Giardia and Other Protozoa

1
Giardia and Other Protozoa
2
Giardia duodenalis cyst and trophozoite

• Most common human parasite in USA, especially
  day-care children
• Most common cause of water-borne disease
  outbreaks Ordinary water chlorination not
  sufficient Use filtration methods or organic
  chlorine which kills in 2 minutes at 22oC
• Zoonotic potential Mountain stream controversy
  Beaver fever cat-human, dog-human or
  human-human?
• Dozens of species can be divided into
  morphological groups that do not cross-infect (G.
  duodenalis group in mammals G. muris group in
  rodents, reptiles and birds G. agilis group in
  amphibians)
• Strain differences are important to
  pathogenicity, host preference, drug sensitivity,
  etc.

3
Giardia cysts and trophozoite
4

• Giardia
• Cysts 10-12u Trophozoites 15u
• Prepatent period is 1-2 weeks
• Crowding young non-immune or immunodeficient
  animals
• Upper 2/3 small intestine
• Most are asymptomatic or have soft, mucoid,
  fetid stool /- blood flecks
• Pathogenesis Damages glycocalyx and microvilli
  (50 shorter) of small intestine? malabsorbtion
  syndrome with variable diarrhea that varies from
  soft stool to projectile, voluminous small bowel
  diarrhea Vomiting common.
• Strains are important. Immunity to one strain
  does not confer immunity to successive outbreaks
  from other strains
• FOR DIAGNOSIS, REMEMBER- Giardia is an
  intermittent shedder must do 3 examinations on
  different days call negative, even in clinical
  cases. Fecal ELISA coproantigen detection is
  more consistent

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Diagnosis

• Giardia Pentatrichomonas
  Balantidium Entamoeba
• Direct Smear
• Saline
  
  
• Falling leaf Spiral,
  jerky Rapid, ciliated pseudopod
  
  trophozoites trophozoites
  motility motility
• Lugols -
  /-
  Kills troph, Kills and
  Kills troph, Trichrome or cysts golden,
  distorts cysts Iron
  Hema- eyes, axostyle
  toxylin best
• ZnSO4 Float -
  (cysts) -
  (Sp Gr 1.18) Most accurate
  monkey face
  
• Formalin-
  
  ethyl acetate
• Fecal ELISA -
  - -
  most sensitive

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Treatment
Giardia
Pentatrichomonas Balantidium Entamoeba Metrinida
zole
?
(Flagyl) 25 mg/kg BID, 5d Quinacrine

(Atabrine) 6.6 mg/kg BID, 5d


or 9mg/kg SID, 9d Furazolidone
4mg/kg BID, 7d Fenbendazole

50mg/kg SID, 3-5d Albendazole

25mg/kg BID, 2d Ipronidazole
(Entryl)
126mg/liter, 7d
7
Control and Prevention

• Recurrent kennel/cattery outbreaks may occur
  common pet shop,shelter pups/kittens infected
  often as early as 3 weeks after birth
• 10 Clorox, Roccal, Lysol kill cysts in cages,
  runs
• Quarantine,examine /- treat newly introduced
  animals (new strains)
• Question as to whether treatment really cures
  or just contains infection
• GiardiaVax, a killed vaccine (give twice 2-4
  weeks apart to gt8 week old dogs) was recently
  marketed for multiple strains with the label
  claim of reduced clinical disease, less cysts
  shed Potential use in integrated control
  programs in high risk situations

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Pentatrichomonas

• 8u, variable size, trophozoite is the only
  form, no cysts
• Characteristic spiral, jerky motility
• Dog, cat, human, other spp
• Large intestine
• Opportunistic pathogen?
• Proliferates with fluid diarrhea from other
  causes

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Balantidium coli

• 60u ciliated trophozoite, 50u cyst
  Macronucleus, micronucleus stain well
• Pig, human. Dog incidentally introduced to life
  cycle, contaminated environment
• Large intestine, Ulcerative colitis
• Metrinidazole ?

Ulcerative Colitis
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Entamoeba histolytica

• 30u trophozoite, 15u cyst
• Human, primates Dog and cat incidental
  infection, trophozoites can be
  found but no cysts are shed
• Large intestine Ulcerative colitis,
  diarrhea
  (amoebic dysentery) in humans
  hepatic abcesses may
  occur
• Metrinidazole