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43 Cards in this Set
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Enterobius vermicularis
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Intestinal nematode, NO eosinophilia
Autoinculation from scratching (nails) Symptom: perianal itching Diagnose by perianal tape specimen Mebendazole, albendazole, pyrantel |
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Trichuris trichuria
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Intestinal nematode "whipworm"
Fecal-oral trans; 3mo incubation Local eosinophilia Most infxns asymp; heavy --> diarrhea Rectal prolapse possible Mucous/watery diarrhea Diagnose by stool sample (barrel-shaped eggs) Mebendazole, albendazole |
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Ascaris lumbricoides
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Intestinal nematode "roundworm"
Eggs are ingested, larvae hatch in jejunum Larvae migrate to right heart --> pulmonary circulation Molt in alveolar spaces --> trachea --> esophagus, swallowed --> excretion LOEFFLER's SYNDROME (pulm. hypersens.) Diagnose via stool sample Mebendazole, albendazole, ivermectin |
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Hookworm
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A. duodenalis / N. americans
Intestinal nematode Filariform larvae penetrate skin Entry can cause local dermatitis Larvae migrate through lungs to small intestine; can cause Loeffler's syndrome Major sequela: iron-def anemia due to blood loss (dyspnea, palpitations, tachycardia) Diagnose by stool sample Albendazole, mebendazole, pyrantel |
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Strongyloides stercalis
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Intestinal nematode
HTLV-1 coinfection? Possible hyperinfection (low IL-4,5; Th2 response low, 86% mort.) Infection by filariform larvae; penetrate skin Skin --> lungs --> intestine Unique characteristics: possible auto-infection, larva currens at infxn site Possible Loeffler's syndrome Diagnose by stool sample (less sensitive if chronic), serology Ivermectin (preferred USA), thiabendazole |
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Cutaneous Larva Migrans
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A. braziliens / A. caninum
Humans = aberrant hosts Worms wander aimlessly; do not penetrate under epidermis Itchy papule at site of entry; worm's track visible on skin w/ pruritis Diagnose by clinical history/track appearance Albendazole, ivermectin, topical thiabendazole |
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Visceral Larva Migrans
Ocular Larva Migrans |
Toxocara catis / Toxocara canis
VLM typically in younger pts.; fvr, wheezing, eosnphlia, hptomgly, IgG up OLM typicall in older pts.; less immune respone Eye invaded after svrl mos. infxn; ocular sequelae common Diagnose by serology DEC, albendazole, *thiabendazole* (topical) |
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Anisikiasis
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Tissue nematode
Larvae typically found in sltwatr fish; typically infct marine mammls, can infect humns Larvae burrow into stomach/sm intest. Symptoms ~48hr after ingestion; abd pain, nausea, vomiting (DD of appendicitis?) Humans = deadend host; supportive therapy only Albendazole/corticosteroids? |
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Baylisascaris
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Tissue nematode
Transmitted by raccoon feces; "raccoon ascaris" 50% fatal eosinophilic meningitis Diagnose by tissue detection of larvae No proven treatment |
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Dracunculosis
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Tissue nematode
Infection by drinking contaminated water Nematode lives in connective/subcutaneous tissues Female emerges at center of blister to release eggs in water Blisters/ulcers around feet Diagnose by worm visualization in water Treat by removing nematode "winding" |
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Onchocerciasis
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O. volvulus
Blood nematode "River blindness" Filarial nematode transmitted by bite of black fly Mating in tissue produces tissue-invasive microfilariae Symptoms: itching, dermatitis, papules, possible blindness Diagnose by skin slip exams or serology |
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Loiasis
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Infective agent: Loa loa
Blood nematode Infectious filariform larvae mature in Chrysops fly Microfilariae are most abundant in blood in DAYTIME Differentiate by presence of a sheath AND 3+ terminal nuclei Localized angioedema/calabar swellings from immune response Symptoms more common in visitors Possible meningoencephalitis Diagnose by serology or by tissue examination for microfilariae Diethylcarbamazine (DEC) |
