para : lecture 6 -8

Order Cyclophyllidea

Taenia solium, Taenia saginata, and Echinococcus spp. are discussed in this order.

Taenia solium

Common name: pork tapeworm.

Taenia solium intermediate host

Pig.

Taenia solium definitive host

Human.

Taenia solium intermediate host infection

Pig ingests eggs.

Taenia solium definitive host infection

Human ingests cysticercus.

Taenia solium life cycle: Step 1

Eggs or gravid proglottids are passed in feces and released into the environment.

Taenia solium life cycle: Step 2

Embryonated eggs and/or gravid proglottids are ingested by the normal intermediate host (swine).

Taenia solium life cycle: Step 3

Oncospheres hatch, penetrate the intestinal wall, and circulate to the musculature.

Taenia solium life cycle: Step 4

Oncospheres develop into cysticerci.

Taenia solium life cycle: Step 5

Humans acquire intestinal tapeworm infection by consuming cysticerci in meat.

Taenia solium life cycle: Step 6

Adults live in the small intestine.

Taenia solium adult morphology

The adult worm is found in the definitive host.

Taenia solium scolex

Small and round.

Taenia solium scolex suckers

4 suckers.

Taenia solium rostellum

Armed rostellum.

Taenia solium rostellum hooks

2 circles of hooks.

Taenia solium mature proglottid

Lateral genital pore, trilobed ovary, and 150–200 testes.

Taenia solium gravid proglottid

Longer than wide.

Taenia solium gravid proglottid uterus

7–13 lateral uterine branches.

Taenia solium gravid proglottid egg release

Apolysis.

Taenia solium pathology (taeniasis)

Often asymptomatic.

Taenia solium taeniasis symptoms

Vague abdominal symptoms.

Taenia solium diagnosis: eggs

Eggs can be found in feces.

Taenia solium egg embryophore

Thick and striated.

Taenia solium eggs vs other taeniid eggs

All taeniid species' eggs look the same.

Taenia solium diagnosis: proglottids

Gravid proglottids and/or scolex can be found in feces.

Taenia solium treatment

Praziquantel and niclosamide.

Cysticercosis

Most serious pathology associated with Taenia solium.

Cysticercosis intermediate host

Human becomes an intermediate host even though the normal intermediate host is the pig.

Cysticercosis infection

Human ingests eggs.

Cysticercosis: after egg ingestion

The oncosphere penetrates the intestine.

Cysticercosis: oncosphere destination

The oncosphere develops into a cysticercus in a parenteral site, normally in the pig intermediate host.

Taenia solium cysticercosis life cycle: Step 1

Eggs or gravid proglottids are passed in feces and enter the environment.

Taenia solium cysticercosis life cycle: Step 2

Embryonated eggs and/or gravid proglottids are ingested by the normal intermediate host (swine).

Taenia solium cysticercosis life cycle: Step 3

Oncospheres hatch, penetrate the intestinal wall, and circulate to the musculature.

Taenia solium cysticercosis life cycle: Step 4

Oncospheres develop into cysticerci.

Taenia solium cysticercosis life cycle: Step 5

Humans acquire intestinal tapeworm infection by consuming cysticerci in meat.

Taenia solium cysticercosis life cycle: Step 6

Adults develop in the small intestine.

Taenia solium cysticercosis life cycle: Step 7

Embryonated eggs are ingested by a human host.

Taenia solium cysticercosis life cycle: Step 8

Oncospheres hatch, penetrate the intestinal wall, and circulate to the musculature.

Taenia solium cysticercosis life cycle: Step 9

Cysticerci may develop in any organ, most commonly in subcutaneous tissues, brain, and eyes.

Disseminated cysticercosis

35% of cysticercosis cases; involves viscera, muscle, and subcutaneous tissues.

Ocular cysticercosis

3% of cysticercosis cases.

Ocular cysticercosis pathology

Cysticerci float in fluids and adhere to the retina, causing decreased vision.

Ocular cysticercosis severe outcome

Can cause loss of the eye.

Neurocysticercosis

60% of cysticercosis cases.

Neurocysticercosis location

Brain or spinal cord.

Neurocysticercosis symptoms

Headache, seizure, dementia, and paralysis.

Neurocysticercosis significance

An acquired seizure disorder.

How cysticercosis occurs: self-infection

Hand-to-mouth transmission.

Self-infection in cysticercosis

Patients with eggs in feces can transfer eggs from feces to the mouth.

Self-infection prevention

Good hygiene and treating the infection as soon as possible.

How cysticercosis occurs: environmental contamination

Another person is infected with the adult worm and does not wipe properly or wash their hands, allowing eggs to contaminate the environment.

Internal autoinfection

Reinfection by the parasite without it leaving the host.

Internal autoinfection starting point

An adult worm is present in the definitive host (human) small intestine during taeniasis.

Internal autoinfection: gravid proglottid

A gravid proglottid detaches.

Internal autoinfection: reverse peristalsis

Reverse peristalsis moves the gravid proglottid into the stomach.

Internal autoinfection: stomach to small intestine

The proglottid/eggs move into the small intestine.

Internal autoinfection: eggs

Eggs hatch.

Internal autoinfection: oncospheres

Oncospheres migrate to a parenteral site.

Internal autoinfection: final result

Oncospheres develop into cysticerci, causing cysticercosis.

Cysticercosis diagnosis

MRI scans and serology.

Cysticercosis diagnosis by surgery

Surgical removal and identification.

Cysticercosis treatment

Surgical removal, albendazole, and dexamethasone.

Albendazole in cysticercosis

Affects glucose uptake.

Dexamethasone in cysticercosis

Anti-inflammatory.

Cysticercosis control: sanitation

Prevent pigs from having access to human feces.

Cysticercosis control: hygiene

Good hygiene.

Cysticercosis control: meat inspection

Meat inspection can be performed.

Examples of sites examined during meat inspection

Tongue and masseter muscle.

Cysticercosis in the United States

Very rare.

Cysticercosis control: meat preparation

Meat preparation is another control method.

Cysticercosis in the US

Associated with immigration from Mexico and Central America.

Cysticercosis in some parts of the US

It is the most common cause of seizures in some parts of the United States.

Cysticercosis hospitalizations in the US

About 1,000 hospitalizations per year.

Taenia saginata

Common name: beef tapeworm.

Taenia saginata intermediate host

Cattle.

Taenia saginata definitive host

Human.

Taenia saginata intermediate host infection

Cattle ingest eggs.

Taenia saginata definitive host infection

Human ingests cysticercus.

Taenia saginata egg morphology

Identical to Taenia solium eggs.

Taenia saginata scolex

Cuboidal.

Taenia saginata scolex suckers

4 suckers.

Taenia saginata rostellum

No rostellum.

Taenia saginata hooks

No hooks.

Taenia saginata mature proglottid

Bilobed ovary and 300–400 testes.

Taenia saginata gravid proglottid

15–20 lateral uterine branches.

Taenia saginata gravid proglottid egg release

Apolysis.

Taenia saginata pathology

Most infections are asymptomatic.

Taenia saginata symptoms

Infrequently causes diarrhea and nausea.

Taenia saginata severe intestinal pathology

Intestinal obstruction can occur.

Taenia saginata cysticercosis

Taenia saginata does not cause cysticercosis.

Taenia saginata treatment

Praziquantel and niclosamide.

Taenia saginata control: sanitation

Prevent cattle from having access to human feces.

Taenia saginata control: meat preparation

Cook or freeze meat.

Taenia saginata meat preparation: rare

0% of cysticerci are killed.

Taenia saginata meat preparation: medium

50–67% of cysticerci are killed.