Samar N. El-Beshbishi

Prof. of Medical Parasitology

Mansoura Faculty of Medicine

DiphyllobothriasisDiphyllobothrium latum

Objectives1. Overview on diphyllobothriasis.

2. Geographical distribution.

3. Morphology of Diphyllobothrium latum.

4. Life cycle.

5. Pathogenicity & clinical picture.

6. Diagnosis of diphyllobothriasis.

7. Treatment of diphyllobothriasis.

8. Prevention and control.

Overview• Diphyllobothrium latum is a parasitic flatworm

of class Cestoda, Order: Pseudophyllidea.

• D. latum is the largest tapeworms that can infect people.

• It infects small intestine of various fish eating mammals including humans.

• The disease caused by the flukes is called diphyllobothriasis.

• It causes pernicious anaemia.

Diphyllobothrium latum(The fish or broad tapeworm)

Geographical distribution: Lake regions in Europe, Baltic countries, some foci in America and Russia.

Adult morphology:

Size: 3-10 meters,

3000-4000 segments.

Scolex: elongated almond-shaped, 2.5x1mm, with 2 elongated dorsal and ventral grooves (bothria).

Mature segments: broader than longer (3x15 mm):

Male system: numerous testes.

Female system:

-Bilobed ovary posterior.

-Uterus proceeds anteriorly as a convoluted tube.

- Numerous vitelline glands.

No gravid segments

due to the presence of

separate uterine pore.

Diphyllobothrium latummature segments

Diphyllobothrium latum adult

Egg:

Size: 80 x 40 μ.

Shape: oval, operculated with thick-shell.

Colour: yellowish-brown

Contents: immature ovum.

Coracidium: spherical 6-hooked embryo(Onchosphere) enclosed in a ciliatedembryophore.

Coracidium released from egg

Procercoid: solid elongated organism about 0.5mm, with a spherical caudal end having 6hooks.

Plerocercoid (sparganum): solid elongatedorganism about 1-2 cm, with invaginatedanterior end.

-The body is striated but not segmented.

a. Coracidium

b. Procercoid

c. Plerocercoid

Life cycle:

Habitat: small intestine.

Definitive host (D.H.): man.

Reservoir hosts (R.H.): dogs, cats, bears, pigs, fox, sea lion and fish eating animals.

1st I.H.: copepod crustacean as Cyclops (water flea).

2nd I.H.: fresh water fish e.g. salmon, trout.

Cyclops

Stages in the life cycle: egg coracidium

procercoid larva plerocercoid larva in (I. H.) adult in (D. H. and R.H.).

Infective stage: plerocercoid larva (sparganum)in salmon or trout.

Mode of infection: by ingestion of undercookedor smoked fish containing plerocercoid larva.

Life cycle of Diphyllobothrium latum

- Plerocercoid larva attaches to the intestinalwall and grows to maturity within 6 weeks.

- Immature eggs are laid in the intestine of D.H.and R.H. and pass in feces.

- A full worm lays about one million eggs daily.

- In fresh water, the embryo (coracidium) develops in 2 weeks, hatches & swims.

• Coracidium swallowed by the ist I.H. loses itsciliated embryophore & penetrates intestinalwall body cavity procercoid larva in 2 weeks.

• Infected Cyclops swallowed by the 2nd I.H.digested & procercoid larva liberated.

• Larva penetrates intestinal wall differenttissues & muscles plerocercoid larva(sparganum) in 2 weeks.

Pathogenesis and clinical picture:

Disease: diphyllobothriasis.

1)Intestinal disturbances: hunger pains, dyspepsia,colic, vomiting, weight loss and diarrhea.

2)Pernicious anemia/megaloblastic anemia due to:

-Competition with the host & absorption ofvitamin B12.

-Splitting of intrinsic factor-B12 complex.

-Toxins secreted by the parasite.

3)Neurological manifestations due to:

-Parasite‘s toxic secretions.

-By-products of the degenerating segments.

-Hematological disturbance.

4)Complications:

-Intestinal obstruction by large number ofworms.

-Gall bladder disease caused by migration ofproglottids.

Diagnosis:

I-Clinical.

II-Laboratory:

1.By finding characteristic immature eggs orsegments in feces.

2. Blood picture for anemia.

Treatment:

-Niclosamide (Yomesan).

-Praziquantel (Biltricide, Distocide).

-Atebrine (Quinacrine hydrochloride).

-Mebendazole (Vermox).

-Paromomycin (Humatin).

-In presence of macrocytic anemia, vitaminB12 should be given parentrally.

Prevention and control:

-Proper cooking of fish (at 55 °C for 5minutes), freezing at - 18 ° C for 72 hours orprolonged salting.

-Treatment of patients.

-Periodic deworming of reservoir hosts (dogs,cats, etc.).

-Abstinence from defecation or sewage disposalin water.

Thankyou