Parasites

• Tapeworms can cause symptoms such as abdominal pain, diarrhea, weight loss, anemia, and malnutrition.
• The relationship between parasite and host has evolved through the ages, producing changes in the parasite and its life cycle, affecting the life of its host.
• Adaptation causes changes in the molecular biology, biochemistry, immunology, and structure of the parasite.
• Parasites that are more specialized have shown the greatest changes, most of which are essential for survival.
• The most noticeable adaptations are found in the locomotory and digestive organs.
• Protozoans belonging to the Phylum Apicomplexa have no locomotory organelles, and these organisms are mostly parasitic.
• Free- living flatworms have cilia on their epidermis, while parasitic cestodes and trematodes do not have any.
• Cestodes and trematodes obtain nutrients through their tegument, which is provided with microvilli.
• Flatworms have highly specialized organs of attachment, such as hooks and suckers, which anchor the parasite inside the body of the host and facilitate tissue migration.
• The size and shape of the parasite are also adapted for maintaining its hold in the host.
• Adult Ascaris worms maintain their position inside the intestinal wall by constant movement.
• The integument of parasites is thickened to resist enzymes and juices in the digestive tract of humans and to protect against dessication and physical injury.
• In intestinal flukes, the tegument is covered with spines to prevent abrasion.
• Special coverings of ova, larvae, and cysts protect the parasite during its free-living stage.
• These coverings also aid in resisting digestive juices once the parasite is ingested by the host.
• Reproductive systems of flatworms are highly elaborate and complicated.
• All tapeworms and flukes, with the exception of Schistosoma spp, are hermaphroditic, that is, they contain a complete set of male and female organs capable of producing thousands of ova.
• Furthermore, flukes undergo asexual reproduction in the intermediate hosts to increase the number of progeny.
• Streamlining is exemplified by hemoflagellates and other helminth parasites.
• The trophozoites of Entamoeba histolytica secrete cysteine proteinases, which allow the parasite to penetrate the mucosa and adhere to the underlying layer and surrounding tissues.
• No such enzyme has been found in the commensal Entamoeba coli.
• The cercariae of Schistosoma contain penetration glands, which produce an enzyme capable of digesting the skin allowing entry into the body of the host.
• All cestode embryos have six hooklets, which aid them in tissue penetration before developing into encysted larvae.