A Structural Analysis of Host-Parasite Interactions in Achatina fulica (Giant African Snail) Infected with Angiostrongylus cantonensis.

Angiostrongylus cantonensis is a nematode parasite that resides in the pulmonary arteries of rodents, serving as its definitive hosts. The life cycle involves several species of non-marine gastropods as intermediate hosts, and the African giant snail Achatina fulica is considered one of the most important around the world. Experimental data concerning A. cantonensis infection in the African giant snail remains notably limited. This helminth causes eosinophilic meningitis or meningoencephalitis in humans, representing an emergent zoonosis in Brazil. Understanding the host-parasite relationship through the application of new tools is crucial, given the complex interaction between zoonosis and the intricate mechanisms involving wild/human hosts, parasite adaptation, and dispersion. The objective of this study was to employ SEM as a novel methodology to understand the structural organization of the host tissue, particularly the granuloma formation. This sheds light on the complex balance between A. fulica and A. cantonensis. Nine three-month-old snails were randomly selected and exposed for 24 h to a concentration of 2000 L1/dose of A. cantonensis. A necropsy was performed 37 days after the infection, and the samples were examined using light and scanning electron microscopy (SEM). The histopathological results revealed third-stage larvae of A. cantonensis associated with granulomas distributed throughout the head-foot mass, mantle, and kidney. Scanning electron microscopy of the histological section surface showed that the granuloma is surrounded by a cluster of spherical particles, which are distributed in the region bordering the larvae. This reveal details of the nematode structure, demonstrating how this methodology can enhance our understanding of the role of granulomas in molluscan tissue. The structural characteristics of granuloma formation in A. fulica suggest it as an excellent invertebrate host for A. cantonensis. This relationship appears to provide protection to the parasite against the host's immune defense system while isolating the snail's tissue from potential exposure to nematode antigens.

The Screen of a Phage Display Library Identifies a Peptide That Binds to the Surface of Trypanosoma cruzi Trypomastigotes and Impairs Their Infection of Mammalian Cells.

Background: Chagas is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. On the order of seven million people are infected worldwide and current therapies are limited, highlighting the urgent need for new interventions. T. cruzi trypomastigotes can infect a variety of mammalian cells, recognition and adhesion to the host cell being critical for parasite entry. This study focuses on trypomastigote surface ligands involved in cell invasion. Methods: Three selection rounds of a phage peptide display library for isolation of phages that bind to trypomastigotes, resulted in the identification of the N3 dodecapeptide. N3 peptide binding to T. cruzi developmental forms (trypomastigotes, amastigotes and epimastigotes) was evaluated by flow cytometry and immunofluorescence assays. Parasite invasion of Vero cells was assessed by flow cytometry and immunofluorescence assays. Results: Phage display screening identified the N3 peptide that binds preferentially to the surface of the trypomastigote and amastigote infective forms as opposed to non-infective epimastigotes. Importantly, the N3 peptide, but not a control scrambled peptide, inhibits trypomastigote invasion of Vero cells by 50%. Conclusion: The N3 peptide specifically binds to T. cruzi, and by doing so, inhibits Vero cell infection. Follow-up studies will identify the molecule on the parasite surface to which the N3 peptide binds. This putative T. cruzi ligand may advance chemotherapy design and vaccine development.

Light and scanning electron microscopy study of in vitro effects of artesunate in newly excysted metacercariae of Echinostoma paraensei (Trematoda: Digenea).

Chemotherapy of food-borne trematodes relies on two drugs, praziquantel and tricabendazole, and there is growing interest in finding alternative therapies. Plant oil extracts have long been used in traditional Chinese medicine as sources of bioactive compounds with antiparasitic activity. Species of the genus Echinostoma are used as good models to test effective compounds against food-borne trematodes. This study evaluated the anthelmintic activity of crude artesunate extracts in vitro on newly excysted metacercariae of Echinostoma paraensei by light and scanning electron microscopy (SEM). The flukes were incubated with 1 µg/mL, 10 µg/mL, 25 µg/mL, 50 µg/mL and 100 µg/mL of artesunate for 4, 12, 24, 48 and 72 h. When the exposure time and concentration of artesunate increased, there were changes in motor activity, tegument damage and death. Blebs and swelling were the most common damages quantified on the tegument. The in vitro study reproduced results described for other immature flukes incubated with artemisinin derivatives. Excysted metacercariae of E. paraensei constitute a good model to study in vitro drug effects.