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Bancroftian Filariasis
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Blood nematode
Infection by mosquito bite; adult worms live in lymphatic vessels Damage can result in lymphedema, eventually progressing to elephantiasis Lymphangiasis common Tropical Pulmonary Eosinophilia is possible sequela 4:1 male:female; wheezing/coughing AT NIGHT (active time) Restricted pulmonary function/obstruction Diagnose by serology/nighttime blood smear Treat with DEC |
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Trichinellosis
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Infection via pork products/eating undercooked meat w/ tissue cysts
Key symptoms: GI signs followed by inflammation, fever, PERIORBITAL EDEMA Diagnose by serology Mebendazole or albendazole |
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Schistosomiasis
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Fluke
Disease results from host response to ova Granulomas @ ova accumulation Human infection MUST go through a freshwater snail intermediate (cercariae) Acute schisto: Katayama fever syndr. Immune complex? Fvr, cough, myalgia, GI Swimmer's itch: pruritic eruption @ site of penetration Possible egg emblztion to CNS; S. japonicum -> brain, S. mans./hemat. -> spnl crd Chronic: GI microabscesses, inflammation, polyposis, bladder carcinoma Heavy infection: pulmonary hypertension? Diagnose by FAST-ELISA; stool sample specific but not sensitive Treat with praziquantel |
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Clonorchiasis/Opisthorciasis
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Both reside in biliary tract
Infection by consumption or RAW or PICKLED fish Snail intermediate required for infection Acute: persistent fever, hepatomegaly, eosinophilia Chronic: cholangiocarcinoma, recurrent ascending cholangitis Pathologic changes due to mechanical fluke injury Biliary duct dilation by fluke proline production Diagnose by mulberry cystic dilations on ultrasound CT, MRI also with history of raw freshwater fish consumption Treat with praziquantel (or albendazole) |
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Paragonamiasis
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Lung fluke
Snail intermediate: cercariae -> metacercariae Mcercriae excyst in duodenum, migrate through diaphragm to lung, mature to adult fluke Cause local necrosis, hemorrhage, inflammatory exudates Acute: GI symp, eosinophilia Pleuropulmonary paragonamiasis: Cough, chest pain, shrtns of breath Viscous, rusty sputum possible Light infxns asymptomatic Diagnose by stool, sputum sample, ELISA serology, characteristic CXR Treat w/ praziquantel; cook crabs/crayfish |
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Fasciola hepatica
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"Sheep-liver fluke disease"
Snail intermediate host Cercariae encyst on vegetation; "watercress sandwich" in sheep areas Local hepatic parenchymal destrctn, necrosis, abscesses Cholangitis + stone formation? Can present with ectopic sites: brain, orbit, subcutaneous tissue Acute: hptmgly, esnphlia, anrxia, nausea, vomtng, fvr Chronic: Flukes in biliary passages; abnrml livr fxn Diagnose by eggs in stool, serology Treat with triclabendazole |
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Amebiasis
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Protozoan; no eosinophilia
E. histolytica is clinically relevant Differentiate between histolytica and dispar by galactose adherence lectin Excystation/emergence of trophozoites occurs in small bowel May be 50% infection rate in developing areas Trophozoites invade mucus-protected membrns; destry tissue w/ proteolytc enzyms Classic "flask-shaped" ulcer in tissue Acute amebic colitis; 1-2wk hstry abd pain, tenesmus, bloody/mucous diarrhea no leukocytes in stool bc of lytic effects of protozoans Fulminant colitis grave mortality (50%) Diagnose by stool examination for parasites/stool antigen test Treat amebic liver abscess/colitis with metronidazole; other agts for colonization |
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Giardia
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Fecal -> oral transmission
"Pear-shaped" trophozoite; 8 flagella Parasite attaches to gut microvilli Fat absorption, vit B12 levels down Incubation 2wks, offensive yellow stool, anorexia, abd distention Symptoms can resolve spontaneously Diagnose by stool sample or ELISA serology Treat with metronidazole/tinidazole |
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Cryptosporida
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Protozoan
