all parasites

8/11/2019 All Parasites

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Protozoa


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Entamoeba histolytica Distinguishing features

Amoeba: move with pseudopodia

Trophozoite with ingested RBC in stool

with active disease 4-nuclei cyst in stool with carrier state

Pathogenesis

Fecal-oral transmission fromcontaminated food/water cystingested trophozoite invades colon

with extension to liver, lungs Diseases

Asymptomatic carriage (most common)

Intestinal amebiasis: dysentery (bloodydiarrhea)

Invasive amebiasis: flask-shaped ulcersin colon, liver abscesses RUQ pain,pulmonary abscesses

Treatment Metronidazole

Trophozoites with ingested RBCs with active state

Colonic flask-shaped ulcer

Cyst of carrier state showing 3 of 4 nucleiProtozoa


3/26

Giardia lamblia Distinguishing features

Flagellate: move with flagella

Tear-shaped flagellated trophozoites in

stool with active disease 4-nuclei cyst in stool with carrier state

Most common enteric parasite in the U.S.

Leading infectious agent in waterborneoutbreaks of diarrhea

Pathogenesis

Fecal-oral transmission from contaminatedfood/water cyst ingested trophozoiteattaches to duodenum (no invasion) malabsorption

Diseases

Asymptomatic carrier Fatty diarrhea: non-bloody & foul-smelling

Treatment

Metronidazole

Binucleated trophozoite with 4

pairs of flagella

Cyst of Giardia lamblia

Protozoa


4/26

Cryptosporidium parvum Distinguishing features

Sporozoan: obligate intracellular

parasites Acid-fast oocysts in stool

Pathogenesis

Fecal-oral transmission from

animals/humans oocystsingested inhabit microvilli ofthe SI

Diseases

Waterydiarrhea

Severe, prolongeddiarrhea in IChosts

Also caused by Isospora belli, whichis distinguished by having ellipticalacid-fast oocysts in the stool, and istreated with TMP/SMX

Acid-fast oocysts of Cryptosporidium

Elliptical oocysts of Isospora belliProtozoa


5/26

Trichomonas vaginalis Distinguishing features


Lacks a cyst form: does not survivein external environment

Trophozoites on wet mount ofdischarge

Pathogenesis Sexually-transmitted

Diseases

Vaginitis: greenish, frothy, foul-

smelling vaginal discharge, itching Urethritis (males): mostly

asymptomatic

Treatment

Metronidazole to patient andpatients sexual partners

Trophozoites with 5 flagella, 1 nucleus

Protozoa


6/26

asmo um spec es Distinguishing features

Sporozoan: obligate intracellular parasites

Characteristic trophozoite in RBC (small rings inP. falciparum)

Pathogenesis Transmitted by bite ofAnopheles mosquito

sporozoites in bloodstream migrate to liver hepatocytes burst releasing merozoites thatinvade the RBCs infected RBCs lyse releasingmerozoites that can invade other RBCs immune response fever, chills, sweats, anemia

Hepatosplenomegaly from phagocytosis ofdestroyed RBCs

Diseases Malaria

Plasmodium falciparum (most severe): irregularfeverspikes, blackwater fever = hemoglobinuria, stickyRBCs cause vessel occlusion in kidney, lung, brain

cerebralmalaria (seizures, coma), kidney failure, lungedema

Plasmodium vivax/ovale: 48-hourfever spikes (tertianform), dormant hypnozoites in liver may relapse

Plasmodium malariae: 72-hourfever spikes (quartanform)

Treatment

Chloroquine, mefloquine for chloroquine-resistantP. falciparum, primaquine for hypnozoites

Sm

all ring-shaped

trophozite of P. falciparum

Banana-shaped gametocyte of

P. falciparum

Schuffnersdots and

ameboid trophozoites of

P. vivax

Bar/band form of P.

malariae trophozoite

Rosette schizont of P.

malariae

Jagged RBC of P.

ovale

Protozoa


7/26

Toxoplasma gondii Distinguishing features

Sporozoan: obligate intracellularparasites

Crescent-shaped trophozoites withinmacrophage

Cat is definitive host

Pathogenesis Cysts ingested from cat feces,

undercooked meat (pork)

mononucleosis-like symptoms invasive forms become dormant

Host becomes IC reactivation

Diseases Leading cause of CNS disease in AIDS

patients = encephalitis, chorioretinitis Ring-enhancing lesions on brain scan

Congenital toxoplasmosis: mentalretardation, chorioretinitis, other birthdefects, from transplacental fetalinfection

Treatment Sulfadiazine + pyrimethamine

Ring-enhancing lesions on MRI =

toxoplasmic encephalitis

Crescent-shaped trophozoites in abronchoalveolar lavage

Protozoa


8/26

Trypanosoma cruzi Distinguishing features


Flagellated protozoan (trypomastigote) inblood

Nonflagellated protozoa (amastigote) intissue

Pathogenesis

Reservoir in South/Central Americananimals transmitted by reduviid bug

chagoma (inflammatory nodule) @ bitesite infects blood, tissue

Romanassign (swelling around eye)when protozoan enters throughconjunctiva

Diseases

Chagas Disease (AmericanTrypanosomiasis)

