Lecture 67 - Malaria Flashcards
what kind of parasite causes malaria?
what is the genus that causes malaria?
which species causes 90% of malaria deaths?
what mosquito is the vector of disease?
Protozoa
Plasmodia
Falciparum – only Plasmodium which expresses Var proteins
The female anapholes Mosquito
what are the other species of malaria causing bugs? how are they different ?
Vivax and Ovale —
Distinct liver phase where the bugs can hide for long periods of time
can get multiple infections
“you can get vivax and ovale over and over”
Plasmodia malariae – illness w/o liver phase
plasmodia knowlesi – affects mostly monkeys
Describe the lifecycle of the plasmodium
In the Human:
- infected female mosquito injects sporozoites via saliva when taking blood meal
- Sporozoites quickly travel to liver where they replicate for 1-2 weeks
- In the Liver – sporozoites mature to merzoites
- Merozoites rupture into the blood stream; and begin causing disease
- Invade RBCs where they further replicate and cause disease
- Rupture RBCs with more merozoites
- Some differentiate to male and female gametocytes
In the Mosquito –
- female takes next blood meal
- male and females gametocytes unite
- travel from GI to salivary gland in 1-2 weeks
- Transmit as sporozoite in next blood meal
Malarial Disease –
what stage is symptomatic? what stage is asymptomatic?
what is the important virulence factor P. falciprium?
what is the mechanism of disease?
Asymptomatic: Liver stage (1-4 weeks)
Symptomatic stage: blood stage
Virulence factor: Var Protein expression in RBCs
Causes RBCs to be amorphous/lumpy– causing them to stick to capillary beds of brain, kidneys, lungs
Leading to inflammation, destruction of vessels, ischemia, and organ failure
The malformed RBCs get stuck in capillary beds and are not sifted out via the spleen
Uncomplicated vs Severe malaria
Uncomplicated – No End Organ Damage
symptoms: Fever paroxysms, with chills; HA, myalgias, cough, diarrhea, abdominal pain
Severe Malaria – occurs mostly in children
1) Severe anemia – hgB < 5
2) Cerebral malaria – coma, seizures, AMS
- in Africa this occurs exclusively in children
- in SE Asia and South America this occurs at any age
Leads to high intracranial pressure and eventual death by herniation of the brain
Describe exposure dependent immunity to malaria? what is the significance of this?
Neonatal immunity
Neonates of endemic regions do not get sick bc they carry their mothers’ antibodies
Fetal HgB is also less susceptible to disease
Young Childhood -
Children of endemic regions are subject to repeated infections
diverse antigens – repeat infections
2-5 infections in first year of life – Intermediate Immunity
Don’t exhibit symptoms with intermediate immunity; but allows these people to be carriers – Asymptomatic Parasitemia
P. Vivax –
where is it most commonly found?
whats unique about its pathology?
Clinical manifestations ?
Second most common cause of malaria world wide
Most common form found Outside of Africa
Lacks Var proteins
Unique in its ability to hide in the liver and cause relapsing disease
Not Fatal. Fevers, anemia, splenomegaly, splenic rupture
Malarial Dx:
- Clinical suspicion
- physical exam findings
- Microscopy –
- what other tests, labs?
Pt has had recent travel to endemic region and now presents with AMS, acidotic breathing, prostration, vomiting;
Micro – thick vs thin smear
Rapid Test– detects malarial proteins in the blood; First test to get
Other Labs Findings:
- Blood glucose, bilirubin, urinalysis, creatinine
Thick vs Thin Blood smear
Thick Smear – fix to slide — Blood cells lysed
High sensitivity; simply detecting if the parasite is present
WBCs and parasites remain
Able to determine if parasites are present with high sensitivity
Thin Smear — fix to slide – -Blood cells remain intact
□ See just monolayer of RBCs
□ Able to see parasites in the cells
□ Able to determine parasite
□ Determines parasite density
• Dx of Severe Malaria
Cerebral malaria Respiratory distress Severe anemia Jaundice/icterus Renal insufficiency Hemoglobinuria Shock
Oral Treatments for Malaria:
which is used for p. vivax
Artemether-lumefantrine
Atovaquone-proguanil (Malarone)
Mefloquine
Chloroquine
CQ followed by primaquine
Quinine plus doxycycline/clindamycin
IV Malaria Treatments
Quinine/quinidine –
Artesunate
Other means of treatment for malarial cases?
• Supportive care: ○ Treat and prevent hypoglycemia ○ Gentle Fluid resuscitation Monitory for anemia and CR status ○ Anti-pyretic, anticonvulsant
Treatment of the Anemia - Do NOT treat with Iron
Prevention of Malaria:
Bed Nets
residual spraying
Vaccines:
- Irradiate sporozoites - but this isnt feasible
- Recombinant vaccine based on sporozoite protein
