Arguments against Chemoprophylaxis in Areas at Low Risk for Chloroquine-Resistant Plasmodium falciparum.
Chemoprophylaxis of malaria prevents the disease not the infection (suppressive chemoprophylaxis) with "high levels of confusion and low levels of compliance." The magnitude of danger of contracting malaria for travelers varies in several endemic zones. In West Africa, without prophylaxis, malaria is estimated to have an incidence of 1.4% per person per month. In South and Central America, the incidence is 0.05 and 0.01% per month, respectively. In Asia, the transmission and percentage of infection due to Plasmodium falciparum is much lower. The dangers of chemoprophylaxis in an area at low risk for chloroquine resistant P. falciparum are a reality. Incompletely active drugs change clinical manifestations, and changes in clinical manifestations delay the establishment of a correct diagnosis. The rate of adverse events is 15-20%, and hospitalization due to side effects of prophylaxis occurs in one in 10,000 travelers. Neuropsychiatric side effects have been reported with both mefloquine and chloroquine. A false sense of security can hinder a physician practicing in a nonendemic area from thinking of malaria when a traveler returns with fever. To complicate the picture, in many countries, there is an emerging drug resistance in P. falciparum as well as an emerging chloroquine resistance in P. vivax strains (20% in New Guinea and Irian Jaya). In short, no available chemoprophylaxis is free from toxicity, and its efficacy is never 100%. Alternatives to conventional chemoprophylaxis are encouraged in areas of low morbidity of malaria. In areas where P. vivax occurs primarily, and when the risk of serious side effects from chemoprophylaxis outweighs the risk of life threatening P. falciparum infection, there are four alternative strategies.2,3 The first strategy is that the traveler avoid mosquito bites. With a compulsive attitude, a high degree of protection can be realized with the proper use of pyrethrum-impregnated mosquito netting, topical DEET-containing insect repellents and impregnated protective clothing. Secondly, when the stay in malaria-endemic areas is less than 1 week, the disease will appear after returning home. No chemoprophylaxis is needed during the journey. With the onset of fever, diagnosis and therapy are performed without delay at home. This strategy assumes the participation of an informed physician. A third strategy is standby treatment, which is defined by the World Health Organization (WHO) as the use of antimalarial drugs carried for self administration when fever occurs and prompt medical attention is not available. Standby treatment is a safe option for an informed tourist traveling to areas at low risk of malaria or in areas where chemoprophylaxis may not be effective. Likewise, self therapy might be preferred for travelers who make frequent journeys characterized by brief and successive visits to malarious and nonmalarious areas, and for long-term travelers, and expatriots. Standby treatment minimizes drug overuse, demands early investigation of any febrile illness, and insists that effective treatment is given rapidly for P. falciparum malaria that occurs in nonimmune persons. This strategy is the responsibility assumed by teaching physicians and appears to be more advantageous than classic long-term chemoprophylaxis. A fourth strategy is systematic curative treatment carried out under supervision upon a traveler's return home. The administration of halofantrine after departure from endemic areas was studied for the prevention of P. falciparum malaria after short-term exposure,4 but the adverse cardiac effects of this drug obviates the usefulness of this "radical cure". Possibly the administration of doxycycline or azithromycin after departure from malarious areas could prevent P. falciparum malaria after short-term exposure and with less deleterious side effects. This approach requires more research, and again this will be the responsibility of physicians.
Armengaud
M
Professor of Maladies Infectieuses, University of Toulouse, Maladies Infectieuses et Tropicales Hopital Purpan, Toulouse, France.