Current water purification INEFFECTIVE Daycare centers, foodborne outbreaks, swimming pools, **drinking supplies** Ingested oocysts release sporozoites Can be AIDS-related Acute: diarrhea w/out leukocytosis, mean duration 9 days, oocyte shedding 8-50 days Chronic diarrhea in immunocomproimsed, hypo-IgG Also cholangitis in AIDS pts Diagnose by **acid-fast stain** of oocysts in stool Treat with nitazoxanide (approved in children, AIDS pts) |
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Cyclospora
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Protozoan
Oocysts require days-weeks outside host to sporulate; thus human-human fecal transm unlikely Transmissible thru food/produce (raspberries) Easier to filter in water, resistant to chlorination Common symptoms: watery drrhea, fatigue, anorexia, bloating, crmps, nausea Increased susceptibility in immunocompromised Paratisizes small bowel Diagnose by **acid-fast** staining of stool sample Treat with trimethoprim-sulfamethoxazole (TMP-SMX) |
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Dientamoeba fragilis
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High correlation between E. vermicularis and D. fragilis infections
Water-borne and person-person transmission No colonic invasion, intestinal mucosal irritation Appendiceal fibrosis Intermittent diarrhea, anorexia, weight loss, fatigue Diagnose by trophozoites in stool Treat with tetracycline, iodoquinol, metronidazole, paromomycin |
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D. latum
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Intestinal tapeworm (cestode)
Need intermediate crustacean host AND 2nd intermediate (fish) host Humans infected by ingesting raw fresh/marine fish Major clinical finding: megalopblastic anemia secndry to vit B12 loss pallor, dyspnea, tchycrdia, also neurologic findings Diagnose by demonstrating eggs in stool Treat with praziquantel, make sure to cook fish |
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Taeniasis
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Tapeworm
T. saginata (beef), T. solium (pork) T. saginata is larger; typically more proglottids(segments) T. solium has an "armed" scolex (hooks on crown); T. saginata doesn't Cows/pigs become infected by human feces; humans eat undercooked meat Possible CYSTICERCOSIS w/ T. solium Many infections asymptomatic except for worm movement Diagnose by worms in feces; T. saginata has more branched uterus Treat with praziquantel or niclosamide |
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Cysticercosis
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T. solium is pork tapeworm
Humans = only definitive host Cysticercosis occurs when humans ingest ova from carrier Ova can be carried anywhere in body; typically degenerate and calcify Can be found in muscle, orbit, soft tissue, subcutaneous tissue Disease from CNS(neurocysticercosis)/eye invasion Parenchymal neurocysticercosis *favorable prognosis*; seizures More severe disease from extraparenchymal neurocysticercosis Increased intracranial pressure, hydrocephalus Diagnose by symptoms, imaging, serology Treat with albendazole (superior), praziquantel. Corticosteroids for inflammation, surgery? CSF shunt? |
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Cystic Hydatid Disease
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E. granulosus (tapeworm)
Dogs definitive hosts; sheep, goats, pigs, horses intermediate hosts Humans accidental intermediate host Prevalent where dogs are used to herd sheep Cysts formed by metacestode stage: liver (60-70%), lungs (25%), others Rupture of cyst can lead to anaphylaxis Diagnose by clinical picture, exposure, imaging, serology Treat with albendazole, percutaneous puncture for uncomplicated cysts Surgery + albendazole for complicated cysts |
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Alveolar hydatid disease
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E. multilocularis (tapeworm)
Humans = accidental dead-end hosts; typically acquire eggs from foxes Primary lesion ALWAYS in *liver* Found in colder regions of Northern Hemisphere Lesions occur as yellow-gray cancer-like masses in liver Advanced cases can lead to necrotic, pus-filled cavity Cysts can metastasize Symptoms: jaundice, hepatomegaly, palpable peritoneal masses Mimics hepatic carcinoma Diagnose by imaging (multivesicular lesion pattern); serology available Therapy = surgical resection w/ long-term albendazole; lifelong alb. without surgery |
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Malaria symptoms
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Prodromal body aches (2-3 days prior)
Chills (15-60min) Fever Sweating (2-4 hrs -> sleep) |
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Plasmodium life cycle
