To combat potential outbreaks of Zika virus, some countries have considered using pesticides so strong that they are banned elsewhere. However, if it could quickly be determined that a mosquito population was not carrying the Zika virus, the use of harmful pesticides could be avoided, as could the cost of widespread spraying.
That’s the premise behind a new study published in Science Translational Medicine that was 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 Colorado State 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 loop-mediated isothermal amplification (LAMP) technology, the research team found that they could easily detect Zika virus in human and mosquito samples from the U.S., Brazil and Nicaragua.
Brewster had been using LAMP — which was developed in Japan in 2001 — to detect pneumonia in bighorn sheep through a project with Colorado Parks & Wildlife and the Quackenbush Lab at Colorado State.
LAMP is similar to the technology known as polymerase chain reaction (PCR), which provides a very sensitive analysis of DNA samples. However, LAMP is simple enough to be used in the field instead of in the laboratory, 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 heats up two microliters of water (about the size of the head of a pin) in a tube with a few chemicals or reagents. The sample then becomes cloudy, and the color of the solution changes.
In the Colorado State-led study, researchers saw a change or signal within about 30 minutes, although 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 & Infectious Diseases Laboratory at Colorado State.
“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. However, being able to distinguish between the different strains is important due to the association of the Asian-linked virus with microcephaly, a congenital condition leading to incomplete brain development among newborns.
Researchers from Colorado State University's department of microbiology, immunology and pathology and the Arthropod-borne & Infectious Diseases Laboratory collaborated with an international team on new Zika virus research. Photo: Colorado State University.