all parasites
TRANSCRIPT
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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
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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
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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
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Trichomonas vaginalis Distinguishing features
Flagellate: move with flagella
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
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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
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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
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Trypanosoma cruzi Distinguishing features
Flagellate: move with flagella
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
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Trypanosoma brucei Distinguishing features
Flagellate: move with flagella
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
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Leishmania species Distinguishing features
Flagellate: move with flagella
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
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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
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Platyhelminthes (flatworms)
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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
Platyhelminthes (flatworms)
T i i (b f )
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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
Platyhelminthes (flatworms)
T i li ( k t )
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Taenia solium (pork tapeworm) Distinguishing features
Cestode (tapeworm)
Eosinophilia
Hooks on scolex
Proglottids, eggs in feces
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 )
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Diphyllobothrium latum (fish tapeworm)
Distinguishing features
Cestode (tapeworm)
Eosinophilia
Proglottids, eggs in feces
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 )
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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)
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Nematodes (roundworms)
E bi i l i ( i )
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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
Nematodes (roundworms)
T i h i t i hi i ( hi )
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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
Nematodes (roundworms)
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Necator americanus Ancylostoma duodenale
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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
Nematodes (roundworms)
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
Nematodes (roundworms)
T i hi ll i li
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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
Nematodes (roundworms)
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