There is scarce data on the burden of leptospirosis and its epidemiological characteristics in Argentina. This study aimed to evaluate distribution of leptospirosis cases and identify risk factors for the disease during national laboratory-based surveillance. From January 1999 to December 2005, 812 suspected cases were referred to the national reference laboratory, of which 182 and 463 had respectively, laboratory confirmed and unconfirmed diagnosis of leptospirosis. The diagnosis of leptospirosis was discarded in 167 cases. The most prevalent presumptive infecting serogroup was Icterohaemorrhagie followed by Pomona, Ballum and Canicola. The majority of cases occurred during the worm and rainy months. Confirmed cases were predominantly adults and males, who presented with fever, headache and myalgias. Severe clinical manifestations included jaundice and acute renal insufficiency. Conjunctival suffusion, a hallmark clinical sign of leptospirosis, was found in 55% of confirmed cases, and 43% of the cases with discarded diagnosis (p=0.036). After multivariate analyses, age >30 years (OR=2.16; 1.05-4.41), occupation in a rural setting (OR=3.41; 1.45-8.06), contact with contaminated surface water (OR=2.17; 1.01-4.68), and contact with floods (OR=4.49; 1.17-17.25) were significantly associated with leptospirosis. In conclusion, although activities associated with rural occupations remain important risk factors in Argentina, exposures occurring during flooding events have emerged to be the major risk factor for leptospirosis.

We report an evaluation of the accuracy of ELISA for the detection of Leptospira-specific antibodies in humans. Eighty-eight studies published in 35 articles met all inclusion criteria and were submitted to meta-analysis. Pooled sensitivity and specificity were 0·779 (95% CI 0·770-0·789) and 0·913 (95% CI 0·908-0·917), respectively, and the area under the curve was 0·964. Heterogeneity across studies was statistically significant, but none of the sources of heterogeneity (disease stage, antigen used, antibody detected) could fully explain this finding. Although the convalescent stage of disease was significantly associated with higher diagnostic accuracy, IgM ELISA was the best choice, regardless of the stage of disease. Negative ELISAs (IgG or IgM) applied in the acute phase do not rule out leptospirosis due to the possibility of false-negative results. In this case it is advisable to request a second blood sample or to apply a direct method for leptospiral DNA.

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Aims:  To identify LipL32 epitopes and to evaluate their capability to recognize specific antibodies using ELISA. Methods and Results:  Epitope mapping by means of a library of overlapping peptide fragments prepared by simultaneous and parallel solid phase peptide synthesis on derivatized cellulose membranes (SPOT synthesis) was carried out. Eighty‐seven overlapping decapentapeptides corresponding to the complete sequence of LipL32 were synthesized. According to spot‐image intensities, the most reactive sequences were localized in regions 151–177 (sequence AAKAKPVQKLDDDDDGDDTYKEERHNK) and 181–204 (sequence LTRIKIPNPPKSFDDLKNIDTKKL). Two peptides (P1 and P2) corresponding to these sequences were synthesized, and their reactivity evaluated using ELISA test. Conclusions:  Epitope identification and analysis suggested the existence of two antigenic regions within LipL32. These LipL32 reactive regions were highly conserved among antigenically variants of Leptospira spp. isolates. Peptides containing these regions (P1 and P2) showed a good capability for anti‐leptospiral antibody recognition. Significance and Impact of the Study:  This finding could have potential relevance not only for serodiagnosis but also as a starting point for the characterization of targets for vaccine design.

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Our results indicate that this ELISA test can be a very useful complement to the MAT for the diagnosis of leptospirosis in all the stages and, in particular, in order to diagnose acute disease sooner.

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