Parasitology

Nematohelminthes (Round worms) Helminthology Platyhelminthes (Flat worms) Nematohelminthes (Round worms) Trematoda (Flukes) Nematoda Ceastoda (Tape worms)

Define: Disease:-

Class Cestoda (Tape Worms)

Cestoda

In this course we study: Taenia solium & Taenia saginata Hymenolepis nana & Hymenolepis diminuta Echinococcus granulosus.

Hymenolepis nana & Hymenolepis diminuta

Dwarf tapeworm Rat tapeworm Cosmopolitan Hymenolepiasis Name: Hymenolepis nana Hymenolepis diminuta Definition: Dwarf tapeworm Rat tapeworm Distribution: Cosmopolitan Disease: Hymenolepiasis Pathogenicity: Usually asymptomatic. In case of severe, heavy infection there may be abdominal pain, enteritis and diarrhoea. Anaemia & nervous symptoms can occur in children. Generally there is no effect on the host.

Definitive host: Intermediate host: Diagnostic stage: Hymenolepis nana Hymenolepis diminuta Habitat: Definitive host: Intermediate host: Diagnostic stage:

Human occasionally rodents. Hymenolepis nana Hymenolepis diminuta Habitat: Adult: Mainly in small intestine of human (especially children) ,rats and mice. In ileum of rats and mice, occasionally in human. Larva: In insects principally Fleas and cockroaches. Definitive host: Human occasionally rodents. Rats & mice; human & dogs are accidental hosts.

No intermediate host is required ( rodents). Hymenolepis nana Hymenolepis diminuta Intermediate host: No intermediate host is required ( rodents). Insects including fleas, beetles, cockroaches and other. Diagnostic stage: Eggs in stool. Adult worms and proglottides are rarely seen in stool.

Infective stage: Mode of infection: Treatment: Hymenolepis nana Hymenolepis diminuta Infective stage: Mode of infection: Treatment:

Cysticercoid larvae in body cavity of insect. Hymenolepis nana Hymenolepis diminuta Infective stage: Eggs passed in feces. Cysticercoid larvae in body cavity of insect. Mode of infection: Ingestion of eggs or by Internal autoinfection. By ingestion of cysticercoid larvae in body cavity of insect via rodent or human

* Collective treatment is required for all children of the family. Hymenolepis nana Hymenolepis diminuta Treatment: Niclosamide (Yomesan®) 4 tablets before meal first day and 2 tablets daily for other 5 days. Praziquantel one dose is sufficient. * Collective treatment is required for all children of the family.

Adult worm of Hymenolepis nana Adult worm is small thread like, 2-3 cm in length. It consist of over 100 segments all of which are broader than long.

Gravid segment of Hymenolepis diminuta * Uterine branches is hardly visible. * Each segment 1 mm wide.

of Hymenolepis diminuta (1) Mature segment (2) Gravid segment of Hymenolepis diminuta

Hymenolepis nana Scolex The scolex has four suckers which are not visible in this plane of focus (two are marked by *), and an armed rostellum that is clearly visible. 

Hymenolepis diminuta Scolex   The scolex has four suckers. (two are marked by the *), but no hooks [absence of an armed rostellum].

Echinococcus granulosus

Echinococcus granulosus Name: Echinococcus granulosus Definition: Dog tape worm , or hydated tape worm. Distribution: In the Mediterranean region Disease: Echinococcosis , unilocular hydated cyst. Morphology: Scolex: with 4 suckers and a double hook crowned rostellum. The rest of the body consists of 3 proglottides giving the worm a length of 2.5-9 mm.

Echinococcus granulosus Habitat: Definitive host: Intermediate host:

Echinococcus granulosus Habitat: Adult: In small intestine of doges, foxes and wolves. Larva: As hydated cysts in intermediate host tissues. Definitive host: Carnivores as doges, foxes and wolves. Intermediate host: Cattle, sheep, various herbivores. Human can be a dead end intermediate host.

Echinococcus granulosus Diagnostic stage: Infective stage: Mode of infection:

Echinococcus granulosus Diagnostic stage: In case of human the hydated cyst diagnosed by X- rays, CT or ultrasound. Infective stage: For human eggs of Echinococcus granulosus. Mode of infection: Ingestion of eggs from soil, food or drinks contaminated with dog feces or from dog fur.

Echinococcus granulosus Treatment: Prevention:

Echinococcus granulosus Treatment: Surgical removal of hydated cysts. Long time therapy with albendazole (Alzental ® ,Vermizole ®) is found to reduce the cyst growth. Prevention: Keeping dogs away from slaughters house. Proper hygiene concerning dogs.

Echinococcosis , unilocular hydated cyst When the eggs of Echinococcus granulosus are ingested by the intermediate host, eggs hatch in small intestine giving the hooked embryo which penetrate intestinal mucosa and enters the blood circulation. If the embryo escapes phagocytosis it resides in any tissue, lose its hooks and transforms to a cyst which is 10 mm in diameter. This process may take 5 months.

The cyst is composed from an external laminated hyaline membrane followed by a germinal layer. The cyst is filled with a sterile fluid. Brood capsules are found inside the cyst, consisting of only germinal layer and protoscoleces. Ruptured capsule give thousands of protoscoleces at the bottom of the cyst, that is the hydated sand. Hydated cysts can occur in bones, lungs, liver, brain or kidney.

Adjacent organs are affected due to presence of the cyst beside the inflammatory reaction against it. Cyst can cause blood vessels erosion and haemorrhage. Removal of the cysts must done with care; sever allergic reactions or even dissemination of the hydated sand in the rupture. Cyst rupture could happen also in response to cough or muscle strain.

Adult worm of Echinococcus granulosus It is the smallest cestode; composed only from 3 segments (proglottides).

Hydated sand