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To combat potential outbreaks of the Zika virus, some countries have considered using pesticides so strong that they are banned elsewhere. But if you could quickly determine that mosquitoes were not carrying the Zika virus, the use of harmful pesticides could be avoided, as well as the cost of widespread spraying.
That’s the premise behind a new study published May 3 in Science Translational Medicine, authored by Assistant Professor Joel Rovnak, graduate student Nunya Chotiwan, and research associate Connie Brewster in Colorado State University’s Department of Microbiology, Immunology and Pathology.
The CSU team is using an existing technology in a new way: They have demonstrated a method of biosurveillance that quickly indicates whether Zika virus is present in local mosquito populations. That data can inform decision-making about spraying and other disease-prevention methods.
Using the existing technology — loop-mediated isothermal amplification, or LAMP — the research team found that they could easily detect Zika virus in human and mosquito samples from the United States, Brazil and Nicaragua.
LAMP lights the way to virus detection
Brewster had been using LAMP, which was developed in Japan in 2001, to detect pneumonia in bighorn sheep through a project with Colorado Parks and Wildlife and the Quackenbush Lab at CSU. LAMP is similar to the technology known as polymerase chain reaction or PCR, which provides a very sensitive analysis of DNA samples. But LAMP is simple enough to be used in the field instead of in the lab, and it’s also less expensive.
“With LAMP, you don’t need the sophistication of a machine to analyze samples,” Rovnak said.
Using LAMP, researchers start by squishing a mosquito in water. Rovnak said he then takes two microliters of water (about the size of the head of a pin), and heats it up in a tube with a few chemicals or reagents. The sample then becomes cloudy and the color of the solution changes. In the CSU-led study, researchers saw a change or signal within about 30 minutes, though it can take up to one hour.
“Using LAMP to detect Zika virus would be much less expensive for developing countries,” said Chotiwan, a researcher in the Perera Lab, part of the Arthropod-borne and Infectious Diseases Laboratory at CSU.
“The majority of the countries involved in the current outbreak are not rich,” she said. “It’s important for us to try to develop low-cost surveillance methods that might one day be used in these countries.”
As a rough cost estimate, Rovnak said a heating device, or heat block, for LAMP costs $250 or less. Real-time PCR machines cost between $15,000 and $25,000.
In the study, the research team focused on detecting Zika virus strains from Asia and Africa. Zika virus was first detected in Uganda in 1947 and is predicted to be heading back to the African continent, Chotiwan said.
No one really knows the extent of the original Zika virus in Africa, according to Rovnak. But being able to distinguish between the different strains is important due to the association of the Asian-linked virus with microcephaly, a congenital condition associated with incomplete brain development among newborns.
The Centers for Disease Control and Prevention recently reported local transmission of Zika virus in Cape Verde, off the coast of West Africa. CDC has also issued Zika virus travel advisories for some countries in Africa. In the United States, Zika virus transmission has been reported in Florida and Texas.
Brian Foy, CSU associate professor in the Arthropod-borne Infectious Diseases Laboratory, discovered that Zika virus may be sexually transmitted in addition to being spread by mosquitoes. With two known transmission routes, the virus is an even more formidable foe to public health.
To expand on the early results, the scientists tested Zika virus samples received from researchers in Brazil and from a pediatric hospital in Managua, Nicaragua, as well as samples from the CDC’s Division of Vector-Borne Diseases in Fort Collins.
Next steps include hospital-based tests
Moving forward, clinicians at the pediatric hospital in Managua will test LAMP side-by-side with current, more sophisticated tests. The CSU research team will also test LAMP versus PCR using mosquito and wildlife virus samples from Puerto Rico obtained through a project with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.
How soon could LAMP be made available for more widespread use?
“For now, it’s what would be considered a long slog,” said Rovnak.
“The human diagnostic side of things presents a much more significant challenge,” he explained. “It’s going to take a lot of time and a lot of data before people will allow regulatory agencies to OK LAMP as a bona fide test for a person who’s sick in the hospital.”
Read more about the study, “Rapid and Specific Detection of Asian or African-lineage Zika Viruses.”
Study co-authors include researchers from CSU’s Arthropod-borne and Infectious Disease Laboratory, the Division of Vector-Borne Diseases at CDC, the Ministry of Health in Nicaragua, Heidelberg University and the German Centre for Infection Research, Fundacao Oswaldo Cruz in Brazil, University of Pittsburgh and University of California, Berkeley.