Practical Parasitology 2

HelminthologyHelminths

• Helminths (worms) are multicellular parasites. • They are divided into:

1- Round Worms 2- Flat Worms

(Nemathelminths) (Platyhelminths)

Class Nematoda (Flukes) (Tape worms)

Class Trematoda Class Cestoda

Helminthology

Questions form:• Name of the parasite• Location in the host• Intermediate host• Infective stage• Mode of transmission• Lab diagnosis• Disease

Class Trematoda

General characters

• Flat worms (no cavity),not segmented, bilaterally flattened (except Schistosoma is cylindrical)

• Hermaphrodite (except Schistosoma)

• Body has 2 suckers for attachment :oral, ventral,(except Heterophyes has a 3 rd genital sucker

General characters

• Life cycle show sexual phase (defenitive host) and asexual phase (intermediate host)

• Require one or more intermediate host• 1st intermediate host is a snail • Eggs have an operculum• Infective stage is encysted

metacercaria

(except schistosoma: cercariae)

Heterophyes heterophyes

• Heterophyes heterophyes adult

• Heterophyes heterophyes eggs: Heterophyes heterophyes snail

• Heterophyes heterophyes encysted metacercaria

• Heterophyes heterophyes in small intestine

snail: Pirenella conica Eggs: small, operculated, yellowish brown, thin shell (H.P)

•pear shaped,•very small size, (2mm) •oral,ventral, genital suckers•vitelline glands•2 testis, 1 ovary•simple intestinal ceaca • (L.P)

Heterophyes heterophyes adult in small intestine

Adult worm is present in intestinal villi

Heterophyes heterophyes encysted metacercaria in Bouri and Bolti muscles

Heterophyes heterophyes

• Location of adult: small intestine• Intermediate host: Primary: Pirenella conica Secondary: Bolti and Bouri fish• Infective stage: encysted metacercaria• Mode of transmission: ingestion of raw fish

containing encysted metacercaria• Diagnosis: eggs in stool• Disease: heterophiasis

Fasciola

• Fasciola hepatica adult

• Fasciola gigantica adult

• Fasciola gigantica snail: (lymnaea cailliaudi )

• Fasciola egg

OS: oral sucker

VS: ventral sucker

OV: ovary

TE: testis

Vi: vitelline glands

UT: uterus

INC: intestinal caeca

GP: genital pore

Fasciola hepatica Fasciola gigantica

cephalic cone, 2 shoulders, converging margins, simple medial branches of intestinal caeca,smaller in size

Less prominent shoulders, parallel margins, medial branches are T or Y shaped, larger in size

Snail (Lymnae caillaudi)

Fasciola egg:very large, operculated, yellow, thin shell

• Location of adult: bile duct• Intermediate host : primary : snail Lymnaea truncatula for

F.hepatica and Lymnaea. cailliaudi for F. gigantica secondary: leaves of fresh-water plants• Mode of transmission: ingestion of raw

water-cress containing encysted metacercariae

• Infective stage: encysted metacercaria• Diagnosis: eggs in stool• Disease: Fascioliasis

Schistosoma sp.

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

S. mansoni

S. mansoni male:8-10 mm, has gynacophoric canal, dorsal surface covered with tubercle

S. mansoni female:14 mm, taller and thinner,vitelline glands occupy 2/3 of the body

S.mansoni male&female

S. mansoni snail Biomphlaria alexandrina

Cercaria of S.mansoni: elongated head, biforked tail

S. mansoni egg:oval with lateral spine

S. Hematobium

Egg: oval with terminal spine Snail:Bulinus truncatus

S.mansoni S.hematobium

• Location:veins of large intestine, colon (lower mesentric vein

• Intermediate host:Biomphalaria alexandrina

• Diagnosis: eggs in stool• Infective stage: cercariae• Mode of transmission:direct

skin penetration of cercariae during swimming

• Disease: Intestinal Bilharziasis

• veins of urinary bladder (venous plexus of urinary bladder)

• Bulinus truncatus

• Eggs in urine• Cercariae• direct skin penetration of cercariae

during swimming

• Urinary Bilharziasis