Parasitic diseases are illnesses caused by parasites such as protozoa, helminths, and ectoparasites. These parasites live on or inside a host organism, often causing harm and leading to various health issues. Common parasitic diseases include malaria, amoebiasis, giardiasis, ascariasis, and schistosomiasis. They are commonly transmitted through contaminated food, water, insect bites, or poor sanitation. Symptoms vary but may include diarrhea, fever, fatigue, and weight loss. Diagnosis is done through microscopic examination, antigen detection, or molecular tests. Treatment usually involves specific antiparasitic medications. Parasitic diseases are a major health concern, especially in tropical and developing regions.