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86 Cards in this Set
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- Back
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GI Parasitic Infections
General |
Predominately found in the developing world
Afflicts those where poor sanitation, contaminated food and water are part of the immediate environment A few of these infections endemic to the developed world (Giardia, cryptosporidium, less commonly cysticercosis and amebae, rarely helminths) Occasionally infect travelers, particularly those staying for long-terms in poorly developed areas |
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Intestinal Protozoa
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Entamoeba histolytica
Giardia lamblia Cryptosporidium Others: Cyclospora, Isospora, Microsporida |
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Entamoeba histolytica
Epidemiology |
Worldwide distribution: Most in Central/South America, Africa, Indian subcontinent
3rd leading parasitic cause of death in developing nations (10% of world population infected with Entamoeba) In developed world: Think of in Institutionalized, recent immigrants, and gay males |
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Entamoeba histolytica
Transmission |
Fecal-oral: through contaminated food and water; person-to-person spread may occur
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Entamoeba dispar
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Non-pathogenic, morphologically indistinguishable; need isoenzyme electrophoresis or specific stool antigen tests to differentiate
Much asymptomatic infection attributed to E. histolytica is probably due to E. dispar |
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Entamoeba histolytica
Life Cycle |
Ingested cysts (environmentally resistant) transform to trophozoites upon exposure to stomach acid that colonize and in some individuals subsequently invade intestinal mucosa.
In most the infection is asymptomatic. In some it invades the intestinal mucosa causing colitis and less commonly, through hematogenous or direct spread, distant infection Trophozoites can divide and transform to infective cysts in asymptomatic carriers or symptomatic patients that are pasted in the stool |
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Entamoeba histolytica
Clinical Presentation |
Invasive Bowel Disease
Extraintestinal manifestations - Hepatic involvement/abscess >> rarely lung, pericardium, brain - Rarely Vaginitis, skin ulcerations |
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Entamoeba histolytica
Invasive Bowel Disease |
AKA intestinal amebiasis
Most common manifestation of infection Dysentery, abdominal tenderness, fever Chronic colitis may mimic Inflammatory Bowel Disease |
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Entamoeba histolytica
Complications of Invasive Bowel Disease |
stricture, ameboma, hemorrhage, perforation, intussusception
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Entamoeba histolytica
Virulence Factors |
Galactosamine adherence lectin
Proteinases Lysis of WBC’s |
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Amebiasis
Intestinal Diagnosis |
3 stool exams (90% sensitive) for cysts or trophozoites esp. w/ RBC
Stool antigen detection (differentiates from E. dispar) most with positive serum serologies by day 7. Titers remain positive for years, despite treatment (IHA) |
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Amebiasis
Extraintestinal Diagnosis |
clinical picture, + serologies, “anchovy paste” aspirate
Note: aspiration of amebic cysts free of: 1. WBCs since amebae cytolytic 2. Amebae, since activity peripheral in the abscess |
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Amebiasis
Treatment |
Invasive disease: metronidazole (Flagyl)
- Affects only trophozoites, NOT cysts Intestinal cysts: paromomycin, iodoquinol - Need to treat with these drugs subsequently to eliminate the cyst shedding state NO therapy needed for E. dispar, or other commensals (E. hartmanni, E. polecki, E. ginigivalis, etc.) |
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Another name for Septra
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TMP/SMX
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36 yo previously healthy man bacpacked in Colorado mountains x 2 weeks
On 4th day of trip developed diarrhea. Improved with loperamide (Imodium.) One week later, diarrhea recurred, again improved. Returned to NC feeling well. One week after return --> malaise, copious diarrhea, without fever. Some improvement with TMP/SMX but still having 5-7 loose stools per day, nausea. Weight loss 7lbs. NAME THAT DISEASE |
Giardia
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Giardia Lambia
Epidemiology |
Worldwide distribution
Most common enteric parasite in USA and Canada Cysts found in surface waters where mammalian reservoirs frequent (beaver the prototype) Prevalence of infection approaches 30% in childhood in some developing nations Sporadic infection in US seen in outdoor adventurers. Small epidemics seen associated with day-care or swimming pools. |
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Giardia Lambia
Transmission |
water >> food, person-to-person, zoonosis (dog or cat)
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Giardia Lambia
Life Cycle |
1. trophozoite or freely living stage
2. cyst Ingested cysts transform to trophozoites upon exposure to gastric acid and attach to small intestinal villi where they cause a malabsorptive diarrhea. Some trophozoites transform to environmentally resistant cyst which are passed in the stool |
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Giardia Lambia
Clinical Presentation |
Incubation period: 7-14 days
Manifestation of infection vary widely from asymptomatic to acutely symptomatic, to chronic diarrhea with malabsorption Weight loss, nausea, abdominal pain, steatorrhea, FLATULENCE common Symptomatic infection more common in children Noninflammatory diarrhea. No blood, mucous in stool. No fever. |
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Giardia
Diagnosis |
Microscopic exam of stool for cysts, trophozoites
