Malaria:
Cause:
- 4 species of Plasmodium protozoan parasite which can affect humans – live in liver and RBC
- P. falciparum, P. vivax, P. malariae and P. Ovale
Transmission:
- Requires a vector – female Anopheles mosquito which requires a blood meal to complete its own life cycle
- When feeding on an infected host, parasite in gametocyte form is transferred to gut of mosquito
- Develop into gametes in midgut – fertilisation occurs to form zygote – which travel to midgut wall and form oocysts where they develop into sporozoites
- When oocyst bursts, sporozoites released and travel to salivary gland
- When mosquito feeds on another host, sporozoites transferred to blood stream and travel to liver – enter liver cells
- Sporozoites reproduce in liver cells and form merozoites after 12 days – liver cell ruptures and merozoites released into blood stream
- Enter RBC and reproduce:
- asexual merozoites released when RBC bursts and can infect other RBC – toxins released cause cyclical malaria symptoms (fever, sweats, delirium, headaches)
- sexual merozoites form gametocytes which circulate in blood and ingested by female Anopheles mosquito
Host response:
- Plasmodium protected for most of life cycle as it resides within liver and blood cells
- Circulating infected RBC destroyed in the spleen
- P. falciparium displays adhesive proteins on the surface of infected RBCs, causing blood cells to stick to the walls of small blood vessels
- When in RBC, host produces antibodies against Plasmodium
Major symptoms:
- Shivering, fever, sweats, delirium, headache, joint pain, anaemia, nausea, vomiting, brain swelling, diarrhoea, jaundice and convulsions
Treatment:
- Anti-malarial drugs – chloroquine, quinine (effective against parasites in RBC) and primaquine phosphate (for parasites in RBC and liver cells) are used
- Artemisinin derivatives used in areas experiencing resistance to other drugs
Prevention:
- Using mosquito nets, insecticides and protective clothing to cover body
- DDT used to kill mosquito vectors – resistance and detrimental impacts to environment caused it to be phased out.
- Prophylactic drugs such as quinine, chloroquine, mefloquine and malarone (also for treatment)
- Must be taken daily/weekly – prophylactic effect does not begin immediately (take 2 weeks before entering malaria-endemic areas and 4 weeks after return).
- Due to cost and negative side-effects of continual use – prophylactic drugs usually restricted to travellers and short-term visitors to malarial regions.
Control: (measures to eliminate source of infection, vectors etc to keep incidence of disease to a minimum in the population)
- Practicing vector control – Quarantine, destroying habitat by removing/poisoning breeding grounds and applying oil to standing water to destroy habitat for larva stages, using pesticides
- Education campaigns to recognise the symptoms of malaria and/or help with vector control
- Research into a vaccine against the malaria protozoan (Plasmodium)
These are my Malaria notes