Science commentary

Protection against malaria

Abi Berger, Science editor. 

BMJ

Malaria can be prevented. Unfortunately, travellers to areas where malaria is common often put themselves at risk of contracting the disease by ignoring the key steps in malaria prevention. The steps are simple but if ignored can result in unnecessary morbidity and, in some cases, death. The key steps to protect against malaria are:

AAwareness: know about the risk of malaria

BBites by mosquitoes: prevent or avoid

CCompliance: with appropriate drug regimen

DDiagnosis: diagnose malaria swiftly and obtain treatment promptly.

	Incidence of side effects from prophylactic drugs

Top Incidence of side effects from... References

The number of cases of malaria imported into the United Kingdom is rising (figure), and over half of them are potentially fatal (falciparum malaria). The risks from the disease must be compared sensibly with the risks associated with the drugs recommended for prophylaxis. Obtaining true figures for the incidence of side effects is difficult and in some cases controversial. This is partly because as doctors become more aware of potential side effects, more side effects are looked for and then reported. Also, it is virtually impossible to perform anything other than observational studies on side effects because sending people to malarious areas with placebo drugs only would be unethical.

View larger version (27K): [in this window] [in a new window]   Number of cases of malaria, number of cases of falciparum malaria, and number of deaths from malaria in the United Kingdom, 1977-97. Data supplied by the Malaria Reference Laboratory, London School of Hygiene and Tropical Medicine (E Walker, personal communication)

Two other factors make it difficult to determine the incidence of side effects. Firstly, of the huge number of people taking antimalaria drugs some will get concurrent symptoms and diseases while abroad, and deciding whether to attribute these to the antimalaria drugs is difficult. Secondly, attributing subjective side effects to drugs is a common phenomenon, even for placebo drugs.

With short acting drugs (for example, proguanil, which is taken daily) side effects usually occur after just one dose. With longer acting drugs (for example, mefloquine, which is taken weekly), side effects may not become apparent until after the third dose.

Two large studies have reported the incidence of side effects of mefloquine compared with chloroquine and proguanil. Barrett et al found that both regimens had similar rates of any side effect occurring (40%), although most side effects were trivial.¹ About 0.7% of travellers taking mefloquine reported severe, disabling neuropsychiatric symptoms compared with 0.09% of people taking chloroquine and proguanil. Also a significantly higher number of moderate neuropsychiatric symptoms occurred in mefloquine users compared with travellers who took chloroquine and proguanil. Steffen et al found that 18.8% of travellers taking mefloquine had experienced side effects while 30.1% of the chloroquine and proguanil group reported problems.

	References

Top Incidence of side effects from... References

1. Barrett PJ, Emmins PD, Clarke PD, Bradley DJ. Comparison of adverse events associated with the use of mefloquine and combination of chloroquine and proguanil as antimalarial prophylaxis: postal and telephone survey of travellers. BMJ 1996; 313: 525-528[Abstract/Free Full Text].
2. Steffen R, Fuchs E, Schildknecht J, Naef U, Funk M, Schlagenhauf P, et al. Mefloquine compared with other malaria chemoprophylactic regimens in tourists visiting East Africa. Lancet 1993; 341: 1299-1303[Medline].