Rabies: CDC develops new rapid test, Could lead to fewer shots

GETTYBats are known carriers of rabies – but not in the UK

GETTYBats are known carriers of rabies – but not in the UK

"The LN34 test has the potential to really change the playing field".

In a press release announcing the results, the CDC said availability of such a test could transform how suspected rabies exposure in humans is treated, both in the USA and around the world.

This means doctors and patients can make more informed decisions about who needs treatment for rabies.

The new test, designed for use in animals, can more easily and precisely diagnose rabies infection, according to a study published today in PLOS One. Furthermore, LN34 is able to be run on now used polymerase chain reaction (PCR) testing platforms and can yield results from fresh, frozen, or decomposed animal tissue, as well as tissue "that has been fixed in blocks of paraffin to inactivate the virus".

The DFA test is now the gold-standard and only internationally-approved test for rabies; however, according to the CDC, the DFA, "can only be interpreted by laboratory workers with special skills, extensive training, and a specific type of microscope". The LN34 test can be used on animal tissue that is fresh, frozen, decomposed, or that has been fixed in blocks of paraffin to inactivate the virus.

A dog gets a rabies vaccination
GETTYA dog gets a rabies shot in India

The DFA test can be run only on fresh brain tissue samples that have been kept cold, which can be hard in areas without reliable electricity. Most commonly spread through the bite of an infected animal, according to the CDC, the rabies virus can also spread through scratches, abrasions, open wounds, or mucous membranes contaminated with saliva or other potentially infectious material (such as brain tissue) from a rabid animal. Standard practice now is to vaccinate anyone who might possibly have been exposed to a possibly rabid animal. It could allow doctors and patients to make better informed decisions about who needs treatment for rabies, which is almost always fatal once symptoms start.

During a pilot study, it produced no false negatives, fewer false positive, and fewer inconclusive results. In addition, it produced definitive findings for 80 samples that were inconclusive or untestable by the DFA test-and 29 of those were positive for rabies. Only one sample was indeterminate using both tests.

The New York State Department of Health plans on implementing the new test in state labs after a few more cases are reviewed.

If people are treated within two or three days after being bitten, the human rabies vaccine is highly effective, and victims usually survive.

The number of pre-exposure treatments given in the United States each year is unknown; however, it is estimated to be about 40,000 to 50,000. However, the World Health Organization and the World Organization for Animal Health are considering adding PCR-based tests, such as the LN34 test, for primary diagnosis (meaning they could be used as stand-alone tests to confirm rabies, rather than being used with the DFA test).

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