It is diagnosed that Seema suffers from Malaria.

• Which organ of Seema is affected?
• Which microbe is responsible for this disease?
• What is the system of this disease?

Malaria affects liver.

Parasitic protozoa Plasmodium is the causal organism responsible for Malaria.

I guess its not system, it should be symptoms. Main symptoms of malaria is high fever with shivering cold. Along with this there are various other symptoms, associated with the type of vector, and the tissue or organ the vector targets.