ARS | Publication request: Trapping of Rift Valley Fever (RVF) vectors using Light Emitting Diode (LED) CDC traps in two arboviral disease hot spots in Kenya

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 2012
Publication Date: May 19, 2012
Repository URL: http://www.parasitesandvectors.com/content/5/1/94
Citation: Tchouassi, D.P., Sang, R., Sole, C., Bastos, A.D., Cohnstaedt, L.W., Baldwyn, T. 2012. Trapping of Rift Valley Fever (RVF) vectors using Light Emitting Diode (LED) CDC traps in two arboviral disease hot spots in Kenya. Parasites & Vectors. 5:94.

Interpretive Summary: Understanding the distribution and abundance of mosquito disease vectors is important for determining the timing and extent of a disease epidemic. In the case of Rift Valley Fever mosquitoes in Africa, the mosquito populations fluctuate greatly with the seasons and therefore collecting when few mosquitoes are present is important for predicting epidemics. To maximize trap collections scientists in Africa in collaboration with the USDA-ARS tested the attraction of various species of mosquitoes to colored lights. The advent of energy efficient and super bright light emitting diodes (LEDs) a logical replacement for incandescent light bulbs. Tested in this study were single color lights (red, green, blue and violet) and combinations of colors incandescent bulbs and a combination of red, green and blue LEDs together. The study found multiple colors of light are more attractive than single colors although light intensity was not considered. Some studies have found higher intensities of light are more attractive. LEDs are better in terms of energy use but about the same as incandescent in terms of mosquito attraction.

Technical Abstract: Background: Mosquitoes’ response to artificial lights including color has been exploited in trap designs for improved sampling of mosquito vectors. Earlier studies suggest that mosquitoes are attracted to specific wavelengths of light and thus the need to refine techniques to increase mosquito captures following the development of super-bright light-emitting diodes (LEDs) which emit narrow wavelengths of light or very specific colors. Therefore, we investigated if LEDs can be effective substitutes for incandescent lamps used in CDC light traps for mosquito surveillance, and if so, determine the best color for attraction of important Rift Valley Fever (RFV) vectors. Methods: The efficiency of selected colored LED CDC light traps (red, green, blue, violet, combination of blue-green-red (BGR)) to sample RVF vectors was evaluated relative to incandescent light (control) in CDC light trap in two RVF hotspots (Marigat and Ijara districts) in Kenya. In field experiments, traps were baited with dry ice and captures evaluated for Aedes tricholabis, Ae. mcintoshi, Ae. ochraceus, Mn. uniformis, Mn. africana and Cx. pipiens, following Latin square design with days as replicates. Daily mosquito counts per treatment were analyzed using a generalized linear model with Negative Binomial error structure and log link using R. The incidence rate ratios (IRR) that mosquito species chose other treatments instead of the control, were estimated. Results: Seasonal preference of Ae.mcintoshi and Ae. ochraceus at Ijara was evident with a bias towards BGR and blue traps respectively in one trapping period but this pattern waned during another period at same site with significantly low numbers recorded in all colored traps except blue relative to the control. Overall results showed that higher captures of all species were recorded in control traps compared to the other LED traps (IRR<1) although only significantly different from red and violet. Conclusion: Based on our trapping design and color, none of the LEDs outcompeted the standard incandescent light. The data however provides preliminary evidence that a preference might exist for some of these mosquito species based on observed differential attraction to these light colors requiring future studies to compare reflected versus transmitted light and the incorporation of colored light of varying intensities.