In Argentina, a country considered non-endemic for hepatitis E virus (HEV) infection, serologic evidence of HEV infection has been observed in different human population groups. In other countries, a high degree of genetic relatedness has been observed between human and swine HEV genotype 3 sequences, suggesting zoonosis as one probable route of infection. This is the first identification of swine HEV in South America. HEV RNA was detected and sequenced in the ORF 1 and ORF 2 regions from swine fecal samples from a herd located in Pergamino, in the province of Buenos Aires. These strains all group into genotype 3 and exhibit a close relationship to two novel HEV variants previously identified in Argentina from sporadic acute cases of non-A to -C hepatitis in humans. In addition, using a modified commercial ELISA, the presence of anti-HEV antibodies was surveyed in five provinces across the country and all five showed a prevalence of HEV antibodies, ranging from 4% to 58%. The results suggest that swine could be an important reservoir for virus transmission in Argentina as has been suggested for other non-endemic areas. The Argentine human strains and swine strain described in this article seem to be closely related to a human Austrian strain, suggesting a potential European origin of HEV infection in these cases.

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suMMARY An ELISA method was developed for the measurement of toxoplasma IgG antibodies in human serum using antigen-coated polystyrene beads as a solid phase and anti human IgG-horse radish peroxidase conjugate as an enzymatic tracer. In order to assess ELISA sensitivity and specificity, a between methods comparison was made using 'conventional' serological tests as reference (dye-test, crossover-linked immunoassay, passive haemagglutination, indirect immunofluorescence). From an analysis of the group classifications obtained some considerations emerged: the ELISA specificity looks comparable with that of the 'reference' tests, as no sample classified as negative by all these tests was ELISA-positive, and vice versa; ELISA appears to correlate better with haemagglutination and immunofluorescence, on the basis of the respective class frequencies; in particular, the number of positives, which is much lower for the dye-test and crossover-linked immunoassay, suggests that a higher sensitivity is reached in the former cases.None of the several tests mostly used for the serodiagnosis of toxoplasmosis appears fully adequate for mass-screening purposes as far as analytical reliability, experimental ease, and promptness of response are concerned. As a matter of fact some of them need special equipment not widely available, and others cannot be used as single tests owing to the incompleteness of the information obtainable and the poor correlation with the clinical situation.Recently, the enzyme-linked immunosorbent assay (ELISA) has been proposed as a promising serological test for infective and infestive diseases. '-5 Also in our laboratories attempts were made to evaluate the actual potential of ELISA in the diagnosis of toxoplasma infections. In particular, this study was aimed at defining the specificity and sensitivity of an ELISA method we have recently developed through a comparison with other serological tests assumed as references, such as the dyetest, crossover-linked immunoassay, indirect haemagglutination, and indirect immunofluorescence.

Our aim was to evaluate the analytical and clinical performance of the SARS-CoV-2 molecular detection kits used in Argentina. Nine real-time reverse-transcription polymerase chain reaction (RT-qPCR) and three reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assays were evaluated using the World Health Organization (WHO) recommended test as reference method. A secondary standard calibrated for the E, N and RdRp genes against the Pan American Health Organization—World Health Organization—International Standard was used to calculate the limit of detection (LoD). A panel of artificial clinical samples, 32 positive and 30 negative for SARS-CoV-2, were analyzed to estimate the kappa concordance (κ) and the diagnostic performance. Differences among the LoD values for the target genes amplified by each kit were >1 log copies/reaction. The κ for the RT-qPCR kits was greater than 0.9, whereas that for the RT-LAMP assays ranged from 0.75 to 0.93. The clinical performance of RT-qPCR kits showed 100% specificity and high sensitivity, although with variations according to the gene analyzed. The E and N genes provided greater clinical sensitivity, whereas the RdRp gene increased the clinical specificity. The RT-LAMP assays revealed a variable diagnostic performance. The information provided can be useful to choose the most appropriate diagnostic test and may contribute to the establishment of a consensus in the diagnosis of SARS-CoV-2 in Argentina and the region.

In 2000, two cases of human trichinellosis were detected in the Sierra Grande area of Rio Negro province, Argentina. As part of an investigation of the aetiology of these cases, 300 pigs slaughtered for consumption in the area between 2000 and 2002 were checked for Trichinella infection, by artificial digestion of a muscle sample. Twelve (5.6%) - four (7.3%) of the 55 checked in 2000, five (4.8%) of the 105 investigated in 2001, and three (2.1%) of the 140 investigated in 2002 - were found infected. Blood samples were collected from other pigs aged > 6 months old, so that sera could be tested, in ELISA and by western blotting, for anti- Trichinella antibodies. Of the 181 animals checked in the initial serological survey, 36 (19.9%) were found seropositive for Trichinella. When 35 of the seronegative pigs were re-checked 6 months later, three (8.6%) were found to have seroconverted. Four (15.4%) of 26 local rodents, caught in Sherman-type traps, were also found positive when checked for infection by artificial digestion. It appears that about 20% of pigs in the study area are infected each year, this high level of transmission being sustained by a high prevalence of infection in the local rodent populations.