Published on February 25, 2014
Intestinal Protozoa Amoeba: Entamoeba histolytica Flagellates: Giardia lamblia & Trichomonas parvum/hominis Ciliates: Balantidum coli Sporozoa: Isospora belli Cyclospora cayetanensis Cryptosporidium parvum/hominis Sarcocystis hominis
Entamoeba histolytica Amoebiasis World wide distribution – 3rd after malaria and schistosomiasis Hand-mouth; fecal-oral; sexual transmission Increasing in homosexuals Resistant to chlorine Major complications: amoebic abscesses in liver, brain, lung Amoebic pericarditis (rare) is most dangerous complication of amoebic liver abscess
Clinical Classification of Amoebiasis Asymptomatic infection Colonization without invasion Symptomatic infection Invasion with mild symptoms Intestinal disease Dysentery, colitis, amoeba Extraintestinal amoebiasis Liver, skin, lung, pleura, brain
Pathogenesis of Amoebiasis Ingested cysts trophozoites in large intestine 75% remain in lumen 15% invasive disease; adherence/digestion of epithelium; formation of flask-shaped ulcers bacterial superinfection may occur dissemination liver abscess rupture pericardial disease
Clinical Presentation of Amoebiasis Asymptomatic Mild GI discomfort Diarrhea, pain, blood, mucus Weight loss Organ specific symptoms Dx: history, cysts/trophozoites, ELISA/PCR
Intestinal Flagellates Giardia lamblia Giardia intestinalis Giardia duodenalis Trichomonas hominis Epidemiology: worldwide Traveler’s/backpacker’s diarrhea: hikers/campers Day care centers Zoonotic; water, food (fecal-oral)
Life Cycle of Giardia Ingestion of cysts trophozoites attach to duodenal brush border causing irritation and obstruction of absorption cysts in colon; passed in feces See them moving in stool
Clinical Presentation of Giardia Watery diarrhea, abdominal cramps Weight loss No blood, no pus, no fever Steatorrhea – fatty and foul-smelling Lactose intolerance Antibody deficiency Dx: fecal cysts/trophozoites; enterotest; ELISA; duodenal aspiration
Comparison of Clinical Presentations Amoebiasis Giardiasis Asymptomatic Non-inflammatory watery Mild GI discomfort Inflammatory Diarrhea, pain, blood, mucu s Weight loss, fever Organ specific symptoms Dx: history, cysts/trophozoites, E LISA/PCR History: international travel diarrhea, abdominal cramps Steatorrhea – fatty and foulsmelling No blood, no pus, no fever Weight loss Lactose intolerance Antibody deficiency Dx: fecal cysts/trophozoites; enterotest; ELISA; duodenal aspiration History: Camping in Northern US wilderness; drink mountain water
Oral Flagellate Trichomonas tenax
Intestinal Ciliate Balantidum coli – Balantidiasis The only ciliated protozoa! Common parasite of animals No extraintestinal spread Easily treated, not very common Seen in ppl who are around animals all the time Farmers, zoo workers Tx: tetracycline
Intestinal Sporozoa Isospora belli Cyclospora cayetanesis water or produce Cryptosporidium parvum/hominis water and food Non-inflammatory diarrhea Infection by ingestion of oocyst infection of intestinal epithelium Sexual & asexual stages – sporogony/schizogony Self-limiting in immunocompetent; Severe in AIDS or other immunocompromised individuals Dx: acid-fast oocysts in stool & history
Urogenital Flagellate Trichomonas vaginalis Sexual transmission
Amoeboflagellates Primary CNS pathogens Naegleria fowleri Enter thru olfactory neuroepithelium causing primary amoebic meningoencephalitis (PAM) in healthy ppl Trophozoites in CSF and tissue Acanthamoeba culbertsoni Balamuthia mandrillaris Acanthamoeba and Balamuthia enter thru lower respiratory tract or thru broken skin causing granulomatous amoebic encephalitis (GAE) in immunocompromised individuals Trophozoites and cysts in tissue
Haemoflagellates Trypanosoma & Leishmania Insect borne Found in blood, tissue, lymph and CSF Amastigote and trypomastigote most imp forms
Trypanosomiasis T. Gambiense Tsetse fly; West Africa T. Rhodesiense Tsetse fly; East Africa T. Cruzi Reduviid bug, Americas
T. Cruzi – American trypanosomiasis Chagas disease Vector: reduviid bug (triatomine bug) Zoonotic South/Central America Infection thru eyes or open cuts, transplacental, at parturition or breastfeeding, blood, uncooked or contaminated food Patho: bug feces infection of local tissue ulceration & inflammation spread localization in mesenchymal tissues of heart, GI, esophagus, etc markedly enlarged heart, esophagus, and megacolon tachycardia, chest pain, ECG changes, constipation
