The presice diagnosis of filarisis is presently based in the demonstration of the parasites in the night blood is incovinient, inconsistent and not sensitive in detecting low microfilaraemia. Further, microfilariae are not  normally seen in peripheral blood in acute and chronic infections as well as occult filarial infections, making  it  difficult to diagnose clinically for successful treatment. Most of the clinicians rely on their clinical acumen  in the diagnosis of clinical filariasis.  

Immunodiagnosis:

SEVA FILACHEK (IgG & Ag assay) dipstick based ELISA system has been explored in several ways at MGIMS using penicillinase enzyme, microfilarial antigen and filarial antibodies in diagnosis of filarial infection in different clinical groups(3). The detection of IgG antibody (titre 1:3000 & above) against specific microfilarial antigen was found to be useful for detecting microfilaramic and most of the clinical filarial cases. Free and immune complexed filarial antigen (titre 1:3000 & above) are detected using filarial serum immunoglobulin G (FSIgG). Filarial antigen detection was found to be more useful in epididymoorchitis and allergic state such as Tropical eosinophilia .  The test system showed a sensitivity and specificity of about 80% (4,5).   

 Antibody detection by Indirect Penicillinase ELISA & antigen detection by Inhibition Penicillinase ELISA :

The antibody detection test is based on the detection of specific IgG antibody to Brugia malayi mf ES antigen by indirect penicillinase ELISA. The mf ES antigen coated CAM sticks are incubated with diluted (1:300) filarial sera followed by anti-human IgG penicillinase conjugate. After washing, when the sticks are finally incubated with blue coloured starch-iodine-penicillin ‘V‘ substrate, the disappearance  of  the colour earlier than control indicates the presence of filarial antibody. The free and IC antigen detection is done by inhibition ELISA.The CAM sticks, sensitized with FSIgG isolated from clinical patient’s sera are incubated with appropriate test sera (1:300) followed by mf ES antigen penicillinase conjugate. The presence of filarial antigen is indicated by the persistence of the blue colour of starch-iodine-penicillin ‘V‘ substrate. The free antigen detection assay was found to be useful to detect microfilaraemic patients (80%), whereas, IC antigen detection was useful to detect clinical filariasis viz; chronic filariasis (80%), acute filariasis (88%) & occult filariasis (78%). Both the free and IC antigen detection assays have given specificity of 88% (Bhunia et al, in communication).