um, a foetus IS sheltered in a different organism!
LoL, the things some people come up with. The mother herself produces the fetus from HER OWN body.. A parasite is an external species that comes from an OUTER source... So unless a fetus with wings from another species flew into the womans uterus and attached itself to her, then the fetus is not a parasite..
Secondly, nearly all species of parasites don't have backbones or spines and are microbes..
PROTOZOA
Making up approximately 70 percent of all parasites, protozoa are invisible to the naked eye. They are one-celled microscopic organisms, but don't let their size fool you. Certain protoans, through their intensely rapid reproductive ability, can take over the intestinal tract of their host; and from there go on to other organs and tissues. Some feed on red blood cells. Some protozoa produce cysts - closed sacs in which they may be safely transported through food and water from one person to another. In the cyst state, protozoans are safe from destruction by human digestive juices. These one-celled 'vampires' can actually destroy the tissues of their hosts. According to experts, an estimated 7 million people across the U.S. have some form of protozoa living inside of them. Common protozoa include:
Endolimax nana,
Giardia lamblia,
Entamoeba histolytica,
Cryptosporidum parvum,
Blastocystis hominis,
Trichomonas vaginalis,
Toxoplasma gondii,
Cyclospora cayetanensis,
Cryptosporidium muris,
Pneumocystis carinii,
Plasmodium malariae,
Plasmodium ovale,
Plasmodium vivax,
Plasmodium falciparum,
Leishmania donovani,
Leishmania tropica, and
Leishmania braziliensis.
NEMATODE
While the protozoans are only single-celled, nematode creatures are multi cellular. The adult worms multiply by producing eggs called ova or larvae. The eggs usually become infectious in soil or in an intermediate host before humans are infected. It is interesting to note that unless the worm infection is heavy, many individuals do not show signs of disease. While it may be unpleasant to consider, it is true that the human host can coexist quite comfortably with a few worms, unless they reproduce in great numbers and create organ obstruction. Experts claim that 'some type of worm is already in the intestines of over 75 percent of the world's population'. This is a frightening statement. Common nematode include:
Roundworm (Ascaris lumbricoides),
Hookworm (Necator Americanus, Ancylostoma duodenal), P
inworm (Enterobius vermicularis),
Roundworm (Toxocara canis, Toxocara cati),
Heart worm (Dirofilaria immitis),
Strongyloides (Stronglyoides stercoralis),
Trichinella (Trichinella spiralis),
Filaria (Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, Loa loa, Mansonella streptocerca, Mansonella perstans, Mansonella ozzardi), and
Anisakine larvae.
CESTODA
Among the oldest known parasites, tapeworms are considered humanity's largest intestinal inhabitant. They each have a scolex (head) that attaches to the intestinal wall. As long as the head remains attached to the intestinal mucosa, a new worm can grow from it. Tapeworms do not contain digestive tracts but get their nourishment by absorbing partially digested substances from the host. They are whitish in color, flat, and ribbon-like, with a covering that is a transparent skin-like layer. Common cestoda include:
Beef tapeworm (Taenia saginata),
Pork tapeworm (Taenia solium),
Fish tapeworm (Diphyllobothrium latum), and
Dog tapeworm (Dipylidium caninum).
TREMATODE
Trematode are leaf-shaped flatworms also known as flukes. They are parasitic during nearly all of their life-cycle forms. The cycle begins when larvae are released into freshwater by infected snails. The free-swimming larvae can then directly penetrate the skin of the human host or are ingested after encysting in or on various edible, vegetation, fish, or crustaceans. Common trematode include:
Intestinal fluke (Fasciolopsis buski),
Blood fluke (Schistosoma japonicum, Schistosoma mansoni) Schistosoma haematobium),
Liver fluke (Clonorchis sinensis),
Oriental lung fluke (Paragonimus westermani), and
Sheep liver fluke (Fasciola hepatica).