malaria

see also:

• travel medicine
• the febrile returned traveller
• transdermal detection of malaria in blood using laser to create nanobubbles in the RBC and then acoustic assessment of them bursting - low cost, battery powered devices may revolutionise diagnosis

• high risk especially in travellers to West Africa (2%), Nigeria (1.3%), the Solomon Islands (1.1%), Ghana (0.6%) and Papua New Guinea (0.4%) without prophylaxis
• malaria was declared eradicated from Australia in 1981 however the region of northern Australia north of 19°S latitude is the receptive zone for malaria transmission
• gene for thalassemia identified in a hunter-gatherer Vietnamese man 7000yrs ago suggesting malaria was an issue in SE Asia before farming practices commenced¹⁾
• malaria caused by Plasmodium falciparum generally presents within six weeks of return from an endemic area, although onset may be delayed by prophylactic mefloquine.
• malaria caused by Plasmodium vivax may present 6-12 months after exposure.
• patients infected with P vivax or P ovale may relapse after more than a year, because of the hypnozoite stage in the liver
• no signs or symptoms are specific to malaria, although fever is invariable.
• may mimic acute gastroenteritis, acute abdomen, pneumonia and meningoencephalitis

• WHO handbook (pdf)

• risk of acquiring malaria depends on factors such as:
  • country and area visited
  • time of year
  • duration of visit
  • type of activities undertaken
• malaria can pose a serious problem for pregnant women and postsplenectomy patients, it is strongly recommended that they do not go to malarious areas, particularly those areas with drug-resistant falciparum malaria

• use effective personal insect repellent and an insecticide for indoor use
• wear light-coloured long trousers and long-sleeved shirts in the evening
• sleep in screened accommodation or using mosquito nets, which can be pyrethroid impregnated
• avoid outside activities between dusk and dawn
• avoid perfume and aftershave

• RTS,S (Mosquirix)
  • work on it began in 1987, then trialled and piloted in 2019 in Ghana, Kenya and Malawi, endorsed by WHO in 2021
  • prevents 39% of malaria cases and 29% of severe malaria cases among small children in Africa
  • 70% reduction in hospitalisation or death when young children were given both the RTS,S and antimalarial drugs
• R21/Matrix-M vaccine
  • similar efficacy as RTS,S but released late 2023 with more availability and cost effectiveness
  • 4 doses needed, the first three doses at monthly intervals from five months old, followed by a booster at two years old.

• there is no drug regimen that is completely safe and effective against malaria
• in some places, including many major cities and tourist resorts in malaria-endemic countries, the risk of malaria is low and no prophylaxis needs to be taken
• prophylaxis for children may also prove problematic:
  • doxycycline is not recommended for children 8 years or less
  • mefloquine is not approved for use in children in Australia, but has been widely used overseas
  • the combination of chloroquine and proguanil has been widely used for malaria prophylaxis in pregnant women and children, but this regimen can no longer be relied on in most areas including Africa, South-East Asia and the Pacific Island Nations

• chloroquine once weekly
  • starting 1 week before entering, and continuing until 4 weeks after leaving the malarious area

• including Pacific Island Nations, South-East Asia, Indian subcontinent, China, Africa, South America and the Middle-East
• adults:
  • doxycycline 100 mg orally, daily
    • starting 1 to 2 days before entering, and continuing until 4 weeks after leaving the malarious area

• or, if body weight > 11kg and creatinine clearance > 30 mL/min, daily atovaquone and proguanil:
  • (eg. Malorone 250/100 or Malorone Junior 62.5/25)
  • non-PBS for prophylaxis!
  • start 1-2 days prior and cease 7 days after leaving malarial area
  • adults and children > 40kg take 1 Malorone 250/100 tablet same time each day with food (eg. breakfast)
  • if vomit within 1 hour of dose, take a repeat dose
  • these interfere with pyrimidine biosynthesis pathways
  • better adverse event profile than mefloquine or chloroquine/proguanil
  • if used as a prophylactic, should not be used to Rx infection!

• thick and thin blood films - repeat 6-12hrly for 24-48hrs if negative
• seek urgent infectious diseases expert advice

• urgent Rx is essential if the patient has any of the following:
  • any degree of altered consciousness, jaundice, oliguria, severe anaemia or hypoglycaemia
  • a parasite count above 100 000/mm^3 (greater than 2% of red blood cells parasitised)
  • the patient is vomiting or clinically acidotic
• see therapeutic guidelines
• if immediately available, start iv artesunate, otherwise start iv quinine dihydrochloride load dose then maintenance
• once patient stable and able to tolerate oral foods, give Rx as per uncomplicated falciparum
• seek expert advice

• oral artemether+lumefantrine is the drug of first choice
• alternatively:
  • atovaquone+proguanil tablets (C/I if prophylaxis was with these meds), or,
  • quinine sulfate + either doxycycline (if age > 8hrs), or clindamycin (if pregnant or child)

• oral chloroquine

• either:
  • artemether+lumefantrine, as for uncomplicated Plasmodium falciparum malaria, or,
  • mefloquine (but C/I if mefloquine used as prophylaxis)

• add primaquine to above Rx
  • NB. C/I if G6PD as risk of severe haemolysis