Leishmania Life Cycle in Sandfly and Human Host

Leishmania belongs to genus trypanosomes that causes disease leishmaniasis. These genus are spreaded fastly by sandflies, who belonged to the Phlebotomus genus in the old period and now they come under the Lutzomyia genus. About 93 species of sandfly are present in the ecosystem. Most commonly infected hosts by leishmania are hyraxes, canids, rodents and humans and their primary hosts are vertebrates. Parasitic leishmania are commonly known for their multiplying tendency inside sand fly. There are various types of leishmania one among them is visceral leishmania, which is commonly known as Kala-azar and they are most fatal as they cause anemia, weight loss, irregular periods of fever and enlargement in spleen and liver. Another type is cutaneous leishmania and they are commonly present and causes ulcers, skiing damage that causes scars. These species are mostly active during night i.e they are nocturnal in nature and they require humid and warm temperature for their survival.

Classification of Leishmania

Phylum: Protozoans

Order: Kinetoplastids

Family: Trypanosomatidae

Genus: Leishmania

Causing Agents

Leishmaniasis is a vector borne disease that is transmitted by sand flies and they are caused by protozoa named Leishmania. There are more than 20 species of Leishmania which causes human infection they are:  L. donovani complex with 2 species (L. donovani, L. infantum [also known as L. chagasi in the New World]); the L. mexicana complex with 3 main species (L. mexicana, L. amazonensis, and L. venezuelensis); L. tropica; L. major; L. aethiopica; and the subgenus Viannia with 4 main species (L. [V.] braziliensis, L. [V.] guyanensis, L. [V.] panamensis, and L. [V.] peruviana). All these species are morphologically the same from one another but can be differentiated from one another by iso enzymes and molecular methods.

Life cycle of Leishmania

Leishmaniasis is caused in two different stages:

1. Sand Fly Stage: In the very first stage infected sand fly find a suitable host for themself and inject the promastigote parasites into the skin during blood meal. Promastigote is also a type of Leishmania which are elongated, flagellated and infective parasites that grow in the midgut of female sandfly for further infection process.

2. Human Stage: After reaching promastigotes into the wound, they are either ingested or phagocytized by macrophage cells. Transformation of the cell into the tissue stage of the parasite is done by promastigotes and this parasite is known as amastigotes. Amastigotes multiply simply by division process. Due to this multiplication process they form large groups, and now they are ready to infect mononuclear phagocytic cells. They show symptoms. After all this when a sand fly finds an infected host, it ingests these infected cells as soon as they sucks blood from the host and by this fly gets infected with the parasite. Development of amastigotes to promastigotes occurs inside the gut of sandflies.  After developing, the parasite migrates to the sucking organ of the fly known as proboscis. After arriving at the proboscis, it is only a matter of time when the sandfly bites a human host and passes on the disease leishmaniasis.

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How to Diagnosis Leishmaniasis Disease

There are various laboratory methods by which we can diagnose leishmaniasis disease. Some of them are:

1. From bone marrow we can examine parasites under a microscope, in special culture and by  molecular test. Example: for detection of visceral leishmaniasis we can use this method.

2. By blood test we can detect antibodies produced in response to parasites. 

Prevention and Control

No vaccines or drugs are available to prevent infection and the best way to stay away from leishmaniasis is preventive measures, some of these preventive measures are given below:

1. Cover as much skin as you can, to avoid getting in contact with parasites. 

2. Apply skin repellent to exposed skin areas and under the sleeves and pant legs and the most effective repellent is DEET.