Chagas’ Disease Chagoma, Romana’s sign Hepatosplenomegaly, lymphadenopathy Myocarditis w/ CHF; Meningoencephalitis Tx: nifurtimox, benznidazole
Leishmaniasis sand fly Vector – Phlebotomine 3 forms Leishmania tropica: dermal/cutaneous form Leishmania brasiliensis: mucocutaneous form Leishmania donovanii: visceral form Most severe form (KALA AZAR) – 100% fatality if untreated Hypoalbuminemia; hypergammaglobulinemia Irregular fever, marked weight loss, anemia, hepatosplenomegaly Amastigotes in deep tissue – liver, spleen, bone marrow Drug: Sodium stibogluconate
Visceral leishmaniasis Patho: Parasite localization in macro of RES PANCYTOPENIA high output heart failure myocarditis/pericarditis Leishmania – HIV coinfection on the rise
Tissue Sporozoa Plasmodium (blood & tissue) Malaria; Vector: female anopheles mosquito Babesia (blood) Babesiosis; Vector: Ixodes scapularis Ixodes also carries lyme disease and human granulocytic anaplasmosis Toxoplasma gondii (tissue) Toxoplasmosis; Vector: cat Most commonly reported parasitic disease following heart transplantation Two life cycles, two hosts: sexual (sporogony) – definitive host; Asexual (schizogony) – intermediate host
Plasmodium P. falciparum, ovale, vivax, malariae
Parasite detection: HRP2 detection, parasite LDH ... Dipstick tests
Complications of Malaria Parasitized RBCs adhere fibrin thrombi microinfarcts in brain, heart CHF, encephalopathy death Phagocytosis by macro macro hyperplasia hepatosplenomegaly nephrosis death
Pathology of Malaria Fever, anemia, jaundice Hepatosplenomegaly, hepatorenal syndrome Pulmonary edema, CHF Blackwater fever – dark urine Encephalopathy – cerebral malaria
Protection against Malaria Absence of receptor (“duffy antigen” FyaFyb) G6PD deficiency HbS Thal
Malaria hypnozoites P. vivax & P. Ovale Use primaquin against hypnozoites Chloroquine against severe malaria Quinine in severe parasitemia and resistant malaria Metronidazole for amoebic liver abscesses Also for giardiasis, trichomoniasis, dracunculis medinensis
Babesiosis Similar to malaria; co-infection w/ Lyme disease; Ixodes scapularis Fever, chills, sweating, myalgias, fatigue, hepatospleno megaly, hemolytic anemia
Toxoplasmosis Infection flu-like latency reactivation if pt becomes immunocompromised myocarditis, pericarditis, CHF
Helminthology Platyhelminthes Cestodes – tapeworms Tx: Praziquantel, Niclosamide Trematodes – flukes Tx: Praziquantel Nemathelminthes (Nematodes) Intestinal worms Tx: Mebendazole Tissue worms - filaria
Trematodes Hermaphroditic flukes Mammals – definitive hosts Snails – 1st intermediate hosts Fish, crustacea, vegetable – 2nd intermediate hosts Schistosomes Mammals – definitive hosts Snails intermediate hosts
Clinical Classification Lung fluke Paragonimus westermanii CRAB Liver fluke Clonorchis sinensis FISH Fasciola hepatica PLANT/VEGETABLE Intestinal fluke Heterophyes heterophyes FISH Fasciolopsis buski PLANT/VEGETBALE Tx: Praziquantel for all trematodes
Schistosomiasis (blood fluke) Direct skin penetration by cecariae S. Mansoni – intestinal (side spine) S. Japonicum – intestinal (no spine) S. Hematobium – urinary (terminal spine) Tx: Praziquantel Picture: Left, S. mansoni Middle, S. Haematobium Right, S. japonicum
Diphylobothrium Latum Broad or fish tapeworm Very big From ingestion of larvae in RAW fish Clinical: Low serum B12, eosinophilia Atrophic gastritis Megaloblastic anemia Dx: history, presentation, eggs in stool Tx: Praziquantel, Niclosamide
Taeniasis Beef tapeworm – T. Saginata Ingestion of larvae in undercooked/raw beef Pork tapeworm – T. Solium Ingestion of eggs in undercooked/raw pork Associated w/ heart problems Dx – eggs/proglottids in human feces; adult in intestines Tx: Praziquantel, Niclosamide
Nemathelminthes Intestinal nematodes Ascaris lumbricoides – Roundworm Strongyloides stercoralis – Threadworm Ancylostoma duodenale – Hookworm Necator americanus – Hookworm Enterobius vermicularis – Pinworm Trichuris trichiura – Whipworm Trichinella spiralis – Porkworm Infections characterized by eosinophilia and high IgE levels; hygiene and lifestyle is important
