Zymogram analysis of nine strains of Toxoplasma gondii all highly virulent for mice was performed with the API enzyme research kits®. The parasite strains had been maintained by continuous intraperitoneal infection in mice for many years separately in different laboratories in Europe and were retraced to five isolates (RH, BK, 928, KB, Alt). The API research kits® use chromogenic substrates for a semiquantitative detection of 84 enzymes, including the classes aminopeptidases, glycosidases, esterases, lipases, phosphatases and phosphoamidases. From the zymograms Manhattan distances were calculated and a hierarchical tree of the parasite strains was established by complete linkage.
All strains could be easily integrated into two distinct clusters. However, the correct designation of some strains as direct descendant of a definite isolate seems to be questionable.
Zymogram analysis is suitable for a quick enzymatic characterisation of any mouse virulent Toxoplasma strain and for a simple comparison to defined reference strains. Thus, it allows a rapid detection of any strain confusion during isolation procedures or long term propagation.

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Success of the recently developed precocious vaccine for controlling coccidiosis in chicken largely depends on the extent of immunological heterogeneity among strains. In this study, seven single-oocyst-derived strains of Eimeria tenella isolated from Dhaka (D91/1), Mymensingh (M91/1, M91/2 and M91/3), Chittagong (Ch91/1 and Ch91/2) and Sylhet (S91/1) districts of Bangladesh were compared for pathogenicity and cross-protection in vivo. Strain M91/1 was found to be more pathogenic compared to M91/2 and M91/3, and caused a significant (P<0.05) depression in weight gain and blood haematocrit values, and a higher mortality. None of these three strains were different from other strains. Two immunising doses produced a solid homologous immunity. Following heterologous challenge with strain Ch91/1, there was an increased oocyst output and significant (P<0.05) depression in weight gain in chicks immunised with S91/1. The results suggest that S91/1 was less immunogenic than strain Ch91/1, although neither of these two strains were different from other strains. It is suggested that this difference was not due to a difference in fecundity or pathogenicity, rather it was more likely to be a fundamental difference in antigenic repertoire.

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Leishmania spp. , the agents of human visceral, post kala-azar dermal and cutaneous leishmaniasis, are the intracellular parasites that must be recognised and internalised by host macrophages for its pathogenesis. The involvement of specific ligand-receptor interaction necessary for the entry of different Leishmania promastigotes into murine macrophages were investigated. The effect of two enzymes on the attachment and uptake of Leishmania promastigotes by macrophages which might be found in the wound caused by the bite of the phlebotomine sandfly vector were also examined. With the two sugars tested, mannose and galactose were produced a significant inhibition of uptake in viscerotropic and dermotropic form of leishmaniasis, respectively. Mild trypsinization inhibited the uptake potential in all cases, with much higher value in the case of post kala-azar dermal leishmaniasis. Treatment of neuraminidase to macrophages enhanced attachment in all three strains to some extent. These results indicate that the nearly similar type of inhibition profile of dermal and cutaneous strains were probably due to the similar type of skin habitat.

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Six species of insect trypanosomatids of the genus Crithidia were analyzed using different biochemical and molecular biology techniques, such as kinetoplast DNA(kDNA) restriction pattern analysis, kDNA cross-hybridizations, zymodeme analysis and, computer analysis of kDNA minicircle sequences for C. fasciculata and C. oncopelti. Our results indicate that C. deanei andC. oncopelti have widely diverged from the other species we analyzed, since their kDNA did not cross-hybridize with that from the other species, indicating that a great divergence of kDNA sequences has occurred during the evolution of this genus. Comparison of kDNA minicircle sequences of C. fasciculata and C. oncopelti from the literature, showed no significant sequence homology corroborating some of our data. Restriction profiles of kDNA from the different species showed no genotypic similarity thus supporting the status of separate taxa. Furthermore, no cross-hybridization was detected between kDNA from parasites of the genus Crithidia and kDNA from parasites of different genera of monogenetic and digenetic trypanosomatids such as Herpetomonas, Blastocrithidia, Trypanosoma, Leishmania, Endotrypanum and Phytomonas.

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