Parasitology Lecture 5 intestinal cestodes

Hymenolepsis nana is also known as what

Dwarf tapeworm

What does the Scolex of Hymenolepsis nana look like

4 suckers and hooks on rostellum

What happens to the eggs of Hymenolepsis nana

Eggs free in host gut as proglottids usually disintegrate in the gut and eggs pass in feces.

The eggs of Hymenolepsis nana contain what?

Oncospheres, which are also known as hooked larvae

Direct life cycle of Hymenolepsis nana

Ingestion of eggs or mouse pills (feces)

Indirect life cycle of Hymenolepsis nana

Ingestion of cysticercoid larvae via ingestion of insects (Tenebrio beetle)

Internal Autoinfection of Hymenolepsis nana

Eggs are laid and hatch in the intestine and the onchosphere penetrates the intestinal villus

Which tapeworm does NOT NEED an intermediate host

Hymenolepsis nana

The Tenebrio Beetle can serve as an intermediate host in which tapeworm?

Hymenolepsis nana

Hymenolepsis nana can spread though person to person contact like which other parasite

Pinworm, also known as Enterobius vermicularis because it is common in children

What are the clinical manifestations of Hymenolepsis nana

Adult worms in small intestines will cause irritation to the gut wall, allergic reactions to worm metabolites, nervousness, headache, dizziness, and diarrhea

Diagnosis of Hymenolepsis nana

Identification of eggs in stool samples

Prevention of Hymenolepsis nana

Personal hygiene and MASS CHEMOTHERAPY (similar to pinworm control)

Taenia tapeworms consist of which two tapeworms

Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm)

Taenia saginata is also known as what?

Beef tapeworm

Scolex of Taenia saginata

Has 4 suckers but lacks hooks

Proglottids of Taenia saginata

Characterized by being longer than wide, having more than 15 uterine branches, and are often found whole in stool. They can be mobile in stool and may migrate out of the anus.

Humans become infected by Taenia saginata by ingesting raw or undercooked beef containing _________

Cysticercus bovis, which is the larval stage of Taenia saginata

How does Taenia saginata complete it’s life cycle

The scolex attaches to the small intestine and the adult worm develops, Gravid proglottids and eggs are passed in the feces to which cattle become infected by ingesting vegetation contaminated with eggs. Onchospheres hatch and penetrate the intestinal wall, circulating to musculature and developing into Cysticercus bovis.

The anatomical differences between humans and bovine means what?

It means that humans cannot get Cysticercus bovis

Where is Taenia saginata endemic in?

All beef-eating areas. Infection occurs through consumption of undercooked beef and cattle can be infected from contaminated grazing areas or feedlot practices

Clinical manifestations of Taenia saginata

Very little pathology present. Symptoms are mild with occasional diarrhea due to reactions to worm metabolites. Intestinal blockage possible but rare.

Diagnosis of Taenia saginata

Identification of proglottids or eggs in stool

Prevention of Taenia saginata

Inspecting and properly cooking beef (to 56 degrees C), proper sewage management to prevent contamination of grazing areas, and controlling beef importation

Taenia solium is also known as what?

Pork Tapeworm

Scolex of Taenia solium

Possesses both suckers and hooks

Proglottids of Taenia solium

Has fewer than 13 uterine branches

Humans can become infected by Taenia solium by ingesting raw or undercooked pork containing what?

Cysticercus cellulosae, which is the larval stage of Taenia solium.

The ingestion of Taenia solium will lead to what condition?

Taeniasis, which is also known as adult tapeworm in the intestine.

Cysticercosis of Taenia solium occurs through what

The ingestion of embryonated eggs which can occur through autoinfection or heteroinfection (close contact with an infected individual)

Pigs become infected by ingesting eggs of ________ from contaminated enviroments

Taenia solium

After eggs of Taenia solium are ingested, onchospheres penetrate the intestinal all and circulate to various organs, developing into what?

