Microbiology-Malaria

Question 1

What are the 5 species of malaria that infect humans?

Answer 1

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

Question 2

How do you differentiate a malaria parasite from a platelet?

Answer 2

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

Question 3

What stage is this parasite in?

Answer 3

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

Question 4

What stage is this parasite in?

Answer 4

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

Question 5

What stage is this parasite in?

Answer 5

Mature trophozoite

Question 6

What stage is this parasite in?

Answer 6

Young Immature Schizont

Question 7

What stage is this parasite in?

Answer 7

Old Immature Schizont

Question 8

What stage is this parasite in?

Answer 8

Mature Schizont: note the pigment clump and merozoite

Question 9

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

Answer 9

P. falciparum, P. malariae or P. knowlesi

Question 10

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

Answer 10

P. vivax and P. ovale.

Question 11

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

Answer 11

P. falciparum

Question 12

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

Answer 12

P. malariae and P. knowlesi

Question 13

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

Answer 13

P. vivax

Question 14

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

Answer 14

P. ovale

Question 15

What parasite is seen on the thick smear below?

Answer 15

P. falciparum

Question 16

What parasite is seen on the thick smear below?

Answer 16

P. malariae

Question 17

What parasite is seen on the thick smear below?

Answer 17

P. vivax

Question 18

What parasite is seen on the thick smear below?

Answer 18

P. ovale

Question 19

Fill in the blanks

Answer 19

*

Question 20

OIFs

Answer 20

Oil immersion fields used to identify presence of malaria under microscopy

Question 21

Quantitative measurements of malaria

Answer 21

*

Question 22

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

Answer 22

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

Question 23

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?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

Risk factors for severe malaria

Answer 25

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

Question 26

5 species of malaria? Vector? Reservoir?

Answer 26

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.

Question 27

Malaria most likely to kill people

Answer 27

P. falciparum

Question 28

Life cycle of malaria

Answer 28

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.

Question 29

Liver cells infected with malaria without amplification.

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

P. malariae

Question 32

Necessary for spread from one person to another

Answer 32

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.

Question 33

Traits in humans that evolved in malaria endemic countries

Answer 33

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)

Question 34

Classic symptoms of malaria

Answer 34

Fever, chills, headache

Question 35

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

Answer 35

Abdominal pain/diarrhea

Question 36

Lab values that hint toward malaria

Answer 36

Elevated LDH, anemia and elevated bilirubin because of hemolysis.

Question 37

3 clinical types of malaria

Answer 37

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

Question 38

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?

Answer 38

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.

Question 39

How does malaria kill people?

Answer 39

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

Question 40

Important prognostic factors of malaria

Answer 40

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

Question 41

Why are falciparum infections most lethal?

Answer 41

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

Question 42

Why do tissues become hypoxic and patients acidotic with malaria?

Answer 42

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.

Question 43

Why do people become hypoglycemic with malaria?

Answer 43

Increased metabolic rate due to infection and decreased consumption

Question 44

Why do people have renal failure with malaria?

Answer 44

Filtration of hemolyzes RBC products

Question 45

Why do people have anemia with malaria?

Answer 45

Hemolysis, sequestration and splenic removal.

Question 46

Diagnosing malaria

Answer 46

Blood smear, antigen testing and PCR.

Question 47

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

Answer 47

Test again

Question 48

Presentation of someone with malaria who took chemoprophylaxis?

Answer 48

Subacute

Question 49

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

Answer 49

Treat empirically?

Question 50

Things to watch for in patients admitted with malaria

Answer 50

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

Question 51

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

Answer 51

Primaquine to eradicate remaining hypnozoites.