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1.  Water vapour and heat combine to elicit biting and biting persistence in tsetse 
Parasites & Vectors  2013;6:240.
Background
Tsetse flies are obligatory blood feeders, accessing capillaries by piercing the skin of their hosts with the haustellum to suck blood. However, this behaviour presents a considerable risk as landing flies are exposed to predators as well as the host’s own defense reactions such as tail flicking. Achieving a successful blood meal within the shortest time span is therefore at a premium in tsetse, so feeding until replete normally lasts less than a minute. Biting in blood sucking insects is a multi-sensory response involving a range of physical and chemical stimuli. Here we investigated the role of heat and humidity emitted from host skin on the biting responses of Glossina pallidipes, which to our knowledge has not been fully studied in tsetse before.
Methods
The onset and duration of the biting response of G. pallidipes was recorded by filming movements of its haustellum in response to rapid increases in temperature and/or relative humidity (RH) following exposure of the fly to two airflows. The electrophysiological responses of hygroreceptor cells in wall-pore sensilla on the palps of G. pallidipes to drops in RH were recorded using tungsten electrodes and the ultra-structure of these sensory cells was studied by scanning and transmission electron microscopy.
Results
Both latency and proportion of tsetse biting are closely correlated to RH when accompanied by an increase of 13.1°C above ambient temperature but not for an increase of just 0.2°C. Biting persistence, as measured by the number of bites and the time spent biting, also increases with increasing RH accompanied by a 13.1°C increase in air temperature. Neurones in wall-pore sensilla on the palps respond to shifts in RH.
Conclusions
Our results show that temperature acts synergistically with humidity to increase the rapidity and frequency of the biting response in tsetse above the levels induced by increasing temperature or humidity separately. Palp sensilla housing hygroreceptor cells, described here for the first time in tsetse, are involved in the perception of differences in RH.
doi:10.1186/1756-3305-6-240
PMCID: PMC3765185  PMID: 23958224
Tsetse; Glossina pallidipes; Biting behaviour; Biting fly; Blood-feeding; Hygroreception; Thermoreception; Dry cell
2.  Standardizing Visual Control Devices for Tsetse Flies: East African Species Glossina swynnertoni 
Background
Here we set out to standardize long-lasting, visually-attractive devices for Glossina swynnertoni, a vector of both human and animal trypanosomiasis in open savannah in Tanzania and Kenya, and in neighbouring conservation areas used by pastoralists. The goal was to determine the most practical device/material that would induce the strongest landing response in G. swynnertoni for use in area-wide population suppression of this fly with insecticide-impregnated devices.
Methods and Findings
Trials were conducted in wet and dry seasons in the Serengeti and Maasai Mara to measure the performance of traps and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a simple enumerator at these remote locations to compare trapping efficiencies of devices. Independent of season or presence of chemical baits, targets in phthalogen blue or turquoise blue cloth with adhesive film were the best devices for capturing G. swynnertoni in all situations, catching up to 19 times more flies than pyramidal traps. Baiting with chemicals did not affect the relative performance of devices. Fly landings were two times higher on 1 m2 blue-black targets as on pyramidal traps when equivalent areas of both were covered with adhesive film. Landings on 1 m2 blue-black targets were compared to those on smaller phthalogen blue 0.5 m2 all-blue or blue-black-blue cloth targets, and to landings on all-blue plastic 0.32–0.47 m2 leg panels painted in phthalogen blue. These smaller targets and leg panels captured equivalent numbers of G. swynnertoni per unit area as bigger targets.
Conclusions
Leg panels and 0.5 m2 cloth targets show promise as cost effective devices for management of G. swynnertoni as they can be used for both control (insecticide-impregnated cloth) and for sampling (rigid plastic with insect glue or adhesive film) of populations.
Author Summary
Glossina swynnertoni is restricted to open savannah in north-western Tanzania and south-western Kenya, where it is a vector of both human and animal trypanosomiasis in wildlife reserves and in neighbouring conservation areas used by pastoralists. Despite the challenge to minimize disease transmission through effective management of the vector in the presence of abundant wildlife reservoirs, little has been done to test the efficacy of modern tsetse traps or targets for controlling G. swynnertoni. We made field tests in the Serengeti and Maasai Mara to determine the most visually-attractive, long-lasting and practical object that induces the strongest landing response in G. swynnertoni. Fly landings were twice as high on 1 m2 blue-black targets as on pyramidal traps when equivalent areas of these devices were covered with adhesive film. Furthermore, blue leg panels in either cloth or plastic and blue or blue-black-blue cloth targets under half the size of traditional targets captured tsetse at equivalent numbers per unit as the latter. These smaller targets and leg panels show promise as cost-effective devices for management of G. swynnertoni populations as they can be used for both control (insecticide-impregnated cloth) and monitoring of this species (rigid plastic with insect glue or adhesive film).
doi:10.1371/journal.pntd.0002063
PMCID: PMC3584985  PMID: 23469299
3.  Small Cages with Insect Couples Provide a Simple Method for a Preliminary Assessment of Mating Disruption 
The Scientific World Journal  2012;2012:960468.
