GI micro Flashcards
single celled parasite. Eukaryote.
Protozoa
Multicellular, eukariotic parasite. Helminths and arthropods
Metazoa
Pseudopod forming - mechanism of inducing apoptosis in host cells. Bloody diarrhea. Fecal-oral - cyst in water. Camping/travel. Cyst and trophozoite found in stool. Cyst is infectious form. Colonic necrosis from cytotoxin permits invasive spread. Invasive to liver (abscess) and lungs. Colonic “flask” ulcers. Dx - Stool ELISA and PCR - specific. Tx - paromomycin (non-invasive), Metronidazole (invasive, follow up with paromomycin)
Entamoeba Histolytica
Ciliated protozoan. Ingested cyst. Fecal-oral. Watery diarrhea w/ blood and pus. Pigs. Dx - trophozoites in stool. Tx - tetracyclins (DOC), Metronidazole, Iodoquinolol. Psych ward breakouts.
Balantidium Coli
Beavers and muskrats.Person to person (asymptomatic carriers). Foul stool, explosive watery diarrhea. Malabsorption syndrome (steatorrhea). Spontaneous recovery. Dx - stool sample 1/dayX3, falling leaf motility (wet mount). Tx - Metronidazole, Tinidiazole. Rasta Fari mask/ horseshoe crab appearance.
Giardia Lamblia
AIDS defining diarrhea. Up to 50+ stools/day lasting mos-yrs. children. Zoonotic, fecal-oral. Infectious oocyst - stable in chloronated water, sporozoite. Infects epithelial cells of the brush border. Dx - oocyst on acid fast stain or IFA. Tx - Natazoxanide (immunocompetant), Anti-retroviral therapy for AIDS (reduces excretion and decreases diarrhea).
Cryptosporidium Parvum
Similar to C. parvum, but human carriers only.
Cryptosporidium Hominis
Human reservoir. Prevalent in AIDS. Fecal-oral. Contaminated food or water. Mature oocyst is infectious - infiltrate epithelium. Steatorrhea - mimics giardia malabsorption syndrome. Dx - oval/eliptical oocyst in feces, also acid fast. Tx - TMP-SMX (DOC), Pyrimethamine with folinic acid.
Cystoisospora/Isospora Belli
Tropical. Explosive watery diarrhea. Immunocompetant. Fecal-oral. Water and food. Relapse. Dx - Oocyst microscopy (round egg), acid-fast stain, fluoresces blue under UV. Tx - TMP-SMX (DOC).
Cyclospora cayetanensis
Microsporidia. Zoonosis, fecal-oral. Water-borne. Immunosuppressed pts. IC pts. AIDS. Chronic watery diarrhea. Dx - TEM (gold standard), IFA, PCR. Tx - Oral fumagillin (E. bieneusi, associated with thrombocytopenia), Albendazole (E. intestinalis)
Encephalitozoon intestinalis, Enterocytozoon bieneusi
roundworms - pinworms, round worms, hookworms. Most common helminths in the US. Diagnosis by egg examination in stool. Poor sanitation and poly parasitic infections.
Nematodes
Fecal-oral. sticky eggs, hatch in small instestine, adults reside in the cecum, lay eggs in the anus. Children. Perianal itching at night. Female worms get disoriented - can cause vaginal symptoms, granulomas. Cellophane tape. Tx - pyrantel pamoate (DOC, OTC), alternative mebendazole (no longer in production, -azoles teratogens).
“Pinworm” Enterobius Vermicularis
Fecal oral. Rural southeast. Ingest infective embryonic egg, (4-16 days) Early phase: larva enters curculation to lungs, swallow, adults develop in the lumen of small intestine, eggs pass in stool. Late phase (6-8 wks) epigastric pain, N/V. Bolus can obstruct/perforate bowel. Dangerous if adult worm migrates to the liver. Dx - early infection: eosinophilia and larvae in sputum. Established infection: eggs in stool (knobby coated, oval shaped, bile stained). Tx - Albendazole (DOC), pyrantel pamoate (pregnant).
Ascaris Lumbricoides “Roundworm”
roundworm of a dog or cat. Ingested eggs, larvae hatch and get lost - migrate through tissues. Dx - ELISA, eosinophilia, dog/cat exposure. Can penetrate any tissue - necrosis, granuloma, bleeding. NO eggs in human feces, YES in pet feces. Tx - Albendazole.
