Characterizing Mosquito Biting Behavior Using the BiteOscope.

The biteOscope enables the high-resolution monitoring and video recording of blood-feeding mosquitoes. Mosquito biting is induced by combining host cues, an artificial bloodmeal, a membrane, and a transparent heater in a transparent behavioral arena. Machine vision techniques enable the tracking and pose estimation of individual mosquitoes to discern behavior and resolve individual feeding events. The workflow allows multiple replicates and large amounts of imaging data to be generated rapidly. These data are suitable for downstream analysis using machine learning tools for behavioral analysis, allowing subtle behavioral effects to be characterized.

Characterizing Mosquito Biting Behavior at High Resolution.

Blood feeding is a critical event in the life cycle of female mosquitoes. In addition to providing nutrients to the mosquito, blood feeding facilitates the transmission of parasites and viruses to hosts, potentially having devastating health consequences. Our understanding of these short, yet important, bouts of behavior is incomplete. How and where a mosquito decides to bite and the success of feeding can influence the transmission of pathogens. A more thorough understanding of these processes may allow the development of interventions that reduce or prevent infections. Here, we present an overview of strategies for studying mosquito biting behavior and introduce the biteOscope, which provides an opportunity to observe and understand this behavior at unprecedented spatial and temporal resolution under tightly controlled conditions. The biteOscope combines recent advances in computer vision and automated tracking with designs for behavioral arenas and controllable artificial host cues that use low-cost and readily available materials.

A closer look at the WHO cone bioassay: video analysis of the hidden effects of a human host on mosquito behaviour and insecticide contact.

BACKGROUND: The WHO cone test is one of three tests currently used to evaluate the efficacy of insecticide-treated bed nets (ITNs). It generates two test outputs, knockdown and 24-h mortality, both indicative of immediate toxicity but that reveal little about the nature of mosquito and ITN interaction or how results translate to real-world settings. METHODS: A human arm held 5 mm behind the net surface acted as a host attractant during cone tests and a smartphone was used to capture mosquito behaviour in the cone. Post-exposure blood feeding and survival for nine days were recorded; ingested blood meal size was determined by measuring excreted haematin. Four strains of Anopheles gambiae (insecticide susceptible: Kisumu and N'gousso; insecticide resistant: Banfora and VK7) were tested with and without the host attractant using untreated, Permanet 2.0 and Olyset nets. Video recordings were scan sampled every five seconds to record mosquito positions on either the net, in flight or in contact with the cone. Generalized estimating equations were used to analyse all data except survival within nine days which was analysed using Weighted Cox Regression. RESULTS: Net contact was the most frequently recorded behaviour in all Anopheles spp. strains on all nets. Adding the human host as attractant triggered excitatory behaviours: in all strains, the magnitude of net contact was significantly decreased compared to tests without a host. ITN exposure altered the observed behaviour of the two susceptible strains, which exhibited a decreased response to the host during ITN tests. The resistant strains did not alter their behaviour during ITN tests. Significantly less net contact was observed during Olyset Net tests compared to Permanet 2.0. The host presence affected survival after exposure: Banfora and VK7 mosquitoes exposed to Permanet 2.0 with a host lived longer compared to tests performed without a host. However, mosquitoes that blood-fed and survived long enough to digest the blood meal did not exhibit significantly reduced longevity regardless of the presence of the host attractant. CONCLUSIONS: Simple modifications to the WHO cone test and extension of post-test monitoring beyond the current 24 h enable detailed behavioural characterizations of individual ITNs to be compiled. The effects observed from testing with a host and including blood feeding suggest that more representative estimates of true of ITN efficacy are gained with these modifications than when using the current testing protocol.

A minimal 3D model of mosquito flight behaviour around the human baited bed net.

