Malaria Prophylaxis

This Section was written by:
Professor T.M.E. Davis B. Med Sc (Hons), MB BS, D Phil (Oxon), MRCP, FRACP,
University Department of Medicine,
Fremantle Hospital, Western Australia.

Antimalarial drug prophylaxis is a difficult area with a number of drug resistant strains of P. falciparum now common, particularly in South East Asia and increasingly in Africa.  Resistance to Fansidar, Chloroquine, Maloprim, Lariam and Halofantrine, Malarone and quinine have all been reported.  Resistance is important because falciparum malaria can be rapidly fatal.  The type of prophylaxis used depends on the area being visited (e.g. country, city, rural area) and local parasite drug resistance patterns.

Pregnant women are especially vulnerable to malaria, which remains an important cause of stillbirths, infant mortality and low birth weight.  Pregnant women are twice as attractive to malaria-carrying mosquitoes as non-pregnant women, perhaps due to a greater volume of exhaled air (21%) and a warmer (0.7°C) skin surface.

Chloroquine offers little or no protection against P. falciparum in South East Asian countries and this is increasingly the case in other regions.  While effective in suppressing P. falciparum in some parts of Africa and most strains of P. vivax, resistant forms of P.vivax are appearing and have been reported in Papua New Guinea, Indonesia, Thailand and India.  Combination chemoprophylaxis such as with chloroquine and Fansidar^TM is not recommended because of the potential for greater adverse clinical effects (including Stevens-Johnson syndrome) and reduced compliance.

It is recommended that travellers commence taking prophylaxis at least a week before visiting a malaria endemic region so that any adverse drug reactions can be observed prior to travel.  In some cases, this will also allow effective blood levels to be achieved.

The major problem is how best to suppress malaria in travellers, particularly those visiting regions where it is known that drug-resistant strains are present.  At present the following is recommended:

Travellers should take active measures to protect themselves against mosquito bites.  This is the best and most effective means of avoiding malaria.  Generally mosquitoes start feeding at dusk.  Therefore, there need be no restrictions on dress during the day but, from just before dusk, clothing should be worn that covers the arms and legs.  In addition, a mosquito repellent should be applied on other exposed parts.  Suitable repellents are "Muskol" and "RID".  Both have a high N,N-diethyl-meta-toluamide (DEET) content (more than 15%) which is the active agent.  Both are available from retail chemists.  Repellents containing more than 30% DEET are not generally recommended.  Care should be taken when using these repellents on children, because serious side effects, sometimes related to excess use, have been reported.  DEET-containing repellents can be applied to a child's clothing rather than the skin but it is important to advise parents to wash the child's hands on entering a screened area.  If wearing very thin clothing, lightly spray the clothing with repellent because mosquitoes may bite through thin clothing.  Knock-down sprays, mosquito coils and pyrethrin-impregnated mosquito nets can also be effective at minimizing vector contact.

Four regimens are set out below. The choice depends on the countries which are to be visited and possible drug sensitivity of the traveller.

• Chloroquine can still be used in some regions but is of limited value in many parts of the world.  Treatment should be started one week before travelling to, and continued for four weeks after leaving a malaria endemic area.  (Adult dose 300mg weekly taken with a meal, at the same time and on the same day each week).  It will suppress but not cure an infection with P. vivax and symptoms may not appear for weeks or months after the traveller has returned home.  For children the dose is 5mg/kg base given once a week on the same day each week.  Since liquid suspensions for children are no longer available, a tablet has to be divided to provide the appropriate dose.  Chloroquine has a bitter taste and should be given to children crushed in a strong flavoured (sweet) drink.  Prophylactic drugs in children should not be given without advice from a medical practitioner, preferably one practising from a health travel medical centre.
  
  Chloroquine is considered a safe drug for pregnant and lactating women and also for children.  However, it is wise to discourage women who are pregnant from travelling to areas where malaria is present because of the difficulties associated with treatment and the risk to the mother and foetus should they get malaria.
  
