While it is impossible to guarantee the saftey of our water supply, measures are being put in place to increase protection and security.  A more conscious effort of securing gates, man-holes,  and tank covers is in effect.  Also funds from the government have increased greatly, funding water facility improvement programs and emrgency response plans in the event that the unthinkable should happen.  Laboratories are developing faster on-site testing for water facilities, as well.

Two of the organisms high on the bioterrorism list of the Center for Disease Control (CDC) are Vibrio cholerae and Cryptosporidium parvum, both of which are Category B bioterrorist threats.  Agents/diseases that fall under this category are give the second-highest priority, because they are moderately easy to disseminate; result in moderate morbidity rates and low mortality rates; and require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance.
  

Vibrio cholerae

• General Characteristics:
  * Gram-negative, curved rod
  * Motile, single polar flagellum
  * Grows in freshwater and saltwater, natural reservoir unknown
  * 3 antigenic types (Inaba, Ogawa and Hikojima), distinct El Tor biotype

• Name of Disease: Asiatic or Epidemic Cholera

• Pathogenesis: V. cholerae attaches to the small intestines via pili
  

• Nature of Disease: Cholera is a serious epidemic disease that has killed millions.  Despite all of our technology and knowledge, it still persists in being a major health problem worldwide.  Originally endemic to India, it spread worldwide, including the US.  The last epidemic in the US was in 1911, with sporadic cases in the last few years.  Most people in the US who naturally become infected do so by eating contaminated shellfish.

• Source of infection: drinking water contaminated by human feces, food washed in contaminated water
• Symptoms:
  * onset of symptoms sudden, within 6 hrs to 5 days of initial exposure
  * abdominal cramps, nausea, dehydration, and shock
  * massive diarrhea, dilute feces with mucus known as "rice-water stool"

• Diagnosis: Only by the isolation of the causative organism from the diarrheic stools of infected individuals.

• Course of Disease: If proper treatment isn't received, about 60% of those infected will die from severe dehydration and electrolyte loss.

• Treatment: oral or IV rehydration with a solution containing sodium chloride, sodium bicarbonate, potassium chloride, and dextrose
  

• Interesting Fact: Gastric acidity is an important defense against V. cholerae in that it reduces the number of viable organisms present.  Therefore, antacids are counterproductive.

Cryptosporidium parvum

• General Characteristics:
  * obligate intracellular parasite, measuring about 3-5 µm.
  * live in the intestinal tracts of fishes, reptiles, birds, and mammals
  * infective stage of organism is oocyst
  * species or strain infecting the respiratory system is not currently distinguished from the form infecting the intestines

• Name of disease:  Intestinal, tracheal, or pulmonary cryptosporidiosis

• Pathogenesis:  attachment to mucosal membranes and rapid proliferation

• Nature of Disease:  Cryptosporidiosis has been recognized as an important opportunistic infection.  It was first recognized in the early 1900s.  Today's concern is that oocysts have been found to infect via drinking water.  Not a great deal is known about the pathogenesis.     

• Source of infection:  drinking water infected with C. parvum oocysts

• Symptoms: * Frequent, watery diarrhea
                     * Nausea
                     * Vomiting
                     * Abdominal cramps
                     * Low-grade fever
  

• Diagnosis:  Oocysts are shed in the infected individual's feces. Sugar flotation is used to concentrate the organisms and acid fast staining is used to identify them. A commercial kit is available that uses fluorescent antibody to stain the organisms isolated from feces. Diagnosis has also been made by staining the trophozoites in intestinal and biopsy specimens. Pulmonary and tracheal cryptosporidiosis are diagnosed by biopsy and staining.

• Course of Disease:  In healthy individuals,  its a self-limiting disease where symptoms persist for 2-4 days then go away.  The young and immuno-compromised run a risk of death due to severe dehydration (symptoms can last for weeks to even a lifetime).  Also, the pulmonary form can prove to be fatal.             
  

• Treatment:  There is no treatment at this time, other than bed rest and plenty of fluids. 

Education and Background Resources
1. "Cryptosporidium parvum: an emerging pathogen": http://biology.kenyon.edu/slonc/bio38/hannahs/crypto.htm#diag

2. "Bad Bug Book:  Cryptosporidium parvum": http://vm.cfsan.fda.gov/~mow/chap24.html

3. "Graphic Images of Parasites": http://www.biosci.ohio-state.edu/~parasite/cryptosporidium.html

4. "Pathogenic Bacteriology": http://microvet.arizona.edu/Courses/MIC420/lecture_notes/vibrio/vibrio.html

5. "Bad Bug Book:  Vibrio cholerae":  http://vm.cfsan.fda.gov/~MOW/chap7.html

6. "Threat of Water Supply Bioterrorism: Who Will It Impact?": http://www1.frost.com/prod/news.nsf/0/CE429F764F437C0E80256AE2003A8F5B

7. "CDC: Public Health Preparedness and Response": http://www.bt.cdc.gov/agent/agentlist.asp#categorybdiseases