Helminthology Helminths 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 Intermediate host Infective stage Mode of transmission Location in the host Lab diagnosis (Diagnostic stage) Disease

Class Trematoda (Flukes)

General Characters 1- Flat worms (no body cavity), not segmented, bilaterally flattened (except Schistosoma is cylindrical) 2- No respiratory nor vascular system. 3- Hermaphrodite (except Schistosoma)

4- Body has 2 suckers for attachment: oral, ventral, (except Heterophyes has a 3 rd genital sucker) 5- Life cycle show sexual phase (definitive host) and asexual phase (intermediate host) 6- Require one or more intermediate host 7- 1st intermediate host is a snail 8- Eggs have an operculum(except Schistosoma) 9- Infective stage is encysted metacercaria (except Schistosoma: cercariae)

General life cycle of trematodes 1. Eggs are released from human (in feces or urine) in fresh water. 2. Eggs hatch into first larval stage (miracidial larva) that invade a snail as 1ry intermediate host. 3. All trematodes except Schistosoma sp. require a second intermediate host which is mostly a water plant or animal. 4. The second larval stage (cercarial or metacercarial larva) comes out of the intermediate host(s). 5. Humans are infected through direct penetration of cercaria (Schistosoma) or ingestion of encysted metacercaria in water plant or animal (all other trematodes).

1- Intestinal Fluke Heterophyes heterophyes Heterophyes heterophyes adult Heterophyes heterophyes eggs Heterophyes heterophyes snail Heterophyes heterophyes encysted metacercaria Heterophyes heterophyes in small intestine

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

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

Heterophyes heterophyes adult in small intestine Adult worm is present in intestinal villi

Heterophyes heterophyes encysted metacercaria in Bouri and Bolti muscles

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 or undercooked fish containing encysted metacercaria Diagnosis: eggs in stool Disease: heterophiasis

2- Liver Fluke Fasciola Fasciola hepatica adult Fasciola gigantica adult Fasciola gigantica snail: (lymnaea cailliaudi ) Fasciola egg Fasciola metacercaria

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 Less prominent shoulders, parallel margins, medial branches are T or Y shaped, larger in size 2 prominent shoulders, converging margins, simple medial branches of intestinal caeca, smaller in size

Snail (Lymnaea cailliaudi) Fasciola egg: very large, operculated, yellow, thin shell

secondary: leaves of fresh-water plants 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

3- Blood Fluke 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 Schistoma cercaria

S. mansoni S. mansoni male: 8-10 mm, has gynaecophoric 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 S. mansoni egg: oval with lateral spine Cercaria of S. mansoni: elongated head, biforked tail

S. haematobium Egg: oval with terminal spine Snail: Bulinus truncatus

S. mansoni S. haematobium 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