Cestoda Chapter 3 Learning Objectives State the general characteristics of thephylum Platyhelminthes. Describe the general morphology of anadult cestode. State the methods of diagnosis used toidentify cestode infections. Compare and contrast the phylumNemathelminthes with Platyhelminthesusing morphologic criteria. Learning Objectives Define terminology specificallyrelated to the Cestoda. State the scientific and commonnames of cestodes that parasitizehumans. Describe in graphic form the generallife cycle of a cestode. Differentiate adult Cestoda usingmorphologic criteria. Learning Objectives Differentiate larval stages of Cestodausing morphologic criteria, therequired intermediate host, or both. Differentiate the diagnostic stages ofthe Cestoda. Discuss the epidemiology andmedical importance of cestodezoonoses. Learning Objectives Given illustrations or photographs,identify the diagnostic stages ofCestoda and the body specimen ofchoice to be used for examination ofeach. Identify the stage in each life cyclefor each cestode that can parasitizehumans. Introduction Classification General body structure
Platyhelminthes (flatworms ) Cestodes ( tapeworms) General body structure Scolex Hooks Suckers Rostellum Neck Proglottids Immature, mature, gravid (proglottids) Reproduction - Hermaphroditic Tapeworm body Tapeworm body Tapeworm body Tapeworm body Tapeworms infecting humans
Hymenolepsis nana-- dwarf tapeworm Taenia saginata beef tapeworm Taenia solium pork tapeworm Diphyllobothrium latum broad fishtapeworm Echinococcus granulosis hydatid tapeworm Hymenolepis nana (dwarf tapeworm)
Method of diagnosis Diagnostic stage Disease name Major pathology and symptoms Treatment Distribution H. nana Tropics and sub tropics Children and institutionalized people
Most common tapeworm in U.S. Requires no intermediate host Autoinfection is common Mice can be definitive host Eggs in feces infective stage Fleas & beetles transport hosts Cysticercoid larva infective stage Hymenolepis nana - (dwarf tapeworm) H. Nana egg - Diagnostic Stage H. Nana egg - Diagnostic Stage H. nana Small scolex Rostellum with 1 row of hooklets Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm)
Method of diagnosis Diagnostic stage Disease names Major pathology and symptoms Treatment Distribution Taenia Life Cycle Taenia eggs Taenia saginatta (beef tapeworm) Life cycle Taenia solium Lifecycle T.Solium (pork tapeworm) armed-
4 suckers Rostellum 20-30 largehooks set in 2rows T. Saginata (beef tapeworm) Unarmed- 4 large cup-shaped suckers T. solium Uterus 7-13 lateral branches Eggs are infective T. saginata Uterus 15-30 lateral branches Diagnostic - Identification Diphyllobothrium latum (broadfish tapeworm)
Method of diagnosis Diagnostic stage Disease names Major pathology and symptoms Treatment Distribution D. latum D. latum Worldwide freshwater Florida, Great Lakes, Alaska
Often asymptomatic ; vague GIdisturbance Macrocytic, pernicious anemia Competes with host for Vitamin B12 D. latum Scolex No Hooks or cup-shaped suckers
Bothria- 2grooved suckerson eithersideofscolex D. latum Operculated egg with terminal knob D. Latum egg D. latum D. latum proglottid Rosette shaped Uterus Echinococcus granulosus (hydatid tapeworm) (dog tapeworm)
Method of diagnosis Diagnostic stage Disease names Major pathology and symptoms Treatment Distribution Echinococcus granulosus
Onlyfound in canine host(DOG OR WOLF ISDEFINITIVE HOST) Intermediate host sheepor other ruminants Human is accidentalintermediate host Eggs ingested Contaminated food orwater Objects contaminatedwith dog feces Dog becomes infected byeating raw meatcontaining hydatid cyst E. Granulosus hydatid cyst with 3 brood capsules E. Granulosus hydatid cyst
Each scolex has suckersand crown of hooks Each scolex grows toadult tapeworm ifingested by dog E. Granulosus hydatid cysts from vertebral column (bone)
Humans cysts in any tissue mostcommon Liver Lung Central nervous system (CNS) Bone bone marrow Disease varies with location ofcysts - No symptoms or death Disease may develop slowly Slow-leaking cyst allergicsensitization Cyst rupture anaphylaxis ordissemination E. Granulosus Rare in Europe or U.S. except in sheep raising areas
Southwest ( Navajo) ; Utah Common in Alaska and Canada Diagnosis history of exposure Radiology X-ray, ultrasound, CT Immunodiagnostic skin testing Serology indirect hemagglutination, ELISA Hooklets, scolices,, cyst membranes in histology tissue preps orbodyfluids Hydatid sand- granular material found in older cysts; free scolices,daughter cysts ; hooklets Biopsy dangerous cyst leakage causes anaphyaxis Zoonoses Cysticercosis Echinococcus granulosus
Dipylidium caninum (dog or cat tapeworm) Human accidentally ingests larva from infected dog orcat flea (IH) Mild infection adults in intestine; egg packets orproglottids in feces Hymenolepsis diminuta ( rat tapeworm) Human accidentally ingests larva from infected flea orgrain beetle (IH) Mild symptoms; often resolves spontaneously; eggs infeces are diagnostic Cysticercosis Echinococcus granulosus H. Diminuta vs H. nana H. Diminuta vs H. nana Zoonoses Dyphlobothrium spp. (dog or cat species)
Location of parasite in humans How infection occurs Disease symptoms Diagnosis