GI Pathogens: Helminths and Protozoa PDF

GI Pathogens: Helminths and Protozoa Michelle L. Steinauer, Ph.D. 1  Conflict of interest Disclosure In relation to this presentation, Dr. Steinauer has no financial interests or other conflicts that need to be disclosed....

GI Pathogens: Helminths and Protozoa Michelle L. Steinauer, Ph.D. 1  Conflict of interest Disclosure In relation to this presentation, Dr. Steinauer has no financial interests or other conflicts that need to be disclosed. 2  Learning Objectives For each of the pathogens discussed know: – Life cycle including course of infection in the human body and mode of transmission (linking this to risk factors) – Geographic distribution – Symptoms and pathology – Diagnostic techniques (may include recognizing images) – Treatment and prognosis Be able to recognize a medical case of an illness caused by these pathogens 3  http://www.parasiteswithoutborders.com/parasitic-diseases-6th-edition/ 4  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 5  Review: Parasite Diagnosis Gold standard: Stool exam – Ova and Parasites (O & P) Multiple stool samples Examine whole specimen – Large worms or fragments – Concentrate eggs Floatation – Most nematode and some cestode eggs Sedimentation – Most trematode eggs – Some cestode eggs 6  Review: Protozoa – overview Unicellular Morphological variation through life cycle – i.e. cyst v. trophzoite – Can have multiple nuclei https://www.doctorsbeyondmedicine.com/listing/protozoa-smallest-parasites-b Giardia lamblia 7 https://en.wikipedia.org/wiki/File:Giardia_lamblia.png  Review: Intestinal Protozoa Life Cycle: Trophozoite: Eating, reproducing, Inside the host Host releases Host ingests cysts into the cysts with environment contaminated with feces food or water Cyst/Oocyst: Environmental stage. More resistant, not actively feeding 8 http://www.shieldhealthcare.com/community/ostomylife/2017/04/01/overview-of-the-gi-tract/, https://smart.servier.com/smart_image/entamo  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 9  Intestinal Amebas Most species are considered to be non-pathogenic http://www.biologydiscussion.com/parasites/laboratory-diagnosis-of-parasitic-diseases/29952 10  Entamoeba histolytica Intestinal amebiasis that can be invasive Distributed worldwide – More common where food and water are contaminated with human feces Only 10-20% of people with the ameba show symptoms Podcast: TWIP featuring protozoa that cause diarrhea and Entamoeba histolytica: http://www.microbeworld.org/podcasts/this-week-in-parasitism/782-twip-17-entamoeba- 11 histolytica  Entamoeba histolytica Life Cycle Colon Trophozoite or “Troph” Environment Cyst Multinucleate 12  Entamoeba histolytica Life Cycle Trophozoites inhabit walls of large intestine Feed on live cells (cytotoxic) Generate flask shaped ulcers Can perforate intestine or enter blood stream 13  Entamoeba histolytica Clinical Presentation: – Asymptomatic ~80%, can be chronic carriers – Watery diarrhea Stool typically tests positive for heme Can last one week to years, intermittent Abdominal pain, discomfort, flatulence – Dysentery Blood and mucous visible in stool Abdominal pain, discomfort, flatulence – Fulminant infection Rapidly progressing, large ulcers, 40% mortality rate – Extraintestinal infection Amebae enter bloodstream and disseminate – Liver most common: form abscess » URQ pain, fever, epigastric pain, weight loss, cough – Lungs – Brain (generally not treatable) – More common in males than females, HIV is risk factor Mechanical inoculation of trophozoites into tissues (eyes) 14  Entamoeba histoytica Pathology Ximénez C, Morán P, Rojas L, Valadez A, Gómez A, Ramiro M, Cerritos