Nursing Dept.
/ First class Parasitology
Entamoeba
E. histolyticahistolytica
E. histolytica produces intestinal and extra-intestinal diseases. It causes
amebiasis.
Cyst Trophozoite
E. histolytica exists as trophozoites, and cysts. The presence of RBC in the
cytoplasm is diagnostic of E. histolytica as it is the only intestinal amoeba to
exhibit this characteristic. They may invade the intestinal wall. Trophozoite when
passed in faeces, die on exposure to air. Trophozoite cannot transmit infection.
The trophozoite must be convert to cyst inside the intestinal area.
Life cycle :-
E. histolytica has a simple life cycle. The
mature cysts are the infective forms of E.
histolytica. They infect human through
contaminated food or water. The cysts pass
upto the ileo-caecal region; then occur
excystation in this region when reach the
alkaline medium of small intestine. The
metacyst rapidly divides to produce eight
trophozoite.
In some infected persons, amoebae invade
the host tissue to leads dysentery.
Pathogenesis:
Invasion of the mucosa by trophozoites of E. histolytica leads to ulceration in
large intestine. Incubation period is 1-4 weeks. The frequency of stools is 6 to 8
per day. Secondary lesions, trophozoites can enter the damaged veins to reach
liver system and form liver abscess (hepatic amebiasis). Amoebic peritonitis is
the most common complication of amoebic liver abscess.
1
Nursing Dept./ First class Parasitology
Other extra-intestinal infections as lung abscess (pulmonary amebiasis), brain
abscess and cutaneous amebiasis.
Symptoms:
More commonly disease develops slowly with intermittent diarrhea, cramps,
vomiting, loss of blood and general malaise. The infection may be causes
appendicitis and some patients infect colitis. In acute case suffers headache,
fever, abdominal cramps. Death may occur from peritonitis or from cardiac
failure.
Treatment:
Metronidazole (Flagyl) for the invasive trophozoites that still in the intestine.
Paromomycin should be used with caution in patients with colitis. Recommended
dosage for adults: metronidazole 750 mg three times a day orally, for 5 to 10 days
followed by paromomycin 30 mg/kg/day orally in 3 equal doses for 5 to 10 days.
Entamoeba gingivalis
Although Entamoeba gingivalis is a non-pathogenic ameba that inhabits the
human oral cavity, it is an opportunistic Amoebozoa. The trophozoite phagocytosed
and partially digested white blood cells (leukocytes) and epithelial cells of the host,
bacteria, and ingested RBCs.
Pathogenesis
E. gingivalis is common in individuals with poor oral hygiene or periodontal
disease. E. gingivalis is found in the mouth inside the gingival pocket near the base
of the teeth and found near the tonsils. Cyst is not found; therefore, transmission is
direct from one person to another by kissing, or by sharing eating tools. The biopsy
take from gingival area may best make diagnosis of E. gingivalis trophozoites, also
tonsils crypts and sputum.
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Nursing Dept./ First class Parasitology
Treatment:
Metronidazole (Flagyl) is the most common treatment for E. gingivalis.
Paromomycin should be used
Acanthamoeba spp.
Trophozoite Cyst
Acanthamoeba sp exhibit in two forms, trophozoite and cyst. Both the forms
occur in infected tissue. The cyst survives in soil for many years.
Pathogenesis:
Acanthamoebae found in soil or water. Trophozoites as well as cysts are infective
to human. The infection is through contamination of traumatized skin or eyes and by
inhalation. Some infections result by inhaling contaminated dust with cyst.
Acanthamoeba can produce keratitis. Contact-lens users are at an increased risk.
Acanthamoeba keratitis (AK) is a rare disease that invade the clear portion of the
front (cornea) of the eye.
Treatment:
Chlorhexadine or Imidazoles and Neomycin.
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Nursing Dept./ First class Parasitology
Naegleria fowleri
Trophozoite Cyst
Naegleria fowleri, colloquially known as a "brain-eating amoeba". N. fowleri has
three stages: motile trophozoite, non-motile cyst and biflagellate.
Pathogenesis:
Human primarily contact this amoeba by swimming in contaminated water.
Infective stage is flagellated trophozoite enters human body through nasal mucosa
(olfactory nerve) and often migrates to the brain then converts to amoeboid
trophozoite, causing rapid tissue damage.
The disease (amebic meningoencephalitis or naegleriasis) is common in young
adults and children. The patient has severe headache, cranial nerve palsies and signs
of meningism. Most patients die within a week. A few patients have survived after
treatment. The cyst doesn’t form in host.
Treatment:
Treatment has often also used combination therapy with multiple other
antimicrobials in addition to amphotericin, such as fluconazole, miconazole and
azithromycin.
