Question

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

There are two hosts in the life cycle of the malarial parasite. One host is the human and the other is the female Anopheles mosquito. The asexual part of the life cycle occurs in the human while the sexual part occurs in the Anopheles mosquito.

1. When an infected mosquito bites human being, it injects the sporozoites of the protozoan into the human body.
2. The sporozoites first multiply in the liver; here they convert into schizont. This stage is called as exo-erythrocytic schizogony.
3. Schizonts rupture and release merozoites into the the RBC. This stage is called as erythrocytic schizogony.
4. Merozoites further infect fresh RBCs.
5. Some merozoites differentiate into microgametocytes and macrogametocytes.
6. When a normal mosquito bites an infected human being, then the gametocytes enter into the mosquito.
7. In the mosquito’s stomach, mating of micro and macro gametocytes occur; this results in formation of zygote.
8. After some time the zygote matures, resulting into an ookinete.
9. This ookinete travels to the mosquito’s salivary gland, converting the normal mosquito into an infected mosquito.

Now, if you have to halt disease progression, then you have to stop the multiplication of sporozoites and the schizont. In simple words, you have to prevent point no. 2 and 3; for this you need to administer drugs to the patient.