R, González E, Hernández E, Oswaldo P. Novelties on amoebiasis: A neglected tropical disease. J Global Infect Dis 2011;3:166-74 15  E. histolytica Ectopic Pathology Hepatic Abscess. Disseminated via Brain Abscess. Disseminated via bloodstream blood stream A computed tomography scan showing a Cranial nuclear magnetic resonance multi-septated abscess (arrow) in the image showing multiple abscesses liver of a 39-year-old woman due to Entamoeba histolytica. with Entamoeba histolytica infection. Herdandez et al 2020. https://doi.org/10.1186/s12879-020-05391- y Fang D , Shu D CMAJ 2010;182:1758-1758 16 E. histolytica Ectopic Pathology Ocular amebiasis. Direct contact with trophs. Photo courtesy of Brent Nickol. 17 Entamoeba histolytica Diagnostics and Treatment Microscopy – Cysts/trophs in stool – RBC – Leukocytes may not be present Antigen ELISA – Stool Cyst 10-20µm Nucleic acid amplification tests (PCR) Treatment – Metronidazole Troph 15-60µm 18  Summary: Entamoeba histolytica Infection due to ingesting cysts 4 nuclei ~10-20 10-20µm Trophs eat tissue Flask shape ulcer in cecum and colon Disseminate via blood Headache stream Upper right Disorientation Diagnosis quadrant pain Amebic colitis Drowsiness Quadrinucleate cysts in Fever and/or amebic Loss of stool Weight loss dysentery consciousness Trophozoites in tissues (15- Loss of upper limb movement 60 µm) Amorphic Eat RBC Treatment: Metronidazole 19  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 20  Cyclospora cayetanensis Worldwide cause of watery diarrhea Similar to Cryptosporidium Recent cause of foodborne outbreaks in the U.S. Important cause of illness in travelers 21 Cyclospora Life Cycle 1-2 weeks 22  Cyclospora Clinical Course Watery diarrhea with abdominal pain, bloating, flatulence, nausea Duration 2 weeks to several months Intermittent 23  Cyclospora Diagnosis and Treatment Microscopy Trimethoprim- – Oocysts in stool 8-10 sulfamethoxazole micrometers – Nitazoxanide also Crypto ~4-5 effective (treatment for – Acid fast Cryptosporidium) – Autofluorescence under UV light – Multiple stools PCR tests 24  Cyclospora Summary Cause of chronic watery diarrhea Often food borne Diagnosis: acid fast cyst 8-10 micrometers Trimethoprim- sulfamethoxazole 25 Species Clinical presentation Entamoeba Watery diarrhea, histolytica Dysentery, invasive disease Giardia lamblia Watery, greasy diarrhea. 2-6 weeks Cryptosporidium sp. Self limited watery diarrhea 1-2 weeks, Acid fast stain HIV—chronic 3-6 um diarrhea Cyclospora Self limited watery Acid fast stain. cayatenensis diarrhea 2+ weeks Oocysts 8-10 up to 1 month. micrometers 26  A 43-year-old patient with history of polysubstance abuse is admitted to the hospital because of persistent bloody diarrhea for the past 1 week. Quantitative analysis of stool shows spherical, quadrinucleate, thin-walled cysts measuring 10-20um in diameter. Which is the most likely pathogen? A. Cryptosporidium parvum B. Dientamoeba fragilis C. Entamoeba histolytica D. Giardia lamblia E. Shigella sonnei Kaplan Test Prep 27  A 24-year-old patient comes to the physician because of prolonged diarrhea. He undergoes esophagogastroduodenoscopy with biopsy of the small intestine. Microscopic examination of the biopsy specimen shows numerous crescent-shaped protozoa adjacent to the epithelial brush border. Which is the most likely etiologic agent? A. Cryptosporidium parvum B. Escherichia coli C. Entamoeba histolytica D. Giardia lamblia E. Shigella sonnei Kaplan Test Prep 28  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas: Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 29  Review: Helminths Cestoda (tapeworms) – Taenia saginata and T. solium – Diphyllobothrium latum (fish) Trematoda (flukes) – Schistosoma spp. (acute) Nematoda (roundworms) – Enterobius vermicularis – Ascaris lumbricoides – Strongyloides stercoralis – Hookworm: Ancylostoma duodenale and Necator americanus Photo credits: http://middleeast.thelancet.com/journals/lancet/article/PIIS0140-6736(03)14117-7/fulltext http://nemaplex.ucdavis.edu/Taxadata/Aduodenale.htm 30  Review: Helminths Multicellular, eukaryotic Can have complex life cycles with many hosts Intestinal helminths pass eggs (ova) in feces. Diagnosis is typically through microscopic examination of feces (Ova and Parasite exam or O & P) Adult helminths do not reproduce inside the human host (except strongyloides!). Thus symptoms are dependent on dose. Parasites that migrate through tissues often elicit eosinophilia Worms are generally long lived (1-20 years) 31 Review: Helminth Eggs 32  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 33 Pinworms: Enterobius vermicularis Geographic Distribution: Widespread Most common intestinal helminth in the U.S. Relatively non-pathogenic, but cause discomfort Clinical picture: – Pruritis of anal area, with nervousness, anxious behavior – Highly contagious, spreads between family members 34  Enterobius Life Cycle Eggs 25 x 60 µm Eggs can last 2-3 weeks in environment 35 Enterobius Diagnostics and Treatment Finding eggs of E. vermicularis on skin of anal region – No O & P – Scotch tape test Flashlight test Treatment – mebendazole – pyrantel pamoate – albendazole 36  Enterobius Summary Causes anal itching Found worldwide Spreads via ingestion of eggs Diagnosis – Scotch tape or flashlight test – Eggs—assymetrical eggs – Adult females ~8-13mm Treat with mebendazole 37  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 38  Ascaris lumbricoides Large robust worms 807-1,221 million people in the world are infected with Ascaris lumbricoides – Most common in regions with inadequate sanitation to prevent contamination of water and food with human feces. – Ascarids in pigs can infect humans 39 http://www.cdc.gov/parasites/ascariasis/ Ascaris Life Cycle Very long lived in the environment 40 Ascaris lumbricoides Clinical Course Dependent on dose (low dose = asymptomatic) – Migratory phase Pneumonitis, generalized toxicity, bronchospasm (~2weeks). Only if large dose. – Adult phase Chronic infections (adult worms live 1-2 years) Abdominal pain, nausea, vomiting, bloating, and diarrhea Failure to thrive, weight loss, nutrient and vitamin deficiency in children Obstruction of the intestine 41 Case 1 Case 2 Case 3 Case 4 42 https://www-ncbi-nlm- nih- gov.proxy.westernu.edu /pmc/articles/PMC4401 964/ 43  Ascariasis http://www.personal.psu.edu/nc j111/Human%20Impact.htm 44  Ascaris Diagnosis and Treatment Diagnosis: Ova and parasite exam (O & P). Microscopy for egg identification or identification of adult worms that are passed Eggs – Bumpy or mamillated, brown 60-70 µm – Long lived – Environmentally resistant Bleach, 5 % formalin, cooking heat Treatment – Albendazole or Mebendazole 45  Ascariasis Pigs are an important source of infection In the U.S., most endemic Ascaris infections are probably due to pig ascarids (Ascaris suum) 46  Ascaris Summary Large round worm Infection via ingestion of eggs – Eggs environmentally resistant Larvae migrate through lungs – Large doses = pneumonitis, eosinophilia Adults in small intestine – Varied symptoms Asymptomatic General GI symptoms ”failure to thrive” Obstructions Diagnosis: O & P – Eggs in stool: ~60-70 micrometers, brown, bumpy Treatment – Albendazole or mebendazole 47  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 48  Strongyloides stercoralis