22

• The life cycle – exoerthyrocytic cycle – 6 stages
• 1)Infected female anopheles mosquito injects sporozoites from salivary glands when she bites

  2)Sporozoites taken to liver through circulation

  3)Motile sporozoites penetrate kupfer cells then heaptocytes. Asexual reproduction occurs in liver.

  4)Known as primary exoerthyrocytic cycle and merozoites are released

  5)Can reinfect liver cells to become secondary exoerthyrocytic cycle.

  6)Merozoites enter bloodstream and infect RBC.
• After exoerthyrocytic stage there is the erthyrocytic stage – asexual reproduction continues. RBC bursts after a time period. Released merozoites then infect other RBC. Malaria caused by toxins released by burst RBC.
• After the erthyrocytic cycle is the anopheles cycle.

  After the merozoites infect the RBC, they produce sexual gametocytes which develop no further in the blood cells.

  Uninfected anopheles female mosquito takes the infected blood.

  The gametocytes in the blood becomes male and female gametes in the mosquitos stomach.

  The male and female microgametes then seek each other out.

  The fertilized zygote then penetrates the stomach wall.

  Forms oocyte and undergoes meiosis and mitosis on external stomach wall.

  The slender sporozoites formed migrate to salivary glands ready to infect another human.
• Epidemiology and pathology of falciparum – found in subtropics and tropical regions.

  Causes malignant tertian malaria. The infected RBC have projection knobs which stick to the blood capillaries causing obstruction which leads to clots and thrombosis.

  Fatal complications leads to blackwater fever and cerebral malaria.

  No exoerthyrocytic stage is unusual.
• Epidemiology and pathology of vivax – most widespread. causes benign tertian malaria. Has recurring fever. Mild symptoms. May persist upto 5 years if left untreated. Liver is resevoir of infection. Spleenic rupture is rare.
• Epidemiology and pathology of malariae - causes quartan malaria. Generally benign in adults. Nephrotic syndrome in children. Untreated can lead it to persist for 40 years.
• Epidemiology and pathology of ovale – least common. Rarely causes ovaale tertian malaria. Benign.
• Malarial drug treatment – recent treatment is ACT’s (artemisinin based cobmination therapy). Ineffective if not used properly.

  Can be used to combat drug resistant falciparum. It is effective and may help in delay resistance development.

  Ensure wide access and affordability to these medicines.
• Malarial control – indoor residual spraying, insecticide treated nets, intermittent presumptive treatment for children and pregnant women. Effective healthcare access, education and communication and capacity to detect, plan and respond to early signs.
• Malaria prevention – insecticide treated nets and indoor residual spraying.

  Insecticide treated nets – physical barrier and insecticidal effect between mosquito and human. This reduces contact. This can kill mosquitos at a large scale where the population is dense.

  Indoor spraying with residual insecticide – rapidly reduce malarial transmission. Spray insecticide inside houses once or twice a year.
• Malarial control – through antimalarial drugs and vaccines
• Malarial treatments – chloroquine is first line treatment for vivax and ovale. Primaquine can be used to treat liver stage parasites for vivax.

  Chloroquine – used for acute attacks. Prevents DNA synthesis during the erythrocytic stage.

  Primaquine – used for exoerythrocytic stage. Potent gametocytocidal activity. It is a recommended preventative medication.