| General Features | Exists in 2 forms: Leishmanial in man (vertebrate host) and Leptomonad in sandfly (invertebrate host). Whole body is covered by a pellicle. Uniflagellate. But in the Leishmanial form, there is no free flagellum, as it is reduced and lies embedded in the cytoplasm. Cytoplasm has microtubules and striations which maybe contractile. Single large spherical nucleus. Vesicular with a distinct nucleolus. |
| Life Cycle | Primary host (Vertebrate): Parasite feeds and multiplies asexually. Secondary host (Non-vertebrate): Does not undergo any change. When sandfly bites, it releases the parasite in Leptomonad form into human body at the bite wound. Upon entering the reticulo-endothelial system (liver, spleen, bone marrow, lymph nodes), they change to Leishmanial form. Leishmanial form undergoes binary fission, increasing in number. When number of parasite increases (50-200) the cell ruptures, and liberated parasites are taken up by new host cells. RE system becomes progressively infected. When a sandfly bites, it takes up Leishmanial parasites, which change to flagellated form in midgut of the sandfly. In 6-9 days, the number of parasites becomes enormous and they spread to pharynx and buccal cavity. When this host bites a human, transmission of parasite occurs. |
| Pathogenicity | Kala Azar: Transmitted through bite of sandflies. Intracellular parasite in leucocytes, cells of liver, spleen, bone marrow, lymphatic glands. Incubation period: 3 to 6 months. Symptoms: Fever, enlargement of spleen, reduction in number of WBCs, anaemia due to reduction in RBCs. In advanced stages, skin becomes rough, dark or pigmented. Death is generally due to secondary bacterial infections. Diagnosis: Microscope examination of blood film taken from spleen or bone marrow of patient, for presence of Leishmanial forms. Examination of WBC counts shows decrease of neutrophils, but an increase in lymphocytes and monocytes. RBC number also decreased. Treatment: Resistance to drugs is increasing in India. Drug used is Amphotericin B. Miltefosine is a newer oral drug with 95% cure rate. Prevent bites of sandfly. |