NTA Level 5 • Semester 1 • PST05103

Taeniasis and Schistosomiasis

Pharmaceutical Microbiology • Source Session/Topic 39

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Session 39: Taeniasis and Schistosomiasis

Total Session Time: 120 minutes

Pre-requisites

• Human anatomy and physiology

Students Learning Tasks

By the end of this session students are expected to be able to:

• Describe taeniasis and schistosoniasis basing oncausative agents,

transmission, life cycle, signs/symptoms of common diseases caused by

helminths (Taenia, Schistosoma, pinworm, whipworm, hookworm,

intestinal roundworm, filarial worm)

• Describe treatment,prevention and control of taeniasis and

schistosomiasis

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board and chalk/whiteboard markers

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Taeniasis and Cysticercosis (15 minutes)

Cause and Transmission

• Taeniasis is a tapeworm disease caused by Taenia saginata (beef

tapeworm), Taenia solium (pork tapeworm), Diphyllobothrium latum (fish

tapeworm) and Hymenolepsis nana. Teaniasis leads to chronic malnutrition

or multi-organ dissemination and dysfunction (Cysticercosis)

• Humans are the only hosts for these Taenia tapeworms.

• Taeniasis is transmitted through consumption of raw or undercooked beef

or pork containing infective cysticerci of the worms.

• T. solium also causes cysticercosis which is a parasitic tissue infection

caused by larval cysts of the tapeworm and is transmitted by consumption

of eggs of the worms.

Life cycle

• Taeniasis is the infection of humans with the adult tapeworm of Taenia

saginata or Taenia solium

• Humans are the only definitive hosts for T. saginata and T. solium. Eggs

or gravid proglottids are passed with feces; the eggs can survive for

days to months in the environment.

• Cattle (T. saginata) and pigs (T. solium) become infected by ingesting

vegetation contaminated with eggs or gravid proglottids

• In the animal’s intestine, the oncospheres hatch, invade the intestinal

wall, and migrate to the striated muscles, where they develop into

cysticerci.

• A cysticercus can survive for several years in the animal. Humans become

infected by ingesting raw or undercooked infected meat.

• In the human intestine, the cysticercus develops over 2 months into an

adult tapeworm, which can survive for years.

• The adult tapeworms attach to the small intestine by their scolex and

reside in the small intestine

• Length of adult worms is usually 5 m or less for T. saginata (however it

may reach up to 25 m) and 2 to 7 m for T. solium.

• The adults produce proglottids which mature, become gravid, detach from

the tapeworm, and migrate to the anus or are passed in the stool

(approximately 6 per day). T. saginata adults usually have 1,000 to 2,000

proglottids, while T. solium adults have an average of 1,000 proglottids.

• The eggs contained in the gravid proglottids are released after the

proglottids are passed with the feces. T. saginata may produce up to

100,000 and T. solium may produce 50,000 eggs per proglottid

respectively.

Taeniasis (T. saginata and T. solium)

[pic]

Cysticercosis (T. solium)

[pic]

• Signs and Symptoms of Taeniasis

o Most people have no symptoms or have mild symptoms

o Colicky abdominal pain

o Body Weakness

o Loss of or increased appetite

o Constipation or diarrhea

o Mild epigastric discomfort

o Nausea

o Weight loss

o Abdominal pain

o Pruritus ani

o Hyperexcitability

• Infection with T. solium tapeworms can result in human cysticercosis

• Cysticercosis is a parasitic tissue infection caused by larval cysts of

the tapeworm Taenia solium. The larval cysts infect brain, muscle, or

other tissue (see life cycle). Cysticercosis is transmitted by swallowing

eggs found in the feces of a person infested with T.solium, e.g.

autoinfection with own fingers

o The cysticerci are most often located in subcutaneous and

intermuscular tissues, followed by the eye and then the brain.

o The CNS is involved in 60-90% of patients i.e. Neurocystercosis

(cysticercosis of the brain) which may manifest as;

▪ Convulsions and/or seizures

▪ Intracranial hypertension

• Headache, nausea, vomiting, vertigo, and papilledema

• Personality and mental status changes (Neuropsychiatric

changes)

• Behavioral changes and learning disabilities more marked in

children and immunocompromised adults

• Treatment and Prevention

o Taeniasis

▪ Praziquantel or Niclosamide with Magnesium sulphate (oral)

o Cysticercosis

▪ Praziquantel or Albendazole with Dexamethasone and

Carbamazepine (oral)

• Taeniasis and cysticercosis are prevented by;

o Health education

o Avoid eating raw pork

o Sanitary inspection of slaughter houses

STEP 3: Schistosomiasis (30 minutes)

• Cause and Transmission

o Schistosomiasis (also known as bilharzia) is a parasitic disease

caused by blood flukes (trematodes) of the genus Schistosoma

▪ Three species of Schistosoma are commonly found in Tanzania;

• Schistosoma haematobium –responsible mainly for urogenital

Schistosomiasis

• Schistosoma mansoni –responsible mainly for intestinal

Schistosomiasis.

