Leptospirosis is caused by several serovars of Leptospira. It is a disease of worldwide occurrence and zoonotic with considerable medical and economic importance. It is an occupational disease and responsible for vision loss. The symptoms of Leptospirosis are mostly confused with flu, liver diseases, meningitis, etc. and in many cases even today it is not being properly diagnosed. One of the major reasons for improper diagnosis is the non-availability of diagnostic kits and methods that can unequivocally demonstrate the presence/absence of Leptospira. The conventional test employed to diagnose Leptospirosis is microscopic slide agglutination test, which is not very useful. The microagglutination test (MAT) and enzymes linked immunosorbent assay (ELISA) have been recently found useful, but these tests are expensive, time consuming, difficult to standardise, and require trained personnel.

Commercially available kits for serodiagnosis are either very costly or not reliable. An agglutination dry-dot test kit uses cross-reactive antigens for antibody detection, is not very reliable and very costly. It detects both IgM and IgG antibodies, so cannot differentiate between an acute or chronic infection. Many other ELISA kits for IgM antibody detection have been introduced in the market by nearly half a dozen

commercial companies. All are imported kits and therefore very costly. All of them need harvested serum or plasma for testing and need laboratory equipment or accessories for doing the test. None of them is field-based.

DRDO has developed simple and affordable kits for bedside tests and quick diagnosis. The kits can also be used for antibody and antigen detection. Both the kits have been evaluated by WHO with satisfactory results. The kits are:

Dot-ELISA Kit for IgM Antibody Detection

The kit provides results equivalent to best available imported kit. It is very simple to use and highly economical. It has been evaluated at National Institute of Communicable Diseases, Delhi; Institute of Microbiology, Madras Medical College, Chennai; and Medical Centre, Cochin. The components of the kit have a storage life of six months at refrigeration temperature. The kit is extremely useful for primary health centres.

Salient Features

Kit is totally field-based; no need to bring patients to laboratory or hospital for testing
Cost of testing is only one-tenth of the imported kit
Delivers results of the test within one hour. Interpretation of results is very simple
Has a built-in reagent control provided for each test
Can directly work on a blood drop pricked from finger
The results can be preserved for records

Sandwich Dot-ELISA Kit For Antigen Detection

Culture of causative Leptospira organism from clinical sample would have provided a definite diagnosis, but owing to the inherent limitations of slow growth and requirement of protein-rich media that is amenable to contamination, it is of no practical value. The alternative stays to be a PCR on clinical sample for confirming diagnosis. PCR for use in clinical samples in leptospirosis has been recently reported, but would not be used as a routine. The cost of performing PCR, the need for a specialised laboratory and the inherent limitation of being highly sensitive therefore, with the risks of having false positive results, are the major problems with PCR to be used extensively for diagnosis.

DRDO has developed a new kit for Leptopsira antigen detection from clinical samples of blood and urine to overcome all these limitations. The kit can make confirmatory disease diagnosis on the day of fever itself so as to initiate specific antibiotic therapy. Like the IgM dot-ELISA kit, this is also very simple to use and economical and totally field-based.

Salient Features

Sensitivity is equivalent to PCR
Delivers results within two hr at the bedside of the patient
Built-in regent control provided for each test
Interpretation of result is very simple
Can directly work on a blood drop pricked from finger
The results can be preserved for records