Parasites: Metazoans Flashcards
Enterobius vermicularis
[Pinworm]
Intestinal Nematode
Epi: mc helminth infx in US
Morph: eggs flattened on one side
Path: infective eggs ingested–>small intestine–>larvae emerge–lymphatics–>venules–>lung (infective form develops)–>larynx–>pharynx–>swallowed to reach small intestine–>mature into adults in cecum and ascending intestine
females go to perianus @ night–>lay eggs–>infective 4-6 hrs later–>perianal irritation–>scratch–>hand/mouth re-infection
Clinic: perianal irritation +/- GI problems
Dx: Scotch tape test for detecting eggs
Tx: 2x Pyrental Pamoate to whole family w/ doses 2 weeks apart
Trichuris thrichiuria
[Whipworm]
Intestinal Nematode
Epi: poor tropic populations, worsens malnourishment
Morph: “whips”=adults, eggs=football shaped w/ bipolar plugs
Path: infective eggs ingested–>small intestine–>larvae emerge–lymphatics–>venules–>lung (infective form develops)–>larynx–>pharynx–>swallowed to reach small intestine–>mature into adults in cecum and ascending intestine
Clinic: diarrhea +/- blood
Dx: eggs in stool
Tx: bendazole, resolves after 2 years without treatment
Ascaris lumbricoides
Intestinal Nematode
Epi: tropical areas, including SE US
Morph: eggs have irregular coating
Path: infective eggs ingested–>small intestine–>larvae emerge–lymphatics–>venules–>lung (infective form develops)–>larynx–>pharynx–>swallowed to reach small intestine–>mature into adults
Here, survive for 1-2 years, produce 200K eggs/day, and excrete eggs in feces
Clinic: **Loeffler’s Pneumonitis: occurs when larvae are in lung; endocarditis and peripheral eosinophilia
**Bowel obstruction +/- perforation +/- ischemia
Obstruction of biliary tree (gall bladder, pancreatitis, etc)
Dx: eggs visible in stool
Tx: Pyrantel Pamoate + Mebendazole
Trichinella spiralis
[Trichinosis]
Intestinal Nematode
Epi: raw pork/bear/deer
***MCC of parasitic myocarditis
Morph: adult in intestine, larvae in tissue
Path: eat poorly cooked meat w/ LARVAE in tissues–>small intestine–>adults emerge–>adults mate–>males excreted in feces and females penetrate intestinal mucosa–>larvae enter circulation–>skeletal muscle
Clinic: UNDERCOOKED MEAT WITH MUSCLE ACHE AND EOSINOPHILIA (as high as 85%)
Dx: Hx of meat consumption
increased eosinophilia and increased CPK
cysts in skeletal muscle biopsy
Tx: Prevention by cooking meat
Bendazole inhibits adults, not larvae in cysts
Necator americanus and Ancylostoma duodenale
[Hookworm]
Intestinal Nematode
Epi: MCC childhood anemia worldwide
Necator–>US, Africa, Australia, South Asia
Ancyostoma–>Mediterranean, North Asia
Morph: Adults have teeth/cutting plates, eggs have outer shell
Path: Larvae penetrate skin on feet–>straight to lungs–>intestine–>larvae form (migratory inflammation and eosinophilia)–>grasp onto intestinal villi and eat tissue (produces anticoagulant)
Clinic: Microcytic anemia in a child, pneumonitis, gastroenteritis; eosinophilia, cognitive and growth retardation
Dx: eggs in stool
Tx: mebendazole
Strongyloides stercoralis
Intestinal Nematode
Epi: immunocompromised host
Morph:
Path: initial infection from larvae in soil–>penetrates intact skin–>enter blood stream–>lungs–>larynx–>pharynx–>intestines–>mature/hatch eggs–>EGGS NOT IN FECES, but hatch larvae and autoinfect or excreted as larvae to lay eggs in soil and infect next person–>can keep ongoing auto infection cycle
Clinic: Asymptomatic w/ eosinophilia
skin-->purpuric papule
lung-->Loeffler's syndrome
intestinal-->pain/diarrhea
IC pts-->acute abdomen, respiratory disease, sepsis, eosinophilia absent (HYPERINFECTION SYNDROME)
Dx: Larvae in stool and sputum
Tx: Ivermectin + Albendazole
Toxecara canis
Tissue Nematode
Epi:
Morph:
Path: Eggs from dog/cat roundworm ingested–>larvae penetrate mucosa–>circulation–>LUNGS, LIVER, EYES
Humans are DEAD END/ACCIDENTAL HOST
Clinic: mc=asymptomatic eosinophilia…also can have granulomas and blindness
***Visceral + cutaneous larva migrans
Dx:
Tx: Diethylcarbamazine