• Scistosoma japonicum responsible for both of intestinal and

urinogenital schistosomiasis

o Schistosoma parasites are transmitted to humans through skin

penetration of the cercariae (infective forms of Schistosoma) when

humans are in contact with contaminated freshwater.

o Life cycle;

▪ Eggs are eliminated with feces or urine and hatch to release

miracidia, which swim and penetrate specific snail (Bullinus)

intermediate hosts

▪ The stages in the snail include 2 generations of sporocysts and

the production of cercariae, which are the infective forms. Upon

release from the snail, the cercariae swim, penetrate the skin of

the human host and shed their forked tail, becoming

schistosomulae.

▪ The schistosomulae migrate through several tissues and stages

to their residence in the veins

▪ Adult worms in humans reside in the mesenteric venules in

various locations. S. mansoni occurs more often in the superior

mesenteric veins draining the large intestine

• S. mansoni causes Intestinal Schistosomiasis

▪ S. haematobium most often occurs in the venous plexus of

bladder but it can also be found in the rectal venules.

• S. haematobium causes Urogenital Schistosomiasis

▪ The females deposit eggs in the small venules of the portal and

perivesical systems. The eggs are moved progressively toward the

lumen of the intestine (S. mansoni and S. japonicum) and of the

bladder and ureters (S. haematobium), and are eliminated with

feces or urine, respectively.

▪ Human contact with water is thus necessary for infection by

schistosomes.

[pic]

• Signs and Symptoms

o Intestinal Schistosomiasis (by S. mansoni)

▪ Swimmer’s itch or Katayama fevers in acute infection phase

• Katayama feer is a systemic allergic reaction to invasion of

the body by Schistosoma larvae.

• Katayama fever is marked by fevers, an urticarial rash,

cough, enlargement of the lymph nodes and viscera, and

eosinophilia.

▪ Colicky abdominal pains

▪ Diarrhoea and dysentery

▪ Anaemia

▪ Hepatomegally

▪ Portal hypertension with bleeding esophageal varices

▪ Decompensated liver disease

o Urogenial Schistosomiasis (by S. hematobium)

▪ Dysuria

▪ Terminal hematuria

▪ Hematospermia

▪ Obstructive uropathy (hydronephrosis, hydroureters)

▪ Glomerulonephritis and amylodosis

▪ Bladder carcinoma

▪ Chronic kidney failure

• Treatment and Prevention

o Praziquantel ((PO) 40mg/kg as a single dose or in 2 divided doses)

o Schistosomiasis is prevented through;

▪ Elimination of snails in fresh water e.g. with molluscicides

▪ Wearing of protective shoes and gloves when in contact with

freshwater during farming and other similar activities

STEP 4: Key Points (5 minutes)

• Taeniasis is caused by Taenia saginata (beef tapeworm), Taenia solium

(pork tapeworm), Diphyllobothrium latum (fish tapeworm) and Hymenolepsis

nana. T. solium causes Cysticercosis when eggs of the worm are swallowed

by humans.

• Taeniasis is treated by drugs such as praziquantel, niclosamide and

albendaole

• Schistosomiasis is caused by S. haematobium and S. mansoni. S.

haematobium causes urogenital schistosomiasis while S. mansoni causes

Intestina Schistosomiasi.

• Schistosomiasis is transmitted through skin penetration by the larvae,

Cercaria, when a human is in contact with fresh water contaminated snails

containing the Schistosomes.

• An important manifestation of schistosomiasis is painless terminal

haematuria.

STEP 5: Evaluation (5 minutes)

• What is Cysticercosis?

• How is Cysticercosis differ from Taeniasis

• How is urogenital schistosomiasis different from intestinal

schistosomiasis?

References

Hugo and Russell (2011), Pharmaceutical Microbiology 8th Edition, Willey-

Blackwel publications

Karen C. Carroll et al (2013); Jawetz, Melnick and Adelberg’s Medical

Microbiology 26th Ed. McGraw Hill Co. Inc.

Greenwood et al (2012); Medical Microbiology, 18th edition Churchill

Livingstone

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