Platyhelminths 2 Cestoidea David Humber

Cestodes - Tapeworms Endoparasites No mouth or alimentary tract Attachment organ - anterior Elongated body - divided into proglottids Adults in intestines of vertebrates Larval stages in 1 or 2 intermediate hosts

Cestoidea Tissue & Intestinal Disease Hydatid disease (6k) Hydatid disease (rare) Coenurosis (rare) Sparganosis (rare) Sparganosis (?) Cysticercosis (?) Tissue cestodes (extra-intestinal) Echinococcus grqnulosa Echinococcus multilocularis Multiceps spp Spirometra mansonoides Diphyllobothrium spp Taenia solium

Cestoidea Tissue & Intestinal Intestinal Cestodes Diphyllobothrium latum Taenia solium Taenia saginata Hymenolepis nana Hymenolepis diminuta Dipylidium canis Cases 16 million 5 million 76 million 36 million Rare

Intestinal Cestodes Tapeworms Attached via a scolex to mucosa (small intestine) Composed of proglottids forming a strobila Each proglottid contains male & female reproductive organs Immature >> Mature >> Gravid

Tapeworms Hymenolepis nana Taenia saginata - Taenia solium Dwarf tapeworm (upto 40mm - largely children) Taenia saginata - Beef tapeworm (upto 25m) Taenia solium Pork tapeworm (upto 7m) World-wide distribution

Hymenolepis nana Dwarf Tapeworm Intermediate host not required infection via intermediate insect host rare commonest tapeworm in UK and US (<1%) Eggs via oral-faecal route Hatch in stomach/small intestine Larvae (onchospheres) penetrate villi Develop into cysticercoid stage Migrate back into lumen

Hymenolepis nana Dwarf Tapeworm Maturation 2-4 weeks Length dependent on parasitemia Scolex - 4 suckers + short rostellum with hooks Eggs released by disintergration of terminal proglottids Eggs immediately infectious

Hymenolepis nana Dwarf Tapeworm Often asymptomatic even with high worm burden headache, dizziness, anorexia, abdominal pain, diarrhea, low grade eosinophilia Heavy infections via auto infection (in intestine) Diagnosis by egg morphology (adults v rarely seen)

Hymenolepis nana Control World-wide incidence 4% Treatment usually Praziquantel previously Niclosamide (both single oral dose) Health education Rodent reservoir?

Taenia saginata Beef Tapeworm Commonest taenia infection (Ethiopia) Ingestion of raw or poorly cooked beef Larvz digested & evaginates in small intestine Scolex 4 suckers no hooks Proglottids 1-2k (lateral unterine branches 15-20)

Taenia saginata Beef Tapeworm Motile proglottids crawl through anus during day Eggs identical to T. solium (viable upto 159 days) Larvae (onchospheres) hatch in cattle intestine Migrate through villi via lymphatics/blood to striated muscle Develop into cysticerci (bladder worm)

Taenia saginata Beef Tapeworm Usually asymptomatic hunger pains, weight loss discomft & embarrassment at voiding proglottids Diagnosis based on recover of gravid proglottid (uterine branches >15) Praziquantel or niclosamide Health education

Taenia solium Pork Tapeworm Recognised since biblical times Risk of cysticercosis Evagination > six hooked four suckers larva (onchophore) in small intestine Attaches to mucosa (penetrates in cysticercosis) Matures in 5-12 weeks Usually long lived (25 years) single worm Less than 1000 proglottids

Taenia solium Pork Tapeworm Usually asymptomatic similar to S. saginata Low grade eosinophilia <15% Treatment praziquantel niclosamide

Taenia solium Cysticercosis Onchospheres penetrate intestine (adult worm not usually found) Distributed via mesenteric venules Most organs including brain, eyes, sucutaneous and intramuscular Sometimes multiple organs (geographical variations)

Taenia solium Cysticercosis Bladder worms upto 60ml in volume (usually around 5 x 800 mm) Diagnosis surgical removal X ray - calcified larvae CT scan or MRI for brain lesions Fine needle aspirate Serology/PCR

Taenia solium Cysticercosis Treatment surgical removal praziquantel (15 day course) only treatment for cysticercus albendazol (8 day course)

Tissue Cestodes Taenia solium Echinococcus grqnulosa Echinococcus multilocularis Diphyllobothrium spp Multiceps spp Spirometra mansonoides

Echinococcosis - Hydatid disease Echinococcus granulosa worldwide Echinococcus multilocularis Europe, Russia, China, Canada Echinococcus vegeli Central & South America

Distribution

Hydatidosis Known since Hipporates 400BC Most serious of the tapeworm infections

Hosts Definitive Host Intermediate Host Canids & felids 59% dogs in Istanbul (E.granulosa) Intermediate Host humans +60 species ungulate,marsupials, elephants,primates, rodents for E. multilocularis

Lifecycle Definitive host Intermediate host Egg production Worm lives 2+ years Cyst evaginates Intermediate host Hatch - onchosphere invades mucosa & penetrates capillaries Cysts form in liver & lungs Secondary metastasis 20+ years Secondary daughter cysts bud in E. multilocularis

Clinical Features Definitive Host Intermediate Host usually asymptomatic Intermediate Host dependent on burden & site usually single - 50% in liver, 3% brain (E.g) incubation +5 years 6-10% diagnosed cases fatal Eosinophilia in 25% cases

Diagnosis Parasitological Radiological (CT & MRI) & ultrasound eosinophilia palpation Radiological (CT & MRI) & ultrasound differente from tumor Immunological Skin test - Casoni test - 18% false +ves Serology

Treatment & Control Surgery Praziquantel or albendazol drainage + 5 mins 10% formalin Praziquantel or albendazol steroids to prevent inflammation aspiration + 95% ethanol Health education sanitation - dogs cats raw meat

Diphylobothrium - Sparganosis Diphylobothrium latum Broadfish tapeworm Definitive host humans/dogs/cats/pigs/bears/otters, seals etc First intermediate host Copepods Second intermediate host trout/salmon/perch/pike

Intestinal infections Limited to fish eating areas raw or improperly cooked dumping untreated raw sewage Adult worms (upto 10m) attach to lining of intestine Ovoid operculated eggs released Eggs dormant in water (8-12 days) motile coracidium hatches ingested by freshwater copepod

Intestinal infections Ciliated embryophore shed & naked hexacanth larva attaches by hooks Bores through intestinal wall into haemocoel Hexacanth metamorphose into procercoid (14-18 days) 500um in length

Intestinal infection In fish procercoid penetrates intestinal wall migrates to muscles develops into plerocercoid (20-40mm) in 7-30 days with fully developed scolex In definitive host attaches to mucosa grows at 30 proglottids a day Full sexual maturity in 3-5 weeks

Sparganosis Some species of Diphylobothrium and Spirometra larva invade

Nematode Infections

Nematodes Half million species 50% free living animal & plant parasites Animal vertebrate & invertebrate hosts infection by ingestion penetration

Nematodes Generally elongated, cylindrical & tapered at each end (99%) fluid filled pseudocoelom logitudinal muscle only no vasculature or respiratory system usually sexual dimorphism (some parthenogenetic) males usually smaller than females most between 1mm and 150mm colourless translucent to opaque with an elastic curticle

Ascaris Large intestinal round worm mouth with I dorsal & 2 ventral lips female 40cm male 30cm Uterus of mature female 20+ million eggs Sheds 200,000 golden brown ovoid eggs per day Eggs resistant to desiccation