H. Reyburn et al., THE EFFECT OF CHEMOPROPHYLAXIS ON THE TIMING OF ONSET OF FALCIPARUM-MALARIA, TM & IH. Tropical medicine & international health, 3(4), 1998, pp. 281-285
The association between chemoprophylaxis and delayed onset of falcipar
um malaria was investigated in a retrospective study of 477 nonimmune
cases reported to the UK Malaria Reference Laboratory (MRL) who had us
ed either mefloquine (n = 56), chloroquine-proguanil (n = 90) or no ch
emoprophylaxis (n = 331). For holiday and short-term travellers using
mefloquine the time between arrival in the UK and diagnosis was found
to be significantly longer than for chloroquine and proguanil (C-P) us
ers or for those who had not used prophylaxis at all (P < 0.004). This
delay was primarily due to a later onset of symptoms. C-P use was not
associated with delay in onset of symptoms or diagnosis when compared
to not using prophylaxis; Possible reasons for the findings are discu
ssed. Mefloquine may continue to exert a partially suppressive effect
on resistant strains of Plasmodium falciparum (Pf). That chloroquine w
ith proguanil was not found to have such an effect may be due to poor
compliance to proguanil or differences in the mode of action and range
of parasite resistance to the two regimens. Differences in drug compl
iance may be one reason why only mefloquine users on holiday or short-
term journeys experienced delays to onset of disease. Drug compliance
amongst cases of breakthrough malaria on chemoprophylaxis may be lower
than is generally recognized. It is important for clinicians and trav
ellers to be aware that the onset of falciparum malaria may be delayed
by mefloquine prophylaxis.