Life cycle in human trematodes

Intestinal Cestodes

Dr Mohiedden M Abdul-Fattah

2-Egg in soil

3-Larva in tissue of IH

Pseudophyllidea: Diphyllobothrium latum

2-Egg in soil

1-Adult in intestine of

Man

3- Larvae in tissue of intestinal villi of

Man

Cyclophyllidea:H. Nana Direct LC

1-Adult in intestine of man

2-Egg in

water

3- 1st Larva in cyclops

4- 2nd larva in fish

Intestinal cestodes

1-Adult in intestine of

ManCyclophyllidea: 1.Taenia saginata2.T. solium3.Hymenolepis

nana. 4.H. diminuta5.Dipylidium

caninum

Man is usually infected by intestinal cestodes when ingests the larvae except H.nana, infection occurs by eggs.

All Cyclophyllidea must need one intermediate host in their life cycle except H. nana

The IH in Taenia is vertebrate host (cattle or pigs). In Hymenolepis and Dipylidium it is invertebrate

insect (fleas, beetles or cockroach) Pseudophyllidea (D. latum) needs two

intermediate hosts in their life cycles: (Cyclops as 1st IH and Salmon fish as 2nd IH.

OUTLINE OF LLIFE CYCLE IN INTESTINAL CESTODES

Taenia saginata

1. Biology: Final host: human. Habitat: small intestine. Exit stage: mature egg or

gravid segments. Diagnostic morphology of

adult: 1. segmented 4-7 meter long

2. with globular scolex without rostellum or hooks.

3. 4 circular suckers.

4. Each mature segment has central tube shaped uterus.

Taenia Life Cycle

4. Lab Diagnosis: Detection of either of the following in

stool: the non hooked scolex of the adult after

treatment, The gravid segment (15 – 20 branches on

each side) . The egg: 30-40 µm, spherical, with outer

thick and inner thin shell and embryo.

2. Epidemiology Distribution: cosmopolitan. Intermediate host: cattle. Infective stage: Cysticercus bovis larva in meat. Mode of infection: ingestion of under cooked

meat containing the infective stage. Reservoir host: None.

3. Host parasite relationship: Light infections remain asymptomatic, but Heavier infections may produce abdominal

discomfort, epigastric pain, vomiting and diarrhea.

5. Treatment: Praziquantel is the drug of choice,(10-

20mg/kg PO for single dose), or Niclosamide (1-2 g children and 4 g for

adults; for single dose). Expulsion of scolex must be assured to

assume a satisfactory treatment.

6. Control: Thorough inspections of beef and pork, Adequate cooking or freezing of meat. cysticerci do not survive temperatures below -10o

C and above 50o C.

Taenia solium

Biology: Man is the only final host but can

act as blind end intermediate host also.

Habitat: small intestine Exit stage from the final host:

scolex, gravid segments and/or mature egg.

Diagnostic morphology 1. segmented 3-5 meter long 2. with quadrate scolex with 4 circular

suckers. 3. It has rostellum with double rows of

hooks. 4. Each mature segment has central

tube shaped uterus

Taenia solium Life Cycle

2. Epidemiology Distribution: where pork is eaten. Transmission Intermediate hosts: pigs (mainly) and man (if

swallowed the eggs). No reservoir hosts. Infective stages: Intestinal adult: - C. cellulosae larva larval infection (cysticercosis): T. solium eggs.

Mode of infection: 1. Adult taeniasis solium: ingestion of infected pork.2. Larva taeniasis solium (cysticercosis): If man ingests T. solium egg, cysticercus cellulosae

develops in human tissues.

3. Host parasite relationship:

Disease due to adult: mild enteritis with indigestion.

Disease due to larva: cysticercosis .

4. Lab diagnosis:

Adult: - Detection of the following in stool samples:

Gravid segment with 12 lateral branches.

scolex with rostellum having double rows of hooks

Eggs similar to that of T. saginata.

Cysticercosis: Imaging (sonar, CT) and serology

5. Treatment: Intestinal: A. Praziquantel is the drug of choice,(10-20mg/kg PO

for single dose), or B. Niclosamide (1-2g for children and 4 g for adults;

(single dose).

