Strongyloidiasis (Strongyloides papillosus) in lambs in Uruguay.

Here, we describe a spontaneous outbreak of strongyloidiasis (Strongyloides papillosus) in sheep in Uruguay. In a flock of 150 lambs, 60 animals became ill and 12 died within 3 weeks. Affected animals showed weakness, weight loss, enophthalmos and, in some cases, sudden death. Postmortem examination revealed muscle atrophy, dehydration, and small intestines with a foamy and liquid content. Histological examination of the duodenum and the jejunum showed a thick mucosa with severe villous atrophy, mononuclear mixed infiltrate in the lamina propria, and a large number of nematodes embedded in the mucosa, with numerous granulomas in the lamina propia. Small intestinal content analysis showed a total of 13,200 female nematodes in the duodenum and 2000 in the jejunum, identified as Strongyloides papillosus (Strongyloididae). This parasite has long been considered to behave as a commensal parasite or at least to cause significant disease only when present in large numbers. This report shows that Strongyloides papillosus can be highly pathogenic in sheep.

Natural Fasciola hepatica infection in nutria (Myocastor coypus) in Uruguay.

Fascioliasis, the zoonotic disease caused by the trematode Fasciola hepatica, is expanding worldwide, with a 17 million people at risk. Rodents, often recognized as a major source of zoonotic diseases, are affected by F. hepatica, with some species playing important roles in the disease epidemiology. The case reported here in a nutria or kiyá (Myocastor coypus) is the first documented case of F. hepatica in this species in Uruguay. Parasitic burden and total egg production detected are markedly higher than reported previously for this species, confirming its potential role as an effective reservoir and disseminator of liver flukes. Although further research is needed, nutria should be considered when designing effective control programs for fascioliasis.

Maintenance of Life Cycle Stages of Fasciola hepatica in the Laboratory.

Fasciola hepatica has a heteroxenous complex life cycle that alternates between an invertebrate intermediate and a mammalian definitive host. The life cycle has five well-defined phases within their hosts and the environment: (1) eggs released from the vertebrate host to the environment and its subsequent development; (2) emergence of miracidia and their search and penetration into an intermediate snail host; (3) development and multiplication of larval stages within the snail; (4) emergence of cercariae and the encystment in metacercariae; and (5) ingestion of infective metacercariae by the definitive host and development to its adult form. Here we describe some protocols to obtain and maintain different developmental stages of F. hepatica in the laboratory for different applications (molecular/cellular biology studies, vaccination trials, etc.).

Pleiotropic alterations in gene expression in Latin American Fasciola hepatica isolates with different susceptibility to drugs.

BACKGROUND: Fasciola hepatica is the main agent of fasciolosis, a zoonotic disease affecting livestock worldwide, and an emerging food-borne disease in humans. Even when effective treatments are available, drugs are costly and can result in tolerance, liver damage and normally they do not prevent reinfection. Drug-resistant strains in livestock have been reported in various countries and, more worryingly, drug resistance in human cases has emerged in South America. The present study aims to characterize the transcriptome of two South American resistant isolates, the Cajamarca isolate from Peru, resistant to both triclabendazole and albendazole (TCBZR/ABZR) and the Rubino isolate from Uruguay, resistant to ABZ (TCBZS/ABZR), and compare them to a sensitive strain (Cenapa, Mexico, TCBZS/ABZS) to reveal putative molecular mechanisms leading to drug resistance. RESULTS: We observed a major reduction in transcription in the Cajamarca TCBZR/ABZR isolate in comparison to the other isolates. While most of the differentially expressed genes are still unannotated, several trends could be detected. Specific reduction in the expression levels of cytoskeleton proteins was consistent with a role of tubulins as putative targets of triclabendazole (TCBZ). A marked reduction of adenylate cyclase might be underlying pleiotropic effects on diverse metabolic pathways of the parasite. Upregulation of GST mu isoforms suggests this detoxifying mechanism as one of the strategies associated with resistance. CONCLUSIONS: Our results stress the value of transcriptomic approaches as a means of providing novel insights to advance the understanding of drug mode of action and drug resistance. The results provide evidence for pleiotropic variations in drug-resistant isolates consistent with early observations of TCBZ and ABZ effects and recent proteomic findings.