Toxocara Canis and Cati
human reservoir. Fecal-oral. South-east US, travel. Larva penetrates and develops in the mucosa of the large intestine. Dx - double plugged barrel/football eggs in stool. Light infection - diarrhea and constipation. Heavy infection - tenesmus, N/V/D, pain. uncommon eosinophilia. Trichuris Dysentery syndrome - bloody mucoid diarrhea. Tx - Albendazole (DOC)
Trichuris Trichiura “whipworm”
humid warm climates, old world hookworm
Ancylostoma duodenale
humid warm climates, new world hookworm. Attach foot, circulation, lungs, swallow, adults attach to small intestine. Fecal to soil, hatches then attaches. Maculopapular eruption with itching at the site of infection on the foot. Microcytic hypochromic anemia. Larval migration - eosinophilia, patchy infiltrate on a chest x-ray. GI infection - non-bilestained, segmented eggs in stool, iron deficiency. Tx - albendazole (DOC), Thiabendazole (larval migration phase), iron therapy for anemia.
Necator amercanus “Hookworm”
Dog and Cat hookworm. Cutaneous larval migrans, can lead to 2ry infection from itching, Loeffler Syndrome: pulmonary infiltrates with peripheral eosinophilia. Sandboxes, beaches. Tx - thiabendazole.
Ancylostoma braziliense
Threadworm. Similar to hookworm except eggs hatch in the intestine. Rabditiform larvae in stool, free living adults. Hyperinfection syndrome (chronic, throughout body) - pneumonitis, diarrhea (bloody or not), malabsorption, and electrolyte imbalance, meningitis, secondary bacteremia. IC pts, corticosteroid therapy, transplant pts. Dx - larval worms in stool. Baermann funnel gauze method - concentrate larvae, duodenal aspirates. Tx - Ivermectin (DOC)
Strongyloides Stercoralis
Larvae ingested in undercooked pork, bear, fox, walrus, rodents. Adults develop in the duodenum and jejunum. Mate and bear offspring - expelled in stool or travel in blood to encyst in striated muscle. Trichinosis - acute stage: periorbital edema, eosinophilia and myalgias. Late stage (5-7 wks) lethal - heart, brain, lungs infected. Dx - marked eosinophilia, serologic confirmation, muscle biopsy. Tx - bedrest, antipyretics, and analgesics. Albendazole (DOC, adult worms).
Trichinella spiralis
Sushi, round worm. Violent abdominal pain, N/V only a few hours after ingestion. Mimics chrons. Eosinophilic granulomas.
Anisakis simplex
Flukes and schistosomes
Trematodes
flatworms that have half of their development in a snail or clam. Metacercaria infect humans. Hermaphroditic. Operculated eggs.
Flukes
Giant intestinal fluke. Immigrants from orient. Water chestnuts. Alternating diarrhea and constipation, N/V. Malabsorption syndrome - malodorious, greasy stool. Dx - bile stained operculated eggs. Tx - Praziquantel (DOC, paralysis)
Fasciolopsis buski
sheep liver fluke. Water cress. Japan, Egypt, former USSR, and central america. Adult worm in bile duct (obstruction). Dx - bile examination for eggs (identical to F. buski) Tx - Bithionol (DOC).
Fasciola hepatica
raw undercooked freshwater fish. Chinese liver fluke. Adult worms found in bile duct. Dx - eggs in stool (knobbed operculum). Tx - Praziquantel (DOC).
Clonorchis sinensis
penetrate skin. Flatworms. No operculum. Male and female worms. Snails.
Schistosomes
hematuria (bladder). Terminal spine.
Schistosoma haematobium
Occasional bloody diarrhea. Egypt. No spine.
Schistosoma japonicum
Bloody diarrhea. Africa and South America. Lateral spine.
Schistosoma Mansoni
tapeworms, ribbon like, segmented bodies. Scolex, operculated eggs.
Cestodes
1 cause of seizures WW. Fecal - oral. Cysticercosis. Calcification of body tissues. Dx - proglottids and eggs in feces. Tx - praziquantel, albendazole - steroids, surgery.
Taenia Solium
Beef. Does not cause cysticercosis.
Taenia Saginata
Gefilte fish. Lance shaped scolex. Tx - Niclosamide, praziquantel, B12 supplementation.
Diphyllobothrium Latum
carnivores and sheep. Hydatid cyst. Tx - Albendazole
Echinococcus granulosus
carnivores and sheep. Hydatid cyst. Tx - Albendazole
Echinococcus multilocularis
Most common tapeworm world wide.
Hymenolepis nana “Dwarf Tapeworm”
ingestion of infected insects in flour or cereals. Parasite of domestic rats.
Hymenolepis diminuta
ingestion of infected fleas. Dog tapeworm.
Dipylidium caninum
