as Ebola continues to rage in three countries-and West Africa projections for the growth of the epidemic seems increasingly health officials say that hope they will soon have an additional tool against the disease: a diagnostic test easy to use, fast, and inexpensive for the virus. Several teams are working on small-kits prototypes disposable devices resembling tests do home pregnancy using a few drops of blood from a fingertip jab and can be easily transported to remote villages or door screening campaigns -wore. At least two potential diagnoses will undergo their first field tests in Guinea and Sierra Leone, this fall.
members of the project PCR using Testing Laboratory European mobile in Gueckedou, Guinea
PHOTO :. EUROPEAN mOBILE CONSORTIUM LABORATORY
rapid detection of infections would be of great help in the implementation of proven methods and real that contained any outbreak of Ebola far: Identify and isolate quickly enough that they do not pass the virus infected people and new victims. Ebola is not easy to spot at the beginning of an infection as its symptoms, such as high fever, muscle and abdominal pain and vomiting, are the same as those of other more common diseases such as malaria and cholera.
current diagnostic tests take at least several hours, and sometimes days. Clinics and teams that trace the contacts of patients at risk of infection based on a molecular test that detects the genes of the Ebola virus in the blood using the polymerase chain reaction (PCR). The test is accurate and reliable, but it requires a blood sample taken by the needle and secure transport to a laboratory with a regular supply of electricity, PCR machines, and laboratory workers equipped to handle highly samples infectious and run the machines.
This complex process causes major problems. suspected patients are often crammed into makeshift rooms, waiting for the test results, which means that uninfected people may inadvertently be exposed to Ebola. If a suspected case happens very far from establishing the closest diagnosis, it may be days before the samples reach the laboratory and return results.
One of the new test comes from a company called Senova in Weimar, Germany, which has sent 2,000 kits of samples to Gueckedou, Guinea, earlier this month, where they are executed in parallel to the standard PCR procedure to determine the degree of accuracy they are. Meanwhile, researchers at Tulane University in New Orleans, Louisiana, in cooperation with Corgenix in Broomfield, Colorado, and other partners say they could begin testing a rapid diagnostic test prototype since early October in Sierra Leone.
Corgenix the test, on the basis of a test for Lassa fever from the same company, allows a health worker to collect a blood sample directly from a pricked finger on a pad one end of a diagnostic test strip. A chemical solution is applied to disinfect and prepare the sample for testing. The sample then moves through the buffer, which separates the blood components, and on the band itself, which is made of a special paper containing labeled antibody dyes which lock on a specific protein of Ebola virus, where appropriate. As the sample moves further up the strip, a second antibody binds to the virus-antibody pair, and a dark line appears on the strip, indicating infection.
In the test Senova, a healthcare worker collects a blood sample from a finger prick using a minipipette and mix the blood with the chemical solution disinfection before apply it to the test strip; , the tests are very similar
Multiple factors influence how the tests work :. the design of antibodies, the buffer solution ", even this type of glue you use to paste [the tests] together," said Robert Garry, a virologist at Tulane who helps coordinate the project with Corgenix. "They look simple, but they are very sophisticated devices." Said Senova he expects to have the first results of the performance of its test in 2-3 weeks. The researchers hope the tests will be very sensitive as although very specific meaning they are missing very few cases of Ebola, while producing almost no false positives.
antibody-based diagnostics are generally not as sensitive as PCR tests, which can copy and detect minute quantities of viruses. but even an imperfect test may be helpful, says Garry. it might not be reliable enough to definitively diagnose individuals, he said, but it could be used as a screening tool in villages difficult to reach. "If you test 10 people and no present positive, you can go to the next village," he said.
Quick Senova prototype diagnostic for Ebola is tested in Guinea.
PHOTO SENOVA GMBH
rapid diagnostic tests may also be useful in screening patients entering the health centers or travelers not Ebola in airports, said Pierre Formenty of the World health Organization (WHO) in Geneva, Switzerland. He said the WHO is developing an "emergency assessment mechanism" for new diagnostic methods.
If it is found that the current version of the test does not work Senova well enough, to find ways of improving it could take months, said Hans Herrmann Söoffing, owner of Senova;. even get prototypes to Guéckédou can take 3 or 4 weeks, he said once optimized, however, the tests are relatively easy to produce; Senova could potentially generate thousands a day, he said Corgenix tests probably cost between $ 1 and $ 2 each, said Garry
in the short term, WHO and.. others focus on increasing the number of laboratory-based PCR. While three laboratories in Guinea meet current needs, Formenty said, additional laboratories are needed in Liberia and Sierra Leone, particularly in Monrovia and Freetown, respectively, the hard-hit capital.
They will need more staff as well. The European mobile laboratory project, which has set up diagnostic facilities in three countries, recently presented his laboratory in Nigeria to Nigerians, said Stephan Günther of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany, which helps run the project. European scientists still run laboratories in Guinea and Liberia, but they can use reinforcements Günther said. virological expertise is required; with 2 weeks of training, "there are thousands of people" who could learn to operate the PCR machine safely, he said.
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