FOR PLAGUE AND CHOLERA
A test using dipsticks for the rapid diagnosis of plague, developed and evaluated at the Institut Pasteur in Madagascar and in Paris, now makes it possible to detect this disease in fifteen minutes at a patient's bedside. This research has just been published in the January 18 edition of "The Lancet". It represents considerable progress in monitoring and combating this re-emerging disease, which is often fatal without early treatment. A small production unit for this test is already in place in Madagascar (Institut Pasteur of Madagascar and Plague Central Laboratory of the Malagasy Ministry of Health). Using the same principle, the researchers of the Institut Pasteur have developed dipsticks for the rapid diagnosis of cholera, which are currently being evaluated in the field.
The test developed by the Pasteur teams is very easy for medical personnel to use: by simply putting a sample in contact with a dipstick capable of detecting the presence of a specific antigen of the plague bacillus, antigen F1, it is possible to establish an accurate diagnosis in fifteen minutes, instead of the two weeks required by bacteriological methods.
It is thus possible to give warning quickly and to instigate necessary control measures: antibiotic therapy for the patient, preventive measures for those in contact and disinsecting of the environment to kill the vector fleas of the disease. This is a considerable step forward in the fight against plague, which, in the absence of early treatment, can kill the infected person in several days.
These rapid-diagnosis dipsticks can detect bubonic plague as well as pneumonic plague, a less frequent but more serious form, which rapidly leads to death if treatment is not undertaken in the 24 hours following the first symptoms. This extremely serious form, directly communicable from human to human, would be the one observed in case of a bioterrorist use of Yersinia pestis.
This diagnostic test also has the advantage of being usable in the most remote and least electrified areas: the transportation and storing of the dipsticks do not necessitate constant refrigeration and performing the test does not require any specific equipment.
Furthermore, these tests can also be performed on samples from rodents, in the case of abnormal mortality of these animals in the villages, thus making it possible to give very early warning, and to take necessary preventive measures (disinsecting and preventive treatment for subjects in contact) in order to avoid the first human cases.
Tested at the Institut Pasteur in Paris on seed stocks of Yersinia pestis from different continents and on other bacteria, the diagnosis dipsticks have shown a sensitivity and specificity of 100%. Their evaluation in Madagascar in collaboration with its Ministry of Health, on 26 peripheral sites in the field, showed a high rate of agreement between the results of dipstick tests performed by health workers and those of bacteriological tests carried out at the same time in the laboratory.
By request of the Malagasy Ministry of Health, who decided to include the use of dipsticks in its Plague National Control Programme, the World Bank has granted financing for the establishment of a production unit at the Institut Pasteur of Madagascar. Now operational, it allows the manufacture of 5,000 to 10,000 kits (dipstick tests and sampling equipment) per year necessary to the country.
The Malagasy Ministry of Health and the Institut Pasteur of Madagascar organised training in the use of the diagnosis kits, which was attended by nearly everyone responsible for the country's district health services. The rapid-diagnosis kits are now available in nearly 300 basic health centres.
This test is currently being evaluated in several African nations affected by plague, under the aegis of the World Health Organisation. The possibility of enabling other countries to benefit from these tests is now being studied.
These rapid-diagnosis dipsticks were developed by Suzanne Chanteau at the Institut Pasteur in Paris, in collaboration with Farida Nato. They had been evaluated successfully at the same time in the Paris Institut Pasteur's Yersinia Laboratory, directed Elisabeth Carniel, and in the field by the Institut Pasteur of Madagascar, both of them WHO Collaborating Centres for Plague.
Plague, a bacterial infection due to Yersinia pestis, is essentially a rodent zoonosis, communicable from rodent to rodent and from rodent to human by flea bite. Starting with the first cases of human plague acquired by contact with rodents, inter-human contamination is direct via airborne route or through bites by human fleas.
Responsible for three historic, extremely deadly pandemics, it remains fixed in human memory as a particularly horrifying synonym of pestilence. Usually confined to some isolated areas of the world, plague is currently re-emerging, with the number of cases increasing in several world regions (see attached sheet). For example, in Madagascar, 1,000 to 1,500 suspected cases were declared annually during the last decade compared to 200 to 300 cases throughout the 80s. Approximately twenty other countries are affected, mainly in Africa, but also in Asia, and industrialized nations, like the United States (14 cases in 1994 and 4 cases in 1997) are not being spared.
The possible spread of plague by rapid forms of transportation constitutes a potential danger which must not be underestimated. Furthermore, current fears of international bioterrorism are restoring major interest in studies on plague and its means of diagnosis.
At the same time, dipsticks to facilitate the rapid diagnosis of cholera have been developed. The preliminary results of field trials carried out in Bangladesh and in Madagascar suggest an effectiveness similar to that of diagnostic tests for plague.
Development and testing
of a rapid diagnostic test for bubonic and pneumonic plague
The Lancet, 18 January 2003.
Suzanne Chanteau1, Lila Rahalison1, Lalao Ralafiarisoa2, Jeanine Foulon3, Mahery Ratsitorahina1, Lala Ratsifasoamanana2, Elisabeth Carniel3, Farida Nato3
1 Institut Pasteur of Madagascar, WHO Collaborating Centre for Plague, Antananarivo, Madagascar
2 Plague National Control Programme, Ministry of Health, Antananarivo, Madagascar
3 Institut Pasteur, WHO Collaborating Centre for Plague, Paris, France
- Suzanne Chanteau, chief chemist at the Institut Pasteur, has since been named director of CERMES in Niger.
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