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52 Cards in this Set
- Front
- Back
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• Rotavirus
– Virology |
Viral Diarrhea cause
• Reoviridae family of viruses • dsRNA, non-enveloped virus with 11 genome segments • Icosahedral, double-layered nucleocapsid • Resists acidic pH, drying, detergents |
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Rotavirus--Epidemio
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Fecal-oral spread
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Rotavirus--Path
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• Infection of enterocytes without deeper spread
• Shortening and flattening of villi of duodeneum and proximal jejunum • Interference with transport mechanisms |
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Rotavirus--Manifestations
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• Diarrheal illness in infancy and childhood
• Incubation 1-3 days with abrupt onset of vomiting followed by copious water, brown stools |
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Noroviruses
– Virology |
Viral Diarrhea
• Caliciviridae family of viruses • ssRNA +sense virus • Icosahedral nucleocapsid • Spherical virion • Extremely hardy |
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Norovirus--Epidemio
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• Fecal-oral route of transmission
• Family and community outbreaks any time of year • Problem in closed settings: cruise ships, hospitals, nursing homes, schools |
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Norovirus--Path and Manifestations
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– Pathogenesis
• Replication in small intestine with shortened villi and reduced absorption – Manifestation • Incubation up to 48h followed by vomiting and diarrhea • Usually lasts 1-2 days • Illness in older children and adults |
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Astroviruses
– Virology |
• Astroviridae family of viruses
• + sense ssRNA viruses • Non-enveloped • Icosahedral capsid |
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Astrovirus--Epidemio
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• Mild, self-limiting, short duration
• Peak incidence in the winter • Diarrhea in children under five years old |
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Adenoviruses
– Virology |
• Adenoviridae family of viruses
• dsDNA virus • Non-enveloped • Icosahedral capsid • 51 types |
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Adenovirus--Manifestations
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5-15% of viral gastroenteritis in young children (serotypes 40 and 41)
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Entamoeba histolytica
• Parasitology |
• Lives in intestine as trophozoite
• Microaerophilic, dwell in wall or lumen of colon • Multiply rapidly in anaerobic environment of colon • Cysts passed in feces • Single nucleus, glycogen vacuole, large ribosomal clusters known as chromatoid bodies • As mature become quadrinucleate • Can survive chlorination in municipal water |
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Entamoeba histolytica--Epidemio
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• Humans as reservoirs
• Can pass up to 45 million cysts daily • Most common in tropical and subtropical regions • Fecal-oral transmission |
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Entamoeba histolytica--Path and manifestations
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• Pathogenesis
• Invasion of colon mucosa causes ulceration and diarrhea (bloody) • Manifestation • Amebic dysentery and “sterile” liver abscesses |
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Giardia lamblia
• Parasitology Trophozoite |
• Sting-ray –shaped
• 2 nuclei and central parabasal body • 4 pairs of flagella • Reside in duodenum and jejunum • Tumbling or falling leaf motility • Ventral sucker to attach to brush border |
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Giardia lamblia
• Parasitology Cyst |
• Oval and smaller than trophozoite
• Upon maturation produce quadrinucleate organism with 2 sucking disks, 4 parabasal bodies, and 8 axonemes • Divides to form 2 binucleate organisms • Infective form |
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Giardia lamblia--epidemio
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• Most commonly diagnosed
intestinal parasite in US • Fecal-oral transmission • Common among day care centers • May be waterborne |
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Giardia--Manifestations
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• Diarrhea with foul-smelling, greasy stools
• Symptoms begin 1-3 weeks after exposure • Resolves in 1-4 weeks • Intestinal malabsorption of fat and carbohydrates |
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Cryptosporidium parvum
• Parasitology |
• Tiny spherical obligate intracellular parasite
• Alternate between sexual and asexual reproduction • Infective oocysts excreted in stool of infected animal |
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– Cryptosporidium parvum
Epidemio |
Fecal-oral transmission
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Cryptosporidium parvum--path
