Parasitic Diseases Flashcards
first-line tx for severe malaria
Artemisinin Derivatives (artemether-lumefantrine, artesunate)
**Retains activity vs all spp
- SEs: hemolysis can occur after IV admin (post-artesunate delayed hemolysis) - can occur >7 days after infusion
- resistance noted to be appearing in SE Asia (esp Cambodia)
Chloroquine (4-aminoquinolone)
in areas of known chloroquine sensitivity (i.e. Central America, Panama Canal)
- SEs: pruritis (palms, soles, scalp), cardiac and CNS tox w/ IV tx
SEs of 4-aminoquinolones (antimalarials)
- chloroquine
- mefloquine
- quinine/quinidine
- pruritis (palms, soles, scalp), cardiac, CNS
- dizziness, diarrhea, N/V. Neuropsych = most serious
- cinchonism (combo of tinnitus, deafness, HA, visual disturbances, dysphoria, vomiting, postural hypotension). Cardiac tox (postural hypotension, QT prolongation, ventricular arrhythmias)
First line for malaria ppx (or tx for uncomplicated falciparum/unknown spp) in region w/ chloroquine resistance
atovaquone (an 8-aminoquinolone) + proguanil
Also w/ activity vs: Babesia, toxo, crypto, leishmaniasis, trichomonas
General dx of intestinal, liver, keratitic amebae
two stages: trophozoite (active feeding stage) or cysts (infectious resting form)
- intestinal - both forms can be visualized via microscopy of stool sample. Preferred = stool Ag or PCR. Can see on histopath using PAS or H&E
- liver - imaging (u/s, CT), serology most helpful, or can aspirate and use PCR
- keratitis - corneal scraping for microsopy and cx
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Entamoeba histolytica (diff to distinguish from other spp)
(L = trophozoite w/ ingested RBCs; R = cyst)
- cyst - 12-15um; trophozoite - >20um
- will see trophozoites only in abscesses
chronic severe diarrhea in children and IC adults
a cause of cholangitis in AIDS
cryptosporidium
Dx of Giardia
- usually via demonstration of cysts in stool (occasionally trophozoite)
- 11-12um, oval, 4 nuclei
- trichrome, iron-hematoxylin stains
- variable shedding - requires multiple stool samples
- bx tissue - trichrome/Giemsa stain
opportunistic intestinal pathogens
(HIV-assoc diarrhea, as well as diarrhea in other IC pts)
think of intestinal coccidia and microsporidia
= cryptosporidium, cyclospora, cystoisospora, sarcocystis
*obligate intracellular pathogens
protozoan infection w/ myositis and fever
Malasia
sarcocystitis
Free-Living Amebae Pathogens
- Naegleria fowleri
- Acanthamoeba
- Balamuthia mandrillaris
- Sappinia pedata (new, emerging)
dx of acanthamoeba
can be cx on nutrient agar w/ layer of GN bacteria (they feed on bacteria and act as hosts for legionella, MAC, listeria)
most reliable = 18S rDNA sequencing
Geo spread of malaria
- falciparum
- vivax
- ovale
- malariae
- all tropical regions (densest in Sub-Sarahan Africa)
- most prevalent in Asia (also Central/South America, Middle East, N Africa)
- Africa, Asia
- limited to SE Asia
Which malaria spp persist in liver as hypnozoites and cause relapse?
vivax, ovale
“It’s not OVer!”