BACKGROUND: Advances in digitized video-tracking and behavioural analysis have enabled accurate recording and quantification of mosquito flight and host-seeking behaviours, facilitating development of individual (agent) based models at much finer spatial scales than previously possible. METHODS: Quantified behavioural parameters were used to create a novel virtual testing model, capable of accurately simulating indoor flight behaviour by a virtual population of host-seeking mosquitoes as they interact with and respond to simulated stimuli from a human-occupied bed net. The model is described, including base mosquito behaviour, state transitions, environmental representation and host stimulus representation. RESULTS: In the absence of a bed net and human host bait, flight distribution of the model population was relatively uniform throughout the arena. Introducing an unbaited untreated bed net induced a change in distribution with an increase in landing events on the net surface, predominantly on the sides of the net. Adding the presence of a simulated human bait dramatically impacted flight distribution patterns, exploratory foraging and, the number and distribution of landing positions on the net, which were determined largely by the orientation of the human within. The model replicates experimental results with free-flying living mosquitoes at human-occupied bed nets, where contact occurs predominantly on the top surface of the net. This accuracy is important as it quantifies exposure to the lethal insecticide residues that may be unique to the net roof (or theoretically any other surface). Number of net contacts and height of contacts decreased with increasing attractant dispersal noise. CONCLUSIONS: Results generated by the model are an accurate representation of actual mosquito behaviour recorded at and around a human-occupied bed net in untreated and insecticide-treated nets. This fine-grained model is highly flexible and has significant potential for in silico screening of novel bed net designs, potentially reducing time and cost and accelerating the deployment of new and more effective tools for protecting against malaria in sub-Saharan Africa.

Diffuse retro-reflective imaging for improved video tracking of mosquitoes at human baited bednets.

Robust imaging techniques for tracking insects have been essential tools in numerous laboratory and field studies on pests, beneficial insects and model systems. Recent innovations in optical imaging systems and associated signal processing have enabled detailed characterization of nocturnal mosquito behaviour around bednets and improvements in bednet design, a global essential for protecting populations against malaria. Nonetheless, there remain challenges around ease of use for large-scale in situ recordings and extracting data reliably in the critical areas of the bednet where the optical signal is attenuated. Here, we introduce a retro-reflective screen at the back of the measurement volume, which can simultaneously provide diffuse illumination, and remove optical alignment issues while requiring only one-sided access to the measurement space. The illumination becomes significantly more uniform, although noise removal algorithms are needed to reduce the effects of shot noise, particularly across low-intensity bednet regions. By systematically introducing mosquitoes in front of and behind the bednet in laboratory experiments, we are able to demonstrate robust tracking in these challenging areas. Overall, the retro-reflective imaging set-up delivers mosquito segmentation rates in excess of 90% compared to less than 70% with backlit systems.

Barrier bednets target malaria vectors and expand the range of usable insecticides.

Transmission of Plasmodium falciparum malaria parasites occurs when nocturnal Anopheles mosquito vectors feed on human blood. In Africa, where malaria burden is highest, bednets treated with pyrethroid insecticide were highly effective in preventing mosquito bites and reducing transmission, and essential to achieving unprecedented reductions in malaria until 2015 (ref. 1). Since then, progress has stalled2, and with insecticidal bednets losing efficacy against pyrethroid-resistant Anopheles vectors3,4, methods that restore performance are urgently needed to eliminate any risk of malaria returning to the levels seen before their widespread use throughout sub-Saharan Africa5. Here, we show that the primary malaria vector Anopheles gambiae is targeted and killed by small insecticidal net barriers positioned above a standard bednet in a spatial region of high mosquito activity but zero contact with sleepers, opening the way for deploying many more insecticides on bednets than is currently possible. Tested against wild pyrethroid-resistant A. gambiae in Burkina Faso, pyrethroid bednets with organophosphate barriers achieved significantly higher killing rates than bednets alone. Treated barriers on untreated bednets were equally effective, without significant loss of personal protection. Mathematical modelling of transmission dynamics predicted reductions in clinical malaria incidence with barrier bednets that matched those of 'next-generation' nets recommended by the World Health Organization against resistant vectors. Mathematical models of mosquito-barrier interactions identified alternative barrier designs to increase performance. Barrier bednets that overcome insecticide resistance are feasible using existing insecticides and production technology, and early implementation of affordable vector control tools is a realistic prospect.

Dialectical behavior therapy for high suicide risk in individuals with borderline personality disorder: a randomized clinical trial and component analysis.

