FOR RAPID DIAGNOSIS OF CHOLERA
Dipsticks for the rapid diagnosis of cholera have been developed at the Institut Pasteur in Paris and Madagascar, and have been successfully evaluated in Madagascar and Bangladesh. With these dipsticks, it is now possible to make a diagnosis within a few minutes at the patient's bedside. This diagnostic breakthrough has great potential as an epidemiological tool and could substantially improve cholera surveillance in the remotest areas.
Cholera is a poor-country disease, and epidemics often occur in regions far from analytical laboratories. It may take several days to transport samples to a laboratory and then a further two or three days for reliable diagnosis with classic analytical techniques.
Dipsticks based on the principle of immunochromatography have been developed at the Pasteur Institute in Paris by teams led by Farida Nato (Platform for Production of Monoclonal Antibodies and Recombinant Proteins) and by Jean-Michel Fournier (Head of the Cholera and Vibrios Unit), and at the Pasteur Institute in Madagascar by the team led by Suzanne Chanteau (WHO Collaborating Centre for Plague). They may be stored in waterproof bags at room temperature for several months, making them easily transportable. They are easy to use, and require no specific technical training. All you need to do is immerse the dipstick into a stool sample and wait for 2 to 15 minutes. If two red lines appear on the dipstick, then the patient has cholera, if only one red line appears, the test is negative.
Tests were carried out in two countries in which cholera is epidemic, by Suzanne Chanteau's team in Madagascar and by G. Balakrish Nair (International Centre for Diarrhoeal Disease Research, Bangladesh - ICDDRB) in Bangladesh. In both countries, these rapid diagnostic tests detected both serogroups of the cholera vibrio - O1 and O139 - and had a specificity of 84% to 100% and a sensitivity of 94.2% to 100% (1).
The Pasteur teams and the team from Bangladesh have also demonstrated the effectiveness of these tests for use with rectal swabs. This is particularly important because in times of epidemics or suspected epidemics, patients arriving at outlying health centres may not present the riziform liquid diarrhoea characteristic of cholera. In such cases, the swab used to take the rectal sample is simply dipped in culture medium, which is then incubated at 37º C for 4 hours and then used for the dipstick test. The O1 and O139 dipsticks displayed sensitivities of 96% and 93%, respectively, and specificities of 92% and 98% (2). These dipsticks are the first rapid cholera diagnostic test that can be used with rectal swabs. This is particularly important for reliable evaluation of the number of cholera cases during an epidemic, and for early detection of the emergence of a new epidemic.
The simplicity and efficacy of these dipsticks should improve patient care and epidemiological surveillance, even in the remotest regions.
Cholera remains a serious illness, both for individuals and groups. According to the WHO, the number of people exposed to this disease has risen spectacularly in the wake of the deterioration in socio-economic conditions that has occurred over the last few years in many regions of the world, creating conditions for a world-wide problem. In 2002, 52 countries officially declared a total of 142,311 cases of cholera to the WHO, with 4,564 deaths. But these figures do not, by any means, give an accurate representation of the reality of the situation, because of under-declaration and ineffective surveillance systems. For example, in Bangladesh alone, the number of cases of cholera occurring each year is estimated to be somewhere between 100,000 and 600,000.
Until 1992, Vibrio cholerae O1 was the only known cholera agent. In that year, a strain belonging to a new serogroup - O139 - appeared in India and Bangladesh. This vibrio was subsequently identified as responsible for epidemics in several Asian countries, and may well become the origin of an eighth cholera pandemic, which would be particularly serious as there is no cross-protection between the two serogroups.
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(1) "One-step immunochromatographic
dipstick tests for rapid detection of Vibrio cholerae O1 and O139 in stool samples".
Clinical Diagn. Lab. Immunolo.. 2003, 10: 476-478.
Nato F., A. Boutonnnier, M. Rajerison, P. Grosjean, S. Dartevelle, A. Guenolé, N.A. Bhuyan, D.A. Sack, G.B. Nair, J.M. Fournier and S. Chanteau
(2) "Use of Dipsticks
for rapid diagnosis of cholera caused by Vibrio cholerae O1 and O139 from rectal
swabs". Journal of Clinical Microbiology. August 2003, Vol 41,
N.A. Bhuyan1, Firdausi Qadri1, A.S.G. Faruque1, M.A. Malek1, M.A. Salam1, Farida Nato2, J.M. Fournier2, S. Chanteau3, David A. Sack and G. Balakrish Nair1
1 Laboratory and Clinical Sciences Divisions, international Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
2 Institut Pasteur, Paris, France
3 CERMES, Niamey, Niger
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