Plasmodium - Malaria Flashcards
Types of Plasmodium
- falciparum (Most Cases)
- malariae
- vivax
- ovule
Incidence/Prevalence
150 million current cases
1-1.5 million deaths per year
Endemic 91 countries
40% pop lives in areas - Endemic
1683 ‘traveller’ cases in UK
52 Scotland
5 deaths
Symptoms
- Early Infection
- Fever
- Headache
- Chills - Late disease
- Anaemia
- Respiratory distress
Life Cycle (two parts)
- Vector
- Female Anopheles mosquito
- Sexual Development - Mammalian Host
- Humans only
- Asexual development
Asexual development
- Infected mosquito eats blood - injects anti-coagulant and sporozoites stage parasites.
- Sporozoites infect liver cells (30min)
- Develop into schizonts
- Rupture and release merozoites
- Merozoites infect RBC. (pass through blood cell stage).
- Some mature into gametocytes and are ingested by another Anopheles mosqutio.
Diagnosis - Smear
Microscopy is the gold standard
1. Thick smear
- Detects the presence of parasites
2. Thin smear
- Species-level identification
Advantages (smear)
Cheap & low-technology
Disadvantages (smear)
Requires well-trained competent microscopists and rigorous quality control & drug treatment may be difficult to identify species
Blood stage paracites
- Ring
- Trophozoite (identified in blood smears) (rings initially delicate, become compact as trophozoite develops)
- Schizont (asexual replication, nuclear division without cytoplasmic division) (Large multi-nucleated form)
- Gametocyte
Rapid Diagnostic Test (rDT)
- Complements blood tests
- Detects specific P. falciparum antigens
- Detects and antigens specific to all 4 human malarial species in blood.
rDT Disadvantages
May not detect low-level parasitaemia & not quantitive
Antimalarial Treatment Depends on?
- Plasmodium species
- The part of the world where the infection originated (resistance)
- Severity of symptoms
- Pregnancy
Antimalarial Drugs
- Chloroquine
- Target blood-stage parasites - Quinine
- Target blood-stage parasites - Primaquine
- Targets dormant liver forms - Doxycycline Clindamycin
- Used in combo with quinine - Artemisinin
- ACT is a combination-based therapy
Artemisinin
Used in Malaria-ridden parts of the world. reduce mortality by 20% overall and by over 30% in children. In Africa alone, more than 100,000 lives are saved each year.
Problems with Treatment
- No drug is effective against all stages
- Resistance is a problem
- Unpleasant side effects
- Prevention is better than cure
Chemoprophylaxis
- Antimalarial tablets are recommended for visits to an area where there is a malaria risk.
- Reduce the risk of malaria by about 90%.
Antimalarias
- Mefloquine (aka Lariam)
- Doxycycline (aka Vibramycin-D)
Prevention/Eradication
1. Vector control with insecticides
- Insecticides
- Successful in Italy
-Unsuccessful in developing countries
-Mosquito nets treated with insecticides have a remarkable impact - Larvicides
- destroy mosquito larvae
- Vector control without insecticides
Sterile insect technology (SIT) project
Theory
1. Female Anopheles mate only once
2. If the males are sterile the females will lay infertile eggs
- SIT project released sterile UV irradiated mates (tend to be less fit and die)
Transgenic Mosquito(TM)
Sterile Males
- Developed in joint project between WHO & Indian MRC
- Oxitec in London develop sterile mosquito
Transgenic Mosquito with reduced parasite developement
- TM expressing bee venom phospholipase in their gut
- Ability to transmit parasite greatly decreased
Vaccine & Molecular techniques
- Best solution for individuals resident in endemic areas
- Preferred for travellers entering endemic areas
Three Vaccine Targets
- Pre-erythrocytic (RTS, S Vaccine)
- Blood Stage Vaccines
- Transmission blocking Vaccines
Pre-erythrocytic (RTS, S Vaccine)
- The vaccine contains parts of two proteins found on the sporozoite surface
- Prevents the parasite from emerging from the liver and progressing to the erythrocytic stage
