Arbo-Parasites Flashcards
Leishmaniases are what type of parasite?
protozoa
where do leishmania parasites reside within the host?
intracellularly inside macrophages
what is the vector for leishmaniasis?
sand flies
life cycle of leishmania parasite between humans and sand flies
sandfly injects promastigote into human, phagocyt by macrophage, turns into amastigote (pathogenic), amastigotes multiply in cells, ingested when a sand fly bites, transform into promastigotes in midgut of sandfly
in what ways can leishmania be transmitted other than through sand fly vectors?
parenteral, congenital, occupational (needle stick), sexual
New World leishmania species cause ______ leishmaniasis.
cutaneous, mucocutaneous
cutaneous leishmaniasis
self-healing, slowly enlarging nodule at bite site that turns into ulcer and leaves hypo-pigmented scar
mucocutanous leishmaniasis
nodular and ulcerative lesions of the oral-nasal-pharyngeal mucosal surfaces, nasal septum lesion or hoarseness is first indication, Brazilian strain
CL and ML are generally confined to?
Central America, tropical South America, Middle East and Northern Africa
visceral leishmaniasis
much more severe disease with classic pentad: fever, cachexia, splenomegaly, pancytopenia, high levels of IgG
90% of VL is in what 5 countries?
Bangladesh, India, Nepal, Sudan, & Brazil
Leishmaniasis is exacerbated by?
primary immune disease (AIDS), immunosuppressive drugs, organ transplantations
Diagnosis of leishmaniasis in the US
find the parasites (invasive procedure: scrapes, aspirates, biopsies) – can visualize/stain amastigotes inside macrophages (promastigotes in culture) or do PCR; histo not very sensitive
parasite burden is highest in what type of lesihmaniasis?
visceral
other countries have this diagnostic test, which is similar to a PPD test and very helpful at detecting organism at low burden
DTH (delayed type hypersensitivity test)
there are specific drugs to treat certain strains of CL, but this drug covers everyone
antimony
Treatment for VL
Amphotericin B (resistance, esp. in India), pentavalent antimony
How to prevent leishmaniasis
sandflies are terrible fliers, windy areas are safer, bed nets, rodent control
What is schistosomiasis?
waterborne parasitic fluke infection (flat worms) – 97% of cases in poor regions of Africa
Schistosomiasis life cycle.
Cercariae released by snails into water, penetrate humans, enter circulation, migrate to portal vein and mature into adults, paired worms lay eggs that are shed in stool or urine, hatch releasing miracidia which penetrate snail and develop into sporocysts, then released as cercariae
Age distribution of schistosomiasis
frequently affects young teen boys, called “male menarchy” because boys pee red in their teens
risk factors for urinary schisto
male, close to water source, previous infection, 8-13 yo
the majority of schisto infections are?
urinary/urogenital
Diagnosis of schisto
none, serology is negative for months
What determines whether schisto is urinary vs. intestinal/hepatic?
depends on where the worms migrate to lay their eggs (haematobium to venous plexus of bladder, mansoli to mesenteric vessels)
how to schisto evade host immune response?
accretion of host molecules on their surface!
what do schisto eggs do once they are laid?
100/day; spikes on outer shell + dissolving enzymes = bore their way through blood vessel to enter bladder or intestine (leads to mechanical damage of vessels, blood loss, granulomas, inflammation)
symptoms of urinary schisto lead to what long-term problems?
growth retardation, undernutrition, cognitive delays, poor performance, renal failure, infertility in women, increased transmission of HIV
symptoms of intestinal schisto leads to?
liver enlargement, diarrhea, loss of appetite, liver disease
diagnose schisto by?
detecting s. haematobium eggs in urine, s. mansoni eggs in stool
treatment and control of schisto
praziquantel
African trypanosomiasis is transmitted by _________.
tsetse fly
African sleeping sickness life cycle.
metacyclic trypomastigote injected by fly, enters bloodstream, multiplies, blood meal of tsetse fly, turn into procyclic trypomastigotes, leave gut and turn into epimastigotes, multiply in saliva, turn into metacyclic trypomastigotes
West African sleeping sickness has a ____ reservoir, likes ____ climate, and causes _____ disease.