Angiostrongylus cantonensis infection in molluscs in the municipality of São Gonçalo, a metropolitan area of Rio de Janeiro, Brazil: role of the invasive species Achatina fulica in parasite transmission dynamics.

The aim of this study was to analyse the infection dynamics of Angiostrongylus cantonensisin its possible intermediate hosts over two years in an urban area in the state of Rio de Janeiro where the presence ofA. cantonensis had been previously recorded in molluscs. Four of the seven mollusc species found in the study were exotic.Bradybaena similaris was the most abundant, followed by Achatina fulica, Streptaxis sp., Subulina octona, Bulimulus tenuissimus, Sarasinula linguaeformis and Leptinaria unilamellata. Only A. fulica and B. similaris were parasitised by A. cantonensis and both presented co-infection with other helminths. The prevalence of A. cantonensis in A. fulica was more than 50% throughout the study. There was an inverse correlation between the population size ofA. fulica and the prevalence of A. cantonensis and abundance of the latter was negatively related to rainfall. The overall prevalence of A. cantonensis in B. similaris was 24.6%. A. fulica was the most important intermediary host of A. cantonensis in the studied area and B. similaris was secondary in importance for A. cantonensis transmission dynamics.

Angiostrongylus cantonensis infection in molluscs in the municipality of São Gonçalo, a metropolitan area of Rio de Janeiro, Brazil: role of the invasive species Achatina fulica in parasite transmission dynamics

The aim of this study was to analyse the infection dynamics ofAngiostrongylus cantonensisin its possible intermediate hosts over two years in an urban area in the state of Rio de Janeiro where the presence ofA. cantonensis had been previously recorded in molluscs. Four of the seven mollusc species found in the study were exotic.Bradybaena similariswas the most abundant, followed byAchatina fulica, Streptaxissp., Subulina octona, Bulimulus tenuissimus, Sarasinula linguaeformisand Leptinaria unilamellata. Only A. fulicaand B. similariswere parasitised by A. cantonensis and both presented co-infection with other helminths. The prevalence of A. cantonensisin A. fulicawas more than 50% throughout the study. There was an inverse correlation between the population size ofA. fulicaand the prevalence of A. cantonensisand abundance of the latter was negatively related to rainfall. The overall prevalence of A. cantonensisin B. similariswas 24.6%. A. fulicawas the most important intermediary host of A. cantonensisin the studied area andB. similariswas secondary in importance for A. cantonensistransmission dynamics.

Morphological and genetic identification of Anisakis paggiae (Nematoda: Anisakidae) in dwarf sperm whale Kogia sima from Brazilian waters.

Anisakid nematodes have been identified in a wide variety of fish and marine mammal species. In Brazil, Anisakis physeteris, A. insignis, A. typica, A. nascetti, and those of the A. simplex complex have been reported infecting fishes and cetaceans. In this study, specimens collected from a dwarf sperm whale Kogia sima (Owen, 1866) stranded on the northeastern coast of Brazil were identified through morphological and genetic analyses as A. paggiae. Anisakids were examined through differential interference contrast light and scanning electron microscopy (SEM). Morphological and morphometric analysis revealed that these specimens belonged to Anisakis sp. clade II and more specifically to A. paggiae, exhibiting a violin-shaped ventriculus and 3 denticulate caudal plates, which are taxonomic characters considered unique to this species. Genetic analysis based on the mtDNA cox2 gene confirmed our identification of A. paggiae. Phylogenetic trees using both maximum likelihood and neighbor-joining methods revealed a strongly supported monophyletic clade (bootstrap support = 100%) with all available A. paggiae sequences. Integrative taxonomic analysis allowed the identification of A. paggiae for the first time in Brazilian waters, providing new data about their geographical distribution. Moreover, here we present the first SEM images of this species.