Diagnostic accuracy of an IgM enzyme-linked immunosorbent assay and comparison with 2 polymerase chain reactions for early diagnosis of human leptospirosis.

Enzyme-linked immunosorbent assay (ELISA) tests and polymerase chain reaction (PCR) may play a key role for early detection and treatment of human leptospirosis in developing countries. The aims of this study were to develop and validate an IgM ELISA under field conditions and to compare the diagnostic accuracy among IgG, IgM ELISAs, conventional PCR (cPCR), and real-time PCR (rtPCR) for early detection of human leptospirosis. Overall accuracy of IgM ELISA was sensitivity of 87.9%, specificity of 97.0%, and area under the curve of 0.940. When the 4 methods were compared, IgM ELISA showed the greatest diagnostic accuracy (J=0.6) followed by rtPCR (J=0.4), cPCR (J=0.2) and IgG ELISA (J=0.1). Our results support the use of IgM ELISA and rtPCR for early diagnosis of the disease. Moreover, due to their high specificity, they could be also useful to replace or supplement microscopic agglutination test as a confirmatory test, allowing more confirmations.

Enzyme-linked immunosorbent assay to diagnose human leptospirosis: a meta-analysis of the published literature.

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.

Clinical characteristics and risk factors of human leptospirosis in Argentina (1999-2005).

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.

A survey of zoonotic pathogens carried by Norway rats in Baltimore, Maryland, USA.

Norway rats (Rattus norvegicus) carry several zoonotic pathogens and because rats and humans live in close proximity in urban environments, there exists potential for transmission. To identify zoonotic agents carried by rats in Baltimore, Maryland, USA, we live-trapped 201 rats during 2005-2006 and screened them for a panel of viruses, bacteria, and parasites. Antibodies against Seoul virus (57.7%), hepatitis E virus (HEV, 73.5%), Leptospira interrogans (65.3%), Bartonella elizabethae (34.1%), and Rickettsia typhi (7.0%) were detected in Norway rats. Endoparasites, including Calodium hepatica (87.9%) and Hymenolepis sp. (34.4%), and ectoparasites (13.9%, primarily Laelaps echidninus) also were present. The risk of human exposure to these pathogens is a significant public health concern. Because these pathogens cause non-specific and often self-limiting symptoms in humans, infection in human populations is probably underdiagnosed.

Associations between leptospiral infection and seropositivity in rodents and environmental characteristics in Argentina.

Our objective was to look for associations between leptospiral infection in rodents and selected environmental and rodent characteristics in Santa Fe, Argentina. Rodents (n = 214) were trapped alive from January 1998 to December 1999 in three environmental settings. Kidneys from 118 rodents were cultured and serum samples from 201 were processed by enzyme-linked immunosorbent assay (ELISA). Logistic regression was performed with ELISA seropositivity as the dependent variable and rodent characteristics were offered as independent variables. Overall prevalence of positive ELISA reactions was 42% (84/201). In urban areas, leptospiral isolations belonged to the Ballum serogroup; in natural corridors, they belonged to the Icterohaemorragiae serogroup. M. musculus (house mouse) was the most-frequently captured species and the predominant one in urban areas. Most isolates and seropositivity results were obtained on this species. Adults and subadults had higher seroprevalences than juvenile rodents. Oligoryzomys flavescens had higher seroprevalence than Akodon azarae, Mus musculus, Rattus rattus and Rattus norvegicus.

[Outbreak of human leptospirosis after a flood in Reconquista, Santa Fe, 1998]. / Brote de leptospirosis humana luego de una inundación en Reconquista (Santa Fe), 1998.

Since April of 1998 a high number of leptospirosis cases were detected, coming from the area of Reconquista Central Hospital in Santa Fe province. Since January of that year a notable increase in rainfall and river levels was observed causing inundation. As screening test, macroscopic agglutination (MAT) using 10 serotypes of L. interrogans. Among the 122 patients studied 71 were TR positive and 52 were also ELISA positive, leptospirosis diagnosis being confirmed in 40 of them. Five infecting serogroups were identified: Icterohaemorrhagiae (7/40), Ballum (5/40), Sejroe (3/40), Pomona (3/40) and Canicola (2/40). In the remaining cases (20/40), co-agglutinins were found at the same titer against two or more serotypes of leptospires. Infection prevalence was higher in men and productive age (21 to 40 years). The clinical symptoms more frequently observed were headache, fever and myalgias. All cases occurred after the rains and in the period when the area was flooded. Their clinical presentation, time distribution, geographical localization and high frequency of contact with the risk factor inundation could indicate that, independently of search activities, there was an outbreak.

Brote de leptospirosis humana luego de una inundación en Reconquista (Santa Fe), 1998 / Outbreak of human leptospirosis after a flood in Reconquista, Santa Fe, 1998

Since April of 1998 a high number of leptospirosis cases were detected, coming from the area of Reconquista Central Hospital in Santa Fe province. Since January of that year a notable increase in rainfall and river levels was observed causing inundation. As screening test, macroscopic agglutination (MAT) using 10 serotypes of L. interrogans. Among the 122 patients studied 71 were TR positive and 52 were also ELISA positive, leptospirosis diagnosis being confirmed in 40 of them. Five infecting serogroups were identified: Icterohaemorrhagiae (7/40), Ballum (5/40), Sejroe (3/40), Pomona (3/40) and Canicola (2/40). In the remaining cases (20/40), co-agglutinins were found at the same titer against two or more serotypes of leptospires. Infection prevalence was higher in men and productive age (21 to 40 years). The clinical symptoms more frequently observed were headache, fever and myalgias. All cases occurred after the rains and in the period when the area was flooded. Their clinical presentation, time distribution, geographical localization and high frequency of contact with the risk factor inundation could indicate that, independently of search activities, there was an outbreak.(AU)