Ascaris lumbricoides - Roundworm One of the most common human infections worldwide Patho: Stage 1: “infective” eggs ingested larval migration cough, hemoptysis (bloody sputum), dyspnea, hemorrhagic pneumonia, asthma attacks, pulmonary infiltration, urticaria Stage 2: adult in intestine dependent on worm load pain, distension, nausea, anorexia, malnutrition (growth stunting in children), intestinal obstruction Stage 3: adult migration acute pancreatitis or obstruction, biliary obstruction, jaundice, appendicitis, peritonitis Dx: larvae in sputum; ova & parasites in stool Tx: Mebendazole
Strongyloides stercoralis Threadworm Direct skin penetration 2 distinct adult forms Filariform (infective form): larvae penetrate intact skin initiating infection enter circulatory system lungs penetrate alveolar spaces reach small intestine mature to adult female (not male) produce uninfective larvae autoinfection Uninfective infective in intestine and stool Uninfective adults in soil or become infective Rhabditiform (uninfective form)
Strongyloides Clinical Features Acute disease: Ground itch, cough, dyspnea, wheezing, fever, epigastric pain Chronic disease: Abdominal cramping, diarrhea, pain Severe disease Hyperinfection syndrome Extraintestinal spread (CNS, etc) **dissemination in AIDS pts** Dx: larvae in stool, urine, duodenum, enterotest Tx: Ivermectin
Enterobius Vermicularis - Pinworm Common in US; children Eggs on perianal folds perianal itching Pricking anal pain, restlessness, sleeplessness Dx: see them around anus, eggs on scotch tape Tx: pyrantel pamoate or mebendazole Enterobius vermicularis
Necator Americanus & Ancylostoma Duodenale – Hookworms Worldwide distribution; Enter thru FEET Clinical stages: Cutaneous Stage: ground itch Pulmonary Stage: pulmonary hemorrhage Cough, wheezing, pneumonitis Intestinal Stage: GI discomfort, blood loss
Hookworm Infection Complications Protein losing enteropathy Fe deficiency anemia Tachycardia Stillbirth Poor physical development Dx: history and eggs in stool Tx: mebendazole + dietary supplements Wear shoes!!
Trichuris Trichura - Whipworm Fecal-oral transmission; rare Clinical: Light infection: asymptomatic Moderate infection: Discomfort, gas, diarrhea/constipation Heavy infection Distension, vomiting, diarrhea, weight loss **RECTAL PROLAPSE** Dx: history & eggs in stool Tx: mebendazole
Trichinella Spiralis - Porkworm No eggs No external phase Dead end transmission! – ingestion of undercooked meat larvae turn to adults in intestinal cells migrate to muscle encyst
Clinical Presentation of Trichinella Spiralis Diarrhea, constipation Fever, myalgia, fatigue Macular or petechial rash Periorbital edema, conjunctivitis/retinal hemmorrhage Splinter hemmorhage; heart problems Dx: muscle biopsy, positive serology, presentation symptoms Tx: Thiabendazole – before tissue invasion Rest + analgesics for after invasion
Tissue Nematodes = Filaria Adults in tissue Eggs not produced; microfilaria produced Wuchereria bancrofti – mosquito Brugia malayi/timori – mosquito Loa loa – deer fly Onchocerca volvulus – simulium black fly Dracunculus medinensis – Cyclops (water flea)
Elephantiasis/Lymphatic filariasis Wuchereria bancrofti Brugia malayi & Brugia timori Patho: microfilaria adult worms in lymphatics more microfilariae lymphoedema inflammatory reaction elephantiasis Early: acute inflammation, hypereosinophilia, massive lymphatic dilatation, bacterial and fungal infections, infection by wolbachia bacteria (tx: tetracycline) Late: lymphoedema/elephantiasis; chyluria (lymph in urine) Tx: DEC + Albendazole or Albendazole + Ivermectin
Elephantiasis Dx: presentation, very high increase in eosinophils, IgE, IgG4, and specific antifilarial Ab; microfilariae in blood (nocturnal periodicity) Sheath = pathogenic; no sheath = nonpathogenic
Onchocerca Volvulus River blindness/onchocerciasis Vector: Simulium Black Fly Larvae in subcutaneous tissue Patho: adult in onchocercoma millions of migrating microfilariae death due to immune response onchodermatitis/keratitis Dx: Skin biopsy nodules tons of little worms Tx: DEC or Ivermection (single dose)
Dracunculiasis Dog, horse, cow, monkey Vector: Cyclops (Water Flea) Debilitatin skin eruptions worms come out of them!! Tx: metronidazole/thiabendazole Dracunculus medinensis
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