Balamuthia mandrillaris

Taxobox
color=khaki
name="Balamuthia mandrillaris"
regnum=Protista
phylum=Amoebozoa
genus="Balamuthia"
species=B. mandrillaris
binomial="Balamuthia mandrillaris"

"Balamuthia mandrillaris" is a free-living leptomyxid amoeba which is known to cause disease in humans, especially the deadly neurological condition known as primary amoebic meningoencephalitis. "Balamuthia" has not been definitively isolated in nature, but it is believed to be distributed throughout the temperate regions of the world. This is supported somewhat by the presence of antibodies to "Balamuthia" present in healthy individuals. The Balamuthia genus is named in honor of the late Professor William Balamuth for his contributions to the studies of parasitic and free-living amoebas.

Morphology

"Balamuthia mandrillaris" is a free-living, heterotrophic amoeba, consisting of a standard complement of organelles surrounded by a three-layered cell wall, and with an abnormally large, vesicular nucleus. On average, a "Balamuthia" trophozoite is approximately 30-120 µm in diameter. The cysts fall approximately in this range as well. [ [http://mic.sgmjournals.org/cgi/content/full/150/9/2837 Balamuthia mandrillaris from soil samples - Dunnebacke et al. 150 (9): 2837 - Microbiology ] ]

Life Cycle

"Balamuthia"'s life cycle consists of a cystic stage and a trophozoite stage, both of which are infectious, and both of which can be identified as inclusions in the brain tissue on microscopic examination of brain biopsies performed on infected individuals.

Pathology

"Balamuthia mandrillaris" may enter the body through the lower respiratory tract or through open wounds. Upon introduction, the amoebas may form a skin lesion, or migrate to the brain. Once in the brain, "Balamuthia" causes a condition known as granulomatous amoebic encephalitis (GAE), which is usually fatal. The symptoms of infection by "Balamuthia" are unclear, as only a few definitive cases of "Balamuthia" infection have been described thus far. "Balamuthia"-induced GAE can cause focal paralysis, seizures, and brainstem symptoms such as facial paralysis, difficulty swallowing, and double vision.

"Balamuthia" is also known to cause a variety of non-neurological symptoms, and often causes skin lesions, through which the amoeba may enter the bloodstream and migrate to the brain. Many patients experiencing this particular syndrome report a skin lesion (sometimes similar to those caused by "Staphylococcus aureus" or other bacteria), which does not respond well to dermatologic treatment. The lesion is usually localised and very slow to heal, or fails to heal altogether. In some presentations, the lesion may be mistaken for certain forms of skin cancer. Balamuthia lesions on the face may also lead to amebic keratitis, and usually results in facial swelling.

"Balamuthia" encephalitis is an extremely deadly disease, and as of 2008, only seven recoveries had been reported [ [http://www.bms.ed.ac.uk/research/others/smaciver/balamuthia.htm Balamuthia ] ] , both with lasting brain damage.

Prevalence

Infection with "Balamuthia" is extremely rare, and the amoeba is not considered a cause for public health concern, despite its wide geographic range, since only immunocompromised individuals are at a significant risk of contracting "Balamuthia" meningoencephalitis.

Culturing and Identification

"Balamuthia" is most easily identifiable in a brain biopsy performed on an individual suffering from "Balamuthia" meningoencephalitis. The amoeba cannot be cultured on an agar plate coated with gram-negative bacteria because unlike most amoeba, "Balamuthia mandrillaris" does not feed on bacteria. Instead the amoeba must be cultured on primate hepatic cells or human brain microvascular endothelial cells, or HBMECs, the cells that constitute the blood-brain barrier. [Martinez, A. Julio, Visvesvara, Govinda S. (2001) “Balamuthia mandrillaris infection.” Journal of Medical Microbiology 50, 205-207]

Treatment

"Balamuthia" infection has only been successfully treated in two cases. Both were treated with a cocktail of antibiotics and antiparasitics, although it is unclear if any or all of these medications played a part in treatment. Both victims suffered permanent neurological deficits as a result of their infection.

Deaths related to Balamuthia mandrillaris

Matt Moore, a firefighter from Murrieta, California, fell ill last November. When a biopsy was done in January, they found his brain had been invaded by Balamuthia mandrillaris. He died at approximately 11:30 P.M., on March 10th, 2008. [CBS 13 AP News Report [http://cbs13.com/local/murrieta.brain.amoeba.2.675933.html] ] According to the California Encephalitis Project report published in the July 18, 2008 Morbidity and Mortality Weekly Report, a total of 10 encephalitis cases were known to have been caused by the amoeba between 1997 and 2007.

Other Pathogenic Amoebas

*"Acanthamoeba" spp.
*"Naegleria fowleri"

Related Amoebas

*"Gephyramoeba" spp.

External links

* [http://www.bms.ed.ac.uk/research/others/smaciver/balamuthia.htm A summary of "Balamuthia",]
* [http://www.ajtmh.org/cgi/content/full/70/6/666 A case study of a "Balamuthia" patient.]
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12843060&dopt=Abstract "Balamuthia" on PubMed.]
* [http://www.dpd.cdc.gov/DPDx/HTML/ImageLibrary/FreeLivingAmebic_il.asp?body=A-F/FreeLivingAmebic/body_FreeLivingAmebic_il_th.htm Photomicrographs of Balamuthia and Other Pathogenic Amoebas]
* [http://mic.sgmjournals.org/cgi/content/full/150/9/2837 Description of Clinically-Isolated "Balamuthia"]
* [https://rad.usuhs.edu/medpix/medpix_image.html?imageid=39919 MR and CT Imaging of Balamuthia Mandrillaris] from MedPix

ources

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5728a2.htm?s_cid=mm5728a2_e