Strongyliasis Geographic distribution: widespread in tropical and subtropical regions – ~100 million cases per year? – U.S.: immigrants and local transmission in Appalachia – Autoinfection Long lived infections--Can last for decades! https://static1.squarespace.com/static/57e567d315d5db08326c632d/t/57fcfc002994caed2c22926d/1477431113858/6th+EDITION+1st+PRINTING.pdf  Strongyloides stercoralis Clinical Course Dermatitis at site of penetration (ground itch, serpiginous creeping eruption) – Larva currens-moves 5-15 cm in an hour Pneumonitis with migration through tissues. Eosinophilia. Watery diarrhea, abdominal discomfort, epigastric pain especially after eating, but often asymptomatic Children may have chronic infections with chronic diarrhea, anorexia, malnutrition, impaired growth. Hyperinfection and disseminated infection – Autoinfection due to immunosuppression (particularly with glucocorticoids or HTLV-1 infection) – acute enteritis, with severe diarrhea and ulcerating disease of the small and large intestine. secondary bacterial enterocolitis and meningitis. – Worms may enter CNS directly Larva Currens Larva currens. Can move 5-15 cm in one hour 52  Strongyloides Diagnosis Microscopy: O & P exam – Larvae Biopsy of intestinal tissue Sputum during hyper-infection Larvae are typically seen in stool, eggs less commonly found – Larvae CNS during hyper-infection – Larvae Serologic tests  Strongyloides Treatment Ivermectin Albendazole  Strongyloides Summary Chronic GI helminth infection – Decades due to Autoinfection Symptoms vary – Asymptomatic, periodic diarrhea, epigastric pain Infection via skin penetration – Serpiginous rash Migration through lungs and then small intestine – Penetrate mucosa, cause inflammation and ulcerations Larvae passed in stool Some larvae are retained – Burrow into intestinal wall and mature to adults – Reduced immunity can lead to hyperinfection where large numbers of larvae “wander” through various tissues Treatment ivermectin or albendazole 55  Select GI Pathogens: Parasites Protozoa (single cell) – Amebas Entamoeba histolytica – Cyclospora cayatanensis – Giardia duodenalis – Cryptosporidium spp. Helminths (worms) – Cestodes (tapeworms) Taenia saginata and T. solium Diphyllobothrium latum (fish) – Nematodes (roundworms) Enterobius vermicularis Ascaris lumbricoides Strongyloides stercoralis Hookworm: Ancylostoma duodenale and Necator americanus 56 Review Slides 57  Giardia lamblia Geographic distribution: Widespread. Most commonly diagnosed parasite in the US due to local transmission from animal reservoirs and travel. 58  Giardia Life Cycle Formed stool Cysts: 4 nuclei 10 µm Trophozoites: 2 nuclei Flagellated Small intestine Diarrhea 13 µm http://www.dpd.cdc.gov/dpdx/HTML/Frame s/G-L/Giardiasis/body_Giardiasis_mic1.htm http://filebox.vt.edu/users/chagedor/biol_4 59 684/Microbes/giardia.html  Giardia Pathogenesis Adhere to epithelium of upper small intestine Sucking disk High numbers Malabsorption – Flatten villi – Cover surface Yoder et al 2012 Surveillance Summaries. CDC http://en.wikipedia.org/wiki/File:Giardia-spp.-- infected--gerbil-intestine.jpg 60  Giardia Clinical Presentation and Pathogenesis Presentations – Asymptomatic carrier – Watery Diarrhea, greasy and foul smelling from malabsorption of fats: steatorrhea. Abdominal cramps, bloating, flatulence. – Biphasic: diarrhea/constipation – Acute and self limiting (weeks) or chronic with weightloss. 