- “gold standard” - Identifies 50-70% of infections with 1 stool, 90%+ with 3 stools Fecal suspension ELISA for antigen > 90% sensitive Microscopic exam of duodenal fluid (Entero-Test or string test), duodenal aspirate, tissue - Difficult to do |
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Giardia
Treatment |
Metronidazole
- divided doses x 7 days Quiacrine (if cannot tolerate metronidazole) - drug production d/c in USA in 1992 |
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Giardia
Prevention |
Water prurification
Good sanitation, hand washing |
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Giardia
DDX |
viruses
noninvasive bacteria cryptosporidiosis Cyclospora tropical sprue |
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Cryptosporidium parvum
Epidemiology |
Coccidian parasite
Worldwide distribution Recognized as a veterinary pathogen 1907, 1st human case 1976 Can cause disease in immunocompetent and immunocompromised host |
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Cryptosporidium parvum
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Intracellular pathogen; microvilli
Oocysts move into intestine where excyst to sporozoites; Oocysts resistant to disinfection; ID50 is 130 cysts or so Pathogenesis of diarrhea unclear; microvilli atrophied and blunted. Sporozoites seen along apical surfaces of intestinal epithelial cells |
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Cryptosporidium parvum
Transmission |
water>>fecal-oral>person-person
Occasionally person to person or zoonotic |
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Cryptosporidium parvum
Outbreaks |
Outbreaks seen in day-care settings, swimming pool associated, and food-borne (apple cider, fresh vegetables)
A few waterborne outbreaks described that are of huge dimensions. Not eliminated by water treatment. Transmission through water distribution systems in these cases. Agriculture, particularly cattle implicated. Calves probably the most important shedders. |
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How do you get cryptosporidium out of water?
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need to boil the water
chlorination is not good enough |
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Cryptosporidium
Clinical Presentation |
7-10 day incubation period
Diarrhea, crampy abdominal pain Varies from intermittent, scant to continuous, watery, voluminous (up to 17L/day) Self-limited in immunocompetent Can be devastating in immunocompromised, particularly AIDS patients - Chronic infection with uncontrolled diarrhea, abdominal pain and weight loss; cholangitis, cholecystitis occurs |
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Cryptosporidium
Diagnosis |
Microscopic (modified Acid Fast Stain)
ELISA stool antigen detection |
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Cryptosporidium
Treatment |
NO TREATMENT
Currently, no widely accepted palliative or curative therapy - Anti-motility agents (Lomotil) somewhat effective in alleviating symptoms - Antiretroviral therapy to control HIV and reconstitute immunity helps |
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Isospora belli
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Intestinal Protozoa
Tropical and subtropical climates; AIDS patients Occasionally infects travelers Diarrheal illness Treat with TMP/SXT |
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Cyclospora
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Intestinal Protozoa
Coccidial: Acid fast organism Some developed world outbreaks with imported fresh fruits (raspberries) Treat with TMP/SXT |
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Microsporidia
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Intestinal Protozoa
Opportunist in AIDS patients. Can cause cholecystitis, cholangitis |
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Helminths
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Roundworms (nematodes), tapeworms (cestodes) and flukes (trematodes)
Complex life cycle, generally with two or more hosts Most worms CANNOT reproduce within human host (therefore, need intermediate host or environment). Little or no eosinophilia from intestinal adult worm, though eosinophilia the rule with migration of larvae prior to development of adult or with worm invasion of deep tissues |
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Anoter name for nematodes
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roundworms
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Anoter name for cestodes
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tapeworms
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Anoter name for trematodes
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flukes
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Name the nematodes
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Ascaris
Enterobius Hookworm - Necator americanus - Ancylostoma duodenale Strongyloides |
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Nematodes
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Over 500,000 species
Elongated, bilaterally symmetric bodies containing an intestinal tract and a large body cavity. Few are parasites of humans, however, infection with intestinal roundworms constitutes largest group of helminthic infections of humans. Estimated worldwide: 1 billion cases ascariasis |
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Ascariasis
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Very common intestinal parasitic infection
- Infects ¼ of the world population, ~1 billion! Cosmopolitan distribution but more common in tropical regions. Now rare in US. More common in children |
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Ascariasis
Transmission |
Fecal-oral transmission via conatminated foods or soil contaminated hands
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Ascaris lumbricoides
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Female adult worms with very high egg output which can survive for long periods in the soil
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Ascaris lumbricoides
Life Cycle |
Ingested eggs hatch in small intestine.
