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Coccidia characterized by thick-walled oocysts excreted in feces In Humans Cryptosporidium Isospora Cyclospora Sarcocystis Toxoplasma.

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Presentation on theme: "Coccidia characterized by thick-walled oocysts excreted in feces In Humans Cryptosporidium Isospora Cyclospora Sarcocystis Toxoplasma."— Presentation transcript:

1 Coccidia characterized by thick-walled oocysts excreted in feces In Humans Cryptosporidium Isospora Cyclospora Sarcocystis Toxoplasma

2 GENERAL APICOMPLEXAN LIFE CYCLE

3 Cryptosporidium parvum first human case reported in 1976 monoxenous, wide range of animal hosts several host-adapted species? self-limiting diarrhea in immunocompetent profuse, watery diarrhea associated with AIDS life threatening

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5 Extracytoplasmic Location microvilli extend and fuse to enclose zoite close association between parasite and host intestinal epithelial cell called adhesive zone, feeder organelle, etc

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8 Cryptosporidium Life Cycle Merogony = schizogony Gametogony = gamogony or = gametocytogenesis Sporogony completed in host cell thin (autoinfection) or thick walled oocysts

9 Water Borne Outbreaks of Cryptosporidiosis in the USA Modified from Graczyk et al, Parasitol. Today 13:348 (1997)

10 The Milwaukee Outbreak NEJM 331:161 (1994) massive cryptosporidiosis outbreak following spring thaw >400,000 people may have been affected based on clinical symptoms (acute watery diarrhea) treated water had high levels of turbidity 3/23-4/5/1993 oocysts identified in ice made during this period 100-fold higher prevalence of Cryptosporidium oocysts in stools other enterics (including Giardia, bacteria, viruses) were at ~normal levels

11 Factors Favoring Waterborne Cryptosporidiosis small size of oocysts (4-5 m) reduced host specificity and monoxenous development close associations between human and animal hosts large number of oocysts excreted (up to 100 billion per calf per day) low infective dose (<30) robust oocysts; resistant to chlorine infectious sporulated oocysts excreted in feces

12 Human Cryptosporidiosis associated with epidemic diarrhea in institutions and hospitals highly transmissible (19% household members)

13 Molecular Epidemiology Peng et al (1997), Emerg. Inf. Dis. 3:567 2 genotypes identified from 39 isolates: Genotype 1 only human sources non-infective for mice or calves Genotype 2 human and bovine sources infective for mice and calves

14 Two distinct transmission cycles: anthroponotic (genotype 1) zoonotic (genotype 2)

15 Symptoms of 205 patients with Confirmed Cases of Cryptosporidiosis During the Milwaukee Outbreak

16 DIARRHEA enterocyte malfunction (osmotic) impaired absorption enhanced secretion inflammatory diarrhea mucosal invasion leukocytes in stools secretory diarrhea toxin watery Pathogenesis enterocytes damaged or killed villus atrophy (blunting) Na + absorption permeability crypt cell hyperplasia Cl - secretion inflammation in lamina propria cytokines and neurohormones? enhanced secretion of antibodies (IgA)?

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18 Isospora belli wide geographical distribution (higher prevalence in warmer climates) monoxenous, probably not zoonosis invades intestinal epithelial cells often asymptomatic (seldom reported) symptoms range from mild gastro- intestinal distress to severe dysentery often self-limiting, but can become chronic (wasting, anorexia) symptoms more severe in AIDS patients

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21 Cyclospora cayetanensis first human case in 1979 named in 1993 initially called cyano- bacteria like body (CLB) or large Cryptosporidium related to Eimeria life cycle unknown oocysts mature in environment similar to Isospora? zoonosis?

22 symptoms similar to Cryptosporidium and Isospora watery diarrhea/frequent stools 1-2 week duration typical relapses over 1-2 months associated with food-borne outbreaks 37/64 attendees at luncheon near Charleston SC were positive for Cyclospora raspberries from C. America was source? oocysts detected on market vegetables in Peru presumed source: contaminated water or human waste as fertilizer Clinical Features

23 Intestinal Coccidia Diagnosis demonstration of oocysts in feces acid-fast stain (all three) autofluorescence (Isospora and Cyclospora) direct observation (Isospora) Treatment paromomycin for Cryptosporidium modest benefit lowers parasitemia in AIDS trimethoprim-sulfamethoxazole for Cyclospora and Isospora

24 Cryptosporidium 4-5 m oocysts 4 sporozoites no sporocysts Cyclospora 8-10 m oocyts 2 sporocysts 2 sporozoites each Isospora belli 30 x 12 m oocyts 2 sporocysts 4 sporozoites each

25 Cryptosporidium 4-5 mm oocysts 4 sporozoites no sporocysts Cyclospora 8-10 mm oocyts 2 sporocysts 2 sporozoites each Isospora belli 30 x 12 mm oocyts 2 sporocysts 4 sporozoites each

26 Cryptosporidium 4-5 mm oocysts 4 sporozoites no sporocysts Cyclospora 8-10 mm oocyts 2 sporocysts 2 sporozoites each Isospora belli 30 x 12 mm oocyts 2 sporocysts 4 sporozoites each


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