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P falciparum
- parasitised RBCs not enlarged
- RBCs containing mature trophozoites
- total parasite biomass = circulating parasites + sequestered parasites
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P vivax (ring, trophozoites, schizonts)
- parasites prefer young RBCs
- RBCs enlarged
- all stages present in peripheral blood
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P malariae (ring, trophozoites, schizonts)
- parasites prefer old RBCs
- pRBCs not enlarged
- all stages present in peripheral blood
Epi of Trypanosomal brucei sbb
- favors riverine vegetation
- favors savannah
- Tb gambiense
- Tb rhodesiense
related to outdoor activities
Most often detection of helminthic diseases
ID adult worm, egg, or larvae
Soil transmitted helminths/nematodes (roundworms)
- Ascaris lumbricoides
- Necator americanus
- Ancylostoma duodenale
- Trichuris trichiura
- Strongyloides
- Enterobius (pinworm)
raccoon exposure
severe encephalitis (eosinophilic) or ocular infection
Baylisascaris procyonis (roundworm)
Taiwan, Thailand
eating snails
eosinophilic meningitis
angiostrongyliasis (caused by molluscun-borne rat lungworm)
humans = incidental hosts
Dracunculiasis - epi, life cycle, infection
-
epi - poor communities in rural areas
- Chad, Ethiopia, Mali
- transmitted via small crustacean vector (Cyclops spp) - seasonal
- larvae swallowed in stagnant water → swallowed and penetrate through gut wall into abd cavity/retroperitoneum → females induce a blister, which forms an ulcer, causing person to stick leg in water, where female emerges from SQ tissue
Vector for wuchereria bancrofti
mosquitos (culicine most common; also Aedes in Pacific Islands, Anopheles in Africa)
vector for Onchocerca volvulus
blackfly - Simulium damnosum
requires running water for larval development, so transmission occurs in close prox to water sources
vector of loa loa
deer fly (Chrysops spp) = day biters
West and Central Africa
natural hosts and epi of Fasciola hepatica
found in sheep-rearing areas (highest prevalence in Bolivia, Peru)
acq by ingestion of water/leafy plants that grow in fresh water
humans = accidental hosts
schistosoma spp w/ terminal spine
S haematobium
schistosoma spp that looks like the rising sun
S japonicum
Schistosoma spp with subterminal spine
S mansoni
intestinal trematode (fasciolopsis buski = giant fluke)
how transmitted
snails are important vectors
ingestion of raw watercress, bamboo, water chestnuts
alveolar echinococcus hosts
E multilocularis
definitive host = raccoons, foxes, domestic dogs
Stain most useful for ID of blood parasites
Giemsa stain
Timing of blood samples to coincide w/ peak time of microfilaremia
Day (1000-1400)
Night (2200-0200)
Anytime
- Day: Loa loa
- Night: W bancrofti, B malayi, B timori
- Anytime: Onchocerca, Mansonella
Key areas of distribution for P vivax
Korea
former Soviet Union
Fever patterns of malaria
- erythrocyte cycle duration = 48hrs. Fever pattern = irregular tertian fever
- ”” = 48hrs. Fever pattern = tertian fever
- same as #2
- ”” = 72hrs. Quartan fever
- ”” = 24hrs. Quotidian fever
- P falciparum
- fever w/ no clear pattern. sounds “false”
- P vivax
- P ovale
- P malariae
- malariae is “meh” about fever (only occurs every 4 days or so)
- P knowlesi
- every day you “knowlesi” the fever is coming
Mgmt of complicated malaria
ideal = IV artesunate
alt: quinine or chloroquine
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Romana sign
u/l palpebral edema at site of inoculation of T cruzi (Chagas)
Acute and Chronic phases of Chagas
- Acute: fever, inflammation @ inoculation site (Romana sign if involves conjunctiva), local LAD, HSM
-
Chronic:
- cardiac - biventricular HF, electrical abnormalities, thromboembolic disease, apical aneurysm
- GI - megaesophagus or megacolon, motility dysfunction
morphologic features of babesiosis (via thick/thin smear, stained via Wright or Giemsa)
- infected RBCs are normal sized
- no intracellular pigment
- delicate rings w/ varying morphologies
- multiply infected RBCs
- extracellular forms common (NOT seen in malaria)
- maltese cross (rare)
Toxoplasma Dx
serology, PCR, tissue all available
- IgG+/IgM- : past infection, NOT acute
- IgG-/IgM+ : likely acute infection
- if both IgG and IgM+ : could be either acute or chronic. IgM Abs can remain + for up to 12mos
in adv HIV or SOT: helpful to have IgG results prior to tx, as they can be misleading when IS. Will go with clinical picture most often + histo or PCR
Tx of toxoplasma
- Immunocompentent: self-limited. If end-organ disease, can use pyrimethamine + sulfadiazine + leucovorin x2-4wks
- Immunocompromised: either TMP/SMX or dapsone+pyrimethamine or atovaquone x6wk minim until reconstitution
- from drinking water or swimming pools (R to chloronation)