IMPORTANCE: Dialectical behavior therapy (DBT) is an empirically supported treatment for suicidal individuals. However, DBT consists of multiple components, including individual therapy, skills training, telephone coaching, and a therapist consultation team, and little is known about which components are needed to achieve positive outcomes. OBJECTIVE: To evaluate the importance of the skills training component of DBT by comparing skills training plus case management (DBT-S), DBT individual therapy plus activities group (DBT-I), and standard DBT which includes skills training and individual therapy. DESIGN, SETTING, AND PARTICIPANTS: We performed a single-blind randomized clinical trial from April 24, 2004, through January 26, 2010, involving 1 year of treatment and 1 year of follow-up. Participants included 99 women (mean age, 30.3 years; 69 [71%] white) with borderline personality disorder who had at least 2 suicide attempts and/or nonsuicidal self-injury (NSSI) acts in the last 5 years, an NSSI act or suicide attempt in the 8 weeks before screening, and a suicide attempt in the past year. We used an adaptive randomization procedure to assign participants to each condition. Treatment was delivered from June 3, 2004, through September 29, 2008, in a university-affiliated clinic and community settings by therapists or case managers. Outcomes were evaluated quarterly by blinded assessors. We hypothesized that standard DBT would outperform DBT-S and DBT-I. INTERVENTIONS: The study compared standard DBT, DBT-S, and DBT-I. Treatment dose was controlled across conditions, and all treatment providers used the DBT suicide risk assessment and management protocol. MAIN OUTCOMES AND MEASURES: Frequency and severity of suicide attempts and NSSI episodes. RESULTS: All treatment conditions resulted in similar improvements in the frequency and severity of suicide attempts, suicide ideation, use of crisis services due to suicidality, and reasons for living. Compared with the DBT-I group, interventions that included skills training resulted in greater improvements in the frequency of NSSI acts (F1,85 = 59.1 [P < .001] for standard DBT and F1,85 = 56.3 [P < .001] for DBT-S) and depression (t399 = 1.8 [P = .03] for standard DBT and t399 = 2.9 [P = .004] for DBT-S) during the treatment year. In addition, anxiety significantly improved during the treatment year in standard DBT (t94 = -3.5 [P < .001]) and DBT-S (t94 = -2.6 [P = .01]), but not in DBT-I. Compared with the DBT-I group, the standard DBT group had lower dropout rates from treatment (8 patients [24%] vs 16 patients [48%] [P = .04]), and patients were less likely to use crisis services in follow-up (ED visits, 1 [3%] vs 3 [13%] [P = .02]; psychiatric hospitalizations, 1 [3%] vs 3 [13%] [P = .03]). CONCLUSIONS AND RELEVANCE: A variety of DBT interventions with therapists trained in the DBT suicide risk assessment and management protocol are effective for reducing suicide attempts and NSSI episodes. Interventions that include DBT skills training are more effective than DBT without skills training, and standard DBT may be superior in some areas. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00183651.

Jaw-movement smoothness during empty chewing and gum chewing.

A major goal of motor coordination is the production of a smooth movement. Jerk-cost, which is an inverse measure of movement smoothness, has been evaluated during gum chewing in previous studies. However, the effect of the gum bolus is still unclear. The aims of this study were to compare the jerk-cost values of normal gum chewing with those of empty chewing. Thirteen subjects undertook, empty chewing, then chewing of gum, and then a second empty chewing. Jerk-cost was calculated from an accelerometer attached to the skin of the mentum. There was a significantly higher smoothness (i.e. lower jerk-cost, P < 0.05) during the opening and second-half closing phases in empty chewing compared with gum chewing. There were no significant differences in jerk-costs (i.e. opening or closing) between the first and the second empty-chewing sequences. These results suggest that the influence of the mechanical effects of tooth contact on jerk-cost is not restricted just to the occlusal phase of chewing, but rather the effect influences the entire opening and closing phases of chewing.

From pain to movement: a tribute to professor Barry J. Sessle.

