Human Intestinal Parasites

Tapeworms belong to a branch of the platyhelminths known as the cestodes and are entirely parasitic.

They consist of an anchoring organ or scolex which attaches them to the intestinal wall with suckers or hooks to help it hold fast. Growing out behind the scolex are proglottids - repeating organs which are complete reproductive organisms in themselves. These continue to grow out from the scolex in a chain until the last segments break off and are passed out with the faeces.

Adult tapeworms do not feed off humans, but rather take our digested food.  Tapeworms lack a digestive tract and absorb nutrients directly across the skin or cuticle. Health problems occur when the tapeworm becomes too large and blocks the bowel, robbing us of nutrients.

Tapeworms may grow to a reasonable size and, because they are found deep in the tissue,  may start taking up valuable space. If the cyst settles in the brain, eye or liver, normal function of these organs may be severely restricted.

The Beef Tapeworm

A complete specimen may grow to 8m in length - nearly the length of the digestive tract of an adult human. With such a large body, these worms can cause nutritional deficiencies. The intermediate host for this worm is the cow. Apart from nutritional problems, this tapeworm generally causes mild to moderate abdominal symptoms (nausea, pain, etc).

The Pork Tapeworm

A relative of the Beef Tapeworm the intermediate host of this parasite is the pig. Humans are infected by eating undercooked pork. It is slightly smaller than the beef tapeworm but more dangerous. If someone has a pork tapeworm, they pose a risk to themselves and others around them of developing cysticercosis. These cycticerci may lodge in the brain, eye or muscle, causing serious problems.

The Broad Fish Tapeworm

This tapeworm is found in large marine fish. If the flesh of these fish containing the parasite is served raw (commonly as sushi or sashimi) or undercooked, the adult tapeworm may develop in humans.

The Dog Tapeworm

A common parasite found in domestic dogs.

This parasite grows to 10-15cm.  Individual segments resemble cucumber seeds in size and shape. The intermediate host for dog tapeworms are dog and cat fleas. When the flea bites, the dog may bite at the flea and swallow the larval tapeworm.

If humans swallow infected fleas, they may become infected. Allowing the dog to lick your face may transfer the larval tapeworms to your mouth.  Crushing fleas between your fingernails spreads the parasites across your hands. Dogs should be routinely wormed

The Hydatid Tapeworm

This tapeworm normally cycles between carnivores such as dogs, wolves or foxes  and herbivores such as sheep.

If a human should ingest eggs from dog's faeces, the hydatid cysts can grow in the liver and lungs and also in the brain.

The only means of treating hydatid cysts is by surgery.