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]

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Monsters Inside Me Learning Objectives

• Just for fun, check out these links: • Know life cycles, diagnostic criteria, epidemiology, pathogenicity, • (, 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

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On the Menu Cestodes (Tapeworms)

• Adult cestodes have been found in • 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

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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

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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 (, newly independent states of the former , North America, Asia), Uganda and Chile.

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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 March 2004 to January 2005. – and 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. – in Latin American cuisine

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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 or cholangitis. • Placing fish in a concentration of brine (12% • Treatment: , NaCl) • Fish inspection

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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

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. 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

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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 of CNS.

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Disease Features

• Neurocysticercosis causes diverse manifestations including , 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.

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Worldwide prevalence of Cysticercosis neurocysticercosis

• Dx by demonstrating the cysticercus in the tissue involved • Very difficult to treat, but varying success: praziquantel, in combination with corticosteroids to reduce swelling caused by immune attack on dead worms • Prevention-early detection, eliminating adult tapeworms, promoting personal hygiene

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4 Echinococcus spp. background

• Hydatid disease • Causes cystic =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 is more prevalent in the released that spread elsewhere in the body. northern hemisphere. . Most cysts develop in the liver or lungs.

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Echinococcus multilocularis Echinococcus life cycle

• Causes alveolar echinococcosis • Foxes and other wild canids are the definitive hosts and rodents (voles and deer mice) serve as normal intermediate hosts. • Alveolar hydatids – Much more aggressive lesions than hydatid cysts . Fatality rates in infected humans approach 50%

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Global distribution of zoonotic strains of Echinococcus

E. granulosus

Budke et al., 2006

• E. multilocularis occurs in the northern hemisphere, including central Europe and the northern parts of Europe, Asia, northern India, Iraq, Alaska, Canada

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5 Other species Clinical Disease

• E. oligarthrus and E. vogeli: neotropical species • Location of cyst determines extent of pathological localized exclusively in Central and South America conditions associated with disease • E. granulosus infections remain silent for years – Only 3 cases of E. oligarthrus infection have been before the enlarging cysts cause symptoms in the reported in the literature (1 from Brazil, 1 from affected organs. Venezuela, and 1 from Surinam); • Hepatic involvement can result in abdominal pain, a mass in the hepatic area, and biliary duct – 168 E. vogeli cases have been reported in 12 countries obstruction. in Central and South America • Rupture of the cysts can produce fever, eosinophilia, and anaphylactic shock, as well as cyst • There are periodic reports of these species dissemination.

infecting humans, but since the case fatality rate • E. multilocularis affects the liver as a slow growing, is often very high, it is important to discuss them destructive tumor, with abdominal pain, biliary obstruction, and occasionally metastatic lesions into (as we will see later). the lungs and brain.

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Diagnosis Treatment

• X-rays, ultrasonography E. granulosus (hydatid cyst) and/or other imaging • Surgery+Albendazole techniques supported by • Praziquantel is useful preoperatively or in case of spillage of cyst positive serologic tests. contents during surgery. • Percutaneous aspiration-injection-reaspiration (PAIR) with ultrasound guidance plus albendazole therapy has been • A: Protoscoleces in a effective for management of hepatic hydatid cyst disease hydatid cyst removed from A F lung tissue E. multilocularis (alveolar cyst) • Surgical excision is the only reliable means of cure. • F: E. multilocularis in • Albendazole can stabilize and sometimes cure infection liver tissue.

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Prevention Echinococcosis: scope of problem

• Removal of dogs from areas • Multiple hosts that can spread the disease • where domesticated Importation of hosts • Certain cultural practices deter prevention and control strategies, herbivores resistance to control mechanisms • • Diseases cause severe monetary losses due to disability and sickened Deworming dogs livestock • Removal of infected entrails – Tunisia: significant direct and indirect losses in both humans and animals of between $10-19 million annually. from abattoirs . The reported incidence in humans is 1.5 to 2.05 cases per 100 000 inhabitants and between 12% and 17 % of the cattle at slaughter is infested. • Precautions handling wild – The estimated global human burden of echinococcosis may be as high as animals by hunters, trappers 1,009,662 DALYs - or an annual loss of $7-8 million. A maximum annual livestock production loss of over 2 billion dollars is also estimated.

Source: WHO

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6 2006 Case Study

• 72 yr old man from French Guiana-abdominal pain and a palpable epigastric mass. The patient hunted jaguars in the rain forest of French Guiana and owned dogs. An exploratory laparotomy showed a hard, whitish liver tumor. Histopathologic examination of a biopsied sample of the tumor showed multilocular cysts. Albendazole treatment was started immediately after surgery. • Computer tomography showed a multilocular cystic mass in the left side of the liver • Serological, hook morphology, and molecular confirmation of E. vogeli • 1st E. vogeli case reported in French Guiana

• Problem: E. vogeli and E. oligarthrus have primarily sylvatic life cycles and the number of human cases might be underestimated because of the small number of patients who receive surgical treatment

• Signifcance: Healthcare providers need to be alert to the existence of neotropical echinococcosis and should consider the possibility of its emergence in Central and South America. Although rare, this disease is still lethal in untreated cases.

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