Ameba

Here are common amebas (Fig. 11-2):

Entamoeba histolytica: Also known as E. histolytica, this microorganism is transmitted between humans through the ingestion of cysts that are

Fig. 11-2. A common type of ameba is the Amoeba proteus.

excreted in the feces of infected people. It is the causative agent of amebic dysentery.

• Naegleria fowleri: This ameba causes primary amebic meningoenceph-alitis (PAM) that results in headache, fever, vomiting, stiff neck, and loss of bodily control. N. fowleri enters the body through the mucous membranes (when the person swims in warm water) and travels to the brain and spinal cord.

• Acanthamoeba polyphaga: This ameba lives in water (including tap water) and infects the cornea of the eye leading to blindness. It can also cause ulcerations of the eye and the skin. A. polyphaga is also known to invade the central nervous system, resulting in death.

Flagellates move by structures called flagella. They have two or more spindle-shaped flagella in the front of the cell that they use to pull themselves through their environment. Food enters flagellates through a mouth-like grove called a cytosome.

Here are common flagellates:

• Trichomonas vaginalis: Commonly known as T. vaginalis, this flagellate is the cause of trichomoniasis, which is a sexually transmitted disease. T. vaginalis is found in the male urinary tract and the vagina of females.

• Giardia lamblia: This flagellate is commonly known as G. lamblia and causes giardiasis. Giardiasis causes nausea, cramping, and diarrhea when food or water contaminated by fecal material is ingested. G. lamblia lives in the small intestines of humans and other mammals.

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