Has a primitive mouth called a cytostome, a nucleus, food vacuoles, and a pair of contractile vacuoles
The infective stage is the cyst and the pathogenic stage is the trophozoite, which invades the mucosal lining of the terminal ileum, cecum, and colon
The trophozoites typically exhibit rotary, boring motility (through cilia) and contain two nuclei (a small-dot-like micronucleus adjacent to a kidney bean-shaped macronucleus)
The cyst also contains two nuclei although the micronucleus may not be readily observable
Similar to Acanthamoeba, the parasite Naegleria is also classified as a free-living protozoan
It shares many characteristics with Acanthamoeba
The parasite is also found worldwide in soil and contaminated water environments
Unlike Acanthamoeba, Naegleria can survive in thermal spring water
The known pathogen worldwide is Naegleria fowleri, which is the only amoeba with three identified morphologic forms—trophozoite, flagellate, and cyst forms
The trophozoite exhibits the typical amoeboid motility which is described as "slug-like"
The flagellate form is pear-shaped and is equipped with two flagella that are responsible for the parasite's jerky or spinning movement
The non-motile form is the cyst
The amoeboid trophozoite form is however the only form that is known to exist in humans
The life cycle of the parasite involves a vector, the female sandfly of the Phlebotomus and Lutzomyia genera
Leishmania spp. are obligate intracellular parasites
It has three morphologic forms—the amastigote, promastigote, and epimastigote
The infective stage is the promastigote
The promastigote form may be seen only if a blood sample is collected and examined immediately after transmission
Epimastigotes are found primarily in the vector
The pathogenic stage and diagnostic form are the amastigote which is found primarily in tissue and muscle, as well as the central nervous system within macrophages and in cells of the reticuloendothelial system
The typical amastigote is round to oval in shape and contains a nucleus, a basal body structure called a blepharoblast, and a small parabasal body located adjacent to the blepharoblast
Both the blepharoblast and parabasal body are collectively known as the kinetoplast
The promastigote is long and slender, with a kinetoplast located in its anterior end, and a single free flagellum extending from the anterior portion
Used as screening for large populations at risk but is not used for diagnosis
Definitive diagnosis is done by demonstration of the amastigote from Giemsa stained slides of specimens from blood, bone marrow, lymph nodes, and biopsies of infected areas
1. Culture of blood, bone marrow, and other tissues may also be done, which will show the promastigote forms
2. Serologic tests are now also available such as an indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), or direct agglutination test (DAT)