Malaria Flashcards
Where does the term malaria come from?
“bad air”
How did the WHO try to prevent the spread of malaria?
DDT to kill mosquitos, draining swaps and covering water with oil to decrease mosquito reproduction, and chloroquine prophylaxis and treatment (this program failed)
What is the causative agent of malaria?
family: protozoa
class: sporozoa
genus: plasmodium
species: falciparum, vivax, ovale, and malariae (knowlesi)
What are the four species of plasmodium that cause malaria in humans?
falciparum, vivax, ovale, malariae and plasmodium knowlesi (very rarely)
What kind of disease is malaria?
a vector disease; definitive host is female anopheles mosquitos; humans are intermediate hosts
Is malaria a global problem? Did it use to be?
not anymore - it’s mostly a problem around countries near the equator, but it used to be a global problem in the 1900s
Where can P. falciparum be found?
worldwide in tropical/subtropical areas (especially in Africa)
What can P. falciparum cause? Why?
it can cause severe malaria due to its rapid multiplication in the blood which can cause severe blood loss resulting in anemia
Where is P. vivax found?
in Asia, Latin, America, and in some parts Africa
Where does P. ovale reside?
mostly in Africa and the islands of the western Pacific
Where is P. malariae found?
found worldwide, only human malaria that has a three-day cycle
What can P. malariae cause?
causes a long-lasting, chronic infection
What does a general plasmodium life cycle look like in a human?
1) mosquito takes a blood meal and injects sporezoa into the skin of the human
2) plasmodium develops in liver
3) invades red blood cells
What two hosts does plasmodium have?
mosquito and human
What are the stages of plasmodium development in erythrocytes?
starts as ring -> trophozoites -> immature schizonts -> mature schizonts -> micro-gametocytes -> macro-gametocytes
What can cause anemia in plasmodium patients?
when the erythrocytes rupture it can cause anemia (especially in macro-gametocyte form)
What is the incubation period?
7 to 30 days most commonly; antimalarial drugs taken for prophylaxis can delay the appearance of symptoms
What are classical malaria attacks?
an attack lasting 6-10 hours; starts with cold stage (sensation of cold/shivering), then hot stage (fever, headaches, vomiting, seizures in kids), and then a sweating stage (sweats, return to normal temperature, tiredness)
What is the prevalence of uncomplicated malaria?
RARE
How does malaria present?
fevers, chills, sweats, headaches, nausea and vomiting, body aches, and general malaise
What are the virulence factors of P. falciparum?
1) invades all stages of RBC development
2) infection can result in high level parasitemia
3) P. falciparum erythrocyte membrane protein 1 (PfEMP1) is responsible for sequestration within the vital organs
4) cytoadherence
- parasite to sequester in deep vascular beds
- avoid splenic clearance
What type of malaria did we have in the US?
P. vivax
What does P. vivax cause?
recurrence of the disease many months later without reinfection; only interacts with immature RBCs; lower initial level of parasitemia
Is there a dormant form of malaria?
YES, it can become symptomatic weeks or months later
What do hypnocytes represent?
silent transmission reservoir
What is evolutionary about plasmodium vivax and ovale?
it can survive winter, stays in human liver during winter
What can plasmodium malariae be mistaken as?
lymphoma
What is important to the P. malariae lifecycle?
it clears a liver completely and initiates erythrocyte cycle; causes so little disturbance patient may not notice symptoms
What is P. knowlesi?
historically a disease of macaque monkeys, but have seen recent outbreaks in Malaysia and other Southeast Asian countries
What blood cells does each Plasmodium spp. effect?
falciparum - All RBCs
vivax - young RBCs
ovale - young RBCs
malariae - old RBCs
What plasmodium has the highest severity of attack? the lowest?
falciparum = most
vivax/ovale = middle
malariae = least
What are overall characteristics of P. falciparum?
most likely to be fatal, no latent stages in liver, disease of the tropics, some protection from sickle-cell trait
What are overall characteristics of P. vivax and P. ovale?
liver stages produce latent infections, can survive in temperate climates, previously found in US
What are overall characteristics of P. malariae?
low-grade chronic infection that can persist for at least 50 years
How do we diagnose malaria with a thick blood smear?
with a THICK BLOOD SMEAR, it is inexpensive, and sensitive; however, it’s more difficult to identify species level, there is a delay waiting for it to dry, and requires an experienced observer
What does plasmodium look like under a microscope?
banana shaped
How can we use thin smear to diagnose malaria?
THIN SMEAR is rapid, more accurate species identification, inexpensive, shows red cell morphology; however, it less sensitive and requires an experienced observer
How can we use PCR testing to diagnose malaria?
sensitive, expensive, excellent species identification, causes mixed infections
What other method can we use to diagnose malaria?
a rapid diagnostic test (RDT)
How can we prevent malaria?
1) vaccination, the WHO now recommends a vaccine
2) insect precautions
- screened housing
- mosquito netting over the beds
- clothing
- insect repellent
- insecticides
What does the malaria vaccine (RTS,S/Mosquirix) work against?
P. falciparum malaria in children living in regions with moderate to high transmission
What prophylactic medications are suggested?
atovaquone/proguanil (Malarone) is MOST, mefloquine (Lariam), doxycycline, and chloroquine
How do we treat malaria?
oral medication: chloroquine, arthemeter/lumefantrine, atovaquone/proguanil, mefloquine; IV medication: artesunate, quinine; treatment of hypnozoites in the liver: for P. vivax/ovale use primaquine
What is the recent concern for malaria?
concern it will develop drug resistance; most concern for border areas of Myanmar/China
What is elimination the solution to?
RESISTANCE
Malaria is…
preventable, treatable, and beatable
