Parasitology & Malaria Flashcards
Define parasite
An organism living in or on a host and dependent on the host for nutrition – causing damage
What are the two groups of endoparasites and what are the features of organisms within these two groups?
-
Protozoa
- UNIcellular
- Eukaryotes (membrane bound nucleus)
- Some have insect vectors
- No eosinophilia
-
Metazoa
- MULTIcellular
- They are helminths/worms
- Free living, intermediate hosts and vectors
- Cause eosinophilia if they invade the blood
What are the five types of plasmodium that cause malaria? List them from most common to least common
- F MOV K*
- Plasmodium falciparum
- Plasmodium malariae
- Plasmodium ovale
- Plasmodium vivax
- Plasmodium knowlesi
Discuss the asexual reproduction of P. falciparum
G-ZOO
Gametocyte –> Zygote –> Ookinete –> Oocyte
Outline the life cycle of P. falciparum is mosquitos
G-ZOOS
Gametocyte –> Zygote –> Ookinete –> Oocyte –> Sporozoite
- Within a 15 day period, gametocytes sequester and develop within the bone marrow and, once mature, enter the peripheral circulation for ingestion by a mosquito where they emerge as extracellular male and female gametes in the midgut.
- Mating occurs by fusion of micro- and macrogamete to form a zygote transforming over 24 hr into a ookinete that migrates through the mosquito midgut epithelium and encysts to become an oocyst where asexual sporogenic replication occur
- Motile sporozoites are released into the hemocoel by oocyst rupture and pass into salivary glands where they can be injected into the next human host
Outline the life cycle of P. falciparum in the human
Sporozoites –> schizonts –> merosomes
Merozoite –> Gametocyte –> Zygote –> Ookinete –> Oocyte
- Malaria infection is initiated with the injection of sporozoites into the dermis by a feeding female anopheline mosquito.
- The sporozoites enter the vasculature and are transported to the liver, where they exit the sinusoids through Kupffer or endothelial cells and enter a hepatocyte.
- Active invasion is preceded by cellular traversal until a suitable hepatocyte is found.
- They form a parasitophorous vacuole membrane (PVM) and undergo exo-erthryocytic schizogony until tens of thousands of daughter merozoites are released in packets of merozoites into the vasculatur
- There they encounter erythrocytes and begin a chronic cycle of erthryoytic schizogony in the bloodstream.
- The merozoites that have infected the red blood cells and are feeding are known as trophozoites
- These mature into schizonts
- The merozoites that have infected the red blood cells and are feeding are known as trophozoites
- A proportion of asexually reproducing merozoites are reprogrammed to undergo gametocytogenesis.
- Within a 15 day period, gametocytes sequester and develop within the bone marrow and, once mature, enter the peripheral circulation for ingestion by a mosquito where they emerge as extracellular male and female gametes in the midgut.
- Mating occurs by fusion of micro- and macrogamete to form a zygote transforming over 24 hr into a ookinete that migrates through the mosquito midgut epithelium and encysts to become an oocyst where asexual sporogenic replication occurs. Motile sporozoites are released into the hemocoel by oocyst rupture and pass into salivary glands where they can be injected into the next human host.
What are the two types of host for plasmodium?
- Female anopheles mosquito
- Humans
What are the two stages of malaria in humans?
- Liver
- Blood
Describe the symptoms of malaria.
- Paroxysmal = sudden reoccurrence or intensification of symptoms
- Occurs every 4-8 hours
- Symptoms
- Headaches
- Vomiting
- Fever
- Chills
- Muscle pain
State some complications of malaria.
-
Severe anaemia
- due to intravascular haemolysis
- Cerebral malaria
- Kidney failure
- Swelling and rupturing of the spleen
- Liver failure
- Shock
- Pulmonary oedema
- Abnormally low blood sugar
What are the treatments for uncomplicated malaria?
-
Chloroquine
- Hemoglobin is composed of a protein unit (digested by the parasite) and a heme unit (not used by the parasite)
- The parasite releases the toxic and soluble molecule heme
- To avoid destruction by porphyrin ring of the heme group, the parasite biocrystallizes heme to form hemozoin, a non-toxic molecule
- Hemozoin collects in the digestive vacuole as insoluble crystals
- To avoid destruction by porphyrin ring of the heme group, the parasite biocrystallizes heme to form hemozoin, a non-toxic molecule
- Chloroquine caps hemozoin molecules to prevent further biocrystallization of heme, thus leading to heme buildup
- Chloroquine binds to heme forming a complex that is highly toxic to the cell and disrupts membrane function resulting in cell lysis and ultimately parasite cell autodigestion
What is the treatment for severe malaria?
Artemisinin-based combination therapy
How is malaria diagnosed?
- Blood film + Giemsa stain
- Stain specific for phosphate groups of DNA
- Also used to stain chromosomes in chromosome banding
What is the vector for Malaria?
- Females of Anopheles genus
- Spread by bite of mosquito that was previously infected from a human blood meal - parasites multiply within liver cells and RBCs
How many malaria cases are there in the world?
- About 3.3 billion people (half world’s pop) are at risk for malaria
-
250 million malaria cases and nearly one million deaths each year
- In Africa, 1 in 5 childhood deaths are due to effects of malaria - An African child has an average b/t 1.6-5.4 episodes of malaria fever each year
What is the insect vector for leishmania?
Sandfly