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• Involves jejunum primarily
• Mild to moderate villous atrophy, crypt enlargement, mononuclear infiltrate of lamina propria |
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Cryptosporidium parvum--manifestations
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• Explosive, profuse, watery diarrhea 1-2 weeks after exposure
• Persists 5-11 days and then rapidly abates |
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Ascaris lumbricoides
• Parasitology |
• Nematode; intestinal roundworm
• Largest and most common intestinal helminths • Lifespan of 6-18 months • Highly resistant to environmental conditions |
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Ascaris lumbricoides--Path
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• Adults can block intestine, interfere with digestion and absorption of food, migrate into bile or pancreatic ducts
• Females lay eggs in intestines • Eggs are expelled with feces and hatch upon ingestion by another host • Infective larvae develop after several days incubation • Larvae penetrate gut wall, are carried in blood through the liver to the lungs, climb the bronchi and trachea, get swallowed, and go back to intestine • Adult worms live in lumen of intestine |
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Trichuris trichiuria
• Parasitology |
• Whipworm
• 30-50mm in length • Tail of male is coiled • Eggs = thick, brown shell with translucent knobs at ends • Gravid female lays eggs in lumen of gut in cecum • Eggs pass out through feces and are immature • Eggs must incubate for at least 10 days to become infectious |
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Trichuris trichiuria--Epidemio
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• Fecal-oral transmission
• In tropical regions, infection rate is ~ 80% • 2 million in rural southeast US primarily in family and institutional clusters |
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Trichuris trichiuria--Path
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• Produce localized ulceration and hemorrhage
• Ulcers provide enteric bacteria a portal of entry and results in sustained bacteremia |
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Trichuris trichiuria--Manifestations
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• Moderate to heavy infections in children cause chronic diarrhea, impaired nutrition, and retarded growth
• Heavy infections can lead to prolapse of rectum |
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Ancylostoma duodenale
info |
Old World hookworm
• Mediterranean basin, Middle East, northern India, China, Japan |
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Necator americanus--
info |
New World hoodworm
• Tropical areas of South Asia, Africa, South America, and southern US |
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Hookworms
• Parasitology |
• Intestinal bloodsucking worms measuring about 10mm
• Small roundworms with expanded mouths for attachment to intestinal mucosa • A. duodenale = 4 sharp tooth-like structures • N. americanus = dorsal and ventral cutting plates • Adults may survive 2-14 years |
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Hookworms--Path
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• Eggs hatch in soil within 48h and release rhabditiform larvae
• After doubling in size, larvae molt and become infective filariform larvae • Infective larvae penetrate skin (both species) or mucous membranes after ingestion (Ancylostoma) • Larvae migrate via lemphohematogenous system to right side of heart and then to lungs where they rupture into alveolar spaces and are coughed up, swallowed, and pass to small intestine • Ingest a plug of tissue, rupture capillaries, and suck blood |
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Hookworms--Manifestations
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• Lead to anemia and protein loss
• Larval penetration associated with local dermatitis and immediate hypersensitivity reaction • Peripheral and gut eosinophila characteristic |
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Stronglyoides stercorales
• Parasitology |
• Smallest intestinal nematode = 2mm
• Live in humans as larvae and parthenogenetic females • Infective larvae penetrate skin • Adults can persist for upwards of 30 years |
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Stronglyoides stercorales--Manifestations
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• Intestinal infection usually symptomatic; may be pulmonary
disease • Heavy worm loads can present with peptic ulcer-like disease • Peripheral eosinophila • May be vomiting, diarrhea, paralytic ileus, and malabsorption • External autoinfection produces transient, raised, red, serpiginous lesions over buttocks and lower back |
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Enterobius vericularis
• Parasitology |
• Pinworm = oldest and most widespread helminth
• Small roundworm in large bowel • Female = 10mm with sharply pointed tail • Male = 3mm with curved tail and copulatory spicule • Clear, thin-shelled, ovoid eggs flattened on one side |
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Enterobius vericularis--Epidemio
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• Transmission via swallowing eggs carried on fingers or in dust or handling infected bedclothes
