malaria Flashcards
(40 cards)
Plasmodium falciparum is responsible for ~500,000 deaths yearly
yeppp; major cause of morbidity and mortality in the developing world
most aggressive
Causes of Human Malaria:
- Plasmodium falciparum (Pf)
- P. vivax (Pv)
- P. ovale (Po)
- P. malariae (Pm)
- P. knowlesi (Pk)
- Plasmodium falciparum (Pf)
Occurs worldwide
Responsible for greatest morbidity + mortality - P. vivax (Pv)
Occurs in Latin America, Asia, Middle East, North and East Africa - P. ovale (Po)
Only found in Central-West Africa - P. malariae (Pm)
Limited worldwide distribution - P. knowlesi (Pk)
Recently identified cause of human malaria in Malaysia, Borneo, other parts of SE Asia
what are we looking in a parasite smear in malaria?
trophozoites (ring forms)
some forms of parasites in malaria are latent in the
liver
Parasites reduce RBC membrane deformability resulting in hemolysis and increased splenic clearance leading to
anemia
Once within RBCs, parasites digest hemoglobin
toxic metabolite (hemozoin) is stored in the parasite’s food vacuole
why is P. falciparum so mean?
no latent stage goes directly to do the RBC and invades them alllllll.
No latent stage (no hypnozoites)
Only invade senescent (old) RBCs
Mildest form of malaria, can persist at low levels for years
No sequestration
P. malariae
After the initial liver stage, some parasites remain dormant as hypnozoites for weeks-years, allows for clinical relapses
Only invade reticulocytes (young RBCs)
Generally less severe disease
No sequestration
P. vivax/Ovale
increased disease severity for malaria (4)
- children
- pregnancy
- non-immune host
- HIV infection
decreased severity for malaria (4)
- premunition- sustained repeated infection but last only a couple of months
- sickle cell trait
- absence of Duffy blood group- no infection
- certain HLA types and thalassemia traits
Mean incubation period for malaria
= 10-15 days
Acute malaria attack classically has three stages:
- Chills or rigors (30-60 mins)
- High fever with diaphoresis, HA, GI symptoms
- Period of intense sweating
Do we see some enlargement of an organ in malaria?
yep, splenomegaly and hepatomegaly is seen
severe malaria
badddddd, mortality is >20%, there is an intense cytokine response to parasite proteins released during shizont rupture and there are metabolic derangements
** pregnancy is a risk for severe disease
cerebral malaria
cuased by P. falciparum that results in sequestration and resultant host immune response
We see Sludging of Capillaries.
it leads to confusion, seizures and coma and about 10% of children who survive will have long term neuro-psychological deficits
malaria diagnosis
use a thick and thin smear; where the thick is more sensitive but thin is more specific
**stained with Giemsa/Wright’s
Normal size RBCs; Small ring forms (”stereo headphones”);
Multiply infected cells; High grade parasitemia
Rare banana shaped gametocytes;
Developing forms almost never seen
P. falciparum:
Rapid Antigen Detection Tests (RDTs)
Detect parasite proteins (histidine rich protein-2 of Pf and parasite specific LDH or aldolase antigens) in finger prick blood samples
- Advantage: easy to use, require minimal equipment/ skill
- Disadvantage: cannot quantify parasitemia, cannot pick up low level infection, remain positive for 7-14 d post-Rx
other diagnostic tests for malaria
- PCR
Can detect <10 parasites per 10L of blood; species specific
>90% sensitive; ~100% specific
Turnaround time is slow and testing is expensive
Can remain positive for several weeks after curative treatment
Can be done at CDC for free (along with resistance testing) - Serology
Detects Ab against malaria parasites
Does not detect current infection per se, but rather measures past exposure
Principles of Management: Definitions:
Prophylaxis
Medication taken at regular intervals to kill one or more life stages of the parasite to ______ clinical illness
Critical to prophylactic treatment is administration _______________; dosing/duration is drug dependent
Treatment
1. __________ eradication of RBC trophozoites and schizonts
- ________ eradication of RBC trophozoites, schizonts and hepatic schizonts(hypnozoites)
Principles of Management: Definitions:
Prophylaxis
Medication taken at regular intervals to kill one or more life stages of the parasite to prevent clinical illness
Critical to prophylactic treatment is administration before, during and after exposure; dosing/duration is drug dependent
Treatment
1. Clinical cure: eradication of RBC trophozoites and schizonts
- Radical cure: eradication of RBC trophozoites, schizonts and hepatic schizonts(hypnozoites)
active against blood stage; used for treatment and prophylaxis
Blood schizonticide:
active against liver stages of parasite; used for treatment and prophylaxis
Tissue schizonticide:
active against sexual forms of parasite, interrupts transmission to mosquito
Gametocide:
