Why or how are tapeworms beneficial or harmful to humans?Why or how are tapeworms are beneficial or harmful to humans?
Tapeworms and other intestinal parasites have been heavily studied because it has been known for decades that children who had tapeworm or similar infections in early childhood are much less likely to develop asthma or allergies. The current theory is that immunoglobulin produced in response to the worm infection blocks receptors on the developing mast cells, which are the immune system cell type responsible for histamine release. The theory, called the hygiene hypothesis, contends that the immune system of a child who lives too sanitary a life will, when these mast cells are developing, go "looking" for an antigen to identify. If there is no challenge to the immune system, the body develops antibodies to some normally innocuous environmental protein, such as cat dander or pollen, and this in turn leads to asthma, allergies, or both.
Here is a link to a paper on the phenomenon. I chose to share this one because at the end it has a lot of other links to more articles dealing with this topic. http://ajrccm.atsjournals.org/cgi/content/full/168/3/266
There are a large number of tapeworms that are known to affect humans. All tapeworms initially attach themselves to the intestinal walls of humans, from where they access nutrients as the food eaten by the victim is digested, and grow in size.
Some varieties of tapeworms are relatively harmless as they only reside in the intestines and are in due course expelled from the body of the victim with fecal matter. Though if the worms reside in the intestine for a long duration of time, they grow large in size and can block the bile duct.
The more dangerous varieties of tapeworms can migrate to other organs and tissues like the muscles, lungs, liver, eye and even the brain. Here they lead to the formation of cysts which gradually grow larger in size and eventually lead to organ failure and can even cause death.
Tapeworms are not beneficial to humans in any way.
Tapeworms and other parasites have been shown to have a calming effect on the human immune system. This means that parasites can curb some of the symptoms of autoimmune conditions and diseases; such as asthma and allergies which are caused by an overactive immune system. This believed to be the case because throughout early man's history parasites were ever present, and our immune systems evolved and developed while we hosted these parasites. This relationship is considered symbiotic, meaning each organism gains something from the other.
The traditional view is that tapeworms are decidedly harmful as they can damage the intestinal wall. Further, when they multiply, they can produce malnutrition. In large numbers, they reduce the ph acid-base level in human intestines, which in turn lowers the rate of digested foods, which is further lowered because they block digestive enzymes. It sounds to me like they are not friendly nor easy to keep in control, even if they may add to immuno-efficiency.
I have just finished reading Seabiscuit which gives a rather horrific account of how racing jockeys in the 1920s and 1930s used to keep their weight down by any means possible. Certainly tapeworms were bought and used for this purpose, as they effectively reduce weight and then can be extracted surgically once the desired weight has been achieved. Obviously this is not to be recommended as a weight loss plan!
One of my absolute favorite lessons when teaching about the literature of the 1920s was my lesson on fads. Fortunately or unfortunately, tapeworm-swallowing was one of those fads! Both for young ladies (and apparently for jockeys) ... it was quite fashionable. Tapeworms do, in fact, encourage weight loss in the human body, ... albeit in a most horrible, disgusting, parasitic, and bloody way.