Cholera

Introduction

Cholera is an acute infection of the intestinal tract caused by the Vibrio Cholerae bacteria. The cholera bacteria is a naturally ocurring one, found in both coastal and brackish (black) waters. Aquatic filter feeders, such as oysters and clams, are of particular concern as they can contain concentrated levels of the bacteria. This concentration is brought about by their feeding habits. Crabs are also of concern because they love eating oysters and clams. Seafood-related cholera cases are most prevalent in spring and fall when water temperatures rise. In these conditions, plankton and algae (mullosk and crustacean's favorite foods) bloom causing a bloom in the amount of bacteria. Surface and well water are also sources of infection as the cholera bacteria can remain dormant for long periods of time. Public wells are a well-documented culprit, being responsible for infecting whole populations. Transmission of the disease is by direct fecal-oral contact or the ingestion of contaminated food/water.^[1][2][3]

Cholera is present in Asia, Eastern Europe and Africa, including North Africa to the Iberian Penninsula. A small number of cases have been reported throughout the Americas with the majority being from South America. Africa is responsible for 95% of the cases reported to the World Health Organization (WHO).^[1]

Prevention

The risk of contracting cholera while traveling is very low.

• If you drink water, buy it bottled or bring it to a rolling boil for 1 minute before you drink it. Bottled carbonated water is safer than uncarbonated water.
• Ask for drinks without ice unless the ice is made from bottled or boiled water. Avoid popsicles and flavored ices that may have been made with contaminated water.
• Avoid ice cream and unpasteurized milk, both are often contaminated.
• Eat foods that have been thoroughly cooked and that are still hot and steaming.
• Avoid eating raw fish and seafood, such as sushi and/or raw oysters.
• Avoid raw vegetables and fruits that cannot be peeled. Vegetables like lettuce are easily contaminated and are very hard to wash well.
• When you eat raw fruit or vegetables that can be peeled, peel them yourself. (Wash your hands with soap first.) Do not eat the peelings.
• Avoid foods and beverages from street vendors. It is difficult for food to be kept clean on the street, and many travelers get sick from food bought from street vendors.

The cholera bacteria is a very hardy bacteria. It can survive on food kept at room temperature for 5 days or more and freezing does not kill the organism. ^[4]

Pre-Exposure Vaccines

Presently, two oral vaccines are available. The Dukoral™ vaccine (by SBL Vaccin AB) is available internationally with the exception of the United States, where it has not received FDA approval. A variant of Dukoral™ is only available in Viet Nam. Dukoral™ has an effectiveness rate of 85-90% after 6 months post treatment but decreases quickly over time. Adults will see an effectiveness level of ~62% at one year post treatment. Following the preventative practices listed above will provide adequate protection against cholera.^[1][2][3]

Symptoms and Treatment

Symptoms

Cholera has a very short incubation period - ranging from 2 hours to 5 days duration. The majority of people exposed to cholera never develop symptoms but do remain carriers of the disease and shed the bacteria over a period of 7-14 days. Of those experiencing symptoms, the majority will only present with mild to moderate diarrhea. These cases are frequently attributed to other causes. Only 1 in 10 patients will present with symptoms typical of cholera, which include severe, watery diarrhea (also refered to as "rice-water" stools because of the milky appearance), nausea, vomiting, dehydration, muscle cramping and shock - the latter two due to the dehydration/electrolyte imbalance. Children may also experience lethargy, fever, convulsions and coma. Patients suffering from immune deficiency-related diseases are at a higher risk for the most severe form of the disease.^[1][2][5]

Treatment

The World Health Organization has established guidelines for the treatment of cholera which includes the use of Oral Rehydration Salts (ORS). This combination of water, salts and sugars (electrolytes) replenishes those lost due to the dehydration caused by the diarrhea. In severe cases, antibiotics may be administered. Patients will be treated symptomatically.^[1][2][6]