Spirometra Faust, Campbell et Kellogg, 1929 is a genus of cestodes belonging to the family Diphyllobothriidae. To date, amphibians, reptiles, and mammals are known second intermediate hosts of these parasites; humans can also be infected (the zoonotic disease is known as sparganosis or spirometrosis). Although the number of phylogenetic studies on Spirometra spp. has increased worldwide in recent years, there are few in South America. Specifically in Uruguay, molecular studies have shown that tapeworms of S. decipiens (Diesing, 1850) complexes 1 and 2 are present in this country. In this study, we characterised the larvae of Spirometra present in the annual fish Austrolebias charrua Costa et Cheffe. Phylogenetic analysis of the cytochrome c oxidase subunit I (COI) sequences of these larvae showed that they belong to S. decipiens complex 1. This is the first report of teleost fishes serving as a second intermediate host for tapeworms of the genus Spirometra in nature.

The family Lernaeopodidae includes 14 genera parasitizing elasmobranchs. Fourteen species of this family have been cited from Argentina, four of which were found on chondrichthyans. Schroederichthys bivius Müller and Henle and Galeorhinus galeus (Linnaeus) from Argentina harbored parasitic copepods of the genus Lernaeopoda. The objective of this study was to identify the species using an integrative approach. The morphology was examined by Optical Microscopy and Scanning Electron Microscopy and the molecular analysis was based on partial sequences of the COI mtDNA gene. Despite differences in the antenna, antennule, mandible, maxilliped and maxillae among the specimens, the morphological and molecular analyses revealed that they belonged to Lernaeopoda bivia Leigh-Sharpe, 1930. The species so far reported for Argentina are L. bivia and L. galei Krøyer, 1837, which are distinguished by the size (less and greater than 7 mm, respectively). Here, we report partial sequences of the COI mtDNA gene of L. bivia for the first time, obtained from eleven specimens attached to the mouth, fins, anal slit and claspers of the two shark hosts. The COI mtDNA gene tree shows that the Lernaeopoda group forms a sister clade with Pseudocharopinus bicaudatus (Krøyer, 1837), while the genus Pseudocharopinus does not appear to be a natural group. We propose that the material described from Argentinean waters as L. galei was misidentified and actually belongs to L. bivia. The wide variability within the specimens of L. bivia emphasizes the importance of using an integrative approach to revise the taxonomy of the Lernaeopoda species from all over the world.

La familia Synbranchidae presenta una distribución Neotropical con reportes parasitarios en Méjico, Brasil y Argentina, lo cual evidencia la falta de estudios en cuanto a la parasitofauna de estas anguilas. La inspección parasitológica clásica realizada en cinco anguilas (Synbranchus marmoratus Bloch, 1795) capturadas en Laguna del Sauce en Uruguay, reveló la presencia de parásitos de la subfamilia Massoprostatinae, los cuales fueron teñidos y montados mediante procedimientos convencionales, con Carmín de Langeron y Entellan, respectivamente. La subfamilia Massoprostatinae es monotípica, siendo Massoprostatum Yamaguti, 1958 su único género y M. longum Caballero, 1948 su única especie. A la fecha, esta especie solo se ha reportado en cocodrilos en Méjico y Colombia. Comparaciones morfológicas y biométricas de caracteres con relevancia taxonómica para la familia tales como el tamaño de la paraprostata, relación del tramo anterior y posterior del cuerpo y la distribución de las glándulas vitelarias, muestra que los ejemplares corresponden a un nuevo género y especie: Parvaprostatum synbranchi. La falta de reportes dificulta concluir si Massoprostatinae es realmente específica para cocodrilos y por lo tanto, no se puede aseverar si el presente reporte en anguilas implica un cambio de hospedador. Mas allá de la posibilidad de que los parásitos correspondan a metacercarias progenéticas, el desarrollo conspicuo de estructuras como el órgano tribocítico y los órganos reproductores, la presencia de contenido alimenticio en los ciegos intestinales y el hecho de que se hallaron desenquistados y grávidos, hace que los especímenes sean morfológicamente confiables para la identificación a nivel específico. El reporte de un nuevo hospedador y una nueva localidad enfatizan la necesidad de estudios que permitan entender los ciclos de vida subyacentes en especies de la subfamilia Massoprostatinae.

Background: Fasciola hepatica causes important economic losses in ruminants with only pharmacological treatments currently available, which produces several secondary problems. Because of this, vaccines have become an interesting alternative. Leucine aminopeptidases (LAPs) are attractive vaccine targets against fasciolosis since they play essential roles in the parasite such as host invasion and nutrient acquisition. To characterize immune responses, we produced two recombinant F. hepatica LAPs (FhLAP1 and FhLAP2), formulated with ISCOM-matrices (IMXs) nanoparticles from Quillaja brasiliensis saponins. Methods: Forty female Corriedale sheep were assigned to four groups (n = 10): FhLAP1/IMX, FhLAP1/FhLAP2/IMX, IMX (control), and FhLAP1/Adj50 (Adjuvac 50). Animals received two subcutaneous immunizations at weeks 0 and 4 and were challenged orally with 200 metacercariae at week 6. Results: FhLAP1 and FhLAP1/FhLAP2 induced specific IgG responses, with the predominance of the IgG1 response. However, these responses were lower than those generated by FhLAP1 formulated with Adj50. A qPCR analysis revealed that FhLAP1/IMX stimulated a Th1-type response profile before the challenge, but this profile was not sustained after infection. The post-infection profile of FhLAP1/FhLAP2/IMX was more congruent with expected values despite not achieving a robust IFN-γ expression. No significant differences in the fluke burden were observed. Conclusions: Further research on the optimal antigen/adjuvant combination in ruminants is encouraged. For instance, a higher concentration of adjuvant in the formulation used in this work may enhance the strength and duration of the inflammatory response and improve protective immunity against fasciolosis.