Evaluation Of Lambda-Cyhalothrin (Icon®) Incorporated Into 1, 4-Dichlorobenzene (Pcb®) For The Control Of Leishmaniases And Malaria Vectors

Abstract

Leishmaniases and human malaria, transmitted by phlebotomine sand flies (Diptera: Psychodidae) and anopheline mosquitoes (Diptera: Anophelinae) respectively, are diseases of public health importance in Kenya. Control of phlebotomine sand flies (Diptera: Psychodidae) and mosquitoes (Diptera: Anophlenae) remains a priority as they pose a significant public health threat in many parts of the world, transmitting the agents of several zoonotic and parasitic diseases to humans. Efficient vectoring role of sand flies and mosquitoes is enhanced by specific biological and behavioural characteristics that may be targeted by control measures to limit pathogen spread or vector abundance. The overall aim of this study was to evaluate the efficacy of 1,4-dichlorobenzene (PCB®), an organic compound with insecticidal and antimicrobial properties incorporated into lambda-cyhalothrin (ICON®), a synthetic pyrethroid, in the control of leishmaniasis and malaria vectors in the laboratory and field settings. In the laboratory, survival and mortality of sand flies and mosquitoes was monitored following exposure to the treatments while in the field the study involved vector collections before treatments and monitoring the number of vectors after treatments using the entry-exit trap. Paired t test was used to analyze the average number of sand flies and mosquitoes collected before and after treatment and to compare between groups. There was high mortality of mosquitoes exposed to ICON® / PCB® combination compared to either PCB® or ICON® independently and their mean difference was significantly different (15.17±5.59, P=0.021; 17.66±6.96 P=0.03, respectively). This implies that the combined product was more effective in killing the vectors compared to the individual insecticides. Likewise, the mean number of sand flies that survived following exposure to ICON® /PCB® xvii combination was less compared to those exposed to PCB® or ICON® (2.17 ±0.91, P=0.03 and 2.5 ±1.06, P=0.03, respectively). There was significant decrease in sand fly densities after treatment with ICON® (P=0.03, t=1.81, SEM±25.99) or PCB® (P=0.02, t=1.81, SEM±11.46322), but the densities of sand fly were not comparable before and after treatment with the combination of ICON® /PCB® or ICON® (P=0.11, t=1.83, SEM±66.30). The decrease of sand fly populations following exposure to ICON®, PCB® or ICON®/PCB® is an indication that all the trial insecticides can be used in their control. Overall, significant reduction of mosquito densities after treatment with ICON® (45.4±18.043, P= 0.02) and ICON®/PCB® (95.7±43.15, P= 0.03) was observed. However, there was no significant difference when mosquitoes were exposed to PCB® (193.3±131.94, P= 0.09) for a period of six months. The differences in mosquito densities seen in collection from the houses which had ICON® and the combination of ICON®/PCB® showed that PCB® alone could not be effective. Lambdacyhalothrin and paradichlorobenzene alone or in combination can be used safely for the effective control of indoor-feeding sand fly and mosquito vectors of human disease.