INDEX - PATHOGENIC AMOEBAE
Acanthamoeba spp.
A genus of free-living soil amoebae that produces no flagellate stage. Its organisms are pathogens for several
infections in humans and have been found in the eye, bone, brain, and respiratory tract.
Transmission is through water based fluids or the air.
Primary amoebic meningoencephalitis (PAM), Naegleria fowleri and granulomatious amoebic encephalitis (GAE),
acanthamoebic keratitis or acanthamoebic uveitis.
PAM occurs in persons who are generally healthy prior to infection. Central nervous system involvement arises
from organisms that penetrate the nasal passages and enter the brain through the cribriform plate. The organisms
can multiply in the tissues of the central nervous system and may be isolated from spinal fluid. In untreated cases
death occurs within 1 week of the onset of symptoms
GAE occurs in persons who are immunodeficient in some way; the organisms cause a granulomatous encephalitis
that leads to death in several weeks to a year after the appearance of symptoms. The primary infection site is
thought to be the lungs, and the organisms in the brain are generally associated with blood vessels, suggesting
vascular dissemination.
http://www.cfsan.fda.gov/~mow/chap29.html
Initial signs and symptoms of PAM start 1 to 14 days after infection. These symptoms include headache, fever,
nausea, vomiting, and stiff neck. As the amebae cause more extensive destruction of brain tissue this leads to
confusion, lack of attention to people and surroundings, loss of balance, seizures, and hallucinations. After the
onset of symptoms, the disease progresses rapidly and usually results in death within 3 to 7 days.
two factors have lead to problems over the last twenty years; AIDs and contact lenses. Immunocompromisation as
a result of AIDs infection has lead to many secondary Acanthamoeba infections, and contact lens wearers are at
risk from Acanthamoeba keratitis.
Many amoebae also harbour bacterial pathogens such as Legionella and offer them asylum within their chemically
resistant cysts. http://www.bms.ed.ac.uk/research/others/smaciver/amoebae.htm
Balamuthia
The first known isolate of this amoeba was from a Mandrill Baboon (Papio sphinx) at San Diego Wild Animal Park
(Visvesvara et al, 1990). Balamuthia mandrillaris (presently the only described species in the genus) was soon
recognised as causing encephalitis in humans (Anzil et al, 1991). Since then more than 80-90 incidents of
granulomatous amoebic encephalitis (GAE) caused by Balamuthia have been reported (Schuster et al, 2001;
Schuster et al, 2003), with only two cases that have survived (Deetz et al, 2003) to date. There is of course a
strong suspicion that infection and probably all amoebal infections are grossly underestimated due to the general
similarity of the symptoms caused by other agents (bacterial, viral) and the general lack of awareness of amoebal
pathogenicity.
Although it is often described as being a free-living amoeba (Bakardjiev et al, 2003; Rideout et al, 1997) only
recently has the amoeba been isolated from the environment (Schuster et al, 2003).
http://www.bms.ed.ac.uk/research/others/smaciver/balamuthia.htm
Entamoeba
the parasite does not kill the host cell but rather induces its self-destruction.
E histolytica probably is second only to malaria as a protozoal cause of death. The prevalence of amebic colitis
and liver abscess is estimated at 40-50 million cases annually worldwide, resulting in 40,000-110,000 deaths.
http://thewatchers.us/5-1-Entamoeba.html
Entamoeba histolytica is a pathogenic amoeba second only to the malaria parasite Plasmodium in importance as
a protistan killer of people. It kills an estimated 100,000 people each year (W.H.O. bulletin 75, 1997). Entamoeba
gingivalis infects the mouths of humans, another relative Entamoeba dispar colonises the gut of many more
people than E. histolytica without apparent effect.
http://www.bms.ed.ac.uk/research/others/smaciver/entamoeba.htm
Entamoeba hystolytica: Causes dysentary and ulceration of the colon and liver. E. hystolytica survives in an
amoeboid form in the intestines. Spherical cysts are excreted in the feces.
http://www.water.ncsu.edu/watershedss/info/protozo.html
Hartmannella
Accused by some of producing human keratitis.
http://www.bms.ed.ac.uk/research/others/smaciver/Pathogenic%20amoeba.htm
Naegleria fowleri
A species of parasitic protozoa having both an ameboid and flagellate stage in its life cycle. Infection with this
pathogen produces primary amebic meningoencephalitis
Transmission is through water based fluids or the air.
PAM [Primary Amoebic Meningoencephalitis] and GAE [granulomatious amoebic encephalitis] both lead to death in
most cases. Eye infections may lead to blindness.
http://www.thewatchers.us/5-1-naegleria-fowleri.htlm