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Microbiology USMLE step 1 > Parasitology > Flashcards

Parasitology Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Causal agent of amebiasis

A

Entamoeba Histolytica

Protozoa
Amebiasis: bloody diarrhea, liver abscess
Transmission: cyst in the water, fecal -oral
Dx: serology and/or trophozoites with engulfed RBC in the cytoplasm or cyst with up to 4 nuclei in the stool
Tx: metronidazole

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2
Q

Giardiasis

A

Causal agent : Giardia lamblia

  • transmission: fecal oral, cyst in the water.
  • diagnosis: multinucleated trophozoites or cyst in the stool

Disease: giardiasis: fatty diarrhea with bloating, flatulence and foul-smelling .

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3
Q

Cryptosporidium

A

Causal agent of severe diarrhea in AIDS.

Mild disease (watery diarrhea) in inmunocompetent hosts.

Transmission: oocysts in water, undercooked meat

Diagnosis: oocysts on acid fast stain in stool

Tx: prevention , nitozoxanide

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4
Q

Protozoa- CNS INFECTION

A
  • Toxoplasma Gondii
  • Naegleria fowleri
  • Trypanosoma Brucei
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5
Q

Toxoplasmosis

A

Toxoplasma gondii

  • transmission: cyst in meat, oocysts in CAT feces; transplacentario
  • definitive host: cats
  • intermediate host: human
  • Dx: serology (biopsy) you can see tachyzoite.
  • Tx: sulfadiazine + pyrimethamine

Diasease: Toxoplamosis

  • after birth: asymptomatic or non-specific flu like illness with fever and lymphadenopathy
  • congenital: first trimester : * chorioretinitis * hydrocephalus. * intracranial calcifications
                  Third trimester : Inapparent, may lead with a progressive blindness in the child later in life (teens)

-Reactivation in AIDS: brain abscess seen as ring-enhancing lesions on MRI. Chronic headaches.

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6
Q

Free living amoebas that occasionally infect humans

A
  • Naegleria fowleri

- Acanthamoeba

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7
Q

Naegleria fowleri

A

-Disease: rapidly fatal meningoencephalitis
Symptoms: Severe headaches, Nausea, fever, Altered sense of smell .

  • Transmission: swimming in fresh water lakes : enters via cribriform plate.
  • Diagnosis: * Amoebas in spinal fluids * Motile trophozoites in CSF.
  • Treatment : Amphotericin B
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8
Q

Acanthamoeba

A

Keratitis
Granulomatous amebic encephalitis

  • Transmision: free living amebas in contaminated contact lens solution
  • Treatment: topical miconazol
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9
Q

Trypanosoma brucei

A

AFRICAN SLEEPING SICKNESS

  • Symptoms: enlarged lymph nodes, recurring fever, somnolence, coma.
  • Transmission: tsetse fly bite
  • Diagnosis: trypomastigote in blood smear
  • Treatment: acute: suramin
    Chronic: melarsoprol
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10
Q

Protozoa- hematologic infections

A
  • Plasmodium : vivax/ovale, falciparum, malariae

- Babesia

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11
Q

Babesia

A

Disease : BABESIOSIS
Fever and hemolytic anemia
Predominant in northeastern of USA
Coinfection with Borrelia (Lyme disease)

  • transmission: Ixodes tick bite
  • Diagnosis: Blood smear: ring form , Maltese cross , Terras in RBC
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12
Q

Plasmodium

A

MALARIA
Fever spikes, headache, anemia, splenomegaly. This symptoms appears when merozoites are liberate from RBC.

HbS and other kind of abnormal hemoglobin have resistant to get infect by this Protozoa.

Two phases :

  • Sexual in the female mosquito (anopheles): form sporozoites in her stomach, they migrate to salivary glands to infect humans through the bite.
  • Asexual phase : in humans, we get the sporozoites from the mosquito bite, they travel in blood to liver cells and transform in trophozoites and then merozoites, causing RBC lysis and merozoites go infected other cells.

Types of plasmodium:

  • P. Vivax/ovale: 48hr cycle (tertian) . Diagnosis: schuffner dots in blood smear.
  • P. falciparum : 72 hrs cycle (malignant tertian or quartan) : irregular fever spikes, causes cerebral malaria. Diagnosis on blood smear multiple ring forms crescent or banana shaped gametes.
  • Treatment: Chloroquine
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13
Q

Protozoa - visceral infection

A
  • Trypanosoma cruzi: Chagas disease

- Leishmania donovani

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14
Q

Leishmania

A
  • L. donovani: visceral leishmaniasis
  • L. braziliensis : mucocutaneous leishmaniasis
  • Leishmania spp: cutaneous leishmaniasis
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15
Q

Leishmania donovani

A 
VISCERAL LEISHMANIASIS ( kala- azar)
- Symptoms: 
Spiking fever
Hepatoesplenomegaly
Pancytopenia
  • Transmission: sandfly
  • Diagnosis: macrophages containing amastigotes
  • Treatment: amphotericin B, sodium stibogluconate.
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16
Q

Trypanosoma cruzi

A

CHAGAS DISEASE (American Trypanosomiasis)

Dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus.

