Question

Step 1: Respond to the following prompts. Briefly summarize the complex life cycle of a vector-borne pathogen of your choice. Describe the point in the life cycle at which we should intervene to halt disease progression.

Answer 1

Leishmaniasis is one of the parasite infections affecting in tropical and temperate countries and classified as a neglected tropical disease. The disease is caused by protozoan parasite called Leishmania species transmitted to humans by the bites of the infected female phlebotomine sand fly - a tiny – only 2–3 mm long insect vector. Only the female sand fly transmits the parasites and bites usually in the evening and at night. The lifecycle is digenetic and consists of two forms; promastigote and amastigote. The life cycle is summarized below:

(i) Sandfly takes a blood meal (injects promastigote stage into the skin)

(ii) In humans, promastigotes are phagocytized by macrophages or other types of mononuclear phagocytic cells.

(iii) Promastigotes transform into amstigotes.

(iv) Amastigotes multiply in cells of various tissues and infect other cells.

(v) From humans, another sand fly takes a blood meal (ingests macrophages infected with amastigote)

(vi) Ingestion of parasitized cell.

(vii) Amstigotes transform into promastigote stage in the gut.

(viii) Divide in the gut and migrate to proboscis of sandfly.

(ix) The cycle repeats.

To prevent the infection, we can halt the process in lifecycle at some stage. If we stop the step in which the promastigotes transform into amastigotes it will prevent the infection or the other step is the prevention of multiplication of amastigotes in humans. These are the major steps in pathway in which we can end the disease.