Parasitology is classified into three main groups

Protozology

(proto = primitive)

Study of protozoa

Helminthology

(Helminth = Worm)Study of helminth

Entomology

Study of arthropods

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

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 3rd 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)

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

1 .Heterophyes heterophyes

• Pear shaped,• Very small size, (2mm) • Oral,ventral, genital suckers• Vitelline glands• 2 testis, 1 ovary• simple intestinal ceaca • (L.P)

Heterophyes heterophyes cont.

Heterophyes heterophyes cont.

• 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.

OS: oral sucker

VS: ventral sucker

OV: ovary

TE: testis

Vi: vitelline glands

UT: uterus

INC: intestinal caeca

GP: genital pore

Fasciola sp.

Fasciola hepatica Fasciola gigantica

cephalic cone, 2 shoulders, converging margins,smaller in size

Less prominent shoulders, parallel margins, larger in size

Fasciola sp. cont.

Snail (Lymnae caillaudi) Fasciola egg:very

large, operculated, yellow, thin shell (H.P)

Fasciola sp. cont.

• 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.

Fasciola sp. cont.

a. Schistosoma mansoni

Schistosoma mansoni male: 8-10 mm, has gynacophoric canal, dorsal surface covered with tubercle (4X)

Schistosoma mansoni female: 14 mm, taller and thinner,vitelline glands occupy 2/3 of the body( 4X)

Schistosoma sp.

Schistosoma mansoni snail Biomphlaria alexandrina

Cercaria of Schistosoma mansoni : elongated head, biforked tail (H.P)

Schistosoma mansoni egg: oval with lateral spine (H.P)

a. Schistosoma mansoni cont.

b. Schistosoma hematobium

Egg: oval with terminal spine (H.P)

Snail: Bulinus truncatus

Schistosoma mansoni Schistosoma hematobium

LocationVeins of large intestine,

colon (lower mesentric

vein

Veins of urinary bladder

(venous plexus of urinary

bladder

Interm. hostBiomphalaria

alexandrina

Bulinus truncatus

DiagnosisEggs in stoolEggs in urine

Infective stageCercariaeCercariae

Mode of

transmission

Direct skin penetration of cercariae during swimming

Disease: Intestinal Bilharziasis Urinary Bilharziasis

HelminthologyQuestions form:

• Name and sex of the parasite

• Class to which the parasite belongs

• Location in the host

• Intermediate host

• Definitive host

• Infective stage

• Mode of transmission

• Lab diagnosis

• Disease