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Locomotor > Eukaryotic parasites 3: malaria > Flashcards

Eukaryotic parasites 3: malaria Flashcards

1
Q

Can malaria be trasnmitted through person-to-person contact?

A

No

Transmitted by mosquitoes

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2
Q

What are the two major types of malaria?

A

P.falciparum

P.vivax

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3
Q

Which populations are at the greatest risk of malaria?

A

Young children

Pregnant women

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4
Q

Briefly describe the global burden of malaria?

A

Up to 1 million deaths per year

300-500 million cases per year

A leading cause of childhood deaths

Compounds poverty

Impedes economic development and education

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5
Q

Describe the consequences of malaria during pregnancy?

A

Low birth weight

Miscarriages and stillbirths

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6
Q

Which communities are most affected by malaria?

A

Resource-poor communities

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7
Q

Describe the major obstacles to combatting malaria?

A

No highly effective control measures available

No vaccine

Drug resistance

Insecticide resistance

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8
Q

Which Plasmodium species causes the majority of severe malaria and death?

A

P.falciparum

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9
Q

Which Plasmodium species has a dormant liver stage?

A

P.vivax

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10
Q

Which type of mosquito transmits malaria?

A

Female Anopheles mosquitoes

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11
Q

During which stages of the malaria life cycle is disease present?

A

Only during the blood stage

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12
Q

Describe the life cycle of P.falciparum?

A

Mosquito injects sporozoites > travel to liver> incubate 7-10 days in hepatocyte, replicate > merozoites burst out of liver > infect RBCs

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13
Q

What are the immune responses to malaria mainly directed against?

A

Blood stage parasites

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14
Q

What are the two clinical types of malaria?

A

Uncomplicated/mild malaria

Severe malaria

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15
Q

Describe the clinical features of uncomplicated/mild malaria?

A

Flu-like illness

Fever, headaches, malaise

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16
Q

Describe the clinical features of severe malaria?

A

3 MAIN FEATURES

Severe anaemia

Cerebral complications (coma, convulsions)

Respiratory distress and metabolic acidosis

OTHER

Hypoglycaemia, kidney failure, blood clotting problems

17
Q

Describe the treatment of uncomplicated/mild malaria?

A

Short course of anti-malarial tablets (3 days)

Clearance of P.vivax liver stage (14 days)

18
Q

What is the problem with using anti-malarial tablets?

A

Resistance emerging

Access

Counterfeit drugs

19
Q

Describe the treatment for severe malaria?

A

Anti-malarials: IV artemisinin or quinine (7-10 days)

Supportive treatment: fluids, blood transfusion, etc.

20
Q

Describe how severe malaria develops?

A

Unrestricted replication> parasites accumulate in vital organs, inflammatory response, RBC destruction > severe illness

21
Q

Describe the three main types of immunity to malaria?

A

1) Immunity that prevents severe malaria
2) Immunity that prevents any malria
3) Immunity to malaria in pregnancy

22
Q

Is the development of immunity to malaria slow or rapid?

Why?

A

Slow

PARASITE FACTORS

Multiple antigenic targets

Antigenic diversity

Antigenic variation

HOST FACTORS

Inadequate response

Non-functional/irrelevant responses

Poor development of memory

23
Q

Describe the factors which contribute to immunity and resistance to malaria?

A

Genetic: sickle-cell trait, alpha-thalassemia

Innate immunity: plasma factors (e.g. complement), innate cellular responses (e.g. NK cells), activated macrophages

Acquired immunity

24
Q

Describe the targets, and their mediators, of acquired immunity to malaria?

A

Sporozoites: Abs and T cells

Infected hepatocytes: T cells

Merozoites: Abs

Infected RBCs: Abs and T cells

25
Q

Describe the immune responses to sporozoites?

A

Abs inhibit infection of hepatocytes

26
Q

Describe the immune response to the liver stage of malaria?

A

CD8 T cells against infected hepatocytes

27
Q

Describe the immune responses to the blood stage of malaria?

A

CELL-MEDIATED RESPONSES

CD4 T cells for protection

Splenic clearnace of parasitsed RBCs (monocytes and macrophages)

IFNY production for protection

Pro-inflammatory cytokine production in severe disease

ANTIBODIES TO MEROZOITES

Inhibit RBC invasion and growth

ANTIBODIES TO INFECTED RBCs

Opsonisation for phagocytosis

28
Q

What part of the immune response to malaria is the key focus of most vaccines?

A

Abs to merozoites

29
Q

How can invasion of RBCs by malaria parasites be inhibited?

A

Antibodies

Drugs

30
Q

Describe why a lack of effective immunity to malaria may arise?

A

Wrong immune response e.g. Abs to liver stage of P.falciparum

Wrong target antigen e.g. antigens that are not essential for invasion or attachment

Right antigens, wrong epitope e.g. sites that are not involved in invasion/attachment

Antigenic diversity

31
Q

What are the three strategies to developing a vaccine against malaria?

A

1) Sporozoites/liver stages
2) Merozoites
3) Transmission blocking vaccines

32
Q

Describe the sporozoite/liver stage strategy to developing a vaccine for malaria?

A

Abs block entry to liver

CD8 T cells inhiibt parasite development in liver

Prevents parasites from entering bloodstream

33
Q

Describe the merozoite approach to developing a vaccine for malaria?

A

Abs opsonise merozoites for phagocytic clearance

Blocks infection of RBCs, prevents replication in bloodstream

34
Q

Describe the transmission blocking approach to developing a vaccine for malaria?

A

Stop infection of mosquitoes

Stops transmission, but does not help host

35
Q

Which is currently the most advanced vaccine for malaria?

A

RTS,S vaccine

Phase 3 trial

36
Q

Describe the RTS,S vaccine?

A

Segment of CS protein (major Ag of sporozoites)

Presneted in virus like particle with Hep B surface Ag

Uses potent adjuvants

37
Q

Describe the difference in the acquired immune response to the blood stage and liver stage of malaria?

A

Blood stages mainly involve antibodies

Liver stages mainly involve T cells

Locomotor (28 decks)

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