- Immuncompetent: asx - acute - subacute - chronic high V watery diarrhea (can continue d/t autoinfection from poor hand hygiene)
- Immunocompromised: profound D and severe wasting
- can have biliary tract involvement (acalculous chole, cholangitis, pancreatitis)
cryptosporidium
Dx cryptosporidium
Ag detection assays (DFA, ELISA)
NAAT
stool microscopy (4um) via mAF stain
Tx of cyclospora
TMP/SMX
Tx of cystoisospora
TMP/SMX
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giardia duodenalis
- left: trophozoite
- pear-shaped, 2 nuclei, flagella
- righ: cyst
- 10-14um, mature w/ 4 nuclei, immature w/ 2 nuclei
granulomatous skin lesion in midface/nose → wks-mos of HA, F, visual changes, behavioral changes, focal deficits, increased ICP
balamuthia mandrillaris
two organisms that will show feeding tracks if cultured on a lawn of nonnutrient agar covered with enteric bacteria (E coli)
Acanthamoeba
Naegleria
Early: eosinophilia + F + dry cough/SOB/CP
Most pathology after 6-8wks: malnutrition, pancreatic/hepatobiliary d/t obstruction, intestinal obstruction rare
consider ascaris infection
50-70 x 40-50 um from stool sample
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Ascaris lumbricoides
Tx: albendazole x1 dose
recurrent rectal prolapse
tichuris trichiura
chronic abdominal pain
eosinophilia
iron deficiency anemia
think hookworms (necator, ancylostoma)
migratory urticarial rash
fast moving
may have periumbilical purpura
larva currens w/ strongy
co-infection a/w strongy hyperinfection
HIV
HTLV-1
clinical manifestations of loa loa
- calabar swelling - angioedema of face and exposed extremities
- myalgias, arthralgias, fatigue
- “eye worm” - migration to conjunctiva
- endomyocardial fibrosis leading to myocarditis
- immune-complex nephropathy
- encephalitis (? d/t rx w/ DEC)
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calabar swelling of R hand d/t angioedema from loa loa worm traveling through SQ tissue
Mazzotti reaction
fever, urticaria, swollen/tender LN, tachycardia/hypotension, edema, abdominal pain, followed by fatal encephalopathy ~7 days posttx w/ DEC
d/t rapid killing by DEC of microfilaria in high burden loa loa infection → acute severe inflammatory reaction
**also occurs w/ Onchocerciasis
pretreat w/ albendazole or apheresis
also avoid DEC in individuals co-infected w/ onchocerciasis (tx oncho first, then can tx w/ DEC afterwards)
What and where
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S japonicum
China and SE Asia
What and where
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S mekongi
Mekong river basin (Cambodia to Laos)
What and where
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S haematobium
sub-Saharan and Northern Africa
What and Where
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S intercalatum
western/central Africa
What and where
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S mansoni
sub-Saharan Africa and S America
Tx of schistosomiasis
- praziquantal = gold standard
- not recommended unless dx microscopy and/or serology
- not initiated until at least 6wks from presumed exposure (need full adult maturation, as PZQ doesn’t work vs larval stages)
- exposes parasite Ag to host immune system
- Adult disintegration can release a bunch of eggs
- expulsion by peristalsis
- confirm cure w/ egg excretion surv 2-6mos
complications of chronic infection with fasciola hepatica
- biliary
- pain, cholangitis, cholelithiasis, obstructive jaundice, pancreatitis
- sclerosing cholangitis
- biliary cirrhosis
General tx of parasitic disease
- nematodes
- trematodes
- cestodes
- nematodes (roundworms) - albendazole (except for…)
- strongy - ivermectin
- wuchereria - DEC
- loa loa - DEC (except co-infection w/ oncho or w/ heavy burden)
- oncho - ivermectin (avoid DEC)
- trematodes (flukes) - PZQ
- except fasciola - triclabendazole
- cestodes (tapeworms) - albendazole and/or PZQ
IC pt w/:
- encephalitis w/ mass lesions
- HSM
- F
- myocarditis
chagas (T cruzi)
IC pt w/:
- visceral or cutaneous disease noted (reactivation)
- visceral - F, HSM, pancytopenia
leishmania
IC pt w/:
- encephalitis w/ mass lesions
- pneumonitis
- retinitis
toxoplasma
dx and tx of microsporidia
- dx: modified trichrome stain, calcofluor white, IFA
- tx: albendazole
punctate keratoconjunctivitis (contact lens use, after eye surgery, bathing in hot springs)
Many spp of microsporidia (including vittaforma corneae)
*a microsporidia (obligate intracellular fungi) - produces extracellular infective spores
Encephalitozoon intestinalis
- watery diarrhea
- biliary disease
- disseminated disease (liver, kidney, lung, sinuses)
*a microsporidia (obligate intracellular fungi) - produces extracellular infective spores
enterocytozoon bieneusi
- watery diarrhea
- biliary disease (cholangitis, acalc chole)
*a microsporidia (obligate intracellular fungi) - produces extracellular infective spores