Relationship between parasite load and immune responses in early stages of Leishmania donovani infection in inbred BALB/c mice.

The aim of this study was to determine if a correlation exists between Leishmania donovani parasite load and the corresponding humoral and cellular mediated immune responses in the early stages of Leishmania donovani infection in inbred BALB/c mice. Five groups of ten BALB/c mice each were inoculated intraperitoneally with stationary phase metacyclic promastigotes of Leishmania donovani at doses 1 x 10(2), 1 x 10(4), 10(6) and 1 x 10(8) respectively per mouse. Group five mice were not manipulated in any way and were left to serve as control. At weekly intervals, for five weeks, the mice were assayed for cellular mediated immune responses to leishmania antigen by the delayed type hypersensitivity skin test (DTH) and humoral responses by the direct agglutination test (DAT) and the enzyme linked immunosorbent assay (ELISA). A correlation was established between parasite load and humoral responses as assayed by DAT and ELISA techniques. This study demonstrates that it is possible to diagnose visceral leishmaniasis in experimentally infected laboratory mice by DAT and ELISA. These techniques have the potential in screening large numbers of animals suspected to be reservoirs of visceral leishmaniasis by examining the peripheral blood taken from the tail of the animal.