Trends in Parasitology
Volume 29, Issue 10, October 2013, Pages 483-488
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Review
Is Balamuthia mandrillaris a public health concern worldwide?

https://doi.org/10.1016/j.pt.2013.07.009Get rights and content

Highlights

  • Balamuthia mandrillaris is an emerging pathogen that causes brain and skin infections.

  • Data indicate lack of diagnostic tools and unawareness of clinicians about them.

  • Specific diagnosis or effective therapies for B. mandrillaris are a necessity.

  • Understanding their biology and pathogenesis will assist in future developments.

Balamuthia mandrillaris is an opportunistic, free-living amoeba that can cause skin lesions and the typically fatal Balamuthia amoebic encephalitis (BAE) both in immunocompromised and immunocompetent individuals. Available data for BAE cases indicate that this disease is difficult to detect because knowledge of predisposing factors is lacking, causing a challenge for diagnosing BAE. The number of reported BAE cases is increasing worldwide, and this is a major concern because little is known about the pathogen, no standardized detection tools are available, and most of the treatments are almost empirical. The recently reported cases, novel diagnostics tools, and successful therapeutic approaches against BAE infections are reviewed here.

Section snippets

Deadly opportunistic pathogenic amoeba

Balamuthia mandrillaris, formerly known as a Leptomyxid amoeba [1] was first discovered from the brain necropsy of a mandrill baboon that died of meningoencephalitis. This pathogen produced necrotizing hemorrhagic encephalitis similar to granulomatous encephalitis caused by the Acanthamoeba genus (see Glossary); another opportunistic pathogenic amoeba. However, a new genus and species, Balamuthia mandrillaris, was declared based on microscopy and pathogenicity tests, as well as antigenic and

Epidemiology of BAE

Since the description of B. mandrillaris as the causative agent of BAE associated with or without skin lesions, more than 200 cases have been reported worldwide 5, 6, 7, 8, 12. The American continent has reported the highest number of infected patients, who are located mostly in North America 11, 12 and Latin America 8, 10, 13, 14, 15, 16, 17, 18, 19, but a few cases have also been reported in Asia 20, 21, 22, 23, Australia 23, 24, 25, and Europe (UK, Portugal, and the Czech Republic) 26, 27, 28

Biology of B. mandrillaris

Opportunistic, free-living amoebic infections caused by Naegleria or Acanthamoeba are often related to activities that involve contact with fresh water bodies (swimming in lakes or pools). However, B. mandrillaris is most commonly isolated from soil and dust sources 6, 7, 8, 9, 38, 46, 47 and was isolated once from a plant pot at the house of an infected child in the USA [37]. Some authors have suggested that a genetic factor related to ethnicity might be involved in infection; however,

Clinical presentation and pathogenesis of BAE

BAE can develop in both apparently healthy and immunosuppressed individuals (associated with HIV-related cases, alcoholism, drug users, and malnutrition cases). Children and young adults are the most affected population, with the exception of Peruvian cases, where at least 50% of patients are children 8, 10, 14.

BAE is predominant in rural areas, and men are affected more often by BAE than women are 6, 7, 8, 9, 10, 11, 12, 29. It is also noteworthy that there are geographical similarities

Diagnosis of BAE

Overall, current diagnosis of BAE is challenging and usually postmortem, because symptoms of the infection may be subtle or nonspecific. The rarity of the disease is problematic for BAE diagnosis, because most clinicians may not consider B. mandrillaris as a causative agent of encephalitis once a patient presents with this condition 5, 6, 7, 8, 10, 11, 14. Mainly in the Peruvian cases, the best clue for diagnosis is the skin lesion, especially if it manifests as a central face plaque (nose

Therapy of BAE

Treatment of BAE infection is not standardized. There are several factors mentioned in the previous section such as: (i) nonspecific clinical manifestations; and (ii) the lack of available diagnostic tools and research groups to be able to carry out detection promptly enough to start treatment in the early stages of infection. Moreover, there is a lack of in vitro (i.e., chemotherapy and colorimetric assays) and in vivo models for the evaluation of potential drugs.

Altogether, the current

Concluding remarks

Despite all the recent advances in the study of B. mandrillaris, several questions about this organism and BAE remain unanswered. Although the number of infections due to B. mandrillaris is relatively low, the estimated frequency of data reported so far are likely to be underestimated. Previous reports have accounted for approximately 0.1% of total encephalitis cases in otherwise healthy individuals to be caused by Naegleria fowleri or B. mandrillaris [30]. Therefore, BAE cases should be

Acknowledgments

This work was funded by project RICET (project no. RD12/0018/0012 of the programme of Redes Temáticas de Investigación Cooperativa, FIS), Spanish Ministry of Health, Madrid, Spain and the project “Protozoosis Emergentes Por Amebas De Vida Libre: Aislamiento Y Caracterización Molecular, Identificación De Cepas Transportadas De Otros Agentes Patógenos Y Búsqueda De Quimioterapias” PI10/01298, Spanish Ministry of Science and Innovation, Madrid, Spain. JLM was supported by the Ramón y Cajal

Glossary

Acanthamoeba genus
includes many species of free-living amoebae common in soil and water bodies; some of these amoebae are opportunistic pathogens that can cause Acanthamoeba keratitis, disseminated infections (skin and lungs mostly involved), and granulomatous amoebic encephalitis (GAE) or Acanthamoeba granulomatous encephalitis (AGE).
Acute disseminated encephalomyelitis (ADEM)
an immune-mediated disease of the brain. It usually occurs after a viral infection but may appear in bacterial or

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