The public health threat from Balamuthia mandrillaris in the southern United States

Abstract

Balamuthia mandrillaris, formerly known as leptomyxid ameba, is an opportunistic, free-living ameba, related to Acanthamoeba that can cause skin lesions and granulomatous amebic encephalitis in individuals with compromised or competent immune systems. In order to make recommendations for early diagnosis, management, and prevention of typically fatal Balamuthia amebic encephalitis (BAE), this review described and analyzed laboratory-confirmed US cases of BAE for any consistent behavioral, demographic, environmental, ethnic, iatrogenic, occupational, recreational, or regional exposure factors over the study period, 1980-2010. The ages of all case-patients were stratified by age and gender and compared for statistically significant differences by two-tailed, unpaired t-tests. Potential risk factors were also stratified by age and gender, described, and compared by proportions and rates. The results of this study demonstrated that BAE occurred sporadically in patients of all ages in both immunosuppressed and immunocompetent patients. In addition, BAE exhibited only a few consistent predisposing factors that included male gender, exposure in a southern tier US state, and Hispanic ethnicity. Clinicians should suspect BAE in refractory cases of meningoencephalitis initially managed as aseptic or bacterial infections, especially in patients predisposed to BAE; confirm the diagnosis by immunodiagnostics, brain or skin biopsies, and institute conventional and, possibly, experimental, antiprotozoal therapy immediately. Brain dead victims of BAE are not suitable organ donors and have transmitted fatal BAE to organ transplant recipients.