Mating disruption by sex pheromones is a sustainable, effective and widely used pest management scheme. A drawback of this technique is its challenging assessment of effectiveness in the field (e.g., spatial scale, pest density). The aim of this work was to facilitate the evaluation of field-deployed pheromone dispensers. We tested the suitability of small insect field cages for a pre-evaluation of the impact of sex pheromones on mating using the grape moths Eupoecilia ambiguella and Lobesia botrana, two major pests in vineyards. Cages consisted of a cubic metal frame of 35 cm sides, which was covered with a mosquito net of 1500 μm mesh size. Cages were installed in the centre of pheromone-treated and untreated vineyards. In several trials, 1 to 20 couples of grape moths per cage were released for one to three nights. The proportion of mated females was between 15 to 70% lower in pheromone-treated compared to untreated vineyards. Overall, the exposure of eight couples for one night was adequate for comparing different control schemes. Small cages may therefore provide a fast and cheap method to compare the effectiveness of pheromone dispensers under standardised semi-field conditions and may help predict the value of setting-up large-scale field trials.
doi:10.1100/2012/960468
PMCID: PMC3356754  PMID: 22645483
4.  Water-seeking behavior in worm-infected crickets and reversibility of parasitic manipulation 
Behavioral Ecology  2011;22(2):392-400.
One of the most fascinating examples of parasite-induced host manipulation is that of hairworms, first, because they induce a spectacular “suicide” water-seeking behavior in their terrestrial insect hosts and, second, because the emergence of the parasite is not lethal per se for the host that can live several months following parasite release. The mechanisms hairworms use to increase the encounter rate between their host and water remain, however, poorly understood. Considering the selective landscape in which nematomorph manipulation has evolved as well as previously obtained proteomics data, we predicted that crickets harboring mature hairworms would display a modified behavioral response to light. Since following parasite emergence in water, the cricket host and parasitic worm do not interact physiologically anymore, we also predicted that the host would recover from the modified behaviors. We examined the effect of hairworm infection on different behavioral responses of the host when stimulated by light to record responses from uninfected, infected, and ex-infected crickets. We showed that hairworm infection fundamentally modifies cricket behavior by inducing directed responses to light, a condition from which they mostly recover once the parasite is released. This study supports the idea that host manipulation by parasites is subtle, complex, and multidimensional.
doi:10.1093/beheco/arq215
PMCID: PMC3071748  PMID: 22476265
behavior; insects; nematomorph; parasite manipulation; parasitism; phototaxis
5.  The Anopheles gambiae Odorant Binding Protein 1 (AgamOBP1) Mediates Indole Recognition in the Antennae of Female Mosquitoes 
PLoS ONE  2010;5(3):e9471.
Haematophagous insects are frequently carriers of parasitic diseases, including malaria. The mosquito Anopheles gambiae is the major vector of malaria in sub-Saharan Africa and is thus responsible for thousands of deaths daily. Although the role of olfaction in A. gambiae host detection has been demonstrated, little is known about the combinations of ligands and odorant binding proteins (OBPs) that can produce specific odor-related responses in vivo. We identified a ligand, indole, for an A. gambiae odorant binding protein, AgamOBP1, modeled the interaction in silico and confirmed the interaction using biochemical assays. RNAi-mediated gene silencing coupled with electrophysiological analyses confirmed that AgamOBP1 binds indole in A. gambiae and that the antennal receptor cells do not respond to indole in the absence of AgamOBP1. This case represents the first documented instance of a specific A. gambiae OBP–ligand pairing combination, demonstrates the significance of OBPs in odor recognition, and can be expanded to the identification of other ligands for OBPs of Anopheles and other medically important insects.
doi:10.1371/journal.pone.0009471
PMCID: PMC2830424  PMID: 20208991
6.  Learning influences host choice in tsetse 
Biology Letters  2006;3(2):113-117.
A learning capacity for feeding is described in many insect species including vectors of diseases, but has never been reported in tsetse flies (Diptera, Glossinidae), the cyclic vectors of human (sleeping sickness) and animal trypanosomoses in Africa. Repeated feeding on the same host species by a disease vector is likely to increase the within-species disease-transmission risk, but to decrease it between species.
An experiment with cattle and reptiles in a stable provides evidence that the species of host selected for the second blood meal in tsetse flies depends on the host encountered for the first blood meal when the between-meal interval is 2 days. This preference disappears when the between-meal interval is extended to 3 days. The energetic advantages of this acquired preference and its importance in trypanosomoses epidemiology are discussed.
doi:10.1098/rsbl.2006.0578
PMCID: PMC2375919  PMID: 17251119
tsetse flies; trypanosomosis; feeding preference; learning
7.  Standardising Visual Control Devices for Tsetse Flies: Central and West African Species Glossina palpalis palpalis 
Background
Glossina palpalis palpalis (G. p. palpalis) is one of the principal vectors of sleeping sickness and nagana in Africa with a geographical range stretching from Liberia in West Africa to Angola in Central Africa. It inhabits tropical rain forest but has also adapted to urban settlements. We set out to standardize a long-lasting, practical and cost-effective visually attractive device that would induce the strongest landing response by G. p. palpalis for future use as an insecticide-impregnated tool in area-wide population suppression of this fly across its range.
