Echinococcus granulosus Echinococcus mutilocularis

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1 Diyala University Collage of Medicine Department of Microbiology Practical Parasitology 3 nd stage Lab 19:Cestoda Echinococcus granulosus Echinococcus mutilocularis

2 Dog Tapeworm Hydatid Worm Eggs May be found in feces of host (dogs and herbivores, domestic and wild animals which eat meat) or passed in gravid segment or may adhere to the coat of host when gravid segment disintegrates. It is infective to man. Larvae stage (hydatid cyst) found in varying organs in herbivores (e.g. sheep, goats, cattle and man). Adult worm - lies attached to the mucus of small intestine of carnivores(e.g. canines &felines)

3 Morphology E. granulosus & E. multilocularis are smallest cestode, Measures 3 5 mm in length. Body divided into: Scolex having 4 suckers, armed with 2 rows of hooked rostellum bearing about hooklets. Short neck. Strobila contains 3 proglottids. (One immature, one mature and one gravid). The size of the gravid segment is more than a ½ of the body length. The uterus is unbranched,genital pore is positioned behind the middle line of gravidsegment Eggs are rounded and indistinguishable to those of Taenia Spp.

4 Adult worms are small (3-6 mm in length) It is composed of a Scolex Neck Strobila 3 segments (occassionally 4) Immature Mature Gravid

5 Scolex bears 4 suckers and rostellum with 2 circular rows of hooks.

6 Ova Ovoid in shape Resemble Taenia ova Hexacanth embryo with 3 pairs of hooks Infective to: Man Cattle Sheep and other herbivorous animals

7 Larva Found within the hydatid cyst developing inside the intermediate host Represents the structure of the scolex of the future adult worm Young larva are transformed into a hollow bladder (hydatis, drop of water) Brood capsules develop within the cysts and may contain thousands of scolices On entering the final host, the scolex armed with a rostellum and 4 suckers become adult worms

8 Life cycle Intermediate hosts acquire infection through ingestion of eggs in contaminated substances,eggs hatch in small intestine releasing an oncosphere which penetrate the intestinal wall & carried along the body by blood circulation to organs like liver, lungs etc. These are then transformed into protoscolices in a (hydatid) cyst Infection of the definitive host (dog) is when hydatid cyst(s) in the intermediate host (e.g. sheep) is eaten.

9 Life cycle The cyst wall is digested, the protoscolices are liberated, which develop into adults. The gravid proglottids break away and are expelled singly (may force their way out through anal sphincter). On drying they rupture releasing eggs with fully developed larvae. Hydatid cyst is a bladder that contains inverted scolices, brood sacs with scolices, daughter cysts with their own inverted scolices

10 Life Cycles If the scolices separate from the inner lining of the capsule, they are called hydatid sand. Hydatid cyst may be unilocular, E.granulosus) or alveolar/multilocular (E.multilocularis) Unilocular has a single compartment with 2 layers, the inner layer produces protoscolices &brood capsules, when these detach they are termed as hydatid sand Alveolar have multiple divisions of the cyst into compartments

12 Definitive Host Dog Wolf Fox Jackal Intermediate Host Sheep Pig Cattle Horse Goat

13 Pathogenesis & pathology The pathology is primarily due to impairment as a result of pressure from the growing cyst, symptoms are subject to organs affected, size & number of the cyst. Pulmonary infection result into coughing & allergic responses. Seizures & comma may be a result of brain invasion. Rupture of the cyst release the protoscolices to the circulation, which may lead to secondary echinococcosis.

14 Pathogenesis & pathology Fluid from the cyst may lead to severe allergic reactions (anaphylactic shock). Like osseous, alveolar cysts are usually difficult to remove, the former may lead to spontaneous fracture of bones where the later may lead to strong impairment & obstruction of infected organ and is fatal. May cause calcification of tissue when the cysts die. Few patients are reported to have generalized eosnophilia.

16 Encysted scolices of Echinococcus granulosus in lung "hydatid sand"

17 Encysted scolices of Echinococcus granulosus in lung "hydatid sand"

18 Encysted scolices of Echinococcus granulosus in lung "hydatid sand"

19 Diagnosis Laboratory diagnosis - post-surgical Microscopic demonstration of scolices in hydatic fluid Immunodiagnosis Casonis test, involves skin/intradermal injection of irradiated cystic fluid, which on presence of antibodies A burning swelling will be formed Serodiagnosis Detection of antibodies & antigens due to the parasite by ELISA, etc Imaging methods X-rays, ultrasounds, etc show presence of the hydatid cysts in organs

20 Casoni Test: Intradermal Test Antigen is prepared from filtered hydatid fluid or saline extraction of ground If 0.2mls of hydatid fluid is sterilized by filtration is injected intradermal into the patient suffering from hydatid cysts a wheel is produced in about 15 minutes surrounded by concentric erythromatous zone, which later disappear with a wheal. A second similar reaction (i.e. after 20 minutes) frequently takes place at the same point a few hours (or minutes) later. Between 50% and 100% of infected individual react positively

21 ECHINOCOCCUS MULTILOCULARIS Most of the E. multiculoris are said to be sterile because they don t have protoscolices in their parent cyst. Although there may be few if any protoscolices produced In genera the rupture of hydatid cyst release the hydatid sand.

Cestodes. Tapeworms Complex Life Cycles Definitive host. 1 or 2 Intermediate Hosts. Adult worms Sexual reproduction

Cestodes. Tapeworms Complex Life Cycles Definitive host. 1 or 2 Intermediate Hosts. Adult worms Sexual reproduction Cestodes Tapeworms Complex Life Cycles Definitive host Adult worms Sexual reproduction 1 or 2 Intermediate Hosts Larval Tapeworms (Metacestodes) Some show Asexual reproduction Morphologic Characteristics