Acute phase: myocarditis

Chronic phase: dilated cardiomyopathy,megacolon, megaesophagus

Treatment

Nifurtimox, benznidazole for acute cases

Trypomastigote in blood smear

Amastigotes in heart muscle

Romanassign: swelling around eyeProtozoa


9/26

Trypanosoma brucei Distinguishing features


Antigenic variation of surface coat:causes recurring fevers

Trypomastigotes in blood, CSF,lymph nodes

Pathogenesis Transmitted by tsetse fly

Diseases African Sleeping Sickness (African

Trypanosomiasis): hard red ulcer @bite site recurring fevers CNSinvasion (encephalitis, somnolence,

coma) T. b. rhodesiense (EASS) is more severe

than T. b. gambiense (WASS)

Treatment Suramin (if no CNS involvement)

Melarsoprol (with CNS involvement)

Trypomastigotes in blood smear

Protozoa

h


10/26

Leishmania species Distinguishing features


Nonflagellated protozoans within

macrophages Pathogenesis

Dog/rodent reservoir transmitted bysandfly

Diseases

Cutaneous leishmaniasis: single skinulcer with intact CMI, diffuse nodularlesions with deficient CMI

Mucocutaneous leishmaniasis:nasal/oral mucosal ulcers erosion ofnasal septum/buccal cavity

Visceral leishmaniasis (Kala-Azar):invasion of reticuloendothelial system hepatosplenomegaly, anemia,leukopenia

Caused by L. donovani

Treatment Stibogluconate

Protozoa

Amastigotes within a macrophage

Skin ulcer due to leishmaniasis


11/26

Babesia microti Distinguishing features

Sporozoan: obligate intracellular

parasites Maltese-cross on blood smear

Pathogenesis

Transmitted by Ixodes tick, sametick that spreads Lyme Disease =coinfections with Borrelia

Diseases

Babesiosis: invades RBCs malaria-like illness with feverand mild hemolytic anemia

Treatment

Clindamycin + quinine Protozoa

Pathognomonic maltese-cross


12/26

Platyhelminthes (flatworms)


13/26

c stosoma spec es Distinguishing features

Trematode (fluke)

Eosinophilia

Adult forms evade immune system withmolecular mimicry

Pathogenesis Snailsas intermediate host larvae (cercariae)

released into fresh water penetrate humanflesh (dermatitis) eggs released acuteinflammation Katayama fever

Diseases S. mansoni (South America, Africa), S.

japonicum (East Asia): eggs released inintestinal veins eggs deposited in stool

Eggs carried to liver chronic inflammation granulomas, periportal fibrosis portal HTN

Eggs carried to lung chronic inflammation fibrosis pulmonary HTN

Eggs carried to intestine chronic inflammation polyps

S. haematobium (Africa): eggs released inbladder veins eggs deposited in urine

Eggs lodge in bladder wall chronic inflammation hematuria, association with bladder (squamouscell) carcinoma

Treatment Praziquantel

Egg of S. haematobium: prominent terminal spine

Egg of S. japonicum: non-specific

Egg of S. mansoni:lateral spine

Female resides in grooveof male


T i i (b f )


14/26

Taenia saginata (beef tapeworm) Distinguishing features

Cestode (tapeworm)

Eosinophilia

No hooks on scolex

Proglottids, eggs in feces

Pathogenesis Ingested as cysticerci in

undercooked beef adult scolexadheres to intestine consumeshost food malnutrition

Diseases Usually asymptomatic

Abdominal discomfort, weightloss, diarrhea

Treatment Praziquantel

Gravid proglottid: 15-20branches of the uterus on

each side

Egg:

undistinguishable

from T. scolia

Scolex: no hooks


T i li ( k t )


15/26

Taenia solium (pork tapeworm) Distinguishing features

Cestode (tapeworm)

Eosinophilia

Hooks on scolex


Calcified cysticerci in brain, muscle onCT, biopsy

Diseases Intestinal infection: ingestion of

cysticerci in undercooked pork adultscolex adheres to intestine consumes host food malnutrition

Cysticercosis: ingestion of eggs from

feces larvae form cysticerci in brain,eye, skeletal muscle neurologicaldefects (seizures, hydrocephalus, focaldeficits), blindness

Treatment

Praziquantel

Proglottid: 7-13 branches

of uterus on each side

Scolex: hooks

Cysticerci on muscle biopsyPlatyhelminthes (flatworms)

h ll b h l (f h )


16/26

Diphyllobothrium latum (fish tapeworm)

Distinguishing features

Cestode (tapeworm)