• Infection more common in young and poor |
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Enterobius vericularis--Pathogenesis/manifestations
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• Pathogenesis
• Adult worms attach to cecum • Gravid female migrates down colon and comes out from anus at night to lay eggs • Detection via saline swab or adhesive slide test • Manifestation • Causes perianal pruritis |
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Trichinella spiralis
• Parasitology |
• Minute roundworms (2-3mm)
• Adults live in duodenal and jejunal mucosa • Coiled larvae in muscles |
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Trichinella spiralis--epidemio
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• Acquired by eating raw or undercooked meat containing infective larvae, usually pork
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Trichinella spiralis--Path
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• Larvae pass from submucosa of intestine
into vascular system into right side of heart through the pulmonary capillary bed to systemic circulation and on to rest of body • Larvae penetrate skeletal muscle and die • In striated muscle larvae continue to grow, molt, and encapsulate over several weeks • Calcification of the cyst begins 6-18 months later and larvae may remain viable for 5-10 years • Muscles most often invaded = extraocular muscles of eye, tongue, deltoid, pectoral, intercostals, diaphragm, gastrocnemius |
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Trichinella spiralis--manifestations
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• Diarrhea, nausea, and abdominal pain
during infective phase • Allergic symptoms, skeletal muscle pain, myocarditis • Eosinophila up to 50% of WBCs • Serum IgE and muscle enzymes elevated |
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Taenia saginata
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= beef tapeworm
• Inhabits jejunum • May live up to 25 years • May grow up to 10m • Scolex lacks hooklets but has 4 sucking disks • 1000-2000 proglottids • When gravid, 6-9 proglottids contraining ~100,000 eggs break free and pass into stool • Eggs hatch and embryo may survive for months in soil • If ingested by cow, embryo released and penetrates intestinal wall and is carried by vascular system to striated muscles • Becomes cysticercus • Infection usually asymptomatic but may be some epigastric pain, nausea, irritability, diarrhea, weight loss |
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Taenia solium
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= pork tapeworm
• Inhabits jejunum • Rostellum with double row of hooklets • Mostly found in immigrants from endemic regions |
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Schistosoma mansoni
• Parasitology |
• Blood flukes
• S. mansoni = Africa, South America • Liver pathology most severe • S. hematobium = Africa, Middle East • S. japonicum = Asia • Trematodes with separate sexes • Male carries female in lifelong copulatory embrace |
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Schistosoma mansoni--Path
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• Adults live in blood vessels around intestines or bladder
• Conjoined couple ascend mesenteric vessels and enters the superior mesenteric vein, eventually reaches venous radicals of intestines • Worms deposit 300-3000 eggs adjacent to the mucosa of the bowel lumen or bladder • Spined eggs in feces • Larvae released from eggs ingested by aquatic snails • In snails are transformed to fork-tailed cercariae • Snails release infective cercariae, which penetrate skin |
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Schistosoma mansoni--manifestations
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• Hypersensitivity responses to eggs causes inflammation, granuloma formation, fibrosis, and obstructive disease in intestine, bladder, and liver
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Clonorchis sinensis
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= Chinese liver fluke
• Asia • Eating fish infected with metacercarial stage • Juvenile flukes move from intestine into bile duct and attach to ductal epithelium • Heavy infections = inflammatory response, hyperplasia of biliary epithelium, cholangitis, jaundice, hepatomegaly • Association with cholangiocarcinoma |
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Fasciola hepatica
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= common liver fluke
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Opisthorchis spp
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= animal liver flukes
• Asia and Eastern Europe |
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Echinococcus granulosus
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= dog tapeworm
-Hydatid cysts in LIVER -Rupture of cysts lead to anaphylaxis -Can become secondarily infected with bacteria |
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E. hystolytica
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= amebic liver abscess with necrotic tissue
o Patients with gallstones obstructing biliary system = infective complications from normal GI flora like enterobacteria and anaerobes --> Results in cholangitis and liver abscesses |
