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

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

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. Waterborne Cryptosporidiosis
Factors Favoring
Waterborne Cryptosporidiosis
small size of oocysts (4-5 mm)
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. Pathogenesis DIARRHEA 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)?
DIARRHEA
enterocyte malfunction (osmotic)
impaired absorption
enhanced secretion
inflammatory diarrhea
mucosal invasion
leukocytes in stools
secretory diarrhea
toxin
watery

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

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. Clinical Features 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

23. Intestinal Coccidia Diagnosis Treatment
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 Cyclospora Isospora belli 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
4 sporozoites each

25. Cryptosporidium Cyclospora Isospora belli 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
4 sporozoites each

26. Cryptosporidium Cyclospora Isospora belli 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
4 sporozoites each