Parasitic worm
Parasitic worms or helminths are a division of parasites which, unlike external parasites such as lice or fleas, live inside their host. They are worm-like organisms that live and feed off living hosts receiving nourishment and protection while disrupting their hosts' nutrient absorption, causing weakness and disease. Those which live inside the digestive tract are called intestinal parasites.
Helminthology is the study of parasitic worms and their effect on their hosts.
Parasitic worms are categorized into three groups; cestodes, nematodes and trematodes.
Diseases caused in humans by helminth infection include ascariasis, dracunculiasis, hookworm, lymphatic filariasis, onchocerciasis, schistosomiasis, and trichuriasis.
Reproduction
Parasitic worms are sequential hermaphrodites and reproduce depending on the species of worm, either with the presence of a male and female worm, joining sperm and eggs, producing fertile eggs, such as hookworms, or by breaking off segments that contain both male and female sex organs which are able to produce fertile eggs without the presence of a male or female. (e.g. tapeworms)
All worm offspring are passed on through poorly cooked meat, especially pork, wild fish, and beef, contaminated water, feces, mosquitoes and, in general, areas of poor hygiene and food regulation standards such as Africa, Central and South America and Asia.
Worm eggs or larvae or even adults enter the human body through the mouth, anus, nose or skin with most species attaching themselves to the intestinal tract. With the presence of digestive enzymes, worm egg shells are dissolved releasing a brand new worm; unlike its egg shell, the parasitic worm is protected from the body's powerful digestive enzymes by producing a protective keratin layer.