The disease caused by protozoa is Malaria.

Explanation:
Malaria is a disease caused by the protozoan parasite of the genus Plasmodium. It is transmitted through the bite of infected female Anopheles mosquitoes.

Let's dive into the details of Malaria and its causative agent:

Protozoa - Plasmodium:
- Malaria is caused by a group of protozoan parasites belonging to the genus Plasmodium. There are several species of Plasmodium that can infect humans, including Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale.
- These protozoa are single-celled organisms that have complex life cycles involving both humans and mosquitoes.

Transmission:
- Malaria is primarily transmitted through the bite of infected female Anopheles mosquitoes.
- When an infected mosquito bites a human, it injects the malaria parasites (Plasmodium) into the bloodstream.
- The parasites then travel to the liver, where they multiply and mature.
- After maturing, the parasites re-enter the bloodstream and invade red blood cells, causing them to burst and release more parasites.
- This cycle of invasion, multiplication, and bursting of red blood cells leads to the characteristic symptoms of malaria.

Symptoms:
- The symptoms of malaria include fever, chills, headache, muscle aches, fatigue, nausea, and vomiting.
- In severe cases, malaria can lead to complications such as organ failure, anemia, and even death if left untreated.

Prevention and Treatment:
- Prevention of malaria involves measures to control mosquito populations, such as using insecticide-treated bed nets, indoor residual spraying of insecticides, and draining stagnant water where mosquitoes breed.
- Additionally, antimalarial medications can be used as preventive measures for individuals traveling to areas with high malaria transmission.
- Treatment of malaria typically involves the use of antimalarial drugs, which can vary depending on the species of Plasmodium causing the infection and the geographical region.

In conclusion, Malaria is the disease caused by protozoa, specifically the Plasmodium parasite. It is transmitted through the bite of infected mosquitoes and can cause a range of symptoms, from mild to severe. Proper prevention measures and timely treatment are crucial in controlling and managing malaria.