Coccidia characterized by thick-walled oocysts excreted in feces In Humans Cryptosporidium Isospora...
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Transcript of Coccidia characterized by thick-walled oocysts excreted in feces In Humans Cryptosporidium Isospora...
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Coccidia• characterized by thick-walled oocysts excreted in feces
In Humans
• Cryptosporidium• Isospora• Cyclospora• Sarcocystis• Toxoplasma
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GENERAL APICOMPLEXAN LIFE CYCLE
merozoites sporozoites
zygotegametocytes
MEROGONY
GAMETOGONY SPOROGONY
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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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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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CryptosporidiumLife Cycle
• Merogony• = schizogony
• Gametogony• = gamogony or• = gametocytogenesis
• Sporogony• completed in host cell• thin (autoinfection) or
thick walled oocysts
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Water Borne Outbreaks of Cryptosporidiosis in the USA
Year Location % Inf. suspected cause(s)1984 Braun Station, TX 0.2 sewage contaminated well1987 Carrolton, GA 1.3 water-treatment deficiencies1988 Los Angeles, CA - inoperative swimming pool filters1991 Pennsylvania 0.06 water-treatment deficiencies1992 Jackson County, CO 1.5 water-treatment deficiencies1992 Lane County, OR - oocysts in filter washback water1993 Madison, WI - fecal accident in swimming pool
1993 Milwaukee, WI 40.3spring thaw, water-treatmentdeficiencies
1994 Clark County, NV 0.008 fecal accident in swimming pool
Modified from Graczyk et al, Parasitol. Today 13:348 (1997)
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The Milwaukee OutbreakNEJM 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
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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
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Year Location % Inf. suspected cause(s)1984 Braun Station, TX 0.2 sewage contaminated well1987 Carrolton, GA 1.3 water-treatment deficiencies1988 Los Angeles, CA - inoperative swimming pool filters1991 Pennsylvania 0.06 water-treatment deficiencies1992 Jackson County, CO 1.5 water-treatment deficiencies1992 Lane County, OR - oocysts in filter washback water1993 Madison, WI - fecal accident in swimming pool
1993 Milwaukee, WI 40.3spring thaw, water-treatmentdeficiencies
1994 Clark county, NV 0.008 fecal accident in swimming pool
Human Cryptosporidiosis• associated with epidemic diarrhea
in institutions and hospitals• highly transmissible (19%
household members)
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Molecular EpidemiologyPeng 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
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Two distinct transmission cycles:
• anthroponotic (genotype 1)• zoonotic (genotype 2)
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Symptoms of 205 patients with Confirmed Cases of Cryptosporidiosis
During the Milwaukee Outbreak
SYMPTOMS %Watery Diarrhea
mean=12d; med=9d (1-55d)mean=19/d; med=12/d (1-90)39% recurred after days free
93
Abdominal Cramps 84Weight Loss
med=10lb (1-40lb)75
Fevermed=38.3 (37.2-40.5)
57
Vomiting 48
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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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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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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?
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•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
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Intestinal CoccidiaDiagnosis• 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
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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
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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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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