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.

View full abstract

A kinetoplastic strain of Trypanosoma evansi was induced to become akinetoplastic by pararosaniline. Loss of kDNA minicircles was analyzed by DAPI fluorescence and Southern blot analysis probed with cloned kDNA fragments. Qualitative changes in the kinetoplast prior to akinetoplastidy include various fragmented fluorescence patterns and formation of inter-mediate fluorescence intensity. Thus, kDNA loss induced by pararosaniline is preceded by a gradual decrease in its size. We show that trypanosomes with intermediate amount of kDNA are unstable tending to become akinetoplastic. We further demonstrate that the difference in population doubling time between kinetoplastic and akinetoplastic forms is 4.7 and 5.5 hrs, respectively. Our results indicate that although the mutants have maintained their ability to multiply, their slower doubling rate limits them to dominate in a given population. Moreover, this feature may be one of the possible factors responsible for their inferiority to those with kDNA and for their selective disadvantage in nature.

View full abstract

A species-defined microcosm, consisting of bacteria Escherichia coli DH5a, protozoa Tetrahymena thermophila B and algae Euglena gracilis Z, was synthesized in which all species co-existed for over 130 days. This microcosm was developed as an experimental system to study gene-population interaction in a community.

View full abstract

The recent epidemic outbreaks of visceral leishmaniasis have created a major health problem in India. Whether these outbreaks and the drug-resistance seen in about a quarter of these cases are genetically based remains unknown. To facilitate a better understanding of these possibilities, we have begun to analyse kinetoplast (k) and nuclear (n) DNA heterogeneity of Leishmania isolates from Bihar (DD8, RMRI and SS) and West Bengal (AG and UR6). Schizodeme and Southern blot analyses of their kDNA separated these isolates into three groups, i.e. DD8, RMRI and SS; AG and UR6. This grouping is consistent with the results of restriction fragment length polymorphisms seen at the gp63 and β-tubulin loci by Southern blot analysis of nDNA. The results obtained better define the genetic heterogeneity of Indian visceral Leishmania isolates for further characterization of their relationships to virulence and drug-resistance.

View full abstract

Using several immunologic techniques, the reactivity of anti-bovine collagen Type specific antibodies against Toxoplasma gondii was examined. Antibodies specific for bovine Type I, II and IV collagen showed relatively high affinity to the parasites. Treatment of T. gondii cysts with collagenase, induced cyst wall rupture. Results of the study suggest the presence of collagen cross-reactive component(s) in the parasite. Similarly, the cyst wall outer surface may contain amino acid sequences recognized by collagenase. This paper documents the first report of collagen cross- reactive antigenic components of T. gondii.

View full abstract