33 - -Blood FlukeBlood Fluke Schistosoma sp.

• Schistosoma mansoni male • Schistosoma mansoni female • Schistosoma mansoni male & female• Schistosoma haematobium male • Schistosoma haematobium female• Eggs of Schistosoma mansoni • Eggs of Schistosoma haematobium• Snail of Schistosoma mansoni• Snail of Schistosoma haematobium• S. mansoni cercaria

Schistosoma mansoni

S. mansoni (male)

• 8-10 mm long•has gynaecophoric canal• dorsal surface covered with tubercle

S. mansoni (female)

• 14 mm long•taller and thinner•vitelline glands occupy 2/3 of the body

S. mansoni (male & female)

S. mansoni (snail) Biomphalaria alexandrina

Cercaria of S. mansoni

• elongated head

• biforked tail

S. mansoni (egg)

• oval with lateral spine

Schistosoma haematobium

Egg• oval with terminal spine

Snail

Bulinus truncatus

S. mansoniS. haematobium

Locationveins of large intestine, colon (lower mesentric vein)

veins of urinary bladder (venous plexus of urinary bladder)

Intermediate host

Biomphalaria alexandrinaBulinus truncatus

DiagnosisEggs in stoolEggs in urine

Infective stage

Cercariae

Mode of transmission

Direct skin penetration of cercariae during swimming

DiseaseIntestinal BilharziasisUrinary Bilharziasis

Class Cestoda

General CharactersTape Worms

1- All worms have long flat (no body cavity), multi-segmented body.

2- The body is covered with cuticle that is provided with pores through which the worm uptakes its nutrients (no digestive system).

3- All are hermaphrodites (each segment contains both male and female sexual organs).

4- The adult worm is divided into 3 distinct parts: a- Head or Scolex: usually with 4 muscular suckers and a crownof hooks (rostellum) to attach to theintestinal wall.

b- Neck Region: serves as a generative organ

c- Strobilla: three types of segments (Proglottids). i. Immature: following the neck region

ii. Mature: containing both sex organsand responsible for reproduction iii. Gravid: filled with fertilized eggs

5 -Eggs: contain hexacanth

embryo (oncosphere).

6- All cestodes have an intermediate host except Hymenolepis nana.

Examples of Class Cestoda1- Taenia sp. Taenia saginata Taenia solium

2- Hymenolepis sp. Hymenolepis diminuta Hymenolepis nana

3- Dipylidium caninum

4- Echinococcus granulosus

General life cycle of Cestodes

1. The adult worm matures in human intestine (final host). 2. Eggs shed in feces are released into environment.3. Eggs are eaten by grazing animals (intermediate host).4. Larval forms encyst in animals’ tissue.5. Humans ingest encysted larvae in meat of infected animal

(except in case of Echinococcus granulosus).

Taenia saginata (Beef Tape Worm)

Taenia saginata mature segment: nearly square, bilobed ovary, scattered testis, uterus: median tube (magnifier)

Taenia saginata gravid segment longer than broad branched uterus filled with eggs (magnifier)

Length: up to 10 m

Taenia sp. Egg

circular, radiating (striated) double wall

(H.P)

Taenia saginata

• Location of adult: small intestine of man• Intermediate host : cattle (beef)• Infective stage : Cysticercus bovis• Mode of transmission: eating insufficiently

cooked meat containing Cysticercus bovis• Diagnosis: eggs & gravid segments in stool• Disease: Taeniasis

Hymenolepis diminuta (Rat Tape Worm)

Mature segments: Broader than long characterized by 3 testis and one ovary in each segment (magnifier)

Gravid segments: Broader than long, enlarged uterus containing eggs (magnifier)

Length: 20-60 cm

Hymenolepis diminuta

• Location of adult: small intestine of rat occasionally man

• Intermediate host: rat flea• Infective stage: cysticercoid• Mode of transmission: ingestion of rat flea

containing cysticercoid • Diagnosis: eggs and gravid segments in stool• Disease: hymenolepiasis

Hymenolepis nana (Dwarf Tape Worm)

Mature segments: broader than long, characterized by 3 testis and one ovary in each segment (L.P)

Length: Very small 15-40 mm

Hymenolepis nana

• Location of adult: small intestine of man• Intermediate host: none• Infective stage: eggs• Mode of transmission: eating food

contaminated with eggs or autoinfection• Diagnosis: eggs in stool• Disease: Hymenolepiasis

Dipylidium caninum (Dog Tape Worm)

Mature segment: Longer than broad, 2 genital pores, testis and ovaries

(magnifier)

Gravid segment: Longer than broad, deformed wall, enlarged uterus filled with eggs

(magnifier)

Cucumber seed-like or barrel

shape

Length: 10-50 cm

Dipylidium caninum

Scolex: showing 4 suckers and extended rostellum with four rows of hooks (L.P)

Egg Packet: round to oval and containing 5-15 eggs (H.P)

Dipylidium caninum

• Location of adult: small intestine of dogs, occasionally man

• Intermediate host: dog flea• Infective stage: cysticercoid• Mode of transmission: ingestion of dog flea

containing cysticercoid• Diagnosis: egg packet in stool• Disease: Dipylidium caninum infection

Echinococcus granulosus (Hydatid Tape Worm)

Adult worm: scolex, immature, mature and gravid segments (4X)

Length: 3-9 mm

Echinococcus granulosus

Protoscolex from hydatid cyst

(H.P)

Echinococcus granulosus

• Location of adult: small intestine of dogs• Location of hydatid cyst : liver, lung, CNS and

bone in man, cattle and sheep• Intermediate host: cattle, sheep (man is an end

stage intermediate host)• Infective stage (for human): eggs in feces• Mode of transmission:

man is infected by ingestion of eggs in dog feces • Diagnosis: identification of hydatid cyst by X-ray• Disease: hydatid disease