Malaria prophylaxis for travellers
Travellers planning to visit malaria endemic zones must always, consult with their doctors to make sure that they take a prophylaxis (measure taken for the prevention of a disease or condition) drug which they can tolerate and one which is appropriate for their destination to be protected from malaria.
Current first-line strategies for chemoprophylaxis were designed to prevent death due to severe falciparum malaria. These drugs also have the benefit of largely preventing primary attacks due to non-falciparum species, although not the later relapses that can occur with P. vivax and P. ovale. Currently available drugs are Chloroquine, Proguanil, Mefloquine, Doxycycline, Malarone.
The choice of a drug for a person travelling to areas where there is chloroquine-resistant malaria depends on traveller-related factors including the duration of the trip, the person's age and medical history, whether the person is pregnant, and whether there has been previous drug intolerance, as well as economic considerations. Information relevant to the choice of agent, including contraindications and side effects. Atovaquone-Proguanil is the best-tolerated drug overall, but cost considerations significantly increase with the length of the trip. Clear instructions on adherence to prescribed drugs should be given.
Contrary to a common perception, antimalarial agents such as chloroquine, mefloquine, and doxycycline do not prevent initial malaria infection in humans; rather, they act later on parasites that infect erythrocytes once they have been released from the initial maturation phase in the liver. Therefore, these drugs must be continued for 4 weeks after the last exposure to infective mosquitoes in order to eradicate any parasites that may still be released from the liver in the next month. However, Atovaquone-Proguanil not only acts on these blood-stage parasites but also interferes with the development of actively replicating parasites in the liver; therefore, it can be discontinued 1 week after exposure ends.
Antimalarial chemo-prophylaxis with atovaquoneproguanil and doxycycline should begin 1 to 2 days before travel to areas where malaria is endemic, and chemo-prophylaxis with chloroquine should begin one week before travel. Treatment with mefloquine should begin at least 2 weeks and preferably 3 weeks before travel, mostly to allow for the assessment of possible adverse effects that might warrant discontinuation and prescription of an alternative drug.
Unexplained acute anxiety, depression, restlessness, and confusion are indications for discontinuation and a switch to an alternative agent. The first day in an area where malaria is endemic may not correspond to the arrival date in the country where there is a risk of malaria.
Safety and freedom from side effects are of paramount importance in chemo-prophylaxis and should override complete efficacy; no regimen even approaches 100% prevention against infection with Plasmodium falciparum. Advocates of widespread use of mefloquine have produced figures purporting to support a rarity of side effects (in particular neuropsychiatric ones), which are seemingly far less common when this agent is used in chemoprophylaxis than when it is used in chemotherapy. A great deal of clinical experience indicates, however, that these reports seriously underestimate the prevalence of side effects in travellers: Many travellers refuse to take mefloquine in the light of their experience of its neuropsychiatric side effects.
The regimen of chloroquine plus proguanil has a low incidence of side effects and for much of sub-Saharan Africa is probably only marginally inferior in efficacy to mefloquine. Furthermore, widespread use of mefloquine for chemoprophylaxis raises the likelihood of the emergence of P falciparum resistant to quinine (considerable cross resistance exists between mefloquine and quinine); this is a genuine but understated problem.
It is better recommend that chloroquine plus proguanil for all countries of Africa in which infection with P falciparum is a potential hazard. In addition, travellers should be advised to take standby treatment (usually quinine) for use in the event of a febrile illness that cannot be adequately assessed or treated at a reputable medical centre. Mefloquine should be reserved for chemotherapy of infection with P. falciparum that is resistant to quinine.
The treatment guideline in this article should not be followed without any prior consultation with a registered physician. Email: [email protected]
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