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.