvironmental variables. The overall prevalence of intestinal parasites was 31.87% in humans and 78% in domestic dogs. The most common parasites in humans were Entamoeba coli (18.13%), Entamoeba. histolytica (10%), and Hymenolepis nana (3.75%). In dogs, Ancylostoma caninum (53.6%), Taenia spp. (Echinococcus granulosus) (15.2%) and Toxocara canis (12.4%), were the most prevalent. Zoonotic parasitic diseases identified included cutaneous larva migrans, hydatidosis, and strongyloidiasis. Significant associations were found between parasitic infections and factors such as water source, sanitation infrastructure, barefoot walking, and peridomiciliary habitat of dogs. The findings highlight a high burden of intestinal parasitism in both humans and dogs in neglected coastal communities of Ecuador, driven by inadequate sanitation, poor socioeconomic conditions, and environmental risk factors. The study underscores the need for integrated One Health approaches, including education, improved hygiene, and routine deworming, to prevent zoonotic transmission and improve public health outcomes.

El presente estudio tuvo como objetivo registrar parasitosis gastrointestinales entre humanos y sus perros domésticos, y así correlacionar el riesgo en Salud Pública, en una comunidad urbano-marginal denominada “Las Piñas”, perteneciente al cantón Milagro (Guayas-Ecuador). Se analizaron muestras de heces humanas y de sus perros domésticos a través de pruebas coproparasitarias. De 201 muestras fecales humanas y 257 caninas, se determinaron prevalencias totales de parasitosis intestinal en humanos del 48,25% y en perros domésticos del 74,32%. En humanos se identificaron siete taxones de parásitos: Entamoeba histolytica 30,84%, Entamoeba coli 13,93%, Giardia lamblia 7,96%, Ascaris lumbricoides 3,98%, Trichuris trichiura 3,98%, Ancylostoma duodeale 2,48% y Strongyloides stercoralis 1,49%. Por otro lado, los siguientes nueve especies de parásitos fueron identificados en caninos: Ancylostoma spp. 73,82%, Toxocara canis 36,64%, Strongyloides stercoralis26,17%, Trichuris vulpis 4,18%, Cystoisospora spp. 1,57 %, Dipilidium caninum 1,04 %, Opisthorchis spp. 1,04 %, Alaria spp. 0,52% y Echinococcus granulosus 0,52%. El parásito que coincidió entre humanos y sus perros domésticos fueStrongyloides stercoralis. La importancia para el humano y el canino es que algunas de las especies encontradas en caninos son zoonoticas (Ancylostoma caninum y A. braziliense, T. canis, D. caninum; E. granulosus, A. alata, T. vulpis) y algunas encontradas en el hombre puede compartirlas con los caninos (S. estercoralis, G. lamblia, alguna especie de Opisthorchis).