Enzyme-linked immunosorbent assay for leptospirosis immunoglobulin M specific antibody using surface antigen from a pathogenic Leptospira: a comparison with indirect hemagglutination and microagglutination tests.

A search for a sensitive and specific test for human leptospirosis was made by enzyme-linked immunosorbent assay for immunoglobulin M specific antibody (IgM ELISA) using a surface antigen from L.interrogans serovar bataviae, L. interrogans serovar pyrogenes and L.interogans serovar icterohaemorrhagiae. The IgM ELISA tests using each of the three antigens were evaluated in 103 sera primarily positive by microagglutination test (MA). Optical density of these IgM ELISA tests showed good correlation. The IgM ELISA using antigen from serovar bataviae was compared with MA and indirect hemagglutination (IHA) in 20 sera primarily positive by IHA, and 103 sera primarily positive by MA. IgM ELISA and IHA using antigen prepared from serovar bataviae in 103 sera positive for MA had a sensitivity of 98.06 and 92.23 per cent respectively. In 20 sera primarily positive by IHA, IgM ELISA and MA showed sensitivity of 80 and 45 per cent respectively. The surface antigen used in IgM ELISA is broadly specific making IgM ELISA a sensitive and specific test for human leptospirosis. IHA agreed more with IgM ELISA in comparison to MA. As MA is not sensitive for early infection, IHA and IgM ELISA should be in routine use in general laboratories.

Evaluation of two screening tests for human leptospirosis.

Leptospirosis is prevalent in Thailand but its diagnosis depends primarily on clinical awareness. Serodiagnosis is of great assistance in the diagnosis of leptospirosis but in Thailand microagglutination (MA) is the only serodiagnosis available. MA is not rapid and it is used mainly in the referent laboratory. In addition, its roles in early diagnosis are rarely available. Rapid screening serological test which is sensitive early in the infection is needed. Latex agglutination (LA), indirect hemagglutination (IHA) were developed and evaluated in 100 MA positive sera and 200 blood donors. Later on, IHA and LA were compared with MA in 30 patients with a clinical picture compatible with leptospirosis. IHA and LA had sensitivities of 94 and 98 per cent respectively in MA positive sera. The specificity of IHA and LA in 200 blood donors was 99 and 100 per cent respectively. The study in 30 patients showed that LA and IHA were definitely more sensitive than MA test in sera collected within two weeks after the onset of fever. LA is also one of the most rapid tests for leptospirosis. With either LA or IHA human leptospirosis will be diagnosed more readily and more accurately.

Leptospirosis in man and rodents in North and Northeast Thailand.

A seroepidemiological study of leptospirosis in man and rodents in the North and Northeast Thailand revealed that 0.27% of the rural people from three different ecologic areas were positive. The positivity rate has dropped dramatically when compared to a previous survey (28%). Of 1,135 wild rodents studied, 42 of 365 (11.5%) B. indica and 50 of 676 (7.4%) R. rattus were serologically positive. Others were negative. Only two of 157 R. rattus had positive cultures in which L. javanica and L. autumnalis were isolated. The study shows that wild rats are naturally implicated in human disease as a common reservoir and that the yearly rat eradication campaigns attributed as one of the effective factors in a major reduction of disease to a level of non significant public health hazard.