Malaria and its implications for public health in Far North Queensland: a prospective study

This prospective study's objectives were to describe the features of all episodes of malaria diagnosed in Far North Queensland (excluding the Torres Strait) and to assess how much of a threat they posed to the area's public health. Over a three-year period, 216 episodes of malaria were diagnosed (158 Plasmodium vivax and 68 P. falciparum infections). Most (82%) of the infections were acquired in Papua New Guinea (PNG). Approximately 70% of the episodes occurred in Australian citizens, about half of whom were in malaria-endemic countries for work; the remainder travelled abroad for recreation. Three-quarters of the Australian citizens with malaria had taken either no or inadequate prophylaxis. Australian citizens who had taken adequate prophylaxis were much less likely to develop P. falciparum than other types of malaria compared to those who took either no or inadequate prophylaxis (p = 0.01). Gametocytes were present in 121 (56%) of the episodes of malaria. Mosquito surveillance was carried out in response to 38 (31%) of these gametocytaemic episodes. Significant numbers of Anopheles farauti sensu lato mosquitoes were found close to the residence of a patient in 4 (11%) of these episodes. Only two occasions when local transmission could have possibly occurred were recognised. We do not believe malaria poses an important threat to the health of the public in Far North Queensland. Nevertheless, it remains an important problem for those who travel abroad to malarious areas.