Unilateral peri orbital swelling (romaña sign) characteristic of acute stage.

  • Transmission: triatomine bug (reduviid bug) feces, deposited in a painless bite.
  • Diagnosis: trypomastigote in blood smear
  • Treatment: benznidazole or nifurtimox
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17
Q

Protozoa - sexually transmitted

A

Trichomona vaginalis

TRICHOMONIASIS

  • Vaginitis
  • foul-smelling
  • greenish discharge
  • itching and burning
  • Transmission: sexually
  • Diagnosis: vaginal discharge, strawberry cervix, trophozoites motile on wet mount
  • Diagnosis: metronidazole for patient and partner (prophylaxis)
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18
Q

Nematodes (roundworms)

Routes of infection

A
  • Ingested : Enterobius, Ascaris, Toxocara, Trichinella
  • Cutaneous: Strongyloides, Ancylostoma, Necator
  • Bites: Loa Loa, Onchocerca volvulus, Wuchereria bancrofti
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19
Q

Enterobius vermicularis (pinworm)

A

Intestinal infection causing anal pruritus.

  • Transmission:fecal oral, auto ingested
  • Diagnosis: seeing egg via scotch tape
  • Treatment: bendazoles (albendazole), treat all family.
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20
Q

Ascaris lumbricoides

Giant roundworm

A

Ascariasis: Intestinal infection with possible obstruction at ileocecal valve.

  • Transmission: fecal oral, eggs ingested
  • Diagnosis: bile stained, knobby eggs, adults 6-12” roundworms
  • Treatment: mebendazole, surgery extraction
21
Q

Strongyloides stercoralis

Threadworms

A

Strongyloidiasis (may mimic peptic ulcer)

  • Early: pneumonitis, abdominal pain, diarrhea
  • Later: malabsorption, ulcers, bloody stools
  • transmission: filariform larvae in the soil penetrate the skin
  • Diagnosis: serology, larvae in stool
  • Treatment: Ivermectin or thiabendazole
22
Q

Hookworms:

  • Ancylostoma duodenale
  • Necator americanus
A

Intestinal infection causing anemia by sucking blood from intestinal wall.

Transmission: filariform larvae penetrates intact skin of bare feet

Diagnosis: occult blood may be present, fecal larvae and ova

Treatment: mebendazole and iron therapy

23
Q

Ancylostoma braziliensis

A

CUTANEOUS LARVA MIGRANS : pruritic, serpiginous rash from walking barefoot on contaminated beach.

Transmission: filariform larvae penetrate human skin but can not mature due to real host is dogs and cats .

Treatment: topical steroids and thiabendazole or pyrantel pamoate

24
Q

Trichuris trichiura

A

Whipworm cecum: appendicitis and rectal prolapse

Transmission: eggs ingested

Diagnosis: barrel-shaped eggs with bipolar plugs in stools

Treatment: albendazole

25
Q

Trichinella spiralis

A

TRICHINOSIS

  • fever, vomiting, myalgias, periorbital edema
  • Pathogenesis: intestinal infection;larvae enter bloodstream and encyst in striated muscle cells causing inflammation of muscle.
  • Transmission: viable encysted larvae in meat undercooked are consumed.
  • Diagnosis: muscle biopsy
  • Treatment: bendazoles
26
Q

Visceral larva migrans

A

Toxocara canis

Nematodes migrate to blood through intestinal wall causing inflammation and damage. Organs frequently affected included the heart, liver and CNS.

  • Transmission: fecal oral, eggs ingested
  • Diagnosis: clinical findings and serology
  • treatment : bendazoles
27
Q

Filarial nematodes

A
  • Onchocerca volvulus: onchocerciasis or river blindness disease, transmitted by female blackfly. Cause skin changes, loss of elastic fibers and blindness . Treatment: ivermectin
  • Loa loa: worm in the conjunctiva . Transmitted by deer fly, horse fly or mango fly. Diagnosis: microfilariae in blood, eye and skin swelling. Eosinophilia. Treatment: surgical removal from the eye, but first paralyze with diethylcarbamazine.
  • Wuchereria bancrofti: ELEPHANTIASIS: worms invade lymphnodes and cause inflammation, which can block lymphatic vessels. Takes 9months to 1 year to become symptomatic. Transmitted by female mosquito. Diagnosis: microfilariae in blood. Eosinophilia. Treatment: surgery, ivermectin and diethylcarbamazine.
28
Q

Cestodes ( tapeworms)

A
  • Taenia solium and Saginata
  • Diphyllobothrium latum
  • Echinococcus granulosus
29
Q

Taenia solium

A

Two types of disease, depends in what are you ingested:

  • Eggs ingested: Cysticercosis
  • Cysticerci: intestinal tapeworm (taeniasis)
30
Q

Cysticercosis

A

Eggs of Taenia solium in water, vegetation or food.