Larva pass through intestinal wall into venous system to liver; then through heart to lungs. In lungs larvae mature and pass into airways where they are then coughed up and swallowed. Then complete develop into adult worms in small intestine. During there passage through tissues (intestinal wall and lungs can cause inflammation with eosinophilia One month to complete |
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Ascaris Lumbicoides
Pathogenesis and Clinical Disease |
Asymptomatic infection common in light infections
Larval migratory phase: host reactions - Pneumonitis: hypersensitivity reaction as parasite migrates through. Cough, wheezing, sob, fever, chills, malaise Adult worms - Vague crampy abdominal pain most common symptom - Intestinal obstruction (1/500 infected persons/year) - Aberrant migration can occur into bile ducts, appendix > Causes fever, local pain > If in bile duct jaundice, pancreatitis, hepatitis |
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Ascaris Lumbicoides
Diagnosis |
Diagnosis through stool examination: ova or adult parasites. Easy to do because of large number of ova per adult female.
Adult worms passed per rectum or “coughed up” through retrograde migration from intestine to esophagus. Obstructing biliary worms through endoscopy Larvae migrating through lungs can be diagnosed from sputum exam |
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Ascaris Lumbicoides
Treatment |
Choice
- Mebendazole - Albendazole Pyrantel pamoate |
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Ascaris Lumbicoides
Prevention |
Improved sanitation
Sometimes mass treatment (periodic deworming) |
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Enterobius Vermicularis
Epidemiology |
Most widely prevalent nematode of man
One nematode more prevalent in temperate than tropical climates 42 x 106 cases in USA each year Host: human (predominately children) - School, day care, congregate settings |
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Enterobius Vermicularis
Pathogenesis |
Non-invasive; adults live in cecal area
Local allergic rxns to worm proteins Susceptibility decrease with age --?immunity |
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Enterobius Vermicularis
Clinical Presentation |
Most infections asymptomatic
Perianal itching with subsequent sleep disturbance Very rarely, abnormal migrations: vaginitis, appendicitis, prostatitis |
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Enterobius Vermicularis
Diagnosis |
"scotch-tape test"
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Enterobius Vermicularis
Treatment |
Mebendazole 1 dose or
Pyrantel pamoate 1 dose Repeat dose at 2 weeks May need to treat close contacts/family members |
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Hookworm Species
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Species which produce human disease vary geographically:
- Ancylostoma duodenale - Necator americanus Common in tropics, subtropics, SE USA; rare in regions with < 40” inches annual rainfall. |
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Necator americanus
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North and South America, Central Africa, Indonesia, South Pacific, parts of India
Hookworm |
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Ancylostoma duodenale
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Mediterranean countries, Iran, India, Pakistan, Far East
Hookworm |
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Hookworms
Who is at risk? |
Globally > 1 x 109 people infected
Risk for infection: skin exposures to fecally contaminated soil in endemic areas - local residents of tropics - occupational (infantry troops) - recreational (tourists walking with barefoot or with open footwear)—especially cutaneous larva migrans: see below |
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Hookworms
Life Cycle |
Infective larvae penetrate skin that contacts soil.
Migrates through systemic venous system to lung Mature in lung, migrate up trachea and swallowed Further mature into adults in small intestine. Attach to mucosa and cause slow, chronic blood loss and iron deficiency anemia. Eggs passed into stool. Eggs hatch in soil into infective larvae Gotta have stool in soil! |
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Hookworms
US epidemiologic problems |
Hookworm in the US WAS a major problem in the Southeast and Appalachian mountains.