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1. infected w/ sporozoites via bite of Anopheles mosquito
2. sporozoites infect hepatocytes, generate merozoites 3. merozoites infect RBCs 4. Inside RBCs, either trophozoite maturation or gametocyte genesis |
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Plasmodium vivax
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Found in SE Asia, Americas, NOT in W. Africa
Duffy receptor Acute fever BUT few fatalities Tertian fever Evolving choloroquine resistance; sensitive to *artemisinins* |
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Plasmodium ovale
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Infected RBCs oval with fimbriated edges
Found in Sub-Saharan Africa, W. Pacific islands Younger RBCs Less parasitemia Difficult to distinguish from P. vivax Tertian fever |
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Plasmodium malariae
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Neurosyphilis treatment
Milder strain of malaria *Quartan fever* as opposed to tertian fever Possible complication: nephrotic syndrome |
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Plasmodium falciparum
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Cerebral malaria most common with this species
Anemia common Lactic acidosis, hypoglycemia, hyperparasitemia |
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Invasive stages of malaria
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Ookinete: found in mosquito gut epithelial cells; produces:
Sporozoite: found in mosquito salivary glands, infects hepatocytes Merozoite: infects erythrocytes, produced in hepatocytes Hypnozoite: only P. vivax, ovale, dormant for months, insensitive many drugs |
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Schizogony
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Asexual replication unique to apicomplexans (Plasmodium, Babesia)
Occurs in RBCs and leads to RBC rupture --> merozoite release |
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P. falciparum erythrocyte membrane protein 1
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Exported to erythrocyte surface
Mediates cytoadherence, rosetting, sequestration Target of strain-specific immunity Switching of antigen causes wave of parasitemia |
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Cerebral malaria (P. falciparum mainly)
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Sticky RBC knobs (sequestration)
High TNF levels (increased vasc. endothelial adherence) Poor RBC deformability NORMAL CSF/CT Increased endothelial perm. |
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Host response to malaria
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Challenges:
Specific immunity controls symptoms but not parasitemia; no effect while preg No MHC on RBCs Antigen not effective immune stimulator Large antigen diversity Adaptations: Sickle cell trait/thalassemia G6P dehydrogenase Ovalocytosis (resistance to merozoite invasion) |
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Malarial diagnosis
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< 10 days since exposure: P. falciparum
> 3yr since exposure: P. malariae 10-60 days: any Plasmodium species Severe illness: P. falciparum P. falciparum: multiple ring trophs; stippling w/ coarse dots P. vivax: one ring troph, fine stippling dots P. malariae: no stippling P. ovale: fimbriation of RBCs |
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"Fifth disease" : P. knowlesi
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Resembles early trophozoite P. falciparum, late stage P. malariae
Clues: severe symptoms, travel to Asia, >5000/uL, diverse morphology |
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Malaria treatment
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New gold standard: artemisinins + combination therapy
Chloroquine: kills trophozoites, retinpthy, falciparum/vivax res. Quinine: kills trophozoites, gametocytes EXCEPT falciparum Quinine narrow therapeutic range Mefloquine: expensive, travelers' prohpylaxis, no mono-therapy, GI, neuro Primaquine: broad spectrum, vs relapse, long regimen, not for G6PD-def Best anti-malar prophylxs: mefloquine, doxy, atovaquone-proguanil |
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Babesiosis
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B. microti (Northeast)
B. duncanii (NW) B. divergens (MO, KY, WA, rare europe) Transmitted by tick Typically mild flu-like, severe in elderly/immunocomp/asplenic Complications: Acute respiratory failure, DIC, CHF, renal failure Also severe anemia, parasitemia, fatal in 5-10% Treatment mild: atovaquone + azithromycin severe: clindamycin + quinine B. divergens: RBC exchange + clindamycin/quinine |
