Vibrio cholerae causes an epidemic secretory diarrheal disease called cholera. In intestinal cells, adenylate cyclase is stimulated by a toxin released by Vibrio cholerae. Cholera is often rampant in people returning from a trip and is equally known as a disease of poverty. Large amounts (litres) of rice water stool is passed out by cholera patients. Basic cholera lab tests are not specific. Rapid dipstick tests are available and the cultures of organisms are definitive.
In this article I will talk about the cholera diagnosis, prognosis and treatment at bigmanlab Cameroon. I hope with this first-hand information from a lab technician like myself, you can be able to get more aware of what to do about cholera.
When the effects of severe hypovolemia are offset by intravenous and/or oral rehydration, most patients turn to recover. The increase in bacterial resistance is becoming a problem even though antibiotics shorten the severity and duration of the disease.
What about cholera signs and symptoms?
Vibrio cholerae infection causes a spectrum of illnesses ranging from severe diarrhea to asymptomatic intestinal colonization. In the early stages of the disease, vomiting, rumbling and abdominal discomfort constitute common symptoms of cholera. Most complications in patients with severe cholera are related to significant electrolyte and volume depletion due to diarrhea. Having a fever from cholera is rare.
Cholera symptoms and signs caused by Vibrio cholerae O139 and O1 are similar.
Incubation Period:
Typical, Cholera has an incubation period of 1-2 days. Even though, the incubation period for the disease can range from a few hours to 3-5 days and varies depending on inoculum size and host susceptibility.
Diarrhea:
Rapid and severe electrolyte and fluid loss characterize severe cholera as a clinically different entity even though mild cases of Vibrio cholerae infection are clinically no different from other diarrhea causes. In the early stages of Cholera, feces may contain bile and feces. The profuse passage of watery stools ", rice water" stools that are tinged with mucus is however the hallmark symptom of cholera gravis (severe cholera). It often has the odor of a fish.
Without tenesmus, diarrhea is often painless. In severe cases, fecal excretion in adult can reach up to 1 liter an hour. The maximum rate of fecal excretion is often between 10 and 20 cc per kg per hour in children with severe cholera. In other causes of diarrheal disease, this degree of fluid loss is not often seen.
What about cholera diagnosis?
Vibrio cholerae serogroup O1 or O139 identification and Isolation by culturing fecal samples remains the lab diagnosis of cholera gold standard. Thiosulfate Citrate Bile Salt (TCBS) Selective Agar is good for identification and isolation while Cary-Blair medium is good for transportation. Bigmanlab contains Vibrio cholerae serogroup isolate reagents.
Commercially available rapid test kits do not produce isolates for antimicrobial susceptibility testing and subtyping even though they are useful in outbreak situations, however they should not be used for regular cholera diagnosis. In Cameroon where cholera is common but access to well-equipped laboratory tests is rare, we recommends using rapid testing methods for a suspected cholera case.
What about cholera rapid tests?
Antigen detection:
Many antigen-based rapid tests for cholera diagnosis are commercially available. They are dipstick (lateral flow immunochromatography devices) for example the Cholkit, which only detects O1 antigen and the Crystal VC, that looks in watery diarrheal stools for O139 or O1 antigens.
Molecular testing:
Until now, the practical applications of molecular tests have been limited to surveillance and epidemiological research. PCR testing for Vibrio cholerae (Molecular,) is equally possible, including testing by staining dried stool.
Dark-field microscopy:
I use dark-field microscopy of rice water dregs at bigmanlab (at 400x magnification) to detect very mobile Vibrio cholerae, whose shooting star-like movements can be inhibited by subsequently adding specific antibodies. Though dark-field microscopy is not sensitive enough to be used reliably for cholera diagnosis, it is specific enough for Vibrio cholerae.
What about cholera prognosis?
The elderly, pregnant women and children are at high risk of contracting cholera. Due to better access to health care and better education and sanitation conditions, the risk of dying from cholera has decreased worldwide over the past years. Less than 1% of cholera infected people die, if they get effective rehydration.
What about cholera treatment?
Because this disease can be fatal in a matter of hours, cholera requires immediate treatment.
Rehydrate:
The objective here is to replace lost electrolytes and fluids with ORS (oral rehydration salts), a simple rehydration solution. Oral rehydration salts solution is present as a powder that is made with bottled or boiled water. About half of cholera patients die without rehydration. Mortality drops to less than 1 percent with treatment.
IV fluids:
Severely dehydrated people may equally need intravenous fluids even though most cholera infected people can be helped by only oral rehydration.
Antibiotics:
They can reduce cholera-associated diarrhea and shorten its duration in people who are very sick, even though some antibiotics are not an essential part of cholera treatment.
Zinc supplements:
Zinc can reduce diarrhea and shorten its duration in cholera infected children.
Message from bigmanlab
Always be hydrated. Use oral rehydration solution for vomiting and diarrhea that may be associated with cholera. In Cameroon, you can purchase powdered ORS (oral rehydration salts), which were originally developed by the World Health Organization to dehydration in children with cholera and treat diarrhea.
According to the package directions, mix the powder in clean boiled water or drinking water. Make your own ORS by combining about 1 liter of boiled or bottled water with about 30 milliliters of table sugar and about 2.5 milliliters of table sugar, if an oral rehydration solution is not available.
