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Lab 8 Appendix: The Protozoa

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The protozoa are unicellular animals that are classified on the basis of the organelles used for locomotion (flagella, pseudopodia, cilia or no observable organelle). They have a variety of life cycles reflecting the diverse nature of this phylum. The protozoa contain some of the most important parasites of animals.


Objectives Checklist

Learn to identify:

  • 9 Giardia cysts
  • 9 oocysts of Cystoisospora spp. (2 sizes)
  • 9 Eimeria oocysts
  •  9 Cryptosporidium oocysts (acid fast stained)
  • 9 Toxoplasma (cat) and Neospora (dog) oocysts
  • 9 sporocyst of Sarcocystis.
  • 9 Giardia trophozoites
  •  9 Tritrichomonas trophozoites
  • 9 Babesia spp. in a blood smear
  •  9 Leucocytozoon in a blood smear

    Lab Exercises

    Ciliophora - The Ciliates

    Balantidium coli: domestic animals

    Balantidium coli Balantidium coli trophozoite
    The red arrows indicate the cilia and the green arrow is pointing at the macronucleus.

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    Sarcomastigophora - The Amoebae and Flagellates

    Entamoeba histolytica: domestic animals, humans, primates

    Entamoebia histolytica trophozoite Entamoeba histolytica
    Trophozoite: note the characteristic nucleus.

    Giardia sp.: birds and mammals

    Giardia trophozoite Giardia sp. trophozoite


    Cysts (about 12 Ám): low power (left) and high power (right)
    red arrow = nucleus; blue arrow = remains of the flagella; yellow arrows = median bodies

    Click here to link to the Giardia life cycle.

    Click here for a video of Giardia moving under a microscope.

    Trichomonas spp.: birds and mammals


    Trichomonas sp.
    Trichomonas foetus
    Trichomonas sp.
    Note the undulating membrane (red arrows) along the surface of this flagellate.

    Click here for a video of Trichomonas under a microscope


    Trypanosoma brucei: domestic animals (Africa and South America); birds (North America - occasionally pathogenic)

    Trypanosoma brucei life cycle
    Trypanosoma gambiense

    Above: Diagram of the trypomastigote form of Trypanosoma gambiense.  Note the undulating membrane and the single free flagellum.

      Left: Life cycle of the African trypanosomes. Half the life
      cycle is spent in the Tsetse fly and half in the mammalian host.

    Trypanosoma gambiense smear
    Trypanosoma equiperdum smear
    The trypomastigote form of Trypanosoma gambiense
    in a blood smear.
    The trypomastigote form of Trypanosoma equiperdum
    in a blood smear. 
    This parasite causes a venereal disease ("Dourine") in horses and donkeys.

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    Leishmania donovani: dogs, rodents, humans

    Life cycle: L. donovani lives as a promastigote within the sandfly vector and as an amastigote within the macrophages of its mammalian host.
    Drawing of a L. donovani amastigote.


    Leishmania donovani amastigote
    (white arrow) in lymph node impression smear.

    L. donovani tissue smear of the spleen of an infected rodent.
    The red arrows point to some of the amastigotes which have broken out of the splenic macrophages when the smear was made.
    The green arrows point to the remains
    of the nuclei of the host macrophages.
    Note the kinetoplast and nucleus within each amastigote.

    Click here to link to the Leishmania donovani life cycle.

    Apicomplexa - The Piroplasma, Haemosporidia, and Coccidia

    The Piroplasma

    Babesia canis: dogs

    Babesia canis Babesia canis trophozoites (red arrows) in the red blood cells of a dog

    The Haemosporidia

    Haemoproteus sp.: birds and reptiles

    Haemoproteus sp.

    Haemoproteus sp. in red blood cells

    Note the gametocytes (red arrows) in the red blood cells of this bird. Remember that bird rbc's are nucleated.

    Leucocytozoon smithi: birds

    Leucocytozoon smithi

    Leucocytozoon smithi

    A gametocyte (red arrow) within a leucocyte of a turkey.

    The Coccidia

    Cystoisospora spp.: mammals

    Cystoisospora Cystoisospora felis oocyst (blue arrow, unsporulated, about 40 Ám) and a sporulated Cystoisospora rivolta oocyst (red arrow, about 20 Ám). The oocyst of C. canis (dog) looks like that of C. felis (cat) and the oocyst of C. ohioensis (dog) is similar to that of C. rivolta (cat).

    Eimeria spp.: birds and herbivores

    Eimeria stiedae
    Eimeria sp.
    Eimeria tenella
    Eimeria stiedae oocysts from rabbit feces. These oocysts (and many oocysts of species of Eimeria from livestock) have a micropyle
    (a thinning of the shell) at
    the narrow end.
    Eimeria sp. in the intestine of a goat. Many macrogametes (blue arrows) can be seen.
    Eimeria tenella oocysts from chicken feces
    blue arrow = unsporulated;
    red arrows = sporulated (infectious) This species has no micropyle.

    Click here to link to the Eimeria bovis life cycle.

    Sarcocystis spp.: dog - cattle

    Sarcocystis sp. sporocysts
    Sarcocyst in situ
    Sarcocystis sp. sporocysts (blue arrows)
    The oocysts of Sarcocystis spp. sporulate within the host's intestine and then rupture, releasing the sporocysts, which are thus found on a flotation of the feces.
    Sarcocystis sp. Sarcocyst in the muscle of a cow (the intermediate host). This cyst contains many bradyzoites which, when eaten by the definitive host, will initiate the infection.
    Sarcocystis sp. A sarcocyst (blue arrows, note the internal septum in the center of the cyst of this species) in the muscle of a rodent. Note the Trichinella spiralis larva (red arrow) in the adjacent muscle cell.

    Toxoplasma gondii : cats

    Toxoplasma gondii Toxoplasma gondii An unsporulated oocyst (blue arrow) and a sporulated oocyst (red arrow) seen at high power (40 X). It takes 2 to 3 days for the oocyst (10 Ám) to sporulate.

    Click here to link to the Toxoplasma gondii life cycle.

    Cryptosporidium sp.: birds and mammals (including humans)

    Cryptosporidium sp. Cryptosporidium sp. oocyst
    These oocysts measure about 4 to 5 Ám in diameter.
    This fecal smear was stained by a cold Kinyoun acid-fast technique. Cryptosporidium oocysts stain red (i.e. are acid fast), whereas yeast stains blue or green. This staining technique is normally used for Mycobacterium, but it also has great utility in confirming cryptosporidiosis. Cyrptosporidium oocyts

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    Copyright © 2008 - University of Pennsylvania School of Veterinary Medicine, All rights reserved.
    Faculty: Dr. Thomas Nolan
    Students: Takis Weekes V'11, Molly Church V'09, Diana Knight V'08, Douglas Gilson V'05, Chris Dykhouse V'04, Kimberly Mah V'00

    Comments or Questions contact Dr. Tom Nolan at: