Cholera is a severe diarrhoeal disease, well known for its rapid onset and debilitating effects. It is easy to treat but if left untreated may result in rapidly progressive dehydration and consequently, death.
Cholera results from infection by a bacterium, Vibrio cholerae, often found in coastal saltwater, brackish water and estuaries.
The bacteria multiply rapidly producing an enterotoxin, choleragen. The toxin is one that is absorbed by and acts primarily on the intestinal tract. The toxin acts by attaching and entering the cells of the small intestine, activating an enzyme, adenyl cyclase. In response, the cell secretes large volumes of water and electrolytes (dissolves salts) into the intestine – as much as 20-liters of fluid per day. This causes diarrhoea.
Humans become infected after drinking contaminated water or eating contaminated food. Common sources of foodborne infection include raw or poorly cooked seafood and unwashed fruit and vegetables. Other foods can be contaminated during preparation or storage.
The bacteria present in the faeces of an infected person are the main source of contamination. V.cholerae can remain in the intestinal tract long after recover, being shed by the carrier for up to a year after infection. Consequently, the disease can spread rapidly in areas where sewage and drinking water supplies are inadequately treated.
On average the time from infection to the onset of diarrhoea is 1-3 days. But, it can be less than 1 day and as much as 5 days. The speed on onset and serverity of the disease is dependant on the amount of bacteria ingested and the strength of the person’s immune system.
Due to the massive secretion of fluid into the intestine, diarrhoea results and onset is rapid. One minute you’re fine, next you’re violently ill.
More than 90% of cases are of mild or moderate severity and are difficult to distinguish clinically from other types of diarrhoea. These individuals will present with diarrhoea for 3-5 days. Less than 10% of infected persons develop typical cholera. In these severe cases, patients develop very watery diarrhoea. Stool is without odour and appears cloudy and watery with flecks of mucous, resembling water in which rice has been washed. It is described as “rice water” stool. Vomiting can occur from 6 hours to 5 days after exposure to the bacterium.
It takes the body a few days to produce antibodies to neutralise the toxin.
While the diarrhoea serves to flush the parasites from the intestine, it also causes dehydration. This is the main problem. Also, as essential electrolytes are flushed from the tissues patients may experience muscle cramps.
Diarrhoea and other symptoms should clear within a week.
Besides clinical suspicion, the only diagnostic confirmation is the identification of bacteria in stool.
Rehydration is the most important treatment. This can be done orally (drinking fluids containing glucose and electrolytes) or intravenously. In severe cases, if fluids are not replaced, dehydration increases resulting in hypovolemic shock and renal failure.
For most cases, rehydration is sufficient. The diarrhoea will flush the bacteria from the intestine. Antidiarrhoeal medicines (Imodium) should never be given as they only prolong the illness.
Antibiotics, administered once vomiting has stopped, do shorten the period of diarrhoea and thus the amount of fluid lost, but are secondary to rehydration therapy.
Outbreaks are likely wherever water supplies, sanitation, food safety, and hygiene are inadequate. If you’re swimming in coastal seawater or a river near the coast, downstream from an underdeveloped, overpopulated settlement where sewage flows into the sea or river, you’re at risk. You’re also at risk if you drink water or eat food from high risk sources.
Yes, through proper sewage treatment and water purification; and through the rapid detection, isolation and treatment of infected people.
In high-risk areas wash your hands frequently, especially before food preparation and eating. Eat food while hot and boil or treat all drinking water. Avoid swimming in contaminated rivers. Regarding food and drinks, remember:
Boil it, cook it, peel it, or leave it
The injectable cholera vaccine, previously used, conveyed incomplete, unreliable protection of short duration and is no longer recommended. Two new oral cholera vaccines, which provide good protection for up to 3 years, are now available for use by travellers. However, as these vaccines do not provide 100% protection, basic hygienic precautions should always be followed.
Did you know…?
That you’re more likely to get cholera if you
Author: Lisa de Speville