Parasiitsed

Parasiitsed (parasites) are organisms that live on or inside another organism, the host, and obtain nutrients at the host's expense. They may cause disease and reduce fitness in humans, animals, and ecosystems. Parasites are classified by their location relative to the host: ectoparasites inhabit external surfaces, while endoparasites live inside tissues or organs.

Endoparasites include protozoa (for example Giardia lamblia, Entamoeba histolytica, Plasmodium species) and helminths (nematodes such as Ascaris lumbricoides; cestodes such as Taenia species; trematodes such as Schistosoma). Many have complex life cycles involving one or more intermediate hosts or vectors, such as mosquitoes, snails, or fish, and they may require specific environmental conditions to complete development.

Transmission occurs through ingestion of contaminated food or water, contact with infected soil or surfaces, vector-borne transfer by mosquitoes or ticks, or direct person-to-person spread. The clinical impact ranges from asymptomatic carriage to acute or chronic disease, including gastrointestinal symptoms, anemia, malabsorption, hepatic or neurologic disorders, or systemic illness, depending on the parasite and host factors.

Diagnosis relies on laboratory methods such as detection of parasites or their genetic material in stool, blood, urine, or tissue samples, serology, imaging, or endoscopy. Treatment depends on the parasite group and may include antiparasitic drugs such as metronidazole, albendazole, praziquantel, nitazoxanide, chloroquine, or artemisinin-based therapies. Drug resistance and side effects can complicate therapy.

Prevention focuses on improved sanitation, safe water and food handling, vaccination where available, vector control, protective measures against bites, and routine deworming programs in endemic areas. Parasite infections remain a major global health concern, particularly in low-resource settings, and are the target of ongoing public health efforts and neglected tropical disease initiatives.