  
• Doxycycline is a suitable prophylactic anti-malarial agent to use in high risk areas such as South East Asia.  It must not be used in children under 8 years of age nor in pregnant or breast-feeding women.  Doxycycline may cause contraceptive pills to be less effective so additional precautions should be taken.  It may cause thrush in some women but usually only when taken for long periods.  It may cause severe skin photosensitivity in some individuals.  Doxycycline - Adult dose 100mg daily.  Start 1-2 days before travelling to a malarious area and continue for 2-4 weeks after leaving.  To ensure that the patient is not sensitive to doxycycline it is worthwhile starting treatment 7 days before travelling.  It is recommended that it is not taken for longer than three months without a medical review.
  
  
• Mefloquine (Lariam) is still a widely used prophylactic.  It has a long half life and the convenience of a once weekly dose.  For adults (more than 45 kg bodyweight) the dose is 250mg base weekly, starting one week before arrival in a malarious area.  Side effects have been reported which are generally mild (e.g. Sleep disturbances, gastrointestinal disturbances, dizziness or disturbed sense of balance).  A rare but important adverse reaction is acute brain syndrome which occurs in one in 5,000-20,000 of those taking the drug.  It is not recommended for aircraft pilots or drivers of public transport.
  
  
• Malarone^TM.  This is a combination of atovaquone and proguanil and recent studies have found it a safe and effective prophylactic agent with few side affects.  Unfortunately it is expensive (~US$42 for 12 tablets) and has to be taken daily.  It is not suitable for those sensitive to atovaquone or proguanil.  Treatment should be started 2 days before travel and continued for at least 7 days after a period of potential exposure to malaria.
  
  

Other possible regimens include daily azithromycin, daily high-dose primaquine and short course tafenoquine.

It is emphasised that visitors to large towns or cities are much less at risk of catching malaria than travellers to rural areas.  Bedrooms in multi-storey air-conditioned hotels are usually free of mosquitos. If living "rough" always sleep under a mosquito net.  Make sure that it is free of holes, is well tucked in and ideally impregnated with Permethrin^*.  Alternatively, one of several new and more effective, recently introduced synthetic pyrethroids (e.g. deltamethrin), may be used which has been shown to be effective even after 20 washings of the impregnated net.  Impregnation of the mosquito nets can be done at home prior to travelling.

For adults travelling in rural or country areas where drug resistant P. falciparum malaria has been reported and where medical attention may not be available, standby treatment can be used as an alternative to, or in addition to, chemoprophylaxis.  Potential standby drug regimes are those listed for the treatment of uncomplicated falciparum malaria (see treatment section) and include artemisinin-based regimens that can be purchased ‘over the counter’ in many tropical countries.

There are now test kits for malaria^* designed for those travelling in remote areas.  These antigen detection kits allow a diagnosis of falciparum malaria (and other species in some cases) to be made quickly without other equipment and treatment can be started without delay.  Self-diagnosis with a rapid test kit is not a substitute for a medical consultation but it could be useful in an emergency.  With some kits, species-specific diagnoses are possible but all allow the identification of P. falciparum with reasonable accuracy.

A multi-species, multi-strain vaccine has long been sought.  By its very nature this is a complex and lengthy endeavour.  Although vaccines have been produced, clinical trial results to date have been disappointing and it seems likely that a vaccine is still some time away.

With the increasing spread and intensity of malarial resistance to drugs worldwide, prophylaxis can never be considered completely reliable and malaria must always be considered in febrile patients who have travelled to areas where malaria is endemic irrespective of whether chemoprophylactic agents have been used.  It should be remembered that P. falciparum can sometimes cause sickness and death in a matter of hours and it is important to get to a medical practitioner FAST if you have fever and/or are disorientated.  Test kits and emergency treatments are useful but are only aids.

^* These items should be available from the Health Travel Medical Centre in your State.  A list of sites can be found at: Travel Doctor.