Lecture 16 - Malaria 1 Flashcards
Which infectious diseases are in the top 20 causes of mortality world wide?
What is special about HIV and Malaria?
- HIV
- Malaria
- Diarrhoeal diseases
- Tuberculosis
HIV and Malaria are important because they are caused by a single pathogen.
What is the phylum and genus of Malaria parasite?
Give some features of the phylum
Phylum: Apicomplexa
• Lot of parasites that belong to this phylum: Toxoplasmodium
• Common feature: single cell, polar
• Apical and distal end
• Apical complex is important for the invasion of the host cells
• All apicomplexans infect other cells
Genus: Plasmodium
Why is Malaria an ‘ancient problem’?
- Malaria has been infecting humans for millennia
* The parasite has co-evolved w/ humans
What percent of people on earth will get Malaria this year?
What is significant about this?
10%
This is an incredible selective pressure:
• eg. gene for sickled cell anaemia
• Heterozygotes for sickled cell anaemia are resistant to malaria
• This disease leads to people dying young, but it is less severe than Malaria.
Why was the discovery of the transmission of Malaria important?
Seasonal malaria transmission was endemic in the US, the UK, Italy, much of Europe (every summer)
Once the transmission was uncovered, people in these countries could change their behaviour to prevent transmission
• Removal of water around the house, where mosquitoes were breeding was enough to prevent transmission
NB This was not enough in other countries
What are the four species of Plasmodium that infect humans?
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
Which three tissues can Plasmodium infect?
What is different about the pathogen at this time?
- The insect
- The liver
- Erythrocytes
It is the same pathogen, i.e. the DNA is the same, however there are morphological differences in the parasite.
Where are most deaths due to Malaria?
Equatorial Africa
- Papua New Guinea
- Myanmar
What is seen in South America?
High levels of disease, but less burden of death.
This is because P. vivax is the main species in this area
This species is less fatal
How many cases of Malaria per year in the world?
How many deaths?
300-500 million cases per year
1 million deaths per year
Describe the economic impact of Malaria
Financial burden:
• Bed nets
• Work and School absenteeism
• Represents 10% of annual spending in Africa
What is the vector of the malaria parasite?
Anopholes mosquito
List the stages of the life cycle of the malaria parasite
What type of reproduction is occurring at each stage?
- Mosquito stage
• Sexual reproduction - Liver stage
• Asexual reproduction - Blood stage
How is malaria infection diagnosed?
Haemozoan crystals seen on a blood smear
- Haem in the haemoglobin is toxic to the parasite
- The parasite crystallises the haem into Haemozoan
- Gold particulate crystals visible
What are sporozoites?
- Haploid
- Generated by meiosis (sexual reproduction) in the mosquito
- This is what infects the humans
How does the parasite get into the human host?
- Mosquito vector takes a blood meal in humans
- Saliva is injected to prevent the blood from clotting
- Parasite present in the saliva
Describe the initial stages of infection in the human host
- Sporozoite circulates to the liver
- Moves through Kupffer cells into hepatocytes
- Resides in a hepatocyte and replicates asexually
- can be one parasite, or could be up to 100 - - Emerges from the liver as a Merozoite
NB No disease or clinical syndrome is observed at this point because the numbers are too low.
Differentiate between a merozoite and a sporozoite
Sporozoite: haploid parasite from sexual reproduction in the mosquito
Merozoite: emerges from replication in the liver cells
Describe the later stages of the life cycle
- Merozoites emerge from hepatocytes into blood
- Infect RBCs
- Amplification, eat up the haemoglobin
- Burst out of the RBC
- Infect more RBCs
• initially: 1000 RBCs infected → 10^11
What percent of a person’s RBCs can be infected by the parasite?
1% - 10% of all RBCs can be infected in a patient w/ malaria