No shoes Privies Reflective of general poor sanitary conditions Whole families were affected. Iron deficiency anemia was profound causing asthenia in all and developmental delay in children. |
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When is eosinophilia seen in hookworm infections?
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with migration
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Hookworms
Clinical |
Initial intestinal infection with abd pain and eosinophilia
Chronic infestation with high worm burden: symptoms of iron deficiency anemia and hypoalbuminemia (protein-losing enteropathy) Malnutrition Eosinophilia with lung migration. Pulmonary symptoms tend to be milder than ascaris during migration cutaneous larva migrans from worm penetration (Coolies itch) |
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Hookworms
Diagnosis |
eggs in stool (larvae (if stool not fresh) may resemble strongyloides)
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Hookworms
Therapy |
mebendazole, albendazole, pyrantel pamoate
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Hookworms
Prevention |
Shoes, sanitary disposal of feces (proper latrines) and chemotherapy
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Cutaneous Larva Migrans
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Dog, cat hookworm most common cause
Pathogenesis: Larvae hatch in soil after eggs pass in canine, feline feces. Penetrate, migrate in skin producing inflammatory rxn along cutaneous tract. Pulmonary involvement also occurs. Clinical disease: pruritic, serpiginous lesions develop 1 week post-contact with infected soil Prevention: shoes Treatment: topical thiabendazole |
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Strongyloides Stercoralis
Epidemiology |
Over 200 x 106 persons infected worldwide
Same distribution as hookworm Parasite likes warm, moist soil Chronic infections, lasting up to 40 years, documented: probably because of autoinfection—see below. |
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Strongyloides Stercoralis
Life Cycle |
Strongy eggs can “hatch” before leaving intestine and larvae can mature in and around rectum/anus—larvae than can penetrate perianal skin: cutaneous larvae curans
Basically the same life cycle as hook worm but note autoinfection can occur |
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Strongyloides Stercoralis
Pathogenesis |
Adult worms embedded in small intestinal mucosa lead to local inflammation
Larvae --> tissue inflammation during migration Penetrating larvae may carry enteric bacteria |
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Strongyloides Stercoralis
Clinical Presentation |
Intestinal phase
Migratory phase Hyperinfection syndrome |
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Strongyloides Stercoralis
Intestinal Phase |
diarrhea and malabsorption (esp. in heavy infection)
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Strongyloides Stercoralis
Migratory Phase |
granulomatous colitis, hepatomegaly, pneumonitis and eosinophilia, fever, recurrent serpentine urticarial rash, “larva currens”
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Strongyloides Stercoralis
Hyperinfection Syndrome |
severe manifestations of above, septicemia, high mortality rate
associated with gram negative bacteria Essentially disseminated strongyloides |
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Strongyloides Stercoralis
Treatment |
Ivermectin
Thiabendazole |
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Strongyloides Stercoralis
Diagnosis |
eggs in stool (larvae (if stool not fresh))
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GI Trematodes
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Blood Flukes
Liver Flukes Intestinal Flukes Lung Flukes |
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Blood Flukes
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Schistosomiasis
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Liver Flukes
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Clonorchiasis
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Intestinal Flukes
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Fasciolopsiasis
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Lung Flukes
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Paragonimiasis
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How do cestodes cause disease?
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Adult tapeworms cause little or no symptomatic disease
Larval (cysticercal) tapeworms responsible for serious disease - Cysticercal phase usually seen in INTERMEDIATE host. - However if human ingests eggs rather than tissue phase cysticerci will cause result in intermediate cysticerci in muscles and brain. - From brain seizures. Little or no eosinophilia |
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List the Taeniasis
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T. saginata = beef tapeworm
T. solium = pork tapeworm |
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Which Taeniasis cause cysticercosis?
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T. solium ... seizures
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Where is T. solium found?
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Endemic in Latin America, Africa, Middle East, Central Asia.
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Diphyllobothriasis
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Fish Tapeworm
Causes Vitamin B12 deficiency |
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List the Cestodes
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Taeniasis
Diphyllobothriasis |
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Characteristics of Cestodes
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Hermaphroditic flatworm parasites
Some primarily human pathogens, others have animals as natural hosts but can also cause human infection Lack a digestive system and actively transport host nutrients |
