Failure of malaria chemoprophylaxis with a proguanil-chloroquine combination in Papua New Guinea.

Proguanil 200 mg daily and chloroquine base 300 mg weekly were used as prophylaxis for 120 British Army soldiers from Hong Kong on a seven-week jungle exercise in the highly malarious Sepik district of Papua New Guinea. Compliance was rigidly enforced. Four men developed falciparum malaria whilst in Papua New Guinea and one within a few days of returning to Hong Kong. After stopping chloroquine four weeks after returning to Hong Kong 11 cases of mixed vivax and falciparum malaria and three cases of falciparum alone occurred within a 16-week period. This proguanil-chloroquine combination allows an unacceptably high level of breakthrough malaria and cannot be recommended for visitors to the highly malarious areas of Papua New Guinea.