**5.1 Current tools and emerging technologies for diagnosis of** *Leptospira*

Different tools are being developed for the study of virulence factors, pathogenicity, and basic cell biology of organisms [52]. These are essential for proper treatment and reduction of the severity of the disease. During acute infection, nonspecific symptoms of leptospires mimic the febrile condition, which are essential for proper treatment and reduce the severity of the disease. Therefore, the diagnosis of leptospirosis is highly dependent on the particular laboratory tests [13]. Serology is the dominant one in diagnosis, while the micro-aggregation test (MAT) is the standard serological reference method. MAT is a sensitive test due to the antigenic heterogeneity of *Leptospira*, which require a large number of serovars as antigens. Furthermore, it is useless at early stage of the disease when antibodies are not present or present in less quantity [18]. Detection of disease in early stage helps the epidemiological investigators. However, antigen detection at this stage is more expensive and complex [13]. Current diagnostic tools for *Leptospira* detections other than MAT are rapid antibodybased tests, direct examination of blood, the rapid nucleic-acid diagnosis, [53], dark field microscopy (DFM), IgM ELISA, and polymerase chain reaction (PCR) [13].

## *5.1.1 Direct examination*

This method is cheap, but for direct examination, dark field microscope is required [54]. Theoretically, leptospires may be diagnosed by direct examination of blood during first week after onset of symptoms. Leptospires are 6–20 μm long and their diameter is 0.15 μm. Because of their size, dark field microscopy is required; 10<sup>−</sup><sup>2</sup> –10<sup>−</sup><sup>6</sup> leptospires/mL of blood may be observed during the acute stage of leptospirosis [55].
