Insect repellent and attractants

#The disclosure provides compounds useful as insect repellents and compositions comprising such repellents. The disclosure further provides compounds useful as insect traps.

#Numerous insects are vectors for disease. Mosquitoes in the genus Anopheles are the principle vectors of malaria, a disease caused by protozoa in the genus Trypanosoma. Aedes aegypti is the main vector of the viruses that cause Yellow fever and Dengue. Other viruses, the causal agents of various types of encephalitis, are also carried by Aedes spp. mosquitoes. Wuchereria bancrofti and Brugia malayi, parasitic roundworms that cause filariasis, are usually spread by mosquitoes in the genera Culex, Mansonia, and Anopheles.

#Horse flies and deer flies may transmit the bacterial pathogens of tularemia (Pasteurella tularensis) and anthrax (Bacillus anthracis), as well as a parasitic roundworm (Loa loa) that causes loiasis in tropical Africa.

#FIG. 1 is a schematic showing the relation of compounds and compositions to CO2 sensing in insect vectors. CO2 emitted by human breath, are detected by the CO2 sensitive neurons on the olfactory organs of vector insects. Volatile chemicals of the disclosure can activate or inhibit the CO2 responsive neuron. Agonists are proposed to be used as lures in traps, and antagonists for disruption of host-seeking behavior as repellents and masking agents.

#FIG. 2 depicts electrophysiology measurements of the peg sensillum on the mosquito maxillary palp. The palp, indicated in brown in the schematic of the mosquito head, has several peg sensilla. Each peg sensilla (grey club-like structure in the center) contains three olfactory neurons A, B and C as indicated, of which the ‘A’ neuron gives a robust and specific increase in frequency of action potentials in response to a stimulus of CO2. Extracellular single-unit recordings are performed by inserting a glass microelectrode into the peg sensilla, and puffing an odor such as CO2 towards the mosquito maxillary palps. The signal is amplified to obtain the trace of action potentials. The A neuron has a significantly larger amplitude of action potentials and can be readily distinguished from the spikes elicited by the B and C neurons within the same sensilla.

#FIG. 3 shows inhibition of the CO2 mediated response by antagonist odors in Culex quinquefasciatus. Action potential traces from the peg sensillum of the maxillary palp show spike amplitudes from three neurons, where the highest spike (from neuron A) indicates the CO2 response. A 3-sec stimulus of 0.3% CO2 (indicated by longer black bar), is overlaid with a 0.5-sec stimulus of candidate odors. CO2 stimulus is applied from a tank, while odor is applied from a delivery cartridge containing 50 μl odor at 10−1 dilution in paraffin oil as solvent, placed on a filter paper disc with indicated odor (colored bars). The two stimuli are delivered from two independent odor delivery systems into a single airstream that is directed over the palps. A constant CO2 stimulus was delivered from a cylinder using a computerized system (Microdata). Odor was delivered in a manner that did not affect the concentration of the CO2 stimulus, from a glass cartridge containing 50 μl of odor at the indicated concentrations, using an independent stimulus delivery system (Syntech).

#As used herein and in the appended claims, the singular forms “a,” “and,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an insect” includes a plurality of such insects and reference to “the compound” includes reference to one or more compounds, and so forth.

#Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although any methods and reagents similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods and materials are now described.

#Also, the use of “or” means “and/or” unless stated otherwise. Similarly, “comprise,” “comprises,” “comprising” “include,” “includes,” and “including” are interchangeable and not intended to be limiting.