Lecture 19: Mesozoa: Cestode (Tapeworm) Part 3 PDF

Lecture 19: Mesozoa: Cestode (Tapeworm) Part 3  LESSON LEARNING OUTCOMES Able to EXPLAIN on Taenia saginata, Taenia solium. * Morphology * Life cycle * Pathogenesis/ Disease * Treatment & Prevention ...

Lecture 19: Mesozoa: Cestode (Tapeworm) Part 3  LESSON LEARNING OUTCOMES Able to EXPLAIN on Taenia saginata, Taenia solium. * Morphology * Life cycle * Pathogenesis/ Disease * Treatment & Prevention  The cyclophyllidean larvae are more complex and come in a quite a variety The medically important larvae (T. solium) are cysticercoid, cysticercus and hydatid (some of these larvae provided amplification) (Hymenolepis sp.) (E. granulosus)  EMAF EGCD STAGE FOUND COMMON SPECIES PATHOLOGY THERAPY IN HUMANS NAME Diphylobothrium lutum Adult Diphylobothrium latum Fish tapeworm Pernicious anemia Niclosamide; Praziquantel Hymenolepis nana Adult Dwarf tapeworm Rarely symptomatic Niclosamide; Praziquantel Taenia saginata Adult Beef tapeworm Rarely symptomatic Praziquantel Taenia solium Adult Pork tapeworm Rarely symptomatic Niclosamide; Praziquantel Larvae Brain and tissue Albendazole; Surgery cysts Echinococcus Larvae Hydatid Dog cyst Solitary tissue cysts Surgery; Albendazole granulosus disease Tapeworm (Hydatid cyst) Echinococcus Larvae Alveolar Fox cyst Multilocular Surgery; Albendazole Tapeworm (Alveolar cyst) multilocularis disease cysts  Taenia saginata Beef tapeworm Ranges in length from 6-30 ft Geographic distribution: cosmopolitan: Africa and South America Most common where poor sanitation and no inspection of meat combine Transmission: Ingestion of larval form in undercooked beef In N. America 1 in 100 is infected. In third-world nations could be up to 10% No symptoms or some abdominal discomfort Diagnosis: finding eggs or proglottids in feces  Taenia solium The armed scolex of T. solium (note hooks on top of scolex) T. solium has a scolex (A) with four suckers and a double crown of hooks, a narrow neck, and a large strobila (2-4 m) (B) consisting of several hundred proglottids. About 2 months after ingestion, proglottids begin to detach from the distal end and are excreted in the feces. Each segment contains 50-60,000 fertile eggs. The Lancet (2003) 361: 547  Oncospheres ( larva )→ Cysticercus (juvenile) Life cycle Humans are the only DHs The eggs can survive for days to months in the environment The adult worm attaches by their scolex to the human small intestine. The adults produce proglottids passed with stool The eggs are released after the proglottids are passed with the feces Autoinfection of eggs – human infected with adult worm can ingest eggs produce by that tapeworm / reverse peristalsis of the intestines  T. solium Endemic in less developed countries where pigs are raised as food source. Latin America, most of Asia, sub-saharan Africa, and parts of Oceania. Infection with the adult forms of the parasite produces similar symptoms to infection with T. saginata. Cysticerci: (A) as seen in infected pork; (B) excised into a Petri dish. The white dot in each cyst corresponds to the scolex. The Lancet (2003) 361: 547. The Lancet (2003) 361: 547  Taeniasis in humans is a parasitic infection caused by the tapeworm species Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Taenia asiatica (Asian tapeworm). Humans can become infected with these tapeworms by eating raw or undercooked beef (T. saginata) or pork (T. solium and T. asiatica) containing the larval. People with taeniasis may not know they have a tapeworm infection because symptoms are usually mild or non-existent. Taenia solium tapeworm infections can lead to cysticercosis, which is a disease that can cause seizures, so it is important to seek treatment.  Transmission Taeniasis are found worldwide. Eating raw or undercooked beef or pork is the primary risk factor for acquiring taeniasis. Persons who don't eat raw or undercooked beef or pork are not likely to get taeniasis. Intermediate hosts, such as cows and pigs, are infected with the tapeworm when they come into contact with the worm's eggs or proglottids located in the feces of infected humans. DH – contaminated meat/ pork containing larval (or ingestion of Taenia eggs by fecal contamination) IH – vegetation containing eggs/ proglottids  Symptoms Most people with tapeworm infections have no symptoms or mild symptoms. Patients with T. saginata taeniasis often experience more symptoms that those with T. solium because the T. saginata tapeworm is larger in size (up to 10 meters (m) than T. solium (usually 3 m). Tapeworms can cause digestive problems including abdominal pain, loss of appetite, weight loss, and upset stomach. The most “visible symptom” of taeniasis is the active passing of proglottids (tapeworm segments) through the anus and in the feces. In rare cases, tapeworm segments become lodged in the appendix, or the bile and pancreatic ducts. Infection with T. solium tapeworms can result in human cysticercosis, which can be a very serious disease that can cause seizures and muscle or eye damage.  