Symptoms: seizures, elevated intracranial pressure (ICP), meningoencephalitis, psychiatric disorder, stroke, and/or radiculopathy or myelopathy, if the spinal cord is involved.

Diagnosis: biopsy, MRI

Treatment: praziquantel, corticosteroids in case of cerebral edema and anticonvulsants.

31
Q

Taeniasis (intestinal tapeworms)

A

Raw pork containing the Cysticerci is ingested by humans

Symptoms: asymptomatic or vague abdominal pains

Diagnosis: proglottis or eggs in feces.

Treatment: praziquantel

32
Q

Diphyllobothrium latum (fish tapeworm) 🍣

A

Transmission: ingestion of larvae from raw freshwater fish.

Treatment: praziquantel

Two diseases:

  • Sparganosis: when humans are intermediate hosts, larvae penetrate intestinal wall and encyst. Ingestion of the copepods (crustaceans) carrying the larval forms. Dx: biopsy
  • intestinal tapeworm : megaloblastic anemia, definitive host was humans . Dx: proglottids or eggs in feces.
33
Q

Echinococcus granulosus

A

Intermediate hosts: herbivores, rare humans

Definitive hosts: Sheep

Transmission: ingestion of eggs from dog feces

Disease: Hydatid cyst : liver and lung cysts

Diagnosis: image, serology.

Treatment: albendazole and surgery

34
Q

Trematodes

A
  • commonly called flukes
  • are hermaphrodite except for schistosoma.
  • have operculate eggs which contaminate water.
  • the first intermediate host are snails
  • Schistosoma mansoni
  • Schistosoma haematobium
  • Clonorchis sinensis
  • Fasciola hepatica
  • Paragonimus westermani
35
Q

Intestinal schistosomiasis

A

Schistosoma mansoni agent causal

Acquisition: contact with contaminated water. Larvae skin penetration.

Progression: cercariae skin penetration (itching), mature in veins of mesentery, eggs cause granulomas in liver.

Diagnosis: eggs in the stool. Characteristic eggs with lateral spine. Schistosoma haematobium has a terminal spine.

Treatment: praziquantel

36
Q

Clonorchis sinensis

A

Common name: Chinese liver fluke
Reservoir host: dogs, cats, humans
Acquisition: raw fish ingestion

Disease: biliary tract inflammation : pigmented gallstones. Associated with cholagiocarcinoma.

Treatment: praziquantel

Diagnosis: opperculated eggs

37
Q

Ectoparasites

A

-Scabies (sarcoptes scabiei): mites that burrow into the stratum corneum and cause pruritic. Cause serpiginous burrows in webspace of hands and feet. Transmit by fomites. Treatment: permethrin cream, washing/drying all clothing/bedding.

-Lice ( Pediculus humanus/ phthrius pubis) Lice are ectoparasites that live on the body. Lice feed on human blood after piercing the skin and injecting saliva, which may cause pruritus due to an allergic reaction. Lice crawl but cannot fly or hop.
Lice move from person to person through close physical contact. Spread through contact with fomites (eg, combs, brushes, clothes, hats, scarves, coats, linens) used by an infested person is uncommon. Overcrowding encourages the spread of lice. The body louse can be the vector of Rickettsia prowazeki, which causes typhus; Bartonella quintana, which causes trench fever; and Borrelia recurrentis, which causes relapsing fever.

38
Q

Biliary tract infection, cholangiocarcinoma

A

Clonorchis sinensis

39
Q

Braun cysts and seizures

A

Neurocysticercosis

Taenia solium

40
Q

Liver cysts

A

Echinococcus granulosus

41
Q

Microcytic anemia

A

Ancylostoma

Necator

42
Q

Myalgias, periorbital edema

A

Trichinella spiralis

43
Q

Perianal pruritus

A

Enterobius vermicularis

44
Q

Portal hypertension

A

Schistosoma mansoni, Schistosoma japonicum

45
Q

Vitamin B12 deficiency

A

Megaloblastic anemia

Diphyllobothrium latum

46
Q

Only nematode which produce anemia

A

Necator americanus

Transmission: larvae skin penetration

47
Q

Opportunistic infections in AIDS

A

Cryptosporidium
Isospora
Microsporidia
Cyclospora

48
Q

Pathology of Giardiasis

A

Giardia lamblia make Pathogenesis with ventral sucking disc. Adherence to the mucosa of the upper small intestine.

Microbiology USMLE step 1 (8 decks)

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