Eosinophilia


Pathogenesis

Ingestion of larvae in poorly

cooked freshwater fish

absorbs vitamin B12

megaloblastic anemia

Treatment

Praziquantel

Egg: ellipsoidal with operculum @ 1 end

Proglottid: broader than it is longPlatyhelminthes (flatworms)

E hi l (d t )


17/26

Echinococcus granulosus (dog tapeworm) Distinguishing features

Cestode (tapeworm) with only 3proglottids

Eosinophilia (Calcified) cysts on CT, X-RAY

Presence of daughter cysts withinhydatid cyst is pathognomonic

Pathogenesis

Eggs ingested from dog feces larvae form hydatid cysts in liver,lung

Diseases Hydatid Cyst Disease

Cysts enlarge mass effect abdominal pain, biliary obstruction

Cysts rupture severe anaphylaxis,cough, chest pain

Treatment Surgical removal of cysts

Albendazole

Gross: hydatid cysts in liver

Micro: hydatid cysts

3 proglottids

CT: hydatid cysts of the liver and left kidneyPlatyhelminthes (flatworms)


18/26

Nematodes (roundworms)

E bi i l i ( i )


19/26

Enterobius vermicularis (pinworm) Distinguishing features

Most common helminth infection inthe U.S.

Primarily infects children

Diagnose with Scotch tape test:adhere tape to perianal region andexamine for eggs

Pathogenesis Fecal-oral transmission eggs

ingested

Diseases Perianal itching: females migrate to

perianal area @ night to lay eggs

Treatment Pyrantel pamoate

Albendazole, mebendazole

Egg: flattened sidewith larvae inside


T i h i t i hi i ( hi )


20/26

Trichuris trichiuria (whipworm) Distinguishing features

Barrel-shaped eggs with

bipolar plugs in stool

Pathogenesis

Eggs incubate in moist soil

for 3-6 weeks ingested Diseases

Diarrhea

Abdominal pain

Rectal prolapse

Treatment

Mebendazole, albendazole Egg: football-shaped with bipolar bumps

Whipworm



21/26

Necator americanus Ancylostoma duodenale


22/26

Necator americanus, Ancylostoma duodenale

(hookworm) Distinguishing features

Eggs in stool

Eosinophilia

Pathogenesis Filariform larvae penetrate skin of

bare feet (local itching) lungmigration (pneumonia) swallowed attach to SI

Diseases Pneumonia

Gastroenteritis Iron-deficiency anemia:

bloodsucking from SI

Treatment

Mebendazole, pyrantel pamoate

Eggs in stool: oval,

transparent, with 2-8 cell-

stage visible inside


Strongyloides stercoralis (threadworm)


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Strongyloides stercoralis (threadworm) Distinguishing features

Larvae in stool

Eosinophilia Pathogenesis

Filariform larvae penetrate skinof bare feet (local itching) lung migration (pneumonia) swallowed eggs hatch inintestinal wall inflammation

Diseases Pneumonia

Gastroenteritis Severe autoinfection (in IC)

Treatment Thiabendazole, ivermectin

Larvae in stool


T i hi ll i li


24/26

Trichinella spiralis Distinguishing features

Eosinophilia, serum muscle enzymes

Cysts with larvae on muscle biopsy

Pathogenesis Encysted larvae in undercooked meat

ingested

Diseases

Gastroenteritis: worms penetrate intestinalmucosa

Splinter Hemorrhages

Periorbital swelling

Myalgia: larvae encyst in skeletal muscle

Severe infections Myocarditis: most common parasitic cause

Larvae migrate to heart

Encephalitis: larvae migrate to brain

Treatment Mebendazole against worms in SI

Encysted larva in striated muscle


Wuchereria bancrofti (Pacific Islands Africa) Brugia


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Wuchereria bancrofti (Pacific Islands, Africa), Brugia

malayi (Southeast Asia) Distinguishing features

Microfilariae in blood @ night

Eosinophilia

Pathogenesis Transmitted by mosquito

carried to lymph nodes ofgenitals, lower extremities

Diseases Recurrent fever and swollen

lymph nodes

Elephantiasis: edema, scaly skinin legs, scrotum

Fibrosis around dead worms inlymph nodes lymphaticobstruction

Treatment Diethylcarbamazine against

microfilariae Nematodes (roundworms)

Microfilaria of W. bancroftion blood smear

Elephantiasis of the leg and hydrocele

O h l l


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Onchocerca volvulus Distinguishing features

Found in Africa, Central & SouthAmerica

Microfilariae on skin biopsy

Pathogenesis Transmitted by black flynear rivers

Diseases Skin nodules: fibrosis around adults

Hyperpigmented pruritic rash:inflammation as microfilariae migrate

Lizard skin: dry, scaly skin fromintraepithelial granulomas

River blindness: microfilariae migrateto the eye

Treatment Ivermectin against microfilariae

N d ( d )

Microfilariae on skin biopsy

Adults in nodules

Fibrotic skin nodules

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