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malaria

malaria

see also:

  • prophylactic antimalarials do not eliminate the possibility of malaria, appropriate testing should always be done for a febrile traveller without obvious cause returning from a malaria endemic region.
  • initial blood films may be negative, and repeat films should be taken every six to 12 hours for 36–48 hours before malaria can be confidently excluded.
  • untreated falciparum malaria can be fatal within 24–48 hours of presentation, particularly in children.
  • patients with falciparum malaria require hospital admission until the disease is clearly under control

introduction

  • 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 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

prophylaxis

infection risk

  • 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

avoid mosquito bites

  • 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

chemoprophylaxis

  • 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

areas with chloroquine-susceptible malaria

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

areas with chloroquine-resistant malaria

  • 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

  • doxycycline is active against pre-erythrocytic and asexual bloodstages of Plasmodium falciparum but tetracyclines are only partially active against the pre-erythrocytic stages of P. vivax, and doxycycline has no activity against the relapsing forms (hypnozoites) of Plasmodium vivax

  • 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!

Ix and Mx of the returned traveller with suspected malaria

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

urgent treatment of severe malaria

  • 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

uncomplicated falciparum malaria

  • 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)

vivax acquired outside of Indonesia

  • oral chloroquine

vivax acquired in Indonesia

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

elimination of liver forms of P.vivax or P.ovale

  • add primaquine to above Rx
    • NB. C/I if G6PD as risk of severe haemolysis
malaria.txt · Last modified: 2015/11/09 22:39 by gary1