Supplement

Canadian Recommendations for the Prevention and Treatment of Malaria Among International Travellers

5. Malaria Prevention in the Long-term Traveller or Expatriate

Modern prevention strategies have had a significant, positive impact on the risk of mortality in long-term expatriates, which was reported to be as high as 60% among missionaries in West Africa during the 19th century. However, the effort to develop unique, evidence-based guidelines for the long-term (> 6 months) traveller or expatriate is severely hampered by a paucity of medical literature in this area.

Concerns encountered when addressing malaria prevention in long-term travellers and expatriates include conflicting counsel regarding appropriate chemoprophylaxis and self-treatment, the safety of drugs used for chemoprophylaxis, fear of toxic effects with prolonged use of medication, and lack of adherence to the use of personal protective measures. Confidence but lack of rigour in self-diagnosis coupled with unreliable laboratory diagnosis in many developing countries have resulted in a misrepresentation of drug efficacy by the long-term traveller/expatriate.

Data on the incidence of malaria and the effectiveness and tolerance of currently recommended regimens for long-term travellers are limited to the studies of Peace Corps volunteers, in whom mefloquine was well tolerated and was more effective than chloroquine and proguanil in chloroquine-resistant regions. At present, there is no evidence that long-term use of therapies currently recommended for short-stay travellers causes significant adverse reactions. Doxycycline may be an exception, as studies have been confined to short-term travellers and people using tetracyclines (at lower doses) as therapy for skin conditions. In general, guidelines for the prevention of malaria in long-term travellers or expatriates should not deviate significantly from standard recommendations for the short-term traveller.

A recent, self-reported summary of the malaria prevention strategies of 1192 long-term expatriates, representing a broad range of government and non-government organizations in subSaharan Africa, may provide some assistance in counselling long-term travellers and expatriates. Overall, their compliance rate was approximately 60%. Of those receiving chemoprophylaxis, 54% reported changing their prophylactic regimen, 22% because of adverse effects. The severity of the adverse effects was not associated with any specific drug, but the reported incidence of neuropsychiatric side effects was 10% among people taking chloroquine and proguanil as compared with 17% in the mefloquine group. Mefloquine was the only regimen for which participants reported a change in practice based on media influence. Only a small number indicated that availability and cost were factors in their choice of pro-phylactic regimen. Participants who did not use prophylaxis cited concerns about adverse reactions and long-term effects as the primary reasons for their choice. Personal protective measures were suboptimal: only 38% had screened doors and windows, and 53% used mosquito netting (20% of which were insecticide-treated nets).

There are no data available on self-diagnosis and self-treatment of malaria in the long-term traveller or expatriate population. Without training, there is no reason to believe that the efficacy of these interventions will be any better than that demonstrated in the general travel population. However, given that long-term travellers and expatriates represent a reasonably homogeneous group, training in diagnosis and self-treatment (see Sections 6 and 7), including the use of rapid diagnostic tests for malaria, may prove to be helpful in this population when access to reliable, formal medical care is inadequate. Self-diagnostic kits that require refrigeration will limit access to this technology in some regions.

Section 3e addresses the use of primaquine as terminal prophylaxis to decrease the risk of relapses through its action against the liver stages of P. vivax and P. ovale. Primaquine terminal prophylaxis is administered after the traveller has left a malaria-endemic area, usually during or after the last 2 weeks of chemoprophylaxis. Terminal prophylaxis with primaquine is generally indicated only for people who have had prolonged exposure in malaria-endemic regions, such as expatriates or long-term travellers. Primaquine is contraindicated in pregnant women and individuals deficient in G6PD (see Section 9 for contraindications and precautions).

In conclusion, guidelines for the prevention of malaria in long-term travellers or expatriates should not deviate significantly from the recommendations for short-term travellers (B III - evidence-based medicine recommendation, see Appendix II). The available data indicate that expatriates in high-risk settings have not effectively used personal protective measures (B II - evidence-based medicine). The majority use a prophylactic regimen, but sound counsel does not always guide their choice: a significant proportion is influenced by perception of risk rather than documented problems. Thus the effectiveness of current recommendations will be influenced by the prevailing attitudes in the subculture in which the long-term traveller or expatriate lives (C - evidence-based medicine). At present, there is insufficient evidence for the effectiveness of self-diagnosis with rapid malaria test kits to recommend their routine use. Primaquine should be given as terminal prophylaxis, after consideration of precautions and contraindications, to long-term travellers or expatriates who return from regions with P. vivax transmission (A I - evidence-based recommendation).

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