Limited data exist regarding the incidence of intestinal
microsporidiosis following the introduction of
highly active antiretroviral therapy (
HAART) in Australia. At St Vincent's Hospital, Sydney, all faecal samples submitted for diarrhoea from HIV-infected patients between 1995 and 2006 underwent screening for
microsporidiosis. A total of 3564 patients (7366 faecal specimens) was examined, resulting in 159 patients identified with
microsporidiosis. The incidence of
microsporidiosis declined from 11% in 1995 to 0% from 2004 onwards. At presentation the majority of patients were severely immunocompromised (median CD4 105 cells/mm(3)), with only 16% of patients on effective
HAART. Twenty-four patients (24/76, 32%) died within a median of 22 months following
microsporidiosis diagnosis. Significant predictors of
AIDS-related mortality at presentation included the level of immunodeficiency and receiving no or ineffective
HAART (P<0.05). Patients presenting after 1998 had a significant reduction in the risk of
AIDS-related mortality compared with patients presenting before 1998 (hazard ratio 0.27, 95% CI 0.79-0.92). All 52 (68%) surviving patients were on effective
HAART, with a median CD4 count 382 cells/mm(3) and HIV
RNA of < 50 copies/ml at follow-up (median 4 years). The dramatic decline of intestinal
microsporidiosis in our study reconfirms the importance of effective
HAART in preventing advanced immunodeficiency,
opportunistic infections and associated
AIDS-related deaths.