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The epidemiology and control of primary amoebic meningoencephalitis with particular reference to South Australia
Abstract:
This paper reviews the history, epidemiology and control of primary amoebic meningoencephalitis (PAM), caused by Naegleria fowleri, with particular reference to South Australia. The intention has been to outline misconceptions and uncertainties pervading the earlier literature. Although PAM infections elsewhere have been attributed to cysts in air-borne dust, we believe that contact with water in the domestic environment was not adequately considered as a potential source of these infections. Several reports have cast doubt on the effectiveness of chlorine in controlling N. fowleri, although there is laboratory and South Australian field experience to the contrary. These reports can be traced to a misunderstanding of the circumstances surrounding cases of PAM reported by other workers. Provided that a continuous free chlorine residual of 0.5 mg/l can be maintained in water accessible to N. fowleri, the risk of disease should be negligible. The failure of amphotericin B therapy to save recent victims of the disease, despite relatively prompt intervention, is disappointing. Possible reasons for this, and the reports that rifampin or tetracycline combined with amphotericin might be more successful, are discussed.
Insights
Primary amoebic meningoencephalitis (PAM), caused by Naegleria fowleri, may be linked to domestic water contact, not just airborne dust. Maintaining a chlorine residual of 0.5 mg/l in water is crucial for preventing this rare but severe brain infection.
Area of Science:
- Infectious Diseases
- Public Health
- Environmental Microbiology
Background:
- Primary amoebic meningoencephalitis (PAM) is a rare, devastating brain infection caused by the amoeba Naegleria fowleri.
- Historical literature on PAM epidemiology and control contains misconceptions and uncertainties.
- Previous attributions of PAM to airborne dust may overlook domestic water contact as a primary infection source.
Purpose of the Study:
- To review the history, epidemiology, and control of PAM, focusing on South Australia.
- To clarify misconceptions regarding N. fowleri transmission routes.
- To evaluate the effectiveness of chlorine disinfection and amphotericin B therapy for PAM.
Main Methods:
- Literature review of historical and contemporary PAM cases and control measures.
- Analysis of epidemiological data, particularly from South Australia.
- Examination of laboratory and field data on chlorine efficacy against N. fowleri.
- Discussion of therapeutic outcomes and alternative treatment strategies.
Main Results:
- Domestic water contact is proposed as a significant, potentially underestimated, source of N. fowleri infections.
- Reports questioning chlorine's effectiveness against N. fowleri stem from misunderstandings of case circumstances.
- A continuous free chlorine residual of 0.5 mg/l in accessible water is considered effective in mitigating PAM risk.
- Amphotericin B therapy has shown disappointing results in recent PAM cases, prompting discussion of alternative treatments.
Conclusions:
- Naegleria fowleri transmission may be more closely linked to domestic water exposure than previously emphasized.
- Effective control of N. fowleri in water systems is achievable with a consistent free chlorine residual of 0.5 mg/l.
- Current therapeutic interventions for PAM, such as amphotericin B, require further investigation and potential combination therapies for improved outcomes.