Wuchereria bancrofti
[Elephantiasis]
Tissue Nematode
Epi: tropical areas
Morph: Adults in lymphatics (~10cm), microfilarie in blood stream (~0.25cm)
Path: Microfilariae (aka offspring, but not eggs) transmitted via mosquito bite–>mature in lymphatic vessels and nodes, esp. in testes and lower extremities–>adult in lymphatics–>inflammation–>fibrosis/blockage of lymphatics–>elephantiasis–>microfilariae invade nearby blood vessels to produce a febrile illness
Clinic: takes 9 months-1 year for elephantiasis symptoms to occur
Dx: blood microfilaria at NIGHT
Tx: Diethylcarbamazine, steroids
Oncocerca volvulus
[River blindness]
Tissue Nematode
Epi: Africa and Central America via Stimulum (aka river blackflies)
Morph: Adults=skin nodules, microfilariae=subcutaneous tissues
Path: Blackfly infected human–>microfilariae mature into adults and coil into nodules under skin–>mate–>microfilariae–>migrate to dermis (form black skin nodules and intraepithelial granulomas) and eye (blindness)
Clinic: ***Blackfly=Black skin nodules + Black sight
Dx: microfilaria in superficial skin clips
Tx: Ivermectin
Dracunculus medinesis
Tissue Nematode
Drinking water–>skin inflammation and ulceration
Tx: Niridazole
Loa Loa
Tissue Nematode
Deer/horse/mango flies–>cause swelling in skin and worm crawling in conjunctiva
Tx: Diethylcarbamazine
Schistosoma
[Blood fluke]
Schistosoma mansoni–>America, Africa
Schistosoma japonicum–>Japan
Schistosoma hematobium–>Africa
Trematode
Epi: see other side
Morph: Adults in blood vessels copulating constantly
Path: Freshwater required for eggs to hatch–>larvae emerge from hatched eggs–>swim to SNAILS (intermediate host)–>larvae mature within snail–>once released, infectious to humans–>penetrate skin–>travel to portal system–>mature into adults–>migrate to veins around intestine (Mansoni + Japonicum) or bladder (Hematobium)–>excreted in feces/urine–>enter nearby stream/lake–>repeat cycle
Clinic: Cercariea (mature larvae) and eggs (NOT ADULT WORMS)=inflammation/damage–>Eosinophilia
- All 3 types result in dermatitis where mature larvae penetrated skin
- S. mansoni + japonicum–>periportal fibrosis, granuloma, portal hypertension–>hepatosplenomegaly
- S. hematobium: ***TERMINAL HEMATURIA (on last few drops), bladder granulomas, bladder cancer
Dx: Hx + egg in urine or feces, depending on type
Tx: Praziquantel and snail control
Clonorchis sinesis
[Chinese liver fluke]
Trematode
Epi: Asia, poorly cooked fish
Morph: “Leaf-like”
Path: freshwater eggs–>larvae swim to snails–>infectious carcariae in fresh water fish–>metacercariae ingested by host
Clinic: causes inflammation of liver and biliary tract–>pigmented stones and cholangiocarcinoma
Dx: eggs in feces
Tx; Praziquantel
Pragonimus westermani
[Lung fluke]
Trematode
Epi: Asia, Africa, South America, poorly cooked crab
Morph:
Path: freshwater eggs–>larvae swim to snails–>infectious carcariae in CRAB–>metacercariae ingested by host
Clinic: inflammation–>secondary bacterial infection of lung–>fibrotic lung disease and hemoptysis
Dx: Eggs in sputum
Tx: Praziquantel
Taenia solium (pork) Taenia saginata (beef) [Tapeworm]
Cestode
Epi: cosmopolitan developing world
***young male with seizures from Mexico, India, Africa
Morph: hermaphroditic with no digestive tract
Path: ingest encysted larvae in undercooked pork/beef–>tapeworm attaches to mucosa via scolex–>larvae grows–>gravid proglottids and eggs excreted in feces–>pigs and cattle graze on soil with eggs–>ingest eggs–>eggs develop into larvae–>pig becomes intermediate host–>larvae develop in muscle tissue into fluid-filled sac with larval form inside=CYSTICERUS–>process repeats
if humans ingest infectious eggs in pork instead of larvae (i.e. NOT seen in T. saginata/beef)–>humans develop cystercus in BRAIN (headache and seizures–>”Swiss cheese brain”), EYE, SKELETAL MUSCLE
Clinic: very little with intestinal infection, unless extremely heavy
Dx: eggs in proglittids/stool
Tx: Praziquantel, pork/beef cooking
