Plasmodium malariae is a protozoan parasite that causes malaria in humans. It is transmitted via the bites of infected female Anopheles mosquitoes. Malaria infects hundreds of millions of people annually and kills over a million people, mostly young children. P. malariae has a multi-stage lifecycle involving human and mosquito hosts. Diagnosis involves microscopic examination of blood smears to detect the parasite. Common symptoms include fever, chills, and flu-like illness. Treatment options include drugs like chloroquine, atovaquone/proguanil, and prevention involves mosquito repellents and bed nets.