Table of various hostparasite relationships

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Table of various host-parasite relationships
Considerations Host type vs host that gets
sick H / R / V relationships Pathogen
Intermediate Definitive Source/vector Taenia
animal man pork,
beef Trypanosome arthropod man T.
cruzi reduviid bug T. brucei tse tse
fly Plasmodium man ??? mosquito
mosquito Giardia none man or
ingest feces other animal Entamoeba
none man ingest feces See Figure
20-1 on page 1081
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About protozoans
Microscopic unicellular wall-less Eukaryotes -
Protista Size 1uM (Cryptosporidium) to 150uM
(Balantidium) trophs of most
protozoans 10-30uM (Giardia, Trichomonas) Class
ification 4-6 phyla? in the Kingdom Protista
grouped primarily by mode of motility,
microscopic morphological characteristics
pathological affect on host tissue, and???.
Reproduction both asexual sexual (especially
Sporozoans). Significant life cycle stages of
intestinal protozoans
-trophozoite active, feeding reproduction
the cell -cyst dormant,
resiliant stage NOTE some
Sporozoans, especially circulatory pathogens such
as Plasmodium have other pathologically
significant stages in their life cycle.
Nutrition aerobic heterotrophic respiration
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Brief protozoan taxonomy/classification
A mess!!! several bases of classification, no
universal agreement many systems frequent
changes. The system below is the old 4-class
system based on mode of motility. Intestinal
unless noted otherwise. Kingdom protista ?
Phylum protozoa ? Class Sarcodina (amoeba)
motile by pseudopods several genera
Entamoeba, Iodamoeba, Endolimax, Naegleria (CNS),
Acanthamoeba (CNS)
reproduction is asexual in human pathogens
??? Class Mastigophora (flagellates) motile
by flagella 92 several genera
ex. Giardia, Chilomastix, Dientamoeba,
Trypanosoma (circ), Leishmania (circ),
Trichomonas (intestinal T. hominis STD T.
vaginalis) reproduction is asexual in
human pathogens ??? images?
4
Protozoan taxonomy continued
Entamoeba pseudopods formed by cytoplasmic
streaming
flagellated protozoans
Giardia
?
Trypanosomes
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Protozoan taxonomy continued

• Class Ciliophora (ciliates) motility cilia 1
  genus Balantidium
• reproduction is asexual in human pathogens
  ???
• Class Sporozoa (now commonly called
  Apicomplexa)
• -reproduction both sexual asexual
• -part of the life cycle occurs inside gt1 certain
  host cell types
• -usually 2 or more hosts
• -many genera
• -several forms (vs only troph cyst) see slide
  29
• -some forms motile by gliding, hitching a ride
  in infected cells, etc. but none have organelles
  of locomotion
• ex, Cryptosporidium, Isospora, Sarcocystis,
  Cyclospora,
• circ Plasmodium, Toxoplasma, Babesia,
  Theileria,
• Pneumocystis? Is it protozoa (via drug
  sensitivity) or
• fungi (via DNA homology) or is it
  protista fungi???
• images ?

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Protozoan taxonomy continued
Plasmodium merozoites hitchin a ride in RBCs
Balantidium coli
Toxoplasma tachizoite Plasmodium sporozoites
gliding
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Protozoa life cycle stages/terms

• Trophozoite stage of active feeding and
  reproduction, commonly the pathogenic protozoan
  form. Formed by asexual fission (mitosis), or
  also by gamete fusion in the Sporozoans.
• Cyst stage of inactivity most resiliant stage
  hard to kill. Multiplication occurs within
  cysts of some protozoa excystation releases
  multiples, ex. Entamoeba, Giardia.
• Variations of the basic life cycle on the
  following slide occur in members of the
  non-Sporozoan classes.
• ?

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Standard non-Sporozoan intestinal life cycle

• Entamoeba histolytica and other strictly asexual
  parasites in left column of Fig 20-1. Also see
  Fig 20-2, pg 1083

. .
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Sporozoa life cycle stages/terms

• Oocyst results from fusion of gametes in the
  Sporozoa. Infective stage in most cases passed
  in host feces in case of intestinal protozoans,
  or in blood in gut of the mosquito vector in the
  case of Plasmodium. Sporozoites form in oocyst
  in host via mitosis (asexual fission).
• Sporozoite special term for trophozoite in
  Sporozoans. Formed by mitosis within oocyst
  infects new host cells intestinal mucosa cells
  in intestinal protozoans, or hepatocytes in case
  of Plasmodium. Mitosis (schizogeny) of these
  cells results in formation of merozoites.
  Merozoites can continue mitosis asexual
  reproduction, or
• Merozoite results from mitotic fission
  (schizogeny) of sporozoites. May infect same cell
  type as sporozoite or a different host cell RBCs
  causing clinical malaria in the case of
  Plasmodium. can also go through meiosis to form
  gametes.
• Gametocyte result of merozoite cell fission via
  Meiosis. Fusion of these results in formation of
  oocyst. ?

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Standard ??? intestinal Sporozoa life cycle see
fig 20-5, 1094

• Oocyst passed in feces
• Mitosis results in sporozoites
• Oocyst/sporozoites injested
• Sporozoites infect intestinal mucosa cells
• Schizogeny results in merozoites
• Merozoites continue asexual cycle or
• Meiosis results in gametes
• Gametes fuse to form oocyst
• Oocyst passed in feces ?