This tribute article to Professor Barry J. Sessle summarizes the 6 presentations delivered at the July 1, 2008 symposium at the University of Toronto. The symposium honored 3 "giants" in orofacial neuroscience, Professors B. J. Sessle, J. P. Lund, and A. G. Hannam. The 6 presentations paying tribute to Sessle spanned the period from the early phase of his career up to some of his most recent studies with colleagues in Asia, Europe, and Australia as well as Canada. The studies have included those providing an improved understanding of the cortical control of sensory inputs in pain perception (presented by R. Dubner) and in the control of mastication and swallowing, as well as brainstem mechanisms of orofacial pain (K. Iwata, G. Murray). His current activities in his laboratory and in Denmark are also highlighted (L. Avivi-Arber, P. Svensson). The potential transfer of basic research discoveries toward drug development in pain control that stem from some of his research is also described (B. Cairns). The final section of the paper includes a commentary from Professor Sessle.

Properties and plasticity of the primate somatosensory and motor cortex related to orofacial sensorimotor function.

1. The lateral pericentral region of the cerebral cortex has been well documented in primates to be important in sensorimotor integration and control and in the learning of new motor skills. 2. The present article provides, first, an overview of limb sensorimotor cortical mechanisms and, second, outlines recent evidence pointing to an important role for the face sensorimotor cortex in semi-automatic, as well as trained, orofacial motor behaviour and to its propensity for neuroplastic changes in association with orofacial motor skill acquisition or an altered oral environment.

Neuronal activity patterns in primate primary motor cortex related to trained or semiautomatic jaw and tongue movements.

The present study was undertaken to determine the firing patterns and the mechanoreceptive field (RF) properties of neurons within the face primary motor cortex (face-MI) in relation to chewing and other orofacial movements in the awake monkey. Of a total of 107 face-MI neurons recorded, 73 of 74 tested had activity related to chewing and 47 of 66 neurons tested showed activity related to a trained tongue task. Of the 73 chewing-related neurons, 52 (71.2%) showed clear rhythmic activity during rhythmic chewing. A total of 32 (43.8%) also showed significant alterations in activity in relation to the swallowing of a solid food (apple) bolus. Many of the chewing-related neurons (81.8% of 55 tested) had an orofacial RF, which for most was on the tongue dorsum. Tongue protrusion was evoked by intracortical microstimulation (ICMS) at most (63.6%) of the recording sites where neurons fired during the rhythmic jaw-opening phase, whereas tongue retraction was evoked by ICMS at most (66.7%) sites at which the neurons firing during the rhythmic jaw-closing phase were recorded. Of the 47 task-related neurons, 21 of 22 (95.5%) examined also showed chewing-related activity and 29 (61.7%) demonstrated significant alteration in activity in relation to the swallowing of a juice reward. There were no significant differences in the peak firing frequency among neuronal activities related to chewing, swallowing, or the task. These findings provide further evidence that face-MI may play an important role not only in trained orofacial movements but also in chewing as well as swallowing, including the control of tongue and jaw movements that occur during the masticatory sequence.

Effects of reversible cold block of face primary somatosensory cortex on orofacial movements and related face primary motor cortex neuronal activity.

Our previous studies have revealed that face primary somatosensory cortex (SI) as well as face primary motor cortex (MI) play important roles in the control of orofacial movements in awake monkeys, and that both face MI and face SI neurons may have an orofacial mechanoreceptive field and show activity related to orofacial movements. Since it is possible that the movement-related activity of face MI neurons could reflect movement-generated orofacial afferent inputs projecting to face MI via face SI, the present study used reversible cold block-induced inactivation of the monkey's face SI to determine if face MI neuronal activity related to a trained tongue-protrusion task, chewing or swallowing was dependent on the functional integrity of the ipsilateral face SI and if inactivation of face SI affects orofacial movements. The effects of face SI cold block were tested on chewing, swallowing and/or task-related activity of 73 face MI neurons. Both task and chewing and/or swallowing-related activity of most face MI neurons was independent of the functional integrity of the ipsilateral face SI since SI cold block affected the movement-related activity in approximately 25% of the neurons. Similarly, unilateral cold block of SI had very limited effects on the performance of the task and chewing, and no effect on the performance of swallowing. These findings suggest that movement-induced reafferentation via face SI may not be a significant factor in accounting for the activity of the majority of ipsilateral face MI neurons related to trained movements, chewing and swallowing.