DNA multigene characterization of Fasciola hepatica and Lymnaea neotropica and its fascioliasis transmission capacity in Uruguay, with historical correlation, human report review and infection risk analysis.

BACKGROUND: Fascioliasis is a pathogenic disease transmitted by lymnaeid snails and recently emerging in humans, in part due to effects of climate changes, anthropogenic environment modifications, import/export and movements of livestock. South America is the continent presenting more human fascioliasis hyperendemic areas and the highest prevalences and intensities known. These scenarios appear mainly linked to altitude areas in Andean countries, whereas lowland areas of non-Andean countries, such as Uruguay, only show sporadic human cases or outbreaks. A study including DNA marker sequencing of fasciolids and lymnaeids, an experimental study of the life cycle in Uruguay, and a review of human fascioliasis in Uruguay, are performed. METHODOLOGY/PRINCIPAL FINDINGS: The characterization of Fasciola hepatica from cattle and horses of Uruguay included the complete sequences of the ribosomal DNA ITS-2 and ITS-1 and mitochondrial DNA cox1 and nad1. ITS-2, ITS-1, partial cox1 and rDNA 16S gene of mtDNA were used for lymnaeids. Results indicated that vectors belong to Lymnaea neotropica instead of to Lymnaea viator, as always reported from Uruguay. The life cycle and transmission features of F. hepatica by L. neotropica of Uruguay were studied under standardized experimental conditions to enable a comparison with the transmission capacity of F. hepatica by Galba truncatula at very high altitude in Bolivia. On this baseline, we reviewed the 95 human fascioliasis cases reported in Uruguay and analyzed the risk of human infection in front of future climate change estimations. CONCLUSIONS/SIGNIFICANCE: The correlation of fasciolid and lymnaeid haplotypes with historical data on the introduction and spread of livestock into Uruguay allowed to understand the molecular diversity detected. Although Uruguayan L. neotropica is a highly efficient vector, its transmission capacity is markedly lower than that of Bolivian G. truncatula. This allows to understand the transmission and epidemiological differences between Andean highlands and non-Andean lowlands in South America. Despite rainfall increase predictions for Uruguay, nothing suggests a trend towards a worrying human infection scenario as in Andean areas.

Equine Encephalomyelitis Outbreak, Uruguay, 2023-2024.

We report the genomic analysis from early equine cases of the Western equine encephalitis virus outbreak during 2023-2024 in Uruguay. Sequences are related to a viral isolate from an outbreak in 1958 in Argentina. A viral origin from South America or continuous enzootic circulation with infrequent spillover is possible.

The recombinant gut-associated M17 leucine aminopeptidase in combination with different adjuvants confers a high level of protection against Fasciola hepatica infection in sheep.

Fasciola hepatica M17 leucine aminopeptidase (FhLAP) is thought to play a role in catabolizing peptides generated by the concerted activity of gut-associated endopeptidases on host polypeptides, thus releasing amino acids to be used in protein anabolism. In this study, a recombinant functional form of this homo hexameric metallopeptidase produced in Escherichia coli was used in combination with adjuvants of different types in a vaccination trial in Corriedale sheep against experimental challenge with F. hepatica metacercariae. The experimental assay consisted of 6 groups of 10 animals; 5 of the groups (1-5) were subcutaneously inoculated at weeks 0 and 4 with 100 µg of rFhLAP mixed with Freund's complete plus incomplete adjuvant (group 1), Alum (group 2), Adyuvac 50 (group 3), DEAE-D (group 4) and Ribi (group 5); the adjuvant control group (group 6) received Freund's adjuvant. Two weeks after the booster, the sheep were orally challenged with 200 metacercariae. Immunization with rFhLAP induced significant reduction in fluke burdens in all vaccinated groups: 83.8% in the Freund's group, 86.7% in the Alum group, 74.4% in the Adyuvac 50 group, 49.8% in the Ribi group and 49.5% in the DEAE-D group compared to the adjuvant control group. Morphometric analysis of recovered liver flukes showed no significant size modifications in the different vaccination groups. All vaccine preparations elicited specific IgG, IgG1 and IgG2 responses. This study shows that a liver fluke vaccine based on rFhLAP combined with different adjuvants significantly reduced worm burden in a ruminant species that was high in animals that received the enzyme along with the commercially approved adjuvants Alum and Adyuvac 50.