Cholera is a bacterial infection that leads to severe diarrhea, vomiting and eventually electrolyte loss, dehydration and in some cases death, if left untreated.
Treatment with oral rehydration solution (ORS) to help replenish water and electrolyte loss should be prompt to prevent dehydration and shock.
A diagnosis of cholera involves the following:
Assessment of symptoms which typically include a watery diarrhea along with nausea, vomiting and abdominal cramps. With time, diarrhea and vomiting leave the patient feeling listless and dehydrated.
The culture method is the gold standard or most recommended test for diagnosis of cholera. Stool samples taken from a patient using a sterile cotton bud are placed on a plate containing TCBS (thiosulphate citrate bile salts) agar, a selective medium that isolates the bacteria from the diarrhea. On incubation, Vibrio cholerae appear as yellow clumps which are then analyzed to detect the exact strain of cholera. This definitive diagnosis allows cholera to be distinguished from other bacterial, protozoal or viral causes of dysentery.
In areas where cholera is endemic, rapid immunochromatographic dipstick testing is often available. This involves placing a dipstick strip into a stool sample and reading the lines it then displays. Cholera is confirmed if two red lines appear on the dipstick, whereas it is ruled out if only one line appears. It takes between 2 and 15 minutes for the test to make a diagnosis.
Diagnosis can also be made on testing blood for antibodies against Vibrio cholerae.
Although over 100 serogroups (based on cell surface antigens) of Vibrio cholerae have been identified, only two are responsible for cholera epidemics. These include serogroup O1 and serogroup O139. Serogroup O1 can be divided further into biotypes El Tor and Classical, that are further divided into subtypes Inaba, Ogawa and Hikojima. Until 1992, only serotype 01 was known to cause cholera but later that year large outbreaks in India and Bangladesh were found to be caused by the O139 serotype.
Reviewed by Sally Robertson, BSc