61  Giardia Diagnosis and Treatment Microscopy – Cysts (10µm, 4 nuclei, oval) or Trophs (13µm, tear drop shaped, 2 nuclei) in stool Rapid antigen tests (stool sample) Highly Direct fluorescent antibody test sensitive Nucleic acid amplification tests and specific Treatment: Metronidazole/Tinidazole – Resistance becoming more common Nitazoxanide Patients may experience symptoms after treatment including lactose intolerance due to tissue damage 62 http://manbir-online.com/diseases/Giardiasis.html  Giardia Epidemiology Animal reservoirs Risk factors – Beavers – Travel to regions where – Muskrats fecal contamination of – Guinea pigs food/water likely – Ferrets – Hikers drinking from open water sources – Dogs, cats, camelids seem to have own – Daycare strains 63  Giardia Summary Causes watery diarrhea – Steatorrhea – Greasy, floats on toilet – Malodorous – Abdominal cramping, bloating flatulence – Intermittent and chronic Worldwide occurance – Travelers – Outdoors and drinking from open water sources Diagnosis: – ELISA test, rapid test, PCR, microscopy – O & P cysts oval, 10um, 4 nuclei. Trophs 13 um, tear drop shaped (leaf) 2 nuclei. 64  Cryptosporidium sp. Worldwide is a common cause of watery diarrhea Several species – Cryptosporidium parvum common cause of disease in humans 65  Cryptosporidium Life Cycle Parasite attaches to columnar epithelial cell Unique membrane complex forms unique intracellular environment – Difficult to treat Reproduce within cells, drive apoptosis 66 67  Cryptosporidium Clinical Picture and Epidemiology Clinical Picture: – Asymptomatic carriers – Watery diarrhea with abdominal pain, nausea and vomiting Self limiting in healthy patients 1-2 weeks but can recur and last up to 30 days Children—more severe, accompanied by weight loss – Worldwide, one of the leading causes of diarrhea – Chronic in immunocompromised Cancer chemotherapy patients HIV-AIDS – Untreatable—treat immune deficiency Important risk factors: – Cyst stage environmentally resistant – Resists chlorination Swimming pools Drinking water supply – Zoonotic C. parvum infects cattle, especially calves 68  Cryptosporidium Diagnosis and Treatment Diagnosis Treatment – Microscopy – Healthy immune system Small round cysts (5µm) Nitazoxanide Acid fast – HIV – Rapid antigen test from HAART stool – Nucleic acid amplification tests 69  Cryptosporidium Summary Chronic watery diarrhea with abdominal pain, nausea, and vomiting – 1-2 weeks HIV patients and other immunosuppressed patients, virtually untreatable without restoring immune function People infected by ingesting cysts – Contaminated food or water – Swimming pools – Contact with animals Diagnosis – Acid fast cysts (5 um) – PCR, Rapid antigen test Treatment – Nitazoxanide – Restore immune function (HAART) 70  Diphyllobothrium species Broad fish tapeworm Several species: Diphyllobothrium latum 2-15 meters (25 m is record) Lifespan ~20 years 20 million people worldwide infected Transmission through consumption of raw or undercooked fish https://www.ncbi.nlm.nih.gov/books/NBK540971/  Clinical Manifestaions Often asymptomatic Abdominal pain, diarrhea, constipation, weightloss Megaloblastic anemia, Vitamin B12 deficiency in chronic infections Intestinal obstruction in heavy infections  Diagnosis and Treatment Eggs in feces – Large (75 x 50 µm) – Oval – Operculated Passing of worm segments Praziquantel https://www.cdc.gov/dpdx/diphyllobothriasis/index.html  Taenia solium Pork tapeworm http://middleeast.thelancet.com/journals/lancet/article/PIIS0140-6736(03)14117-7/fulltext  Taenia solium Pork tapeworm Intestinal disease—Adult tapeworms CNS disease/occular disease—Larval tapeworms (Cysticercosis) Life Cycle: Taenia solium  Clinical Manifestations Intestinal disease – Nonspecific intestinal symptoms – Abdominal pain or discomfort, loss of appetite Cysticercosis – Depends on where they encyst and how many – CNS-Neurocysticercosis is the most