Medical Device Link.

Originally Published IVD Technology April 2004

INDUSTRY NEWS

Outbreaks of avian influenza demonstrate the importance of having effective tests for detecting the virus.

The recent outbreaks of avian influenza in Asia have caused considerable concern and brought forth the need for continued vigilance in testing for the virus. U.S. government officials have realized this need and have been working on tests that are more effective in diagnosing avian flu.

Last December, government authorities in South Korea first reported an epidemic of highly pathogenic avian influenza (HPAI) caused by the H5N1 strain of the virus. The detection of this particular pathogenic strain was alarming, primarily because it mutates rapidly and can acquire genes from viruses infecting other animal species. In addition, this strain has a unique capacity to jump the species barrier and cause severe disease in humans.

Since then, the H5N1 avian flu virus has spread to several other Asian countries. One of the hardest-hit nations has been Vietnam. As of February 9, according to the World Health Organization (Geneva) poultry in 57 of the country’s 64 provinces have been affected by H5N1, and consequently around 27 million birds have either died or been destroyed.

While the H5N1 avian virus has not spread to the United States, officials at the U.S. Department of Agriculture (USDA) have been dealing with various other types of avian influenza. For example, in February, commercial poultry flocks in Delaware were discovered to have been infected by a lower pathogenic strain of avian flu. That same month, a flock of chickens outside San Antonio, TX, was also found to have been infected, this time with a highly pathogenic avian virus strain. 

Even though these strains are completely different from the one that has plagued Asia, USDA officials are cognizant of the potential damage that an uncontrolled outbreak of avian influenza can cause. In 1983, an HPAI outbreak in the northeast resulted in the destruction of nearly 17 million birds and cost nearly $65 million.

The USDA agency that has the primary responsibility of monitoring and testing birds for avian influenza is the Animal and Plant Health Inspection Service (APHIS; Riverdale, MD). Currently, the method used by APHIS to test for avian flu is reverse transcriptase–polymerase chain reaction (RT-PCR). By using the RT-PCR platform, USDA researchers developed a test that takes a two-step approach. The first step initially screens for any type-A influenza; the second step is a subtyping test that confirms the sample and what specific subtype it is.

“There was certainly a lot of interest in having rapid, sensitive diagnostic tests,” says David Suarez, PhD, a veterinary medical officer at the Southeast Poultry Research Laboratory (Athens, GA), a division of USDA’s Agricultural Research Service that was involved in developing this test. “That was really the reason why the real-time RT-PCR test was developed. And with RT-PCR, there is a distinct advantage in the ability to get quick test results. So even with a large number of samples, getting a turnaround time of less than 24 hours on those results is certainly a big improvement over other testing methods.”

Eventually, USDA is planning to work with an IVD manufacturer to put all of the various elements of this test into a single kit format and have it produced commercially. 

“The idea is to put the reagents into a kit format that would be very stable, such that a veterinary laboratory would feel very comfortable about pulling them off the shelf and running them,” says Suarez. “By doing so, we’re trying to increase standardization and decrease the lot-to-lot variability in the probes and primers, because right now each laboratory conducting this test is ordering its own reagents. So we will work with a company to try to make the test more accessible in a kit form.” 

USDA officials are aware that other HPAI virus strains may emerge rapidly in the future. These officials recognize the need to continue developing technologies for detecting these rapidly mutating avian flu viruses and have taken steps to address this issue.

“Avian influenza has been a priority issue for several years now,” says Suarez. “In fact, some of the money we had to develop the RT-PCR test in the first place came from government efforts to improve our ability to rapidly diagnose disease outbreaks. So although we’ve had a program in our laboratory on avian influenza for a number of years, we’re tapping into issues dealing with rapid response, which is necessary to mitigate a disease outbreak.”

Copyright ©2004 IVD Technology