Notifications of imported malaria in Western Australia, 1990-2001: incidence, associated factors and chemoprophylaxis

Objective: To assess changes in and factors associated with recent malaria notifications in Western Australia (WA).Design: Retrospective analysis of the WA Notifiable Infectious Diseases Database and enhanced surveillance questionnaires completed by attending medical practitioners.Patients: Cases of malaria notified between January 1990 and December 2001.Main outcome measures: Annual notifications by demographic variables (including age, sex, occupation and place of residence), region/country of acquisition, chemoprophylaxis used, Plasmodium species and outcome.Results: 482 patients were notified (mean age, 31 years; 80% male); 57% lived in Perth, 31% in country areas and 12% in an immigration detention centre. Comparison between the 6-year periods 1990-1995 and 1996-2001 showed that Plasmodium falciparum cases increased from 29 (14%) to 108 (44%; P < 0.001), while Plasmodium vivax cases decreased from 157 (77%) to 122 (50%; P < 0.001); immigrants in detention, defence force personnel and cases from Africa were increasingly represented (P < 0.05 in each case). Only 31% of patients took regular chemoprophylaxis and, among these, the regimen was appropriate in only a quarter. There was a median period of 3 days between symptom onset and diagnosis. One patient died.Conclusions: There has been an increase in P falciparum cases in WA since 1990. This reflects the influx of immigrants in detention, deployment of military personnel to East Timor and increasing numbers of cases from Africa. A significant number of Australian travellers who developed malaria had not taken chemoprophylaxis either regularly or at all, and, of those who had, the regimen was inadequate in most.