Final answer:
The diagnosis of leishmaniasis is based on finding the parasite within infected 2) macrophages.
Step-by-step explanation:
Leishmaniasis is caused by protozoan parasites of the genus Leishmania, which are transmitted by sand fly vectors. When a sand fly bites a human, it injects the protozoan into the skin. The parasites are then engulfed by macrophages, a type of white blood cell, but they have virulence factors that allow them to avoid destruction within the macrophages. The parasites reproduce within the macrophage and spread to other cells.
To diagnose leishmaniasis, the parasites can be visualized in stained smears of infected tissues, isolated in cultures, or detected using PCR-based assays. This allows for the identification of the specific Leishmania species causing the infection. The correct answer is 2) macrophages