1. Cryptosporidium parvum: an emerging pathogen

2. Cryptosporidium parvum: an emerging pathogen
Cryptosporidium is a coccidian protozoan parasite( Sporozoa)
Associated with diarrea in 1976 in a 3-year-old girl in EM of tthe intestinal epithelium
Increasing population of immunocompromised persons and waterborne outbreaks of cryptosporidiosis
Little is known about the pathogenesis of the parasite
Cryptosporidium can infect several different hosts, can survive most environments for long periods

3. Currently identified species
Cryptosporidium species
Origin of isolate
C. parvum
Human, Bovine
C. wrairi
Guinea pigs
C. muris
Bovine, Murine
C. meleagridis
Domestic Turkeys
C. baileyi
Chickens
C. serpentis
Snakes

4. Life Cycle
Complex monoxenous life cycle--completing its entire cycle within a single host with both sexual and asexual cycles, and there are six distinct developmental stages
Excystation of the orally ingested oocyst in the small bowel with release of the four sporozoites
Invasion of intestinal epithelial cells initiation of the asexual intracellular multiplication stage
Differentiation of microgametes and macrogametes
Fertilization initiating sexual replication & Development of oocysts
The formation of new, infectious sporozoites within the oocyst, which is then excreted in the stool

6. Source:

7. Source:

8. Clinical manifestations
In immunocompetent patients
Cryptosporidiosis is an acute, yet self-limiting diarrheal illness
(1-2 week duration), and symptoms include (Juranek, 1995):
Frequent, watery diarrhea
Nausea
Vomiting
Abdominal cramps
Low-grade fever

9. For immunocompromised persons
Illness is much more severe (Juranek, 1995):
Debilitating, cholera-like diarrhea (up to 20 liters/day)
Severe abdominal cramps
Malaise
Low-grade fever
Weight loss
Anorexia
C. parvum infection has also been identified in the biliary tract
(causing thickening of the gallbladder wall) and the respiratory
system.

10. Epidemiology
Infection by C. parvum has been reported in six continents
In patients aged 3 days to 95 years old
Transmission is usually fecal-oral, often through water
contaminated by livestock mammal feces
Person to person transmission through feco-oral route
Cattle farmers, Veterinarians who come in contact with farm animals
Infants and younger children in day-care centers
50% infective dose (ID50) of C. parvum is only 132 oocysts
( Resistant to chlorine treatment)

11. Phase contrast photograph of sporozoite release
Source:
Phase contrast photograph of sporozoite release
from the Cryptosporidium oocyst

12. A sporozoite-specific lectin adherence factor has been identified
Pathogenesis
Upon oocyst excystation, four sporozoites are released which adhere their apical ends to the surface of the intestinal mucosa
A sporozoite-specific lectin adherence factor has been identified
Following attachment cytokines are released from Epithelial cells which activates macrophages
Activated macrophages release histamine, serotonin, adenosine, prostaglandins, leukotrienes, and platelet-activating factor which induce loss of fluid and electrolytes

13. Epithelial cells are damaged
Cell death is a direct result of parasite invasion, multiplication, and extrusion or
2. Cell damage could occur through T cell-mediated inflammation, producing villus atrophy and crypt hyperplasia
Either model produces distortion of villus architecture results in nutrient malabsorption and diarrhea

14. Detection and Diagnosis
Staining methods were then developed to detect and identify the oocysts directly from stool samples.
The modified acid-fast stain is traditionally used to most reliably and specifically detect the presence of cryptosporidial oocysts
ELISA or IFA, has recently been described in diagnosis of cryptosporidiosis
PCR (Polymerase Chain Reaction) has been used for C. parvum

15. C. parvum - Cysts in stool Acid fast
Source:
C. parvum - Cysts in stool Acid fast

16. A scanning electron micrograph of a broken
meront of Cryptosporidium showing the merozoites within. 
(From: Gardiner et al., 1988,An Atlas of Protozoan Parasites in Animal Tissues,
USDA Agriculture Handbook No.651)

17. A scanning electron micrograph of Cryptosporidium
lining the intestinal tract. (From: Gardiner et al., 1988,An Atlas
of Protozoan Parasites in Animal Tissues, USDA Agriculture Handbook No.651)

18. Duodenal biopsy sample from a patient with AIDS
and cryptosporidiosis. Source:

19. Cryptosporidium parvum :Oocysts of Cryptosporidium parvum,
Source:
Cryptosporidium parvum :Oocysts of Cryptosporidium parvum,
in wet mount. The oocysts are rounded, 4.2 µm µm in diameter.  Sporozoites are visible inside the oocysts

20. Cryptosporidium oocysts ( Original image from a Japanese language site
Tentatively titled Internet Atlas of Human Parasitology)

21. Oocysts of Cryptosporidium parvum stained by the modified
Source:
Oocysts of Cryptosporidium parvum stained by the modified
acid-fast method.  Against a blue-green background,
the oocysts stand out in a bright red stain. 
Sporozoites are visible inside the two oocysts to the right.

22. modified acid-fast method non acid-fast oocysts “ghosts”
Source:
modified acid-fast method non acid-fast oocysts “ghosts”

23. Source: http://www.dpd.cdc.gov
Oocysts of Cryptosporidium parvum stained with the fluorescent stain auramine-rhodamine

24. Giardia cyst
C. parvum
Source:
Oocysts of C. parvum (upper left) and cysts of Giardia intestinalis (lower right) labeled with immunofluorescent antibodies

25. Treatment
No safe and effective therapy for cryptosporidial enteritis has been successfully developed.
Since cryptosporidiosis is a self-limiting illness in immunocompetent individuals, general, supportive care is the only treatment for the illness.
Oral or intravenous rehydration and replacement of electrolytes may be necessary

26. Treatment Possibilities:
Encouraging results following use of paromomycin (an aminoglycoside antibiotic) have been reported.
There is also preliminary evidence to suggest that
paromomycin when used at 4 doses of g/day has led to symptom improvement, and even eradication of the parasite.
Although Azithromycin and Lactobin-R (bovine
colostrum immunoglobulin concentrate) have had
some experimental success, no therapeutic agent
has been clearly identified as effective
(Martins & Guerrant, 1994).