Malaria

Question 1

What are 7 details about malaria?

Answer 1

Malaria is a zoonotic infectious disease transmitted
to humans by Anopheles species of mosquitoes.

The disease is caused by a plasmodium that is
carried in mosquito saliva

Humans become infected when an infected female
mosquito inserts her long hollow needle-like
proboscis through the skin and sucks up blood

Four species of malaria infect and cause disease in humans.

Severe life threatening malaria is most commonly caused by Plasmodium falciparum.

Other species, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae generally cause infections with milder symptoms that are rarely fatal

Parasitic Plasmodium species also infect birds, reptiles, monkeys, chimpanzees and rodents

Question 2

What are 10 details about the pathogenesis of malaria?

Answer 2

The clinical symptoms of malaria are caused by the
asexual erythrocytic (blood stage) parasites

When merozoites invade erythrocytes, they digest
hemoglobin, the oxygen-carrying molecule of the body

A toxic breakdown product of hemoglobin (hemozoin
pigment) and other toxic factors accumulate and are
released into the bloodstream along with newly invasive
merozoites (stage of malarial parasite)when the infected
cells lyse (rupture)

Hemozoin and other toxic factors stimulate macrophages and other immune cells to produce cytokines and other soluble factors which incite fever, rigors and potentially fatal immunoreactive pathophysiology

Plasmodial parasites spend most of their human life cycle within hepatocytes and erythrocytes and are therefore protected from attack by the immune system

One exception is in the spleen where infected erythrocytes are immobilized, identified and destroyed

However, Plasmodium falciparum has developed a
mechanism to avoid passage through the spleen whereby infected erythrocytes, adhere to the vascular endothelium of venular blood vessel walls and do not freely circulate in the blood

The sequestration of infected erythrocytes in the small
blood vessels of the brain is the pathogenic mechanism of cerebral malaria

Malarial infection, particularly due to Plasmodium
falciparum, can quickly turn fatal

Life threatening complications include cerebral malarial
infection, hyperparasitemia when more than 5% of
erythrocytes are infected by malarial parasites, severe
anemia due to hemolysis (massive destruction of red
blood cells), splenic rupture, acute respiratory distress
syndrome, abnormalities in blood coagulation, low blood pressure due to cardiovascular collapse, acute kidney failure, metabolic acidosis (excessive acidity in the blood and tissues, and/or hypoglycemia

Question 3

What are 7 details about malaria and sickle cell anemia?

Answer 3

Sickle Cell Anemia is an autosomal recessive
genetic disorder characterized by red blood cells
that assume an abnormal, rigid, sickle shape

Epidemiologic studies revealed that the trait was
relatively common in populations with endemic
malaria because it protects red blood cells from
infection by Plasmodium falciparum

The sickle cell trait is caused by a single base pair
change in the gene for hemoglobin on chromosome
11

Individuals homozygous for the mutated gene have a
morphologically altered form of hemoglobin (Hemoglobin S) that forms “tactoid” crystals in red blood cells causing them to transform into a “sickle” shape

Individuals who are homozygous for the sickle cell gene usually become anemic

The sickled cells are not favorable hosts for the Plasmodium falciparum merozoite.

Individuals with sickle cell anemia who live in regions endemic for malaria are protected from falciparum infection during childhood and survive to reproduce and pass the gene to subsequent generations

Question 4

What are 3 details about malaria and glucose-6-phosphate dehydrogenase?

Answer 4

Glucose-6-phosphate dehydrogenase (G6PD) is an
X-linked enzyme that protects red blood cells
from oxidative stress

Infants with deficiencies in G6PD can develop
neonatal jaundice and hemolytic anemia
following certain environmental stimuli

Populations endemic for malaria have high rates
of G6PD deficiencies which may afford
protection against certain types of plasmodium
infections, particularly Plasmodium vivax

Question 5

What are 3 details about vector control and malaria?

Answer 5

Vector control remains the most generally effective measure to prevent malaria transmission and therefore the cornerstone of the four basic technical elements of the WHO Global Malaria Control Strategy.

Elements of vector control include distribution of insecticide treated bed nets, targeted spraying of insecticides and larvicides, and drainage of mosquito breeding sites to reduce populations of Anopheles mosquitoes

Malaria transmission can be reduced substantially by
distribution of inexpensive mosquito nets and insect
repellents or mosquito-control measures such as spraying insecticides draining standing water where mosquitoes lay their eggs

Question 6

What are 2 details about early diagnosis and treatment for malaria?

Answer 6

Early diagnosis of malaria and its effective and
timely treatment reduces morbidity and prevents
death from malaria.

Advanced diagnostic tools (microscopy and rapid
diagnostic tests) and effective drug therapies
(artemisinin-based combination treatments)
administered by highly trained health care personnel
facilitate effective case management with a high
probability of cure

Question 7

What are 3 details about malaria and chloroquine resistance?

Answer 7

A disturbing feature in the fight against malaria is the
development of large scale resistance by Plasmodia
falciparum to several anti-malarial drugs, most notably
chloroquine

Nevertheless, a variety of anti-malarial medications are
available and most recently, the treatment of Plasmodium falciparum infections in endemic countries has been transformed by the use of combinations of drugs containing an artemisinin derivative.

Severe malaria is treated with intravenous or intramuscular quinine, or increasingly, the artemisinin derivative artesunate which appears to be superior to quinine in both children and adults