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Parasites 1: Trematodes and Cestodes Readings-Cestodes • Ch. 11 (pp. 293-295, 295 [box Lecture 3: Emerging Parasitic 11.1], 304 [box 11.2]) Helminths part 1: Cestodes (Tapeworms) Presented by Matt Tucker, M.S., MSPH [email protected] HSC4933 Emerging Infectious Diseases HSC4933. Emerging Infectious Diseases 2 Monsters Inside Me Learning Objectives • Just for fun, check out these links: • Know life cycles, diagnostic criteria, epidemiology, pathogenicity, • Cysticercosis (Taenia solium, pork tapeworm): &treatment Background: • Know basic attributes of tapeworms and be able to correctly identify the parasites we discuss as cestodes (as compared to http://animal.discovery.com/invertebrates/monsters- other parasites we discuss). inside-me/pork-tapeworm-cysticercosis/ • Know what tapeworms are pseudophyllidean vs. cyclophyllidean Videos: http://animal.discovery.com/videos/monsters- • Understand life cycles of cestodes, noting similarities and inside-me-pork-tapeworm.html significant differences • Know prevention strategies http://animal.discovery.com/videos/monsters-inside- • Understand how serious pathological conditions are caused by me-meter-long-tapeworm.html tapeworms • For each tapeworm, what could make it an emerging problem in the world HSC4933. Emerging Infectious Diseases 3 HSC4933. Emerging Infectious Diseases 4 On the Menu Cestodes (Tapeworms) • Adult cestodes have been found in • Diphyllobothrium latum virtually every species of vertebrate • Taenia spp. animal • Perhaps the most specialized of all • Echinococcus spp. parasites • Two orders encompass cestodes infecting humans: Pseudophyllidae and Cyclophyllidae – The life cycles of pseudophyllideans usually involve a crustacean as a first intermediate host and fish as second intermediate hosts • Unique structure of adults HSC4933. Emerging Infectious Diseases 5 HSC4933. Emerging Infectious Diseases 6 1 Tapeworm Terms • Scolex-knoblike anterior (head) end that has suckers or hooklike parts that in the adult stage serve as organs of attachment to the host • Procercoid-first stage in the aquatic life cycle of certain tapeworms, such as the pseudophyllideans, following ingestion of the newly hatched larva (coracidium) by a copepod. • Plerocercoid-when the procercoid and its host are ingested by a fish, the procercoid enters the new host's tissues and becomes a plerocercoid • Oncosphere-larva contained within the external embryonic envelope within the egg and armed with six hooks, undergoes metamorphosis after penetrating into a tissue site in the intermediate host • Cysticercus-larval stage of many tapeworms, consisting of a single invaginated scolex enclosed in a fluid-filled cyst. • Proglottid-part of tapeworm “body” containing a set of reproductive organs HSC4933. Emerging Infectious Diseases 7 HSC4933. Emerging Infectious Diseases 8 Diphyllobothrium latum D. latum life cycle • Pseudophyllidean • Broadfish tapeworm • Typically the largest human tapeworm • Diphyllobothriasis can be a long-lasting infection • Worldwide infections estimated at 20 million (1999) • Life cycle requires two intermediate hosts • Freshwater fish become infected with Diphyllobothrium sp. • Humans, bears are definitive hosts • Occurs in the Northern Hemisphere (Europe, newly independent states of the former Soviet Union, North America, Asia), Uganda and Chile. HSC4933. Emerging Infectious Diseases 9 HSC4933. Emerging Infectious Diseases 10 Re-emerging Diphyllobothrium? New cases in Brazil • Switzerland, northern Italy, eastern France • Only 1 case in Brazil during January 1998 to December 2003. • Many regional cuisines include raw or • By comparison, 18 cases were diagnosed from undercooked food March 2004 to January 2005. – Sushi and sashimi in Japanese cuisine – All patients who became infected ate raw fish in sushi or sashimi. – Carrpaccio di persico in Italian • New host? – Tartare maison in French-speaking populations – C. undecimalis has not been reported as a D. latum – host, but it is a saltwater fish that spends part of its Fefilte fish in Jewish populations life in fresh water. – Ceviche in Latin American cuisine HSC4933. Emerging Infectious Diseases 11 HSC4933. Emerging Infectious Diseases 12 2 Clinical Features, etc Prevention • Most infections are • Proper sanitation asymptomatic. Manifestations may include abdominal discomfort, diarrhea, • Effective treatment vomiting, and weight loss. • Fish should be well cooked or deep-frozen • Chemical competition-Vitamin B-12 deficiency with pernicious anemia may – Deep-frozen fish and storage (-20C for 7 days or - occur. 