The common bed bug, Cimex lectularius, feeds on the blood of mammal and bird hosts, and is a pest of global importance. Semiochemicals are chemicals involved in animal communication that may affect behaviour and/or physiology. Attractive semiochemicals that play a role in mediating bed bug behaviour could be exploited for the development of a highly effective novel monitoring device. Tracking software was used to record the response of bed bugs to volatiles from paper previously exposed to conspecific bugs in a still-air olfactometer illuminated by infrared lights, through a variety of activity variables. The effect of time of day as an extrinsic factor, and sex, stage, mating status and nutritional status as physiological factors on the response of bed bugs to the volatiles was examined. Bed bugs of both sexes and all stages responded to the volatiles from bed bug-exposed papers, showing significant attraction and orientation towards the volatile source whether they were starved or engorged. Confirmation that the physiological factors examined do not affect the response of bed bugs to the volatiles from bed bug-exposed papers provides evidence that these bed bug-derived volatiles contain aggregation cues, as semiochemicals that promote aggregation should by definition be detected by both sexes and all life stages. A device baited with such semiochemicals could play a major role in limiting the impact of the current bed bug resurgence by enabling timely detection of infestations, along with quantitative evaluation of control and effective surveillance of the geographical distribution of the pest species.
1 March 2018 in Ecotoxicology and Environmental Safety
In Guatemala prior to control initiatives, the main vectors of Trypanosoma cruzi, the causative agent of Chagas disease, were Rhodnius prolixus and Triatoma dimidiata. This study conducted in 2006 in the department of Chiquimula recorded a high level of T. dimidiata infestation and an absence of R. prolixus in all surveyed communities. In Guatemala, the presence of T. dimidiata as domestic, peridomestic and sylvatic populations results in control difficulties as houses are re-infested from the surrounding environment. Entomological surveys, the current method used to select houses in need of control efforts, are labour intensive and time consuming. A time- and cost-effective way to prioritize houses for evaluation and subsequent treatment is the stratification of houses based on the risk of triatomine infestation. In the present study, 17 anthropogenic risk factors were evaluated for associations with house infestation of T. dimidiata including: wall, floor and roof type. There was an increased likelihood of domestic infestation with T. dimidiata associated with the presence of dirt floors (18/29; OR 8.075, 95% CI 2.13–30.6), uncoated bajareque walls (12/17; OR 4.80, 95% CI 1.35–17.1) and triatomine-like faeces on walls (16/26; OR 3.89, 95% CI 1.19–12.7). These factors could be used to target control of T. dimidiata to communities with an increased risk of being infested.
The brown dog tick, Rhipicephalus sanguineus (Latrielle) sensu lato, is an important ectoparasite of dogs and occasionally humans, capable of transmitting several pathogens, such as Rickettsia and Ehrlichia, which are of veterinary and medical importance. The brown dog tick is distributed worldwide and has an affinity for human habitations in much of its range. In some populations, lack of integrated pest management plans and overuse of pyrethroid pesticides and other sodium channel inhibitors has resulted in high levels of resistance to permethrin. Recently, a highly conserved region of the R. sanguineus sodium channel was sequenced, indicating that a single nucleotide polymorphism of thymine to cytosine on domain III segment VI of the sodium channel could confer resistance. A molecular assay targeting a point mutation in the sodium channel was developed and optimized to separate ticks expressing permethrin resistance from those from a susceptible colony. Thereafter, multiple field-collected phenotypically permethrin-resistant populations were evaluated using this molecular assay to determine genotype. As confirmed by DNA sequencing, a point mutation was present at a high rate in phenotypically resistant tick populations that was not present in the susceptible strain. These data suggest an additional permethrin resistance mechanism to metabolic resistance, which has been reported for this tick species, and confirm its association with phenotypic resistance. The results of this study further emphasize the need to preserve acaricide chemistry through rotation of active ingredients used to control ectoparasites.