Flashcards in EXAM #2: MALARIA Deck (46)
What species of mosquito transmits malaraia?
What is the genus that causes malaria? What type of microorganism is this?
This is a protozoa.
What are the five species of Plasmodium that cause malaria? Which are the two most common
1) P. falciparum*
2) P. vivax*
3) P. malariae
4) P. ovale
5) P. knowlesi
Where are P. falciparum and P. vivax most endemic?
P. falciparum= Africa
P. vivax= Asia
Describe the lifecycle of Plasmodium.
1) Mosquito bite introduces SPOROZITES into the blood
2) SPOROTITEZ travel to the liver
3) In the liver, SPOROTIZES divide into MEROZITES
4) MEROZITES are released from hepatocytes and:
- Transform into TROPHOZITES that make RBCs less flexible and cause extravascular hemolysis/ splenomegaly
- SCHIZONTS that cause RBC membrane rupture and intravascular hemolysis
- GAMETOCYTES that are taken up by new female anopheles mosquitoes to continue the lifecycle
What is the hallmark clinical feature of malaria?
MALARIAL PAROXYSM that is due to the synchronous release of merozoites and the lysis of RBCs
What is malarial paroxysm?
Alternating flu-like sx.
- Muscle ache
What are the three stages of malarial paroxysm?
1) Cold stage
2) Hot stage
3) Sweat stage
Describe the pattern of paroxysm for the five Plasmodium species.
- P. vivax and ovale= Q48 hours
- P. malariae= Q72 hours
- P. falciparum= roughly Q36-48
- P. knowlesi= Q 24 hours
What forms of Plasmodium can take on a dormant form and cause symptoms months or years after the initial infection?
P. vivax and ovale
What is the most severe form of Malaria?
What is the severe complication of P. falciparum infection?
****Leads to coma, seizures, and death (in 15-20% of patients)
What is the severe complication of P. vivax and ovale infection?
What is unique about P. malariea?
The parasitic load is so low that it may not be picked up on PBS, which leads to SYMPTOMATIC RECRUDESCENCE (onset of symptoms years after initial infection)
Why is anemia a common complication of malaria?
Asexual stage of parasite destroys RBCs in the process of replication
List the three mechanisms in the pathogenesis of anemia in Malaria.
1) RBC lysis
2) Clearing of uninfected RBCs that get coated with antigen
3) Suppression of erythropoiesis by cytokines
What stage of RBCs are favored by the different species of Plasmodium?
- Falciparum and knowlesi favor both mature and young RBCs
- Vivax and ovale favor RCs
- Malariae prefers old RBCs
Why is P. falciparum the most severe infection causing Malaria?
It infects the greatest number of RBCs
P. falciparum infection can be associated with splenomegaly, hypoglycemia, and microvascular sequestration, why?
Splenomegaly= clearance of infected RBCs
Hypoglycemia= consumption of blood glucose by the organism
In addition to the parasite consumption of glucose, why else can plasmodium cause hypoglycemia?
1) Decreased oral intake
2) Depleted liver glycogen
3) Inhibition of gluconeogenesis
How is Malaria diagnosed?
- Recognize clinical syndrome
- Be weary of travel history (africa/ asia)
- *PBS* is the gold standard of diagnosis in suspected cases
*****Malaria should always be on the differential of a febrile patient that has traveled to a malarious area*****
What are the characteristics of P. falciparum on PBS?
- Red cells with multiple ring forms
- PURPLE BANANAS
What are the characteristics of P. vivax on PBS?
- Large distended RBC
- "Schuffner dots"
What are the characteristics of P. ovale on PBS?
- Large distended "oval" RBCs
- Schuffner dots
What are the characteristics of P. malariae on PBS?
Band forms in RBCs
Describe how Malaria can be diagnosed with immunodiagnosis.
A dipstick detects circulating antigen
List the diseases that confer protection against malaria.
1) Sickle Cell Anemia
4) SE Asian Ovalocytosis
5) Absence of Duffy blood group antigen
How is Malaria prevented?
- Eradicate mosquito vector
- Prophylaxis for travelers
Note that vaccine trials have been disappointing, and drug resistance is a major concern.
What is Babesiosis?
US "Malaria" that is transmitted by ticks BUT without cyclic fever