Neurocysticercosis: A. albendazole (15mg/kg/day PO for 30 days)B. Corticosteroids are used to control the inflammation

due to death of the larva. Symptomatic cysticercosis outside CNS: Surgery is the management of choice.6. Control: like Taenia saginata.

Intestinal Cestodes (Tapeworms): Cyclophyllideaworm Taenia saginata Tenia solium

Man Final host

Reservoir None

Habitat Small intestine

Exit stage Egg: mature, round, striated shell, yellow brown, 30-40 µm,Gravid Segments with branched uterus singly in saginata, in chains (solium)

Intermediate H. Cattle Pigs

Infective stage Cysticercus bovis in beef Cysticercus cellulosae in pork

Mode of infection Ingestion of C. bovis in beef Ingestion of C. cellulosae in pork

Disease 1. Enteritis 2. obstruction 1.Enteritis 2. obstruction• Cysticercosis: induced by

antipaeristalsis or by external autoinfection

diagnosis 1. Detection of eggs or segments passed iin stool

Treatment Oral Praziquantel or by Albendazole

Control 1. Thorough freezing or cooking of pork and beef.2. Sanitary disposal of human sewage 04/11/2316

Hymenolepis nana

1. Biology: Final hosts: Humans and rodents. Habitat: small intestines. Exit stage (diagnostic): mature egg. Life cycle and Diagnostic morphology:

segmented, 0.5 – 1 cm long with retractile armed scolex.

H.nana Life Cycle

2. Epidemiology:

Distribution: cosmopolitan. Children more than adults.

Intermediate hosts: Fleas act as intermediate host when its larva ingests the egg and cysticercoids develops within its body cavity.

Reservoir hosts: rodents.

Infective stage: egg.

Mode of infection: 1-Ingestion of foods and drinks contaminated with egg. 2- Autoinfection.

3. Host parasite relationship:

Disease: mild enteritis and allergy to the worm excretion. Heavy infection may cause diarrhea

4. Diagnosis: By detection of eggs in stool sample. Characteristics of egg: - 30-40 µm, round, colorless,

with hexacanth embryo and polar filaments.

5. Treatment:

6. Praziquantel is the drug of choice,(25mg/kg PO for single dose), or

7. Niclosamide (1g - 2g for children and 4 g for adults; for 7 days). There is relative resistance of cysticercoids to drug therapy.

6. Control: Health education and personal hygiene.

Hymenolepis diminuta1. Biology: Final Hosts: mainly

rats; occasionally man. Habitat: small intestine Exit stage (diagnostic):

the egg; Diagnostic

morphology: segmented, 90 cm long with unarmed scolex.

Life cycle

2. Epidemiology: Distribution: Common parasite of rats allover the world. Human is occasionally infected. Resevoir hosts: rats Intermediate hosts: grain beetles and cockroaches. Infective stage: The cystic larva (cysticercoid). Mode of infection: Ingestion of cereals, dried fruits

contaminated with insects containing the cysticercoid.3. Host- parasite relationship: Disease: affects mainly children and may

suffer abdominal pain, diarrhea, insomnia and convulsions.

4.Lab. Diagnosis: Detection of the characteristic eggs in stool

samples. Egg characteristics: 60- 80 µm, round, yellow

brown, with hexacanth embryo and polar knobs.5.Treatment: Niclosamide (2g first day+ 1g daily for 6 days).6.Control: health education and personal hygiene.

Dipylidium caninum1. Biology: Final Hosts: mainly dogs and cats;

occasionally man. Habitat: small intestine. Exit stage: eggs in feces within egg capsules Life cycle and Diagnostic morphology: scolex

with retractile rostellum armed with 4-6 rows of hooks, with cucumber like segments and length of 30 cm.

Life Cycle of D. caninum

2. Epidemiology: Distribution: Common parasite of dogs, cats.

Accidental in humans specially children.. Intermediate hosts: fleas (pulex) and dog louse. Their larvae ingest the eggs passed in the faeces.

The eggs release onchospheres that develop into

cysticercoids in the haemocele of the adults. Reservoir host: dog Infective stage: The cystic larva (cysticercoid). Mode of infection:

1. Ingestion of cereals, contaminated with insects

containing the cysticercoid.

