Cryptosporidium parvum

Benjamin Harris

Cousins, Grandpa, Sisters

Navi

Epidemiology

• Found on all six continents.

• Distributed through fecal-oral route from infected hosts.

• Most commonly transmitted through contaminated water.

Hosts• Definitive Host: non-specific

(terrestrial mammals)

• Intermediate Host: None

• Infects:– Humans– Livestock– Pets– Almost any domesticated mammal.– First confirmed human case was 3-year-old girl

from rural Tennessee in 1976

Lifecycle

• Sporulated oocyst (containing four sporozoites) are ingested or inhaled by infected host.

• Excystation occurs and sporozoites are released attaching to intestinal or respiratory walls.

• Undergo asexual multiplication (schizogony or merogony) or sexual multiplication (gametogony).

Lifecycle Continued

• Sexual multiplication yields:– Microgamonts (male)– Macrogamonts (female)

• Upon fertilization of zygote, two types of oocysts can be produced.– Thick-walled (typically excreated)– Thin-walled (primarily for autoinfection)

Transmission• Fecally contaminated food and water– Swimming pools, public drinking water,

lakes, rivers.• Animal-person (zoonotic)– Approximately 50% of calves discrete

oocysts.• Person-Person

• High frequency in day-care centers, bathrooms, urban.• Fecal-oral route.

• Small contamination required:– Infective dose (132 oocysts for healthy

persons)

Symptoms

• Nausea• Vomiting• Abdominal Cramps• Low-grade fever• Frequent watery diarrhea

• Much more severe in all respects for immunocompromised persons (HIV/AIDS). CD4 <180 cell/cubic mm.

Pathogenesis

• After excystation, sporozoites adhere to the surface of intestinal mucosa.

• Epithelial mucosa cells release cytokines to activate resident phagocytes which in turn release factors to bring about a specific response elements.– T cell response causes inflammation and can

damage or kill cells.– Cell death directly caused by parasite invasion.

Diagnosis • Identification of oocysts from stool

sample or salvia.– Acid-fast stain most reliable.

• Secondary tests• Enzyme-linked immunoabsorbent assay

(ELISA)• Immunofluorescence (IFA)• PCR (Polymerase Chain Reaction)

Diagnosis Continued

• Real time PCR.

• CDC technique usingspecific primers to detecthighly sensitive rRNA genesequences.

Treatment

• Immediate fluid and electrolyte replacement.

• Immunocompetent patient disease progression is self-limited.

• Immunocompromised patients:– Nitazoxanide (antiprotozoal)– Anti-retroviral therapy

Prevention• Common Sense!– Wash food, especially fruits and

vegtables.– Don’t drink and avoid using

questionable water.– Don’t part-take in risky sexual practices

with infected partner.– Wash hands frequently after coming in

contact with infected patients.– Avoid swimming in contaminated water.

Water Treatment

• Between 1984-1994 six major outbreaks have been documented.– 1993 Milwaukee outbreak caused over 400,000 cases via

municipal water utilities. 84 of which had HIV and 85% of deaths a year after the incident were HIV postive.

• 240,000 times more resistant to chlorination than Giardia

• Smallest cysts are 4 microns in diameter making micro filtration effective.

• Boiling water for 1 minute is also effective.

Resources

• http://biology.kenyon.edu/slonc/bio38/hannahs/crypto.htm#trans

• http://www.dpd.cdc.gov/dpdx/html/Cryptosporidiosis.htm

• http://www.health-writings.com/cryptosporidiosis-symptoms/

• http://water.sesep.drexel.edu/outbreaks/Milwaukee_1.html