Protozoan parasites Flashcards
The definitive host of Toxoplasma gondii is __
Cat
The __ form of toxoplasma gondii is excreted in feces; infective stage (takes a day or so for it to actually become infectious)
Which form lives in tissue cysts? Which form is slow growing vs fast growing?
Tissue cysts: contain bradyzoites >> slow growing form
Tachyzoites: fast growing and replicative form (invades cells and get transformed to become tissue cysts)
How is toxoplasma transmitted?
Transmission:
Ococysts: contaminated food/water, cat litter
Tissue cysts: present in undercooked meat (pork, lamb)
Tachyzoites: transplacentally, organ transplant, blood transfusion
Which toxoplasma form is responsible for acute toxoplasmosis?
Which form is responsible for chronic infection?
Acute: mediated by tachyzoites. Infection = generally subclinical, can cause chorioretinitis if severe (rare)
Chronic: mediated by tissue cysts aka bradyzoites. Infection = mainly asymptomatic (these things activate the imune response which keeps infection at a low level, but can also cause reactivation)
How does a baby get congenital toxoplasmosis?
Congenital toxoplasmosis:
Result of acute maternal infection **during** first part of pregnancy (the earlier along the pregnancy that mom gets infected, the worse the outcome. Can result in a bunch of things going wrong later in life, including ocular toxoplasmosis)
What immunodeficiency state/disease is toxoplasmosis closely ass’d with? (hint: itsthe same one TB is ass’d with)
HIV
How do you diagnose toxoplasmosis acute/chronic/congenital infection? (hint: 2 antibodies measured)
Dx: IgM and IgG titers (see below for specifics)
3 things that make up presumptive Dx of toxoplasmosis
History
Presence of hypodense lesions enhancing with contrast on CT/MRI
+ve antibody test for toxoplasmosis
How do you confirm Dx of toxoplasmosis?
Dx confirmation:
If patient is improving upon therapy
CSF culture/staining + PCR based assay
Rx for toxoplasmosis
Rx for toxoplasmosis:
Pyrimethamine + sulfadiazine + Leukovorin (folic acid suppl)
Rx for toxoplasmosis in pregnancy
Rx for toxoplasmosis in pregnancy:
If infection suspected, start spiromycin
Confirm infection using amniotic +/- fetal blood sample PCR
- infected fetus, continue spiromycin until delivery; + infected fetus, terminate pregaz or use triple therapy (pyrimethamine, sulfadiazine, leucovorin)
Which drug is used for maintenance therapy for toxoplasmosis prevention in HIV patients
TMP/SMX
___ causes Chagas disease and is transmitted by ___
Trypanosoma cruzi causes Chagas disease and is transmitted by triatomine bugs
Describe the lifecycle of trypanosoma cruzi
Triatomine blood meal >> bugs inside triatomine feces >> host scratches bite site >> bug entry into host cells > invasion of muscle tissue >> differentiation into amastigotes >> replication and exit as trypomastigotes >> invasion of other cells
Transmission of Trypanosoma cruzi: triatomine bug takes a blood meal and then defecates. The parasite is inside the feces and when the human host scratches the bite site, the feces make their way into the host and invade muscle cells (smooth or cardiac muscle.
Inside the muscle, the bug differentiates into an amastigote which multiples within the cell then releases more bugs (now trypomastigotes that invade other cells)
Presentation and Dx of acute Chagas disease
Acute Chagas disease: presents with non specific symptoms/symptoms mimicking mononucleosis
Dx: blood smear and Giemsa stain
2 issues caused by chronic Chagas disease are __(hint: one of them involves your favorite organ!)
Cardiac disease
GI issues
Chronic Chagas cardiomyopathy can cause what syndromes of heart disease?
Congestive heart failure
Arrhythmias
Complete heart block
Sudden death
Thromboembolism
GI disease caused by chronic Chagas disease can manifest as ___ and ___ (hint: they’re both megas)
Megaesophagus and megacolon
Dx of Chagas disease (non-chronic)
Blood smear +/- wet mount
Serology
Dx of Chagas disease (chronic infection)
Serology
Parasite isolation from blood culture or xenodiagnosis
PCR
Imaging/ECG/ +/- GI studies
Rx for Chagas disease (2 drugs)
NiFURtimox (like fur, you know, the kind that people wear)
BENZnidazole (like a mercedes benz)
Leishmania spp cause __ and are transmitted by ___
Leishmania spp cause Leishmaniasis and are transmitted by phlebotomine sand flies
Name the 3 kinds of Leishmaniasis that exist
Cutaneous
Mucosal
Visceral
Describe the Leishmania life cycle
Leishmania infect host macrophages >> transformation into amastigotes >> replication and spread to other macrophages
**note that the promastigote stage is inside the sand fly
How is leishmanisis controlled by the immune system? (which cytokines are released?)
Interferon-g, IL-12, IL-1, TNF-a
List the type of immune response (humoral/visceral) seen in each type of leishmaniasis
Full blown visceral disease (symptomatic): (ineffective) humoral response
Visceral subclinical/treated: + cellular (some humoral)
Cutaneous: mostly cellular
Mucosal: Mostly cellular
(see below)
Visceral leishmaniasis is characterized by __ and __
Visceral leishmaniasis: characterized by hepatosplenomegaly and infected macrophages
Visceral leishmaniasis is caused by ___
Visceral leishmaniasis is caused by Leishmania donovani
Mucosal leishmaniasis is mediated by ___ and is caused by which spp of Leishmania?
Mucosal leishmaniasis is mediated by a dysregulation of the immune response to infection
L braziliensis
Disseminated cutaneous Leishmaniasis: due to __
Which spp of Leishmanisis causes disseminated cutaneous Leishmaniasis?
Disseminated cutaneous Leishmaniasis: due to lack of cell mediated response
L. amazonensis, mexicana
What disease process is this and which bug causes it?
Cutaneous leishmaniasis (sand fly bites host and leaves area of central necrosis with infected macrophages)
Caused by L amazonensis or mexicana
Cutaneous leishmanaisis in the Middle East and Africa are is caused by which Leishmania spp?
L tropica and L major (zoonotic)
Ways to Dx visceral leishmaniasis (3)
Bone marrow culture/smear
Serology
Leishmanin skin test (starts out -ve but becomes +ve w/ treatment)
Ways to Dx cutaneous leishmaniasis (4)
Biopsy
Serology
Leishmanin skin test
Speciation
Rx for Leishmaniasis (which 2 drugs are used in the US and which one is used elsewhere in the world?)
Liposomal amphotericin B
Miltefosine
(not in US): pentavalent antimony
