Animals of phylum nematoda are also known as round worms. Some animals are free living and others are parasite. Animals included in this phylum has rounded and elongated bodies and both ends of the body are pointed. Digestive system is present in both of these types. Free living nematodes are found in upper layer of soil, fresh water and sea water. The parasites cause different diseases in human beings. Examples are Ascaris, hook worm, filaria, and trichinella. Ascaris is the animal that is commonly known as round worm. These animals are present in man and cattle. They are larger in size than other nematodes. They suck the digested food from intestine and make the body weak. It lays millions of eggs in intestine that are excreted with remains of undigested food. Sometimes Ascaris makes a hole in the intestine, enters in vital organs of body cavity i.e. Liver, heart and lung and causes death. Their number may sometime increases to an extent that passage of intestine is blocked leading to death. Trichinella is a nematode found in pig flesh. This causes diseases trichinosis in men eating pig meat. During this disease patient has fever, pain in muscles, nausea and dysentery. Due to this disease and for some other reasons to eat pig meat is forbidden in Islam.