Cysticerci

Epidemiology of Taenia solium

Endemic in areas with high pork consumption and lax meat inspection

Taeniasis

Adult worms of Taenia solium present in the small intestine. Like Taenia saginata, this causes asymptomatic to mild symptoms

Cysticerosis of Taenia solium in intramuscular muscle

Encystment in muscle, often calcified and a dead end for the parasite

Cysticerosis of Taenia solium in the brain

No encystment, can grow into into grapelike clusters which causes JACKSONIAN EPILEPSY. Surgery is needed with death common

Cysteicerosis of Taenia solium in the eye

Appears to be a floater in vitreous humor, no encystment. Can get into sub-retinal space. Death of organisms results in massive inflammation causing loss of eye

Other than intramuscular muscles, the brain and the eye, where can Cysticerosis of Taenia solium occur?

Soft tissues like the lungs and liver

Diagnosis of Taenia solium

Proglottids or eggs in stool for taeniasis. X-rays, CT scans, MRI for cysticerosis.

Prevention of Taenia solis

Proper disposal of feces, thorough freezing/cooking of pork, and inspection of pork products

Diphyllobothrium latum is also known as what?

Fish tapeworm

Scolex of Diphyllobothrium latum

Characterized by a Bothrium which is leaf life suckers or sucking grooves

With the case of Diphyllobothrium latum being a large tapeworm, what does this mean?

There is one worm per person. It can grow up to 5-10 meters and can live up to 25-30 years

What are the stages of the Diphyllobothrium latum

Egg → Coracidium → Procercoid Larvae → Plerocercoid larvae → Adult worm

Unembryonated eggs of Diphyllobothrium latum develop into what?

Eggs are passed in feces and embryonate in water, developing into coracidia

Coracidia of Diphyllobothrium latum are ingested by what to then develop into?

Coracidia are ingested by Copepods (crustaceans) where they develop into Procercoid larvae

Crustaceans hosting coracidia are ingested by _____ to which procercoid larvae develop into _____ in the flesh

Freshwater fish; Plerocercoid larvae

The adult Diphyllobothrium latum develops where

The small intestine

Epidemiology of Diphyllobothrium latum

Found in temperate regions with high freshwater fish consumption, such as the Great Lakes and Pacific Northwest regions of the USA, Finland, and Russia.

Clinical manifestations of Diphyllobothrium latum

Generally mild attachment damage and some allergic reaction. Pernicious anemia

What significant manifestation of Diphyllobothrium latum is due to the worm’s high affinity for what?

Pernicious anemia, which is due to the worm’s high affinity for Vitamin B12.

Prevention of Diphyllobothrium latum

Thoroughly cooking fish and preventing sewage contamination of water sources

Diagnosis of Diphyllobothrium latum

Identification of unembryonated eggs in stool which could develop into coracidia

Cestodes are commonly known as what?

Tapeworms, which are flat, ribbon-like parasitic flatworms.

Cestodes possess both male and female reproductive organs, which means they are what?

Hermaphroditic

The general morphology of a tapeworm consists of what 3 parts

Scolex, Neck, and Proglottids

Scolex

This is the anterior end of the tapeworm and serves as the biological holdfast. It is equipped with structures for attachment to the host's intestinal wall, such as suckers and/or a rostellum with hooks. The scolex is not involved in feeding or support.

Neck

Located posterior to the scolex, the neck is an undifferentiated region responsible for budding off new segments. It contains stem cells that give rise to proglottids.

Proglottids

These are the segments that make up the body of the tapeworm, collectively known as the strobila (though some definitions include the neck in the strobila). Proglottids are sexually immature, mature, or gravid (containing fertilized eggs), depending on their age and position along the strobila. As proglottids mature, they develop reproductive organs. Gravid proglottids contain the uterus filled with eggs.

Tapeworms lack a what

Digestive tract

Absorption of nutrients by tapeworms are facilitated by what

Microvilli called microtriches, which increase the surface area for nutrient uptake through processes like pinocytosis, diffusion, facilitated diffusion, and active transport