Spatial repellants considerably scale back an infection with mosquito-borne viruses. Information | Notre Dame Information

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Research professors Neil Lobo (left) and Nicole Achee. Photo by Matt Cashore / Notre Dame University.

Spatial repellants may reduce the risk of infection with mosquito-borne viruses from Aedes, according to new results from a clinical study in Iquitos, Peru. The results of the Peru study are encouraging: study participants whose homes contained the home repellant were 34 percent less likely to be infected with Aedes mosquito-borne viruses than other study participants who received the placebo product without the repellent.

The Iquitos study was part of a multi-year effort by scientists from the University of Notre Dame to determine the protective effects of spatial repellants to prevent human infection with pathogens that cause diseases such as malaria, zika and dengue fever transmitted through mosquito bites.

“This is the first clinical study to conclusively demonstrate that a spatial repellent can protect against Aedes-borne viral infection in humans – a milestone in spatial repellent research and development as an effective intervention in disease control programs,” said Nicole L. Achee. Co-Principal Investigator of the Study and Research Professor in the Institute of Life Sciences in Notre Dame. “This finding helps provide evidence that spatial repellants have the potential to improve public health in areas of the world where mosquito-borne diseases are a significant burden. We are excited.

Dengue fever cases have increased exponentially since 2000, according to the World Health Organization. It is estimated that 390 million infections are reported each year and more than 40 percent of the world’s population are at risk. The most recent Zika outbreak occurred in 2015-16. While the symptoms of Zika are generally mild, it can lead to various complications in women who are infected while pregnant, including microcephaly and congenital anomalies in newborns and Guillain-Barre syndrome. To date, 86 countries and territories have reported evidence of mosquito-borne Zika infection and no treatments are known.

The mosquitoes Aedes aegypti and Aedes albopictus, which can transmit these viruses, usually live in and around homes and prefer to bite people during the day. These traits make people more likely to be bitten in their daily routine.

Spatial repellants release an active ingredient into the air to inhibit certain insect behaviors, such as biting and feeding, and to encourage movement away from a treated area. Achee and co-principal investigator Neil Lobo, research professor of medical entomology at Notre Dame, studied a passive spatially repellent emanator developed by SC Johnson for public health in households where both dengue and Zika can be transmitted. The team conducted a cluster-randomized, double-blind, placebo-controlled study that was conducted over a period of two years. The same team conducted a similar experiment in Indonesia, examining the effects of the same spatial repellent on malaria transmission. This study showed promising results with a reduction in initial infection of approximately 28 percent, while randomized village clusters with low to moderate malaria transmission at baseline showed a reduction in overall malaria infection of approximately 41 percent.

“The significant epidemiological and entomological outcome of this study shows that the spatial defense paradigm can reduce morbidity related to mosquito-borne diseases,” said Lobo. “The focus of this research is to gather evidence that will provide an understanding of what is needed to protect the world’s most vulnerable people from these diseases, and to establish decision-making strategies and guidelines for that purpose. We look forward to taking this important step forward. “

The study included the registration of 18,000 Iquitos residents in 2,400 households and real-time data management by staff from the University of California, Davis. The spatial repellent was replaced in registered households twice a month by a study team led by the US Naval Medical Research Unit Six in Peru.

The key findings of the Peru study come from a report by the Vector Control Advisory Group of the World Health Organization. The group evaluates evidence of the epidemiological effectiveness of new vector control measures and supports the development of global policy recommendations by WHO, including the potential use of spatial repellants as a public health vector control strategy.

Key investigators on the site include Amy C. Morrison and Thomas W. Scott, both from the University of California, Davis, who work with U.S. Naval Medical Research Unit Six. The Notre Dame Center for Research Computing helped develop the design of the Peruvian experimental database. Statistical analysis was performed by Robert C. Reiner Jr. of the Department of Health Metrics Sciences at the University of Washington.

Both Achee and Lobo are members of Notre Dame’s Eck Institute for Global Health.

Funding for the study was provided by the Bill & Melinda Gates Foundation. SC Johnson funded and developed the spatial repellant and donated a product for use in the study.

For more information on the project, see Spatialrepellents.nd.edu.

Contact: Jessica Sieff, Deputy Director for Media Relations, 574-631-3933, jsieff@nd.edu

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