Microbiology-Malaria Flashcards by John Doe

What are the 5 species of malaria that infect humans?

P. falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi.

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How do you differentiate a malaria parasite from a platelet?

Platelets have more than one shade of the same color. Parasites always have a magenta nucleus and a blue cytoplasm.

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What stage is this parasite in?

Ring trophozoite: note the ring, magenta chromatin and blue cytoplasm.

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What stage is this parasite in?

Growing trophozoite: note the pigment granules, blue-purple cytoplasm and magenta chromatin.

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What stage is this parasite in?

Mature trophozoite

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What stage is this parasite in?

Young Immature Schizont

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What stage is this parasite in?

Old Immature Schizont

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What stage is this parasite in?

Mature Schizont: note the pigment clump and merozoite

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Parasites that leave red cells the same color and size or slightly smaller than surrounding cells.

P. falciparum, P. malariae or P. knowlesi

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Parasites that do not leave red cells the same color and size.

P. vivax and P. ovale.

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This parasite has only small delicate rings, Mauer’s clefts, no trophozoites and very rare schizonts. It’s gametes look like bananas.

P. falciparum

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Parasites with band and basket forms, pigment, a few chunky merozoites and all stages of development.

P. malariae and P. knowlesi

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Parasites that are extremely ameboid, have pigment, Schuffner’s dots and many merozoites?

P. vivax

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Parasites that are ameboid, have pigment and fimbriae, Shuffner’s dots and fewer merozoites?

P. ovale

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What parasite is seen on the thick smear below?

P. falciparum

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What parasite is seen on the thick smear below?

P. malariae

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What parasite is seen on the thick smear below?

P. vivax

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What parasite is seen on the thick smear below?

P. ovale

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Fill in the blanks

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OIFs

Oil immersion fields used to identify presence of malaria under microscopy

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Quantitative measurements of malaria

What type of pathogen is malaria? What does it infect?

Protozoa. It infects RBCs, these don’t have MHCs so it’s a good place to hide.

A 28 year old woman presents with body aches, chills and a fever that morning. She has been working in Cameroon for the past two years. What do you need to do next?

Get a blood smear immediately. In non-immune patients falciparum malaria can kill in 24 hours.

Patient returns from the tropics with a fever, what is the 1st thing you need to check?

Malaria, malaria, malaria! Check in any traveler with a fever, this is why you always have to ask a travel history.

Risk factors for severe malaria

Nominate individuals (immunity wanes after living in non-endemic areas for ~5 years), children \< 5, pregnant women, asplenic patients.

5 species of malaria? Vector? Reservoir?

P. falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi. Anophelene mosquito is the vector. All human reservoir except P. knowlesi which is found in macaques and people.

Malaria most likely to kill people

P. falciparum

Life cycle of malaria

Sporozoites injected into blood stream by mosquito -\> Transformation into 10,000+ merozoites in hepatocytes -\> Released back into blood stream -\> Infects RBCs -\> Forms trophozoites -\> Matures into schizonts -\> Forms more merozoites -\> RBC ruptures and they infect more cells.

Liver cells infected with malaria without amplification.

Hypnozoite: only happens with P. vivax and P. ovale. They remain dormant in liver cells for weeks to years and cause cyclic fevers.

Malaria that takes the longest time to burst out of liver cells and cause infection

P. malariae. However, other types can take longer if chemoprophylaxis is not perfectly adherent.

Malaria species that can cause an asymptomatic chronic erythrocyte infection for 20+ years that will present with fever at immunosuppression

P. malariae

Necessary for spread from one person to another

Uptake of male and female gametocytes by mosquito to form trophozoites that will be injected from the salivary gland of the mosquito into another person.

Traits in humans that evolved in malaria endemic countries

Sickle cell trait: red cells that are infected are more readily cleared because of sickling. G6PD. Duffy antigen negative RBCs (necessary for entry into RBCs)

Classic symptoms of malaria

Fever, chills, headache

Symptom that presents in travelers 20% of the time when they have malaria?

Abdominal pain/diarrhea

Lab values that hint toward malaria

Elevated LDH, anemia and elevated bilirubin because of hemolysis.

3 clinical types of malaria

Acute uncomplicated (all species), severe and hyper-reactive malarial syndrome (tropical splenomegaly).

A patient comes in with chills, then develops a fever of 105 and then the fever breaks as the patient begins to sweat. These episodes last 6-10 hours, then recur. How many days apart would you expect to see these paroxysms if he was infected with P. vivax, P. ovale or P. falciparum? What if it were P. malariae?

Vivax, ovale and falciparum is seen every 2 days (tertian fever, basically every other day). P. malariae is every 3 days because this is how the parasites sync up with the red blood cell cycles.

How does malaria kill people?

Severe malaria = damaged tissues. This differs by age. CHILDREN: cerebral malaria, respiratory distress and severe anemia. ADULTS: renal failure, hypoglycemia, shock and coagulopathy. Note that these are see when parasitemia \> 2% in falciparum infection

Important prognostic factors of malaria

Acidosis and parasitemia (\>1% makes you worried).

Why are falciparum infections most lethal?

They have no predilection for RBC age and no inhibition on the degree of parasitemia

Why do tissues become hypoxic and patients acidotic with malaria?

Parasitized RBCs become sticky, stick against capillary walls (sequestration). This results in ischemia distal to the region of RBC sequestration. This is the cause of acute encephalopathy in patients with cerebral malaria, not infection of neurons.

Why do people become hypoglycemic with malaria?

Increased metabolic rate due to infection and decreased consumption

Why do people have renal failure with malaria?

Filtration of hemolyzes RBC products

Why do people have anemia with malaria?

Hemolysis, sequestration and splenic removal.

Diagnosing malaria

Blood smear, antigen testing and PCR.

What do you do if someone has a fever but the malaria test was negative yesterday?

Test again

Presentation of someone with malaria who took chemoprophylaxis?

Subacute

What do you do if you are in the field and there are no diagnostic methods for malaria?

Treat empirically?

Things to watch for in patients admitted with malaria

Respiratory compromise, hypoglycemia, neurologic changes…treat ASAP before they crash. Parasitemia \> 5% with neurologic changes = IV therapy.

If a patient has vivax or ovale what therapy should they receive?

Primaquine to eradicate remaining hypnozoites.