parasita

Parasita is an organism that lives on or in another organism, the host, from which it obtains nutrients and resources, often causing harm. Parasitism is a type of symbiosis in which the parasite benefits and the host is harmed. Parasites span a wide range of life forms, including protozoa, helminths, and arthropods. They can be microparasites, which are small and multiply within hosts, or macroparasites, which are larger and may accumulate over time. They can reside inside the host (endoparasites) or on its surface (ectoparasites).

Life cycles vary: some parasites have direct life cycles with a single host; others require intermediate hosts or vectors to complete development. Transmission can occur via ingestion of contaminated food or water, skin penetration, vector-borne spread, sexual contact, or direct contact between hosts. The interaction with the host's immune system drives coevolution.

Common groups include protozoa (for example, Plasmodium causing malaria; Giardia), helminths (trematodes, nematodes, cestodes such as Taenia), and ectoparasites (fleas, lice, ticks). Parasitic infections contribute to significant global disease burden, especially in areas with limited sanitation, healthcare, or vector control. Symptoms depend on the parasite and can include diarrhea, anemia, malnutrition, organ damage, or chronic fatigue.

Control and prevention rely on sanitation, safe water, vector management (nets, insecticides), vaccination where available, and antiparasitic drugs such as antimalarials, benzimidazoles, or ivermectin. Early detection and proper diagnosis are essential, often using microscopy, antigen tests, or molecular methods.