Methodology/Principal Findings
Trials were conducted in wet and dry seasons in the Ivory Coast, Cameroon, the Democratic Republic of Congo and Angola to measure the performance of traps (biconical, monoconical and pyramidal) and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a practical enumerator at these remote locations to compare landing efficiencies of devices. Independent of season and country, both phthalogen blue-black and blue-black-blue 1 m2 targets covered with adhesive film proved to be as good as traps in phthalogen blue or turquoise blue for capturing G. p. palpalis. Trap efficiency varied (8–51%). There was no difference between the performance of blue-black and blue-black-blue 1 m2 targets. Baiting with chemicals augmented the overall performance of targets relative to traps. Landings on smaller phthalogen blue-black 0.25 m2 square targets were not significantly different from either 1 m2 blue-black-blue or blue-black square targets. Three times more flies were captured per unit area on the smaller device.
Conclusions/Significance
Blue-black 0.25 m2 cloth targets show promise as simple cost effective devices for management of G. p. palpalis as they can be used for both control when impregnated with insecticide and for population sampling when covered with adhesive film.
Author Summary
G. p. palpalis is one of the principal tsetse fly vectors of African Trypanosomiasis. Its range stretches from Liberia in West Africa to Angola in Central Africa. G. p. palpalis inhabits tropical rain forest but has also adapted to urban settlements. Reduction of tsetse populations remains one of the most effective methods to control disease transmission to man and animals, and development of visually-attractive insecticide-impregnated traps and targets for palpalis group tsetse dates from half a century ago. Here we describe field experiments made in wet and dry seasons in the Ivory Coast, Cameroon, Democratic Republic of Congo and Angola to establish the most efficient, long-lasting and practical object that induces the strongest landing response in G. p. palpalis. Independent of season and country, both phthalogen blue-black 1 m2 cloth targets covered with adhesive film proved as good as traps in phthalogen blue or turquoise blue cloth when employed as capturing and landing devices for G. p. palpalis. Pyramidal trap efficiency was inconsistent. As landings on 0.25 m2 square phthalogen blue-black targets were not significantly different from landings on the 1 m2 targets, these smaller targets show promise as simple cost effective devices for the management of G. p. palpalis populations.
doi:10.1371/journal.pntd.0002601
PMCID: PMC3888452  PMID: 24421909
8.  Standardizing Visual Control Devices for Tsetse Flies: West African Species Glossina tachinoides, G. palpalis gambiensis and G. morsitans submorsitans 
Here we describe field trials designed to standardize tools for the control of Glossina tachinoides, G. palpalis gambiensis and G.morsitans submorsitans in West Africa based on existing trap/target/bait technology. Blue and black biconical and monoconical traps and 1 m2 targets were made in either phthalogen blue cotton, phthalogen blue cotton/polyester or turquoise blue polyester/viscose (all with a peak reflectance between 450–480 nm) and a black polyester. Because targets were covered in adhesive film, they proved to be significantly better trapping devices than either of the two trap types for all three species (up to 14 times more for G. tachinoides, 10 times more for G. palpalis gambiensis, and 6.5 times for G. morsitans submorsitans). The relative performance of the devices in the three blue cloths tested was the same when unbaited or baited with a mixture of phenols, 1-octen-3-ol and acetone. Since insecticide-impregnated devices act via contact with flies, we enumerated which device (traps or targets) served as the best object for flies to land on by also covering the cloth parts of traps with adhesive film. Despite the fact that the biconical trap proved to be the best landing device for the three species, the difference over the target (20–30%) was not significant. This experiment also allowed an estimation of trap efficiency, i.e. the proportion of flies landing on a trap that are caught in its cage. A low overall efficiency of the biconical or monoconical traps of between 11–24% was recorded for all three species. These results show that targets can be used as practical devices for population suppression of the three species studied. Biconical traps can be used for population monitoring, but a correction factor of 5–10 fold needs to be applied to captures to compensate for the poor trapping efficiency of this device for the three species.
Author Summary
Tsetse flies transmit trypanosomes that cause sleeping sickness in humans and ngana in animals in sub-Saharan Africa. These diseases remain an intractable burden on human health and livestock production on the continent. Visual devices made of fabrics and impregnated with insecticide have the potential for controlling tsetse and preventing disease transmission as regular removal of a small percentage of the vector population can provide effective control. A variety of devices, notably biconical and monoconical traps and targets, have been used in previous control programmes against tsetse in West Africa. In this study we set out to determine which is the optimal device for control of three tsetse fly species, Glossina tachinoides, G. palpalis gambiensis and G. morsitans submorsitans, in the region. Using the same colourfast fabrics in all devices we show that there is no significant difference between biconical traps and targets in their ability to induce landings by the three species. We conclude that the simpler target would appear to be the most cost-effective insecticide-impregnated device to use in control programmes against these tsetse species. We also provide an estimate of the efficiency of the biconical and monoconical traps for the three species.
doi:10.1371/journal.pntd.0001491
PMCID: PMC3279333  PMID: 22348159

Results 1-8 (8)