Brote de leptospirosis humana luego de una inundación en Reconquista (Santa Fe), 1998 / Outbreak of human leptospirosis after a flood in Reconquista, Santa Fe, 1998

Since April of 1998 a high number of leptospirosis cases were detected, coming from the area of Reconquista Central Hospital in Santa Fe province. Since January of that year a notable increase in rainfall and river levels was observed causing inundation. As screening test, macroscopic agglutination (MAT) using 10 serotypes of L. interrogans. Among the 122 patients studied 71 were TR positive and 52 were also ELISA positive, leptospirosis diagnosis being confirmed in 40 of them. Five infecting serogroups were identified: Icterohaemorrhagiae (7/40), Ballum (5/40), Sejroe (3/40), Pomona (3/40) and Canicola (2/40). In the remaining cases (20/40), co-agglutinins were found at the same titer against two or more serotypes of leptospires. Infection prevalence was higher in men and productive age (21 to 40 years). The clinical symptoms more frequently observed were headache, fever and myalgias. All cases occurred after the rains and in the period when the area was flooded. Their clinical presentation, time distribution, geographical localization and high frequency of contact with the risk factor inundation could indicate that, independently of search activities, there was an outbreak.

Brote de leptospirosis humana luego de una inundación en Reconquista (Santa Fe), 1998. / [Outbreak of human leptospirosis after a flood in Reconquista, Santa Fe, 1998]

Since April of 1998 a high number of leptospirosis cases were detected, coming from the area of Reconquista Central Hospital in Santa Fe province. Since January of that year a notable increase in rainfall and river levels was observed causing inundation. As screening test, macroscopic agglutination (MAT) using 10 serotypes of L. interrogans. Among the 122 patients studied 71 were TR positive and 52 were also ELISA positive, leptospirosis diagnosis being confirmed in 40 of them. Five infecting serogroups were identified: Icterohaemorrhagiae (7/40), Ballum (5/40), Sejroe (3/40), Pomona (3/40) and Canicola (2/40). In the remaining cases (20/40), co-agglutinins were found at the same titer against two or more serotypes of leptospires. Infection prevalence was higher in men and productive age (21 to 40 years). The clinical symptoms more frequently observed were headache, fever and myalgias. All cases occurred after the rains and in the period when the area was flooded. Their clinical presentation, time distribution, geographical localization and high frequency of contact with the risk factor inundation could indicate that, independently of search activities, there was an outbreak.

Development and validation of an ELISA for the detection of leptospire-specific antibodies in rodents.

An enzyme-linked immunosorbent assay (ELISA) for the detection of IgG antibodies in rodents was developed and validated with the microscopic agglutination test (MAT) and leptospiral cultures. Sonicated antigen from cultures of serovars tarassovi and pyrogenes was used. As conjugate, a combination of anti-rat and anti-hamster IgG labeled with peroxidase was used. The optimal cut-off point was determined by plotting the sensitivity and specificity for various cut-off point values by means of receiver operating characteristic (ROC) curve. Concordance between ELISA and each of the MAT titers was measured by kappa (kappa). Proportions of positive results were compared by means of McNemar's test. Total 214 rodents were trapped, but only 117 could be processed by the three techniques (culture, ELISA, MAT; 1:20, 1:40, 1:50) and used for statistical analysis. Although, MAT titers in rodents infected with the serogroup Ballum tended to be lower than those infected with the serogroup Icterohaemorrhagiae, all (20/20) were ELISA-positive and almost all (19/20) were MAT-positive.The percentage of positive results obtained by ELISA, 47.0% exceeded significantly the 40.2% obtained by MAT (1:50). Difference between ELISA and MAT (1:40) was not significant and no differences were observed between ELISA and MAT (1:20). Agreement, specificity, sensitivity and the consequent area under the ROC curve between ELISA and MAT were higher as MAT cut-off points were lowered, being optimal at 1:20. The fact that differences between ELISA and MAT were significant at 1:50, but not at 1:40 or 1:20, supports the suggestion that lower MAT titers should be considered positive in rodents. The ELISA developed to detect leptospire-specific antibodies had optimal sensitivity and specificity in relation to MAT and it is concluded that it may constitute a very useful indicator for epidemiological purposes of past or present leptospiral infection in rodents.

[Report on a leptospirosis outbreak in the city of Santa Fe, Argentina, March-April 1998]. / Descripción de un brote de leptospirosis en la ciudad de Santa Fe, Argentina, marzo-abril de 1998.

In March-April 1998 in a neighborhood in the city of Santa Fe, Argentina, there was an outbreak of an acute disease characterized by fever, headaches, and intense myalgias. This article presents the studies surrounding this outbreak and the attempts to identify the source and the mode of transmission. The epidemiological, serological, and clinical findings indicated that the causative agent was Leptospira interrogans. As a screening test, macroscopic agglutination with heat-resistant antigen was applied, followed by the ELISA test, and, as a confirmatory test, microscopic agglutination for 10 serotypes of L. interrogans. The study covered 32 persons, 8 dogs, and 8 water samples. Among the 32 persons, 12 cases were confirmed, 2 were suspicious, and 18 were negative. Six dogs were found to be infected, and motile spirochetes were found in the water samples. The human sera reacted with the ballum, canicola, icterohaemorrhagiae, and pyrogenes serotypes; the canine sera reacted with the ballum, canicola, and pomona serotypes. The coagglutination found in all the confirmed cases indicates that they were acute cases of leptospirosis, but it was impossible to identify the causal serotype. Except for the index case, the disease was not recognized clinically. Several facts suggest that the outbreak was caused by rain that had flooded the study area. The results of this study emphasize the need for active surveillance of leptospirosis when there are floods and other natural disasters.