Parasitology 4

Question 1

Babesia microti infects _______ whereas Plasmodium infects ______

Answer 1

Babesia: RBCs only, not hepatocytes
Plasmodium: RBCs and hepatocytes

Question 2

What are intermediate hosts of Babesia?

Answer 2

mice, small mammals, humans are accidental hosts

Question 3

What geographic regions have high incidence of Babesia?

Answer 3

NE US, Midwest, same range as Lyme because also transmitted by nymph stage of Ixodes scapularis

Question 4

Describe the lifecycle of Babesia

Answer 4

During a blood meal, a Babesia-infected tick introduces sporozoites into the mouse host. Sporozoites enter erythrocytes and undergo asexual reproduction (budding) In the blood, parasites differentiate into male and female gametes
A second tick must bite the mouse to ingest the gametes. Within the tick, gametes unite and undergo a sporogonic cycle resulting in sporozoites
Humans become infected if bitten by an infected tick

Question 5

To diagnose Babesiosis, microscopy can be used to visualize Babesia inside ________

Answer 5

red blood cells

Question 6

Patients who are acutely ill with Babesia will have _________ and _________

Answer 6

hemolytic anemia, thrombocytopenia

Question 7

Describe pathology of Babesia

Answer 7

usually nothing, but some have hemolytic anemia and
nonspecific flu-like symptoms (fever, chills, body aches, weakness, fatigue)
weeks or months after exposure or if immunosuppressed
Some patients have splenomegaly, hepatomegaly, or jaundice

Question 8

What drugs can be used to treat Babesiosis

Answer 8

combination therapies:
Atovaquone and azithromycin;
Clindamycin and quinine (severely ill patients)

+ supportive care

Question 9

On microscopy, babesia can be distinguished from plasmodium based on the ________ appearance

Answer 9

Maltese cross

Question 10

List the plasmodium species that cause malaria in humans

Answer 10

falciparum
vivax
ovale
knowlesi
ovale
malariae

Question 11

Malaria infects ______ and ______ cells within the human

Answer 11

hepatocytes and erythrocytes

Question 12

Most fatalities from malaria are in _____ and _______

Answer 12

children, prima gravada females

Question 13

Plasmodium has an obligate ____ stage, sporozites hone in within 10 minutes

Answer 13

Liver

Target for vaccine development

Question 14

Falciparum malaria shows ________ lysing of RBCs

Answer 14

synchronous

Question 15

Vivax and ovale malaria can develop a __________ stage that is not seen in falciparum malaria

Answer 15

chronic liver stage

Question 16

Malarial _______ form in human host but must be transmitted to mosquito to fuse

Answer 16

gametes

Question 17

Which species of malaria can cause relapse from liver forms?

Answer 17

vivax and ovale

Question 18

Which species of malaria can cause severe malaria?

Answer 18

falciparum, vivax, knowlesi

Question 19

What is unique about knowlesi malaria?

Answer 19

• monkey reservoir

- shorter erythrocyte phase (more rapid fever spikes)

Question 20

Describe symptoms of malaria

Answer 20

Chills, fever, splenomegaly, myalgia, headache

Question 21

The malaria parasite has evolved “knob proteins” which function to:

Answer 21

exported to RBC surface, make RBCs sticky so they adhere to vascular endothelium, helps parasite avoid the RBCs being removed from circulation

Question 22

What is the underlying pathophysiology of cerebral malaria?

Answer 22

Immune response causes leaky vasculature, breakdown of blood-brain barrier

Question 23

The parasatemia of malaria demonstrates _________, another mechanism the parasite uses to evade immune response and complicates vaccine development

Answer 23

antigenic waves- antigenic variation over the course of a single infection
*** variable parasatemia within a given infection, even if blood sample shows low parasite level, could have serious infection

Question 24

Are corticosteroids useful in treating cerebral malaria?

Answer 24

Unclear, probably limited effectiveness

Question 25

Cerebral malaria is most commonly seen in _______ and _________

Answer 25

travelers and children >2 (able to mount robust immune response which leads to breakdown of BBB)

Question 26

How does malarial infection lead to anemia?

Answer 26

• destruction of parasatized RBCs when parasites develop
• increased rate of removal of uninfected RBCs from circulation
• suppression of erythropoiesis
• immune destruction of RBCs coated with parasite derived molecules

Question 27

Anemia from malaria usually occurs in _________

Answer 27

children <2 yrs, insufficient immune response to control parasites, so greater parasatemia

Question 28

What is the standard method of diagnosing malaria?

Answer 28

Geimsa stain of thick and thin smears

now developing rapid immunoassay, PCR

Question 29

If multiple parasitic rings are noted on a blood smear, the likely cause of the malaria is:

Answer 29

falciparum (or knowelsi)

Question 30

Immunity to malaria can develop in people living in endemic areas, but it is ______ to develop, requires _____ infection, and is _____ lived

Answer 30

slow, multiple, short

Question 31

How is malaria treated?

Answer 31

chloroquine, mefloquine, quinine
multidrug resistance common, especially chloroquine
newer drugs: malarone (atovaquone & proquanil), doxycycline, clindamycin, artesunates

IV quinidine still used for cerebral malaria

P. ovale/vivax must use primaquine for liver stages

Question 32

What is the source of the RTS, S experimental malaria vaccine?

Answer 32

Circumsporozoite protein

Question 33

________ women often lose resistance to infection

Answer 33

pregnant- especially first pregnancy

Question 34

List some host mutations that confer some resistance to plasmodium infection

Answer 34

Sickle cell
G6PD deficiency
Thalassemia
Duffy group negative (receptor for vivax and knowlesi)