2. Accidental swallowing of the infected fleas.

3.Host - parasite relationship: The worms affect mainly children that may

suffer abdominal pain.4.Lab. Diagnosis: - Detection of egg capsules; each

containing 8 – 25 eggs. Or the segments in stool samples.

5.Treatment: Niclosamide (2g first day+ 1g daily for 6 days.

6.Control: health education and personal hygiene.

Intestinal Cestodes (Tapeworms): Cyclophyllideaworm Hymenolepis nana H. diminuta Dipylidium

Man Final host Occasional final host Occasional final host

Reservoir None rodents dogs

Habitat Small intestine

Exit stage Mature, Spheroid egg, thin shelled, 30-45 µm with polar filaments

Mature ovoid 70-80µm with polar knobs

egg capsules with cluster of eggs each 20-30 µm

Intermediate host None or fleas Beetles or fleas Fleas, dog lice

Infective stage Egg or cysticercoid in fleas Cysticercoid in insects Cysticercoid

Mode of infection Ingestion of egg in food or cysticercoid in insect

Imgestion of cysticercoid in fleas

Ingestion of cysticercoid in flea

Disease 1. Enteritis 2.Insomnia Enteritis enteritis

diagnosis Detection of egg in stool Detection of egg in stool

Detection of eggs or segments in stool

Treatment Oral niclosamide or Praziquantel

Control Health education.Personal hygiene

Flea controlRat control

Avoid playing with & treta pet animals

04/11/2328

Diphyllobothrium latumA. Biology: Final host: Fish eating animal including

human. Habitat: Attach to mucosa of ileum or

sometimes jejunum. Exit stage: Immature egg or chains of

mature segments. Diagnostic morphology of adult: segmented 3-10 meter long with scolex that

has no hooks, but with 2 elongated sucking grooves.

Each mature segment has central rosette shaped uterus.

Life cycle of D. Latum

B. Epidemiology: Intermediate hosts: cyclops (1st I.H.) and

fresh water fish; salmon (2nd I.H ). Reservoir host: fish eating animals Infective Stage: pleurocercoid larva in

muscle fish. Mode of infection: ingestion of

undercooked fish containing plerocercoid

C. Host parasite relationship:

1. Macrocytic anemia and neurological problems of vitamin B12 deficiency are seen in heavily infected individuals.

D. Lab diagnosis: Detection of eggs in faeces (many).Yellowish

brown ovoid 70x40 µm with anterior operculum and posterior knob

long chains of segments with rosette shaped uterus.

E. Treatment: 1. Praziquantel is the drug of choice, (10-

20mg/kg PO for single dose), or 2. Niclosamide (1g -2g for children and 4 g for

adults; single dose).

F. Control: 1. Freezing for 24 hours. 2. Thorough cooking or pickling of fish kills the

larvae. 3. Fish reservoirs should be kept free of raw

sewage.

Intestinal Cestodes (Tapeworms): Pseudophyllideaworm Dipyllobothrium latum

Man Final host

Reservoir Fish eating animals: cats, dog, birds

Habitat Small intestine

Exit stage Egg: Immature, operculate, abopercular knob, yellowish brown, 75 X50 µm.Segments with rosette shaped uterus passed in chains.

Intermediate host

1st : cyclops in fresh water2nd : Salmon fish

Infective stage Plerocercoid in fish

Mode of infection

Ingestion of plerocercoid in salmon fish

Disease 1. Enteritis & abdominal colic 2. megaloblastic anemia due to vitmin B12 consumption

diagnosis 1. Detection of eggs or segments passed in chains in stool

Treatment Oral Praziquantel

Control 1. Thorough freezing or cooking of fish 04/11/2333

Man is usually infected by intestinal cestodes when ingests the larvae except H.nana, infection occurs by eggs.

Psuedophyllidea (D. latum) needs two intermediate hosts in their life cycles (Cyclops as 1st IH and Salmon fish as 2nd IH.

All Cyclophyllidea must need one intermediate host in their life cycle except H. nana.

1.The IH in Taenia is vertebrate host (cattle or pigs).

2.In Hymenolepis and Dipyllidium it is invertebrate insects (fleas, beetle, cockroach)

Summary

OUTLINE OF LLIFE CYCLE IN INTESTINAL CESTODES