Latest on Tapeworm
The life cycle of the Taenia tapeworm starts in the host�s intestine, the host being a dog or cat. The worm can be unbelievably long (up to 5 yards for Taenia hydatigena) and is made of segments. Each segment contains an independent set of organs with new segments being created at the neck and older segments dropping off the tail. As segments mature, the reproductive tract of the segment becomes more and more prominent until it consists of a bag of tapeworm eggs. These segments, called proglottids, are passed with the feces into the world where an unsuspecting intermediate host (mouse, rabbit, deer, sheep etc.) swallows one while feeding. 3
The Taenia tapeworms attach to the intestinal walls but cause only mild inflammation at the site of attachment. As a result, most tapeworm carriers show no symptoms (asymptomatic) and usually become aware of the infection only after noticing tapeworm segments in their feces. Segments of the beef tapeworm may spontaneously pass through the anus causing a noticeable sensation. Mild gastrointestinal symptoms, such as nausea or abdominal pain, can occur in infected individuals. In rare cases where the tapeworm segments migrate into the appendix, pancreas, or bile duct, there may be a sudden onset of severe abdominal discomfort. 6
Tapeworm infection is one of the most common internal parasite problems actually observed by dog owners. The presence of tapeworms is indicated by the presence of tapeworm segments passed with the feces. Tapeworm segments are white, pinkish-white or yellow-white, and similar in size and shape to flattened grains of rice. The segments are most frequently observed lying on the animal’s droppings or, less often, moving across a freshly passed stool. Segments are also found on the hair around the anus of the animal or occasionally on the animal’s bedding. 2
Tapeworms evolved from free-living flatworms, but they have undergone some radical changes. Along with the evolution of their proglottids, they also abandoned their digestive tract, opting instead to slurp up their food directly through their skin. They’re so weird now that scientists haven’t even been sure which end is which. Some people have suggested the scolex is the head of the tapeworm. But others have pointed out that while the tapeworm is still in its cyst, the hooks actually form on the other end of its body. What’s more, in related flatworms with recognizable heads and tails, the sperm-organs are closer to the head than the ovaries. In tapeworms, the ovaries are closer to the scolex. 4
The tegument is the body surface of the adult tapeworm and due to this the tapeworms take the host nutrients and not attack the mucosa of the small intestine, or remove blood, hence infections are instead benevolent and most often don’t show any signs of illness (Craig & Ito 2007:524). A carrier can notice the segments (proglottides) when using the bathroom for instance in the feces in a toilet bowl, around a latrine or frequently because the tapeworms are moving around constantly one may find it in the under-garments (Craig and Ito 2007: 524). 8
Although tapeworms in the intestine usually cause no symptoms, some people experience upper abdominal discomfort, diarrhea, and loss of appetite. Occasionally, a person with a tapeworm can feel a piece of the worm move out through the anus or see part of the ribbon-like tapeworm in stool. 7
