Taenia: Taeniasis, Cycticercosis and parasitic adaptations
Posted on : 01-12-2017 Posted by : Admin

 

Taenia Pathogenicity

The adult tapeworm and the cysticercus larvae are harmful to man.  The adult tape worm causes taeniasis and the cysticercus larva causes cysticercosis.

Taeniasis: The symptoms of taeniasis include pain in abdomen, anemia and giddiness, obstruction to passage of food, vomiting, indigestion and eosinophilia.

Cysticercosis: This infection is caused due to the consumption of the infected food and water with oncospheres. When the scolex of the Taenia causes injury to the intestinal wall, it triggers reverse peristalsis and then some gravid proglottids are pushed back in to the stomach. This process is called as retroinfection or autoinfection. The oncospheres may also infect non-pork eaters through contaminated food and water and this is called heteroinfection. The oncospheres released from the gravid proglottids ultimately reach the voluntary muscles and transform themselves into cysticercus larvae. They form cysts in the heart, brain, eye, liver and muscles. It causes necrosis in the brain and results in the disintegration of the living cells. Epilepsy is the most common manifestation in the neuro cysticercosis in man. This disease is more dangerous than taeniasis and is mostly found in children.

 

Prevention of Taeniasis

  • Consumption of properly cooked pork is the important point to be noted to prevent this disease.
  • Also selling of the measly pork should be prohibited
  • Open defecation by humans must be discouraged
  • Hygienic and healthy habits must be inculcated.

 

Differences between Taenia solium and Taenia saginata

Characters Taenia solium
 Taenia saginata
Definitive host Human Human
Intermediate host Pig Cattle
Disease caused Taeniasis and cycticercosis Only Taeniasis
Disease transmission By eating measly pork By eating measly beef
Size of Adult worm 2-7 meters 2-25 meters
Scolex
  • Scolex is armed type
  • Scolex head is globular with four circular suckers
  • Head has a rostellum with two rows of alternating large and small hooks
  • Scolex is unarmed type
  • Scolex head is quadrate with four circular suckers
  • Head does not have rostellum or hooks
Proglottids
  •  A total of 1000 proglottids are present
  • 5-6 Gravid proglottids are expelled at a time
  • 50,000 eggs are produced per proglottid
  • A total of 1000-2000 proglottids are present
  • Only one Gravid proglottid is expelled at a time
  • 100,000 eggs are produced per proglottid
Eggs

Eggs are infectious to humans,

in other words humans who feed on the eggs of T. solium develop cysticercosis

Eggs are NOT infectious to humans,

in other words humans who feed on the eggs of T. saginata DO NOT develop cysticercosis.

   

 

Taenia Parasitic adaptations

Tapeworms live as internal parasites and they have to make several adjustments for the same. The following are few of the adaptations made by these tapeworms to make their life easy in their hosts.

Presence of enzymatic resistant covering

A hard covering called as tegument covers the body of these tape worms. Tegument is enzyme resistant and it protects all the internal organs from the digestive actions of the alkaline fluids of the host. On the other hand tegument is permeable to water and other nutrients.

Absence of locomotory organelles

This parasite lacks organs for locomotion. As there is no need for any locomotory organs both the adult and larval forms lack cilia or flagella.

Osmotic pressure

The osmotic pressure inside the body is higher than that of the surrounding host tissue or fluid. This helps the parasite to reside conveniently in the host body.

Presence of hooks and suckers for attachment

For the attachment purpose a scolex with suckers and hooks are present. This specialised scolex serves the purpose of attachment to the epithelial lining of the host intestine so that the parasite is not ejected from the intestine due to its peristaltic contractions.

Anaerobic type of respiration

Anaerobic type of respiration is found in these parasites as the surroundings they live do not have any free oxygen. Glycogen is the chief reserve food and principal energy source. This glycogen undergoes glycolysis to produce carbon dioxide and fatty acids.

Absence of other body systems

Special circulatory system or respiratory system or sensory organs are absent. Also the nervous system is not well developed as these parasites do not need these systems.

Absence of digestive system

As the parasite lives in the places where digested food is readily available, there is no need of alimentary canal. So these parasites also lack alimentary canal and they absorb the digested food from the host through general body surface. The surface area for absorption is increased by the presence of the microvilli on the outer surface of the tegument.

Protection of zygote

The zygotes are covered by resistant, firm, shell or capsule. Also the embryos are protected from unfavorable conditions by similar coverings.

Presence of complex reproductive organs

Out of all the body systems reproductive system is very well developed. This reproductive system has the capability to produce huge number of eggs (40,000 per gravid proglottid). The reason for production of such huge number of eggs is that these parasites face many challenges for the survival.

Hermaphroditism and proglottization

Self-fertilization within the same proglottid or cross-fertilization with another proglottid of the same worm is ensured by hermaphroditism and proglottization.

  1. What is the difference between taeniasis and cycticercosis?
  2. Write about the preventive measurements of Taeniasis.
  3. Write the differences between Taenia solium and Taenia saginata.
  4. Write all the adaptations of Taenia as a Parasite.
  5. What are parasitic adaptations? How are they helpful for the parasite?

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