human reservoir, humid climate, chronic disease
East African sleeping sickness has a _____ reservoir, likes _____ climate, and causes _____ disease.
wild animal reservoir, savannah, acute disease
primary symptoms of African Sleeping Sickness
chancre, posterior lymphadenopathy
secondary African Sleeping Sickness
system disease (fever, wasting)
advanced African Sleeping Sickness
CNS disease (lethargy, insomnia, seizures, coma) – starve while seizing
trypanosoma’s main virulence factor is?
antigenic variation (periodically switch their variable surface antigen – leads to waves of parasitemia)
Treatment for african sleeping sickness
pentamidine or suramin (doesn’t work for late stage CNS)
Chagas Disease life cycle.
triatomine bug bites, poops, rubbed into wound, once inside cells metacyclic trypomastigote turns into amastigote that multiplies in tissue, transforms into trypomastigote to reinfect other cells or be ingested by triatomine bug (turns into epimastigote briefly inside bug)
Geographic distribution of Chagas.
South America, central america, USA
signs of acute Chagas disease
Romano’s sign (periorbital swelling), acute febrile illness, severe disease in 1%
Chagas Heart Disease develops ______ years after initial infection.
10-20 years later!
Chagas can also cause?
toxic mega colon (loss of neurons in the gut)
Diagnosis of chronic chagas disease
xenodiagnosis (put bugs on them?), indirect fluorescent antibody
Treat acute Chagas disease with?
Benznidazole, Nifurtimox (neither FDA approved, must ask CDC)
Treat chronic Chagas disease with?
No Rx :(, only management
Malaria
obligate intracellular eukaryotic parasite that infects liver cells and red blood cells
Malaria rates are currently _____.
decreasing!
Malaria infections in pregnant women cause?
low birth weight babies
Malaria is transmitted by the _______ mosquito
female anopheles
Malaria life cycle
mosquito bites human, injects sporozoites that are in circ for only 30 min, enter liver (asymptomatic stage), merozoites rupture from liver to infect RBCs (symptomatic stage), turn into trophozoites, then schizonts that rupture and become gametocytes that have sex inside mosquito
The agent in 98% of malaria infections is…
plasmodium falciparum
Why is malaria falciparum so vicious?
invades all RBCs (not just certain types)
Clinical course of uncomplicated malaria
prepatent period (asymptomatic while parasite multiplies in liver), paroxysm (shaking chills, high fever as merozoites are released from RBCs), HA, nausea, vomiting, malaise, etc.
Severe malaria
cerebral (coma, seizures), severe anemia due to RBC lysis, multi organ failure (iCAM, parasite proteins on RBC surface cause them to stick to organ walls)
In areas with lots of infected anopheles, adults are ______.
semi-immune
first time mothers infected with malaria have low birth weight children because?
falciparum parasite turns on specific genes to promote placental cytoadherence, which decreases nutrients crossing the placenta
Vivax malaria is different from falciparum in that it is?
chronic (dormant liver stage
Liver stages of malaria can be treated with ______ except in ______ patients.
primaquine, causes hemolyic anemia in G6PD deficient patients
______ remains prevalent because it is protective against malaria.
sickle cell trait (heterozygote), thalassemia
Diagnosis of malaria
Giemsa blood smears, rapid antigen tests, PCR (species specific)
immunochromatography to diagnose malaria
distinquishes between both major strains, but big variation in quality and can breakdown in areas with poor transportation
this kills female anopheles mosquitos and is non-toxic to humans
indoor residual spray (insecticide)
the mainstay therapy for malaria is?
quinine-related antiobiotics with increasing resitance (newest is Artemisinin Combination Therapy)
Artemisinin is derived from?
chinese herbal remedy
Is there any resistance to artermisinin?
looks more like tolerance, starting to see prolonged clearance time, don’t know what this means
Is there a future for malaria vaccines?
Probably not? (not in the blood long enough)
