ECCO Guidelines on Therapeutics in Crohn's Disease: Surgical Treatment

This article is the second in a series of two publications relating to the European Crohn's and Colitis Organisation [ECCO] evidence-based consensus on the management of Crohn's disease. The first article covers medical management; the present article addresses surgical management, including preoperative aspects and drug management before surgery. It also provides technical advice for a variety of common clinical situations. Both articles together represent the evidence-based recommendations of the ECCO for Crohn's disease and an update of previous guidelines.

Female odours promote the activation of sheltered kissing bug Rhodnius prolixus males and modulate their orientation

The existence of a pheromone emitted during copulation has been reported for Rhodnius prolixus (Hemiptera: Reduviidae) Stål. Adults possess one pair of metasternal glands (MGs) from which female R. prolixus release volatiles mainly at night. We investigated whether these volatiles emitted by adult R. prolixus can modulate sexual-related behaviours of opposite and/or same sex individuals. We first used a shelter bioassay to test if adult activity patterns can be affected by chemical signals emitted by opposite sex conspecifics. We observed that males left the shelter more frequently in the presence of females, showing higher activity and an increase of intrasexual copulation attempts. Females showed no shelter-related activation in the presence of male odours. Second, we used a locomotion compensator device to investigate whether females or males show oriented responses to odours emitted by adults. We found that males oriented towards air currents carrying female odours but females did not orient towards odours emitted by adults. Finally, we observed that males oriented towards the female MG compounds. Thus, a volatile chemical signal emitted by females from their MGs promoted the activation of sheltered males and modulated orientation to air currents.

Female metasternal gland odours mediate male aggregation in Rhodnius prolixus, a triatomid bug

We investigated whether metasternal gland (MG) products mediate male aggregation during mating in Rhodnius prolixus (Heteroptera: Reduviidae) Stål, 1859, through selective occlusion of female MGs. Pairs of insects presenting intact MGs mated and other males aggregated around them confirming conclusions from previous studies. However, when female MGs were occluded, males did not aggregate. Conversely, the occlusion of male MGs did not affect aggregation of males. The present experiments demonstrated that the products emitted by the MGs of a mating R. prolixus female induce other males to aggregate around the mating pair. Aggregation behaviour of males probably results from the eventual release of volatiles from the female's MGs. We reinforce the hypothesis suggesting that the compounds produced by the MGs of R. prolixus act as sexual communication signals for this species.

Behavioral evidence of an ectoparasitic interaction between Triatoma pseudomaculata Corrêa e Espínola (Heteroptera: Reduviidae) and Periplaneta americana (L.) (Blattodea: Blattidae)

The present work tested whether Triatoma pseudomaculata Corrêa & Espínola shows behavioral traits indicating that it is capable of feeding on arthropods. We consistently observed nymphs extending their proboscis in the direction of cockroaches and attempting to bite. Insects presented a preference for biting specific cockroach body parts. Our results suggest that arthropod hemolymph represents an alternative source of food that increases the survival of T. pseudomaculata individuals undergoing long starvation.

Structure elucidation and synthesis of dioxolanes emitted by two Triatoma species (Hemiptera: Reduviidae)

Volatiles from the metasternal glands of two species of true bugs of the Triatominae subfamily, Triatoma brasiliensis and Triatoma infestans, were analyzed by SPME-GC/MS. Two sets of new natural products were found: (4S,5S)- and (4R,5R)-2,2,4-triethyl-5-methyl-1,3-dioxolane (1) (major component) and (4S*,5S*)-2,4-diethyl-2,5-dimethyl-1,3-dioxolane (2) (trace component), (2R/S,4S,5S)- as well as (2R/S,4R,5R)-4-ethyl-5-methyl-2-(1-methylethyl)-1,3-dioxolane (3) (minor component), (2R/S,4S*,5S*)-4-ethyl-5-methyl-2-(1-methylpropyl)-1,3-dioxolane (4) (trace component), and (2R/S,4S*,5S*)-4-ethyl-5-methyl-2-(2-methylpropyl)-1,3-dioxolane (5) (trace component). Syntheses of optically active 1 and 3 were carried out by reacting pure enantiomers of 2,3-pentanediol with 3-pentanone or 2-methylpropanal. The preparation of pure stereoisomers of 2,3-pentanediol involved a novel key step for the synthesis of secondary alcohols: the reduction of a carboxylic ester by means of DIBAH and in situ alkylation of the intermediate by Grignard reaction at low temperature. Starting from the pure enantiomers of methyl lactate, all four stereoisomers of 2,3-pentanediol were synthesized and transformed to the corresponding isomers of 1 and 2. Relative configurations of the natural products and enantiomeric compositions of naturally occurring 1 and 2 were determined by comparison of their mass spectra and gas chromatographic retention times (co-injection) with those of authentic reference samples.

The use of aggregation signals by Triatoma brasiliensis (Heteroptera: Reduviidae)

Triatoma brasiliensis is considered the main vector of Chagas disease in the semiarid zones of North-eastern Brazil. In this work, we describe the spatial pattern of defecation in T. brasiliensis and the spatial relationship of faeces with the shelters of these bugs. Afterwards, we analyse the attraction response of T. brasiliensis larvae to potential odour cues present in their dry faeces, to substances present in their cuticule (footprints) and to the dry faeces of Triatoma pseudomaculata. We show that faecal spots are deposited in a larger density inside the shelter than in the remaining area available for the bugs. T. brasiliensis larvae were significantly attracted towards their own faeces, and also to those of T. pseudomaculata. In contrast to other triatomine species, footprints did not promote attraction in T. brasiliensis. The potential use of communication signals of T. brasiliensis as tools for helping control this species is discussed.