Cysticercosis Infection caused by the pork tapeworm, Taenia solium. Infection occurs when the tapeworm larvae enter human body and form cysticerci (cysts) Oncospheres (larva) → Cysticerci (juvenile/ metacestode) = Cysticercosis 1. Neurocysticercosis (CNS) 2. Cysticercosis in muscle (c. cellulosae) 3. Ophthalmic cysticercosis Development in muscle 4. Subcutaneous cysticercosis The larval (oncosphere) form of T. solium is in an egg that has a protective thick shell Penetrate intestinal wall & circulate to muscles Cysticerci  Multiple subcutaneous nodules on the chest wall Ophthalmic cysticercosis Cysticercosis in muscle (in pork)  Cysticercus cellulosae in bone (oncosphere develop into cysticerci) Calcification in muscles due to cysticercosis  Human cysticercosis When humans plays the role of the DH Larval stages develop in the human host Humans acquire cysticercosis through faecal-oral contamination with T. solium eggs The oncosphere in the eggs is released by the action of gastric acid and intestinal fluids Cross (penetrate) the gut wall and enter the bloodstream (extraintestinal) They are carried to the muscles and other tissues They encyst as cysticerci at small terminal vessels MRI of Neurocysticercosis and ophtalmic cysticercosis multiple cysts. Racemose Cysticercosis-MRI  Neurocysticercosis The parasite infects the CNS Epileptic seizures Intracranial hypertension, hydrocephalus, or both. Occasionally a cyst may grow larger (giant cyst) Racemose form: high mortality. Large translucent vesicle lobulated without scolex which develops in the basis of the brain or in the ventricles. From: NEJM (2001) 345:879 Sometimes several small vesicles surround a pedicle like a bunch of grapes. Geographical variation in clinical manifestations Neuroimaging: MRI of viable (A) and degenerating (B) cysts and CT of calcified cysticerci. The Lancet (2003) 361: 547 Cysticercosis diagnosis Serologic diagnosis: Antibody assays for cysticercosis: 8 kDa antigens, GP50, FAST-ELISA with the 8 kDA antigen Antigen-detection assays: circulating antigens means live parasites. Ongoing viable infection. Monoclonal antibodies seem to detect AGs in CSF. MRI showing parenchymal (A) and extraparenchymal (basal ccs) (B) viable NCC. Antibody assays for taeniasis: TSE33 and TSE38 were recognized by a panel of taeniasis but not cysticercocis, patient serum samples. Neuroimaging diagnosis: CT and MRI provide objective evidence on number and location of cysticerci. Also their viability and the severity of the host inflammatory reaction. MRI showing calcified cyst with surrounding edema  Cysticercosis treatment Treatment should be individualized based on cyst location, level of inflammation and clinical presentation Therapy should include analgesics, antiepileptic drugs, cysticidal drugs, surgical resection of lesions and placement of ventricular shunts Parenchymal cysticercosis with viable cysts: Albendazole 15 (mg/kg/day) with dexamethasone (0.1 mg/kg/day). Praziquantel. Subarachnoid ccs: antiparasitic therapy *No reason to use antiparasitic drugs to treat dead calcified cysts. Symptomatic therapy. Surgical therapy: ventricular shunting to resolve hydrocephalus. Also excision of giant cysts or intraventricular cysts Albendazole Diagnosis (Taeniasis) Diagnosis of Taenia tapeworm infections is made by examination of stool samples; individuals should also be asked if they have passed tapeworm segments (visible symptom) Stool specimens should be collected on three different days and examined in the laboratory for Taenia eggs using a microscope. Tapeworm eggs can be detected in the stool 2 to 3 months after the tapeworm infection is established. Tapeworm in animal feces Eggs both parasite cannot be differentiate  Prevention & Control To prevent the transmission of taeniasis, avoid eating raw or undercooked beef and pork. The USDA recommends the following for meat preparation: For Beef – Cook beef and veal roasts and steaks to at least 145° F (63° C). – Cook ground beef to at least 160° F (71° C). For Pork – Cook pork to an internal temperature of 160° F (71° C) for medium or 170° F (77° C) for well done.  Following Lecture Nematode (round worm)  Before we end… Able to EXPLAIN on Taenia saginata, Taenia solium. * Morphology * Life cycle * Pathogenesis/ Disease * Treatment & Prevention End of Lecture 19 (Part 3)