Previous studies have shown that δ-octalactone is an important component of the tsetse-refractory waterbuck (Kobus defassa) repellent odour blend. In the present study, structure-activity comparison was undertaken to determine the effects of the length of the side chain and ring size of the lactone on adult Glossina pallidipes and Glossina morsitans morsitans. The responses of the flies to each compound were studied in a two-choice wind tunnel. Increasing the chain length from C3 (δ-octalactone) to C4 (δ-nonalactone) enhanced repellency to both species (G. pallidipes from 60.0 to 72.0%, and G. m. morsitans from 61.3 to 72.6%), while increasing the ring size from six (δ-octalactone) to seven members (ε-nonalactone) changed the activity from repellency to attraction that was comparable to that of the phenolic blend associated with fermented cow urine (p>0.05). Blending δ-nonalactone with 4-methylguaiacol (known tsetse repellent) significantly (p<0.05) raised repellency to 86.7 and 91.7% against G. pallidipes and G. m. morsitans respectively. Follow-up Latin Square Designed field studies (Shimba hills in coastal areas in Kenya) with G. pallidipes populations confirmed the higher repellence of δ-nonalactone (with/without 4-methylgu...Continue Reading
African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals. It is caused by protozoa of the species Trypanosoma brucei and almost invariably progresses to death unless treated. Discover the latest research on African trypanosomiasis here.