New Breakthrough: Test Can Determine If Rabies Vaccination Is Needed

Last week, the US Centers for Disease Control and Prevention (CDC) announced a groundbreaking new test for rabies that allows for rapid, sensitive, and specific determination of whether a biting animal is rabid.

Rabies is a deadly disease that is on the rise in Vietnam.

Overview of rabies

Rabies kills about 60,000 people each year, mainly in Africa and Asia. The disease is caused by the rabies virus, which is transmitted from infected animals, dogs, cats, bears, foxes, weasels, squirrels, rats, bats, etc. to humans, mainly through bites. After being bitten by a rabid animal, the disease can have an incubation period of several months before developing rabies.

Once rabies has been detected, with the appearance of rabies symptoms, all patients will die. Therefore, determining whether the biting animal is rabid or not in order to get rabies vaccination is very important. If you do not know the animal that bit you, the best and safest thing is to get rabies vaccination.

Breakthrough test for rabies diagnosis

The US Centers for Disease Control and Prevention (CDC) has developed a groundbreaking new rabies test that can determine whether an animal that has bitten a person is infected with the disease and whether the person who came into contact with it needs to be vaccinated: the LN34 test. The study was published in PLOS One, a journal of the Public Library of Science (PLOS), on Wednesday, May 16, 2018.

The LN34 test uses the PCR (Polymerase Chain Reaction) molecular technique, like tests for influenza, tuberculosis, HIV, etc. This is a key polymerase chain reaction technique in molecular genetics that allows the amplification and analysis of a short segment of DNA or RNA. Previously, this amplification was performed by bacteria and took weeks, but with the PCR technique performed in a test tube it only takes a few hours.

LN34 can be easily performed on fresh, frozen, decomposed tissue samples or tissue samples that have been fixed in paraffin blocks to inactivate the virus, using equipment of common testing laboratories and giving immediate results. Therefore, this new LN34 test can help quickly determine whether an animal has bitten someone rabid or not to decide whether to vaccinate.

In a recent multinational study, 14 laboratories worldwide evaluated nearly 3,000 animal brain samples from the Americas, Europe, Africa, and Asia, of which more than 1,000 were known to be infected with rabies virus from more than 60 rabid mammal species, including dogs, raccoons, foxes, ferrets, and bats. LN34 correctly identified all DFA-positive samples, and correctly identified 80 inconclusive or unverifiable DFA samples.

This study is the largest to date to validate the use of this type of test (a real-time RT-PCR) for diagnosing rabies in animals.

Discuss

This new LN34 test is simpler and easier to use than current tests. In the pilot study, the LN34 test gave no false negatives, few false positives, and very few equivocal results.

Compared to the direct fluorescent antibody (DFA) test, the current gold standard for testing for rabies in animals, the LN34 test is much more accurate and convenient: while DFA can only be performed on fresh, frozen brain tissue samples, and results can only be read by experienced laboratory technicians with specialized microscopes, the LN34 can be performed on a variety of test samples such as fresh, frozen, and decomposed tissue with common laboratory staff and equipment.

Conclude

In medicine, the value of a test is measured by two parameters: sensitivity (Se) and specificity (Sp). The LN34 rabies test has a sensitivity of 99.90% and a specificity of 99.68%, which is truly a "superb" test in medicine. Crystal Gigante, the CDC's lead microbiologist in the study, commented: "Many of the areas most affected by rabies are also the areas least prepared to perform the test" and "The LN34 test is a revolutionary breakthrough that quickly determines who needs rabies vaccination and who does not."

In the current situation of rabies vaccine shortage, the implementation of the LN34 rabies test will be of great help to both the health sector and the community.