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Giardia and Other Protozoa

Giardia and Other Protozoa. Giardia duodenalis cyst and trophozoite. Most common human parasite in USA, especially day-care children

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Giardia and Other Protozoa

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  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

  5. Diagnosis • Giardia Pentatrichomonas Balantidium Entamoeba • Direct Smear • Saline + + + + • ‘Falling leaf’ Spiral, jerky Rapid, ciliated pseudopod trophozoitestrophozoites motility motility • Lugol’s + - + +/- 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

  6. Treatment Giardia Pentatrichomonas Balantidium Entamoeba Metrinidazole + + ? + (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 >8 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

  8. 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

  9. 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

  10. 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

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