serious  Cysticercosis Neurocysticercosis Seizures, headaches Behavioral changes, confusion, loss of balance. Sharma et al 2003. Opthamology 110 (5): 996-1004. www.parasiteswithoutborders.com http://www.infectionlandscapes.org/2012/08/tapeworms.html  Neurocysticercosis Leading cause of seizure disorders worldwide ~29% adult epilepsy due to T. solium in endemic areas US not endemic, but considered an important health problem due to immigration Theodore E. Nash & Hector H. Garcia Nature Reviews Neurology 7, 584-594 (October 2011)  Distribution https://www.researchgate.net/figure/Geographical-distribution-of-Neurocysticercosis_fig2_315499756  Diagnosis Cysticercosis – Imaging (MRI CT scans) Intestinal disease – Proglottids in feces Proglottids in stool (this Treatment photo is actually dog – Praziquantel tapeworm, but is similar) Kills adults and larvae – Surgical removal of larvae  Summary Taenia solium Adult tape worms in the gut = GI symptoms – eating pork raw or undercooked Cysticerci in tissues = various symptoms – Ingesting eggs of Taenia solium (fecal oral) – neurocysticercosis (cysts in brain) – Ocularcysticercosis (cysts in eyes) Treatment – Praziquantel  Hookworms of Humans Order Stongylida Necator americanus Ancylostoma duodenale Acute: – Dermatitis at site of penetration – Pneumonitis during migration – Epigastric pain, nausea – Sometimes vomiting and diarrhea Chronic: – Anemia and protein deficiency from blood loss Physically weak Pale – Physical and mental stunting “failure to thrive” 84  Distribution Warm, wet climates https://web.stanford.edu/group/parasites/ParaSites2009/PinedaANDYang_Hookworm/PinedaANDYang_Hookworm.htm From: Roberts and Janovy. Foundations of Parasitology  Hookworm Diagnosis and Treatment Diagnosis – Eggs in feces 65-75 µm Treatment – Albendazole and Mebendazole http://www.uaz.edu.mx/histo/pathology/ed/ch_9c/c9c_hookworm_egg.htm 87  Cutaneous Larva Migrans Dermatosis from hookworms of dogs or other mammals – Ancylostoma caninum and others “Creeping eruption” Red pruritic eruptions or tracks Capcvet.org  Hookworm Summary Ancylostoma duodenale and Necator americanus cause human hookworm disease Larval worms penetrate the skin of humans, migrate through lungs and go to small intestine – Rash at site of penetration Feeding causes rapid blood loss – Epigastric pain – Weightloss – Iron deficiency anemia – “Failure to thrive” Cutaneous larval migrans – Caused by hookworms of animals Penetrate skin and wander Red puritic lesions or tracks – Cannot complete their life cycle 90 A 22-year-old international student visiting from China presented with fatigue, paleness, and dizziness for one month. He estimates 12 kg of weight loss in the last three months. Lab work indicates iron deficiency anemia. Which pathogen is most likely? A. Ancylostoma duodenale B. Schistosoma japonicum C. Taenia solium D. Diphyllobothrium latum E. Schistosoma mansoni Kaplan, exam prep  How was this person exposed to this pathogen? A. Contaminated water B. Contaminated food C. Ingested eggs in soil D. Larvae in soil penetrated skin E. Larvae in water penetrated skin  A 10-year-old patient has become pale and seems to have lost his normal energy. On examination, the child’s skin is somewhat pale and clammy, and a complete blood count detects a microcytic, hypochromic anemia. A fecal sample from this child will most likely show: A. Brown, rough shelled ova B. Golden, football shaped ova with bipolar plugs C. Living larvae D. Oval, golden, clear, shelled ova E. Spined eggs Kaplan Test Prep 93  Nematode eggs Strongyloides Larvae Ascaris Hookworm Enterobius 180-380 µm 40 x 60 µm Necator or 25 x 60 µm Ancylostoma 65 x 35 µm 94