35C until solid, storing at -35C for 15hrs) • Massive infections may result in – Cooking fish at a temperature of 55°C kills intestinal obstruction. plerocercoid larvae in 5 min • Migration of proglottids can cause cholecystitis or cholangitis. • Placing fish in a concentration of brine (12% • Treatment: Praziquantel, Niclosamide NaCl) • Fish inspection HSC4933. Emerging Infectious Diseases 13 HSC4933. Emerging Infectious Diseases 14 Other important Diphyllobothrium Taenia spp. spp. • D. nihonkaiense • 1977: 3200 yr old mummy found with Taenia egg – Japanese broad tapeworm • Ancient greeks documented tapeworms – 1986- found to be distinct from D. latum • Worldwide distribution-estimated 50 – Wild Pacific salmon as second intermediate host million affected – Cases in Europe emerging • T. saginata: beef tapeworm – In Japan over last 20 years, average of less than 0.5 • T. solium: pork tapeworm cases/100,000 people, but increased to 1 case/100,000 in • T. saginata has higher global prevalence 2008 • T. solium is more prevalent in poorer • Other species linked to Pacific salmon: D. klebanovskii communities where humans live in (Russia), D. ursi (North America) close contact with pigs • Humans are the only definitive hosts • 1980 outbreak in the Pacific U.S. of diphyllobothriasis for T. saginata and T. solium. linked to salmon HSC4933. Emerging Infectious Diseases 15 HSC4933. Emerging Infectious Diseases 16 . Taenia sp. life cycle Clinical features • The majority of T. saginata and T. solium carriers are unaware of their infection. • Gastrointestinal symptoms are due to the presence of the tape worm. • Carriers of T. solium carry a substantial risk of acquiring cysticercosis by fecal-oral autoinfection and members of their households are also at increased risk HSC4933. Emerging Infectious Diseases 17 HSC4933. Emerging Infectious Diseases 18 3 Prevention, Tx, Dx Cysticercosis • Prevention is based on strict meat inspection, health • Caused by ingestion of T. solium eggs, education, cooking pork and beef well, hygiene, and through fecal-oral transmission or possibly widespread sanitary installations. through autoinfection • Prevention of fecal contamination of soil, water, food, • Humans are dead-end hosts of the larval stage humans/animals through safe disposal of sewage; and develop cysticercosis similar to pigs avoidance of sewage water for irrigation use. • Many parts of body are affected, most • Cysticerci killed by irradiation or cooking meat at 56⁰C, commonly subcutaneous tissues, eyes, brain freezing at -5⁰C for 1 week • 50,000 cases of neurocysticercosis reported • Treatment: Praziquantel each year globally • Dx: ID of eggs and proglottids in feces, but not • More than 1,000 new cases of neurocysticercosis diagnosed in the U.S. each possible 3 months following infection, prior to year. “Measly pork” development of adult tapeworms. – A total of 221 cysticercosis deaths were identified in U.S. from 1990-2002 • Neurocysticercosis: most common parasitic disease of CNS. HSC4933. Emerging Infectious Diseases 19 HSC4933. Emerging Infectious Diseases 20 Disease Features • Neurocysticercosis causes diverse manifestations including seizures, mental disturbances, focal neurologic deficits, and signs of intracerebral lesions. **not acquired by eating infected • Severe inflammatory responses to dying pork, but by eating cysticerci can cause sudden death eggs • Extracerebral cysticercosis can cause ocular, cardiac, or spinal lesions with associated symptoms. • Asymptomatic subcutaneous nodules and calcified intramuscular nodules can be encountered. HSC4933. Emerging Infectious Diseases 21 HSC4933. Emerging Infectious Diseases 22 Worldwide prevalence of Cysticercosis neurocysticercosis • Dx by demonstrating the cysticercus in the tissue involved • Very difficult to treat, but varying success: praziquantel, albendazole in combination with corticosteroids to reduce swelling caused by immune attack on dead worms • Prevention-early detection, eliminating adult tapeworms, promoting personal hygiene 23 24 HSC4933. Emerging Infectious Diseases HSC4933. Emerging Infectious Diseases Burneo et al. 2009 4 Echinococcus spp. background Echinococcus granulosus • Hydatid disease • Causes cystic echinococcosis=most frequent • Recognized by Hippocrates in 400 BC • Occurs globally, but more frequently in rural, grazing areas where dogs ingest organs from • Major species infecting humans infected animals. – E. granulosus • Sylvatic cycle where humans accidentally – E. multilocularis infected • Dogs and wild canids are the definitive host – More typically, humans infected where for Echinococcus tapeworms, but zoonotic domestic herbivores raised near dogs potential is important – Humans serve as aberrant intermediate • Hydatid cysts hosts, developing potentially aggressive – Slowly enlarging, mass lesions producing pain and damaging tissue cysts and physical obstruction/pressure on surrounding organs. • Unlike most parasitic diseases, – If the cyst ruptures, "daughter" cysts may be echinococcosis
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