Parasitology 4 Flashcards
Babesia microti infects _______ whereas Plasmodium infects ______
Babesia: RBCs only, not hepatocytes
Plasmodium: RBCs and hepatocytes
What are intermediate hosts of Babesia?
mice, small mammals, humans are accidental hosts
What geographic regions have high incidence of Babesia?
NE US, Midwest, same range as Lyme because also transmitted by nymph stage of Ixodes scapularis
Describe the lifecycle of Babesia
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
To diagnose Babesiosis, microscopy can be used to visualize Babesia inside ________
red blood cells
Patients who are acutely ill with Babesia will have _________ and _________
hemolytic anemia, thrombocytopenia
Describe pathology of Babesia
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
What drugs can be used to treat Babesiosis
combination therapies:
Atovaquone and azithromycin;
Clindamycin and quinine (severely ill patients)
+ supportive care
On microscopy, babesia can be distinguished from plasmodium based on the ________ appearance
Maltese cross
List the plasmodium species that cause malaria in humans
falciparum vivax ovale knowlesi ovale malariae
Malaria infects ______ and ______ cells within the human
hepatocytes and erythrocytes
Most fatalities from malaria are in _____ and _______
children, prima gravada females
Plasmodium has an obligate ____ stage, sporozites hone in within 10 minutes
Liver
Target for vaccine development
Falciparum malaria shows ________ lysing of RBCs
synchronous
Vivax and ovale malaria can develop a __________ stage that is not seen in falciparum malaria
chronic liver stage
Malarial _______ form in human host but must be transmitted to mosquito to fuse
gametes
Which species of malaria can cause relapse from liver forms?
vivax and ovale
Which species of malaria can cause severe malaria?
falciparum, vivax, knowlesi
What is unique about knowlesi malaria?
- monkey reservoir
- shorter erythrocyte phase (more rapid fever spikes)
Describe symptoms of malaria
Chills, fever, splenomegaly, myalgia, headache
The malaria parasite has evolved “knob proteins” which function to:
exported to RBC surface, make RBCs sticky so they adhere to vascular endothelium, helps parasite avoid the RBCs being removed from circulation
What is the underlying pathophysiology of cerebral malaria?
Immune response causes leaky vasculature, breakdown of blood-brain barrier
The parasatemia of malaria demonstrates _________, another mechanism the parasite uses to evade immune response and complicates vaccine development
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
Are corticosteroids useful in treating cerebral malaria?
Unclear, probably limited effectiveness
Cerebral malaria is most commonly seen in _______ and _________
travelers and children >2 (able to mount robust immune response which leads to breakdown of BBB)
How does malarial infection lead to anemia?
- 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
Anemia from malaria usually occurs in _________
children <2 yrs, insufficient immune response to control parasites, so greater parasatemia
What is the standard method of diagnosing malaria?
Geimsa stain of thick and thin smears
now developing rapid immunoassay, PCR
If multiple parasitic rings are noted on a blood smear, the likely cause of the malaria is:
falciparum (or knowelsi)
Immunity to malaria can develop in people living in endemic areas, but it is ______ to develop, requires _____ infection, and is _____ lived
slow, multiple, short
How is malaria treated?
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
What is the source of the RTS, S experimental malaria vaccine?
Circumsporozoite protein
________ women often lose resistance to infection
pregnant- especially first pregnancy
List some host mutations that confer some resistance to plasmodium infection
Sickle cell
G6PD deficiency
Thalassemia
Duffy group negative (receptor for vivax and knowlesi)
