Cysticercosis and Crowding Effect

Cysticercosis

In some tapeworm speices, the oncosphere penetrates the gut of the intermediate host, and upon reaching the parenteral site (in any part of the body) metamorphoses into a cysticercoid or a cysticercus type of metacestode. A cysticercoid is a solid-bodied organism with a fully developed scolex.

Virtually any organ in the body can be infected with cysticerci. The most common location is the eye followed by the brain and then muscles, heart, liver, lungs and coelem. To the right it an x-ray of a infected thigh muscle.

In whatever tissue they invade, a fibrous capsule of host origin surrounds the metacestode (the exceptiong is when the cysticercoid develops in the eye). The effect of the cysticercoid depends on its location. Ocular cysticercosis can cause damage to the retina, iris or choroid. It also runs the risk of being mistaken for a malignant tumor, leading to the unnecessary surgical removal of the eye. Cysticerci in the brain can cause severe central nervous system malfunction, blindness, paralysis, disequilibrium, disorientation or epilepsy. Cysticerci in the skeletal muscle, skin or liver usually go unnoticed, except in the case of massive infection. Taenia solium is the most common tapeworm that forms cysticercoids in its intermediate hosts.

Crowsing Effect

An important condition which can affect tapeworm growth in the intestines is "crowding effect". Crowding effect proposes that within limits, the weight of the individual worms in the intestines of a individual is inversely proportional to the number of worms present. So the total worm biomass and the number of eggs produced are the same and are maximal for the host no matter the actually number of worms present.

It has been found that tapeworms in the presents of others with secrete "crowding factors" that influence the development of the other tapeworms in the population