Category B biological agent

Quick Reference

Environment: water
Microorganism: Gram - rod
Spore former: NO
Motile: YES
Susceptibility: anyone
Communicability: infectious, fecal-oral transmission
Exposure: contaminated food or water
Incubation: 1-5 days
Primary Treatment: antibiotics, fluid replacement
Prognosis: good with treatment
Quarantine recommended: occasionally
Use as a biological weapon: YES

Identification

Cholera is an acute intestinal infection caused by Vibrio cholerae, a facultative anaerobic, Gram-negative, crescent-shaped, motile rod. Outbreaks of Cholera during the 19th century claimed the lives of thousands in many cities across North America and Europe. One of the more famous epidemics occurred in San Francisco in late 1850. In October, a steamship, the Carolina, bound from Panama docked off California's coast carrying survivors of an Asiatic Cholera epidemic that already claimed fourteen lives. In only a few months, at least 300 residents of San Francisco and over 1000 people in Sacramento succumbed to the devastating effects of the disease. The epidemic eventually spread to neighboring towns, but lessened severity.

Laboratory Indicators:

• no hydrogen sulfide production -TSI

• no gas production -TSI

• oxidase +

Pathogenesis

Vibrio cholerae is transmitted through water contaminated with fecal matter. Foodborne infections have been traced to raw or inadequately cooked shellfish and other seafood.

The bacterium colonizes in the small intestine and produces an enterotoxin (Choleragen) that interferes with G-proteins, thus increasing cAMP levels. With Na+ and Cl- ion transporters disrupted, an ion imbalance occurs. Excess water and salts are excreted leading to a watery diarrhea, severe dehydration, and eventually, death.

The incubation period can be very short, less than one day, or up to five days in length. Most people infected with V. cholerae do not become ill, however, the bacterium is present in the faeces for 7-14 days following infection.

Manifestations

Early signs of the disease may include abdominal pain, mild fever, chills, and headache. Symptoms inevitably progress to acute, watery diarrhea followed by lethargy and dehydration. Without treatment, renal failure and shock may occur as the disease progresses.

Treatment

Fluid replacement, intravenous or oral rehydration, is necessary to prevent acute dehydration. Tetracycline or doxycycline is administered to reduce the length of the illness.

With adequate fluid replacement therapy mortality rates are about 1%. Without treatment, the death rate can exceed 60%.

Prevention

The U.S. Center for Disease Control recommends the following guidelines for travelers to high-risk countries:

• Drink only water that you have boiled or treated with chlorine or iodine.
• Other safe drinks include tea or coffee made with boiled water and carbonated, bottled beverages with no ice.
• Eat only food that's been thoroughly cooked and is still hot, or fruit that you've peeled yourself.
• Avoid undercooked or raw fish and shellfish.
• Avoid raw salads and vegetables.
• Avoid food and drinks from street vendors.

"Boil it, cook it, peel it, or forget it"

 

V. cholerae
Electron micrograph of the bacterium

Gram Stain
Gram-negative,
curved rods with polar flagella

Cholera epidemic
1892 German cholera ward

 
Cholera info for travelers

Cholera epidemic of 1850

History of John Snow

Historique.net | Infectious Disease