EVALUATION OF DIRECT AGGLUTINATION-TEST IN THE DIAGNOSIS OF SUBCLINICAL KALA-AZAR AND LYMPHATIC LEISHMANIASIS

Efficacy of direct agglutination test (DAT) in diagnosing sub-clinical visceral and lymphatic leishmaniasis was assessed in the field, with an aim to incorporate the test as an early diagnostic tool in the kala-azar control programme of the State, using trypsinized whole promastigotes of Leishmania donovani as antigen and filter paper collected finger prick blood, as clinical sample. Bone marrow and lymph node biopsies were examined to demonstrate parasites. Frank kala-azar and persons with initial high antibody level (>3,200) were excluded from this report. Following initial DAT screening of 2,150 individuals (which included persons with fever of any duration and those with superficial lymph node enlargement with or without fever), 150 persons with low antibody level (DAT titre 400 and 800) were retested after 6 weeks. Out of these 150 individuals, 100 were diagnosed as lymphatic leishmaniasis either by demonstrating parasites in lymph nodes or by a rise in antibody level; thirty cases as kala-azar progressing from a sub-clinical stage, because of a 2-4 fold rise in antibody level and/or demonstrating parasites in bone marrow. In the remaining 20, the antibody level declined, no parasites could be demonstrated in bone marrow and thus were considered of non-leishmanial origin. It was therefore concluded that the DAT was highly effective in identifying lymphatic leishmaniasis and could be very useful in selecting out infected individuals at their subclinical state for future confirmation of the transformation to clinical state using the same tool without the need for bone marrow biopsies.