Dynamics of thermopreference in the Chagas disease vector Panstrongylus megistus (Hemiptera: Reduviidae)

The thermopreference of resting P. megistus (Burmeister, 1834) adults was studied in a temperature gradient. We also determined the thermopreference for oviposition and ecdysis. Thermopreference of resting individuals depended on the feeding state of the insects. Results demonstrated an initial resting preference of approximately 290 degrees C, which gradually changed to 26-27 degrees C with increasing starvation. A daily variation in thermopreference was also observed with this species. The insects showed a daily maximum preference at the beginning of the dark phase, and a minimum preference during the first half of the light phase. Ecdysis took place all along the gradient, but exhibited a maximum frequency at 30 degrees C. Most eggs were found between 25 and 29 degrees C. Results are discussed in relation to the ecology of P. megistus as compared with other related species, and the existence of mechanisms of behavioral thermoregulation in the group.

Aggregation behaviour in Panstrongylus megistus and Triatoma infestans: inter and intraspecific responses

We tested the aggregation response to inter and intraspecific chemical signals in Panstrongylus megistus and Triatoma infestans. As previously described for T. infestans, larvae of P. megistus significantly aggregated on papers impregnated with their own excrement and on papers marked with cuticular substances deposited on surfaces on which these insects had walked. T. infestans bugs also aggregated on papers impregnated by faeces or by cuticular substances of P. megistus, and P. megistus aggregated on papers contaminated by faeces or by cuticular substances of T. infestans. The response of P. megistus to its cuticular substances was significantly stronger than that to its faeces. The non-specificity of the two signals is discussed in the context of the ecological relationship between both species.

[Microclimatic properties of the Triatoma brasiliensis habitat]

Vector-borne transmission of Chagas disease in Northeast Brazil is basically by Triatoma brasiliensis. It is thus crucial to determine this species' microclimatic preferences as limiting factors for its distribution and ability to infest domestic environments. We analyze the microclimatic properties of the shelters in which these insects are found in wild, domestic, and peridomiciliary environments in the State of Ceará, at Brazil. We measure temperature and relative humidity (RH) every 15 minutes for 3 days. Thermal variation was greatly dampened inside both domiciliary refuges and the more protected internal places in wild stony sites. For RH, we observed a similar dampening pattern, but mean RH was lower in both domiciliary refuges and wild ones inside stony sites as compared to reference levels in the surrounding environment. The results are discussed with regard to this species' microclimatic preferences in the laboratory and its potential as determinants of its geographical distribution.

Performance of yeast-baited traps with Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus in laboratory assays

The effectiveness of a trap for triatomines baited with yeast cultures has been previously demonstrated for Triatoma infestans in laboratory assays. We report here results from laboratory assays testing yeast traps for Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus. All assays were conducted in an open experimental arena 100 cm x 100 cm, with two traps placed at opposite sides of the arena. One of the traps contained a yeast culture, and the other trap contained a saccharose solution as a control. Two series of experiments were done, one without a refuge for the insects and one with a refuge. The results obtained clearly demonstrated that the yeast-baited traps were effective in the laboratory in capturing both T. sordida and P. megistus. For T. sordida, yeast-baited traps captured significantly more bugs than did the control traps (t test P value = 0.03). For P. megistus, when a refuge was provided during the assay, yeast-baited traps also captured significantly more bugs than did the control traps (t test P value = 0.006). In the experiments with T. brasiliensis and T. pseudomaculata, both traps captured some insects, but the yeast traps captured many fewer bugs than was true with the T. sordida and P. megistus bugs. These results indicate that, in the laboratory, yeast traps can capture considerable numbers of T. sordida and P. megistus in one night. We discuss the potential use of yeast traps for detecting and capturing both triatomine species.

Temperature and relative humidity affect the selection of shelters by Triatoma infestans, vector of Chagas disease

The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects preferred refuges at a temperature of 34 degrees C rather than 26 degrees C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperature and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an inner climate favourable to T. infestans. Typical refuges in adobe walls showed strongly damped fluctuations in minimum and maximum temperatures, and delayed changes in these parameters when compared with an external reference. Similarly, the jarilla (Larrea sp.), a plant used for constructing roofing, damps fluctuations in minimum and maximum RH and delays these RH fluctuations when compared to an external reference. We discuss possible effects of environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones.

Yeast culture volatiles as attractants for Rhodnius prolixus: electroantennogram responses and captures in yeast-baited traps

Responses to air currents carrying volatiles from yeast cultures were measured by means of electroantennograms (EAGs) in the haematophagous bug Rhodnius prolixus and we tested yeast-baited traps in the laboratory. The volatiles liberated by yeast cultures generated a clear electrophysiological response, much higher than that obtained during stimulation with clean air. The addition of yeast cultures to the traps dramatically increased overnight capture. A modification performed on the traps was effective for this species, as the bugs were immobilised once they fell into the device. Our results demonstrate that yeast culture volatiles are attractive for R. prolixus. The results obtained by means of electroantennogram techniques represent the first electrophysiological evidence of the perception of yeast volatiles by the antennae of a triatomine bug. We discuss the relevance of our results in view of currently used sampling techniques and control strategies.

Triatoma infestans can be captured under natural climatic conditions using yeast-baited traps

The effectiveness of a trap for triatomines baited with yeast cultures has been previously demonstrated in laboratory assays. We report results from assays testing yeast-traps for Triatoma infestans performed under natural climatic conditions. All assays were conducted at experimental chicken-coops colonised by bugs, situated at an endemic area for Chagas disease in Argentina. Two different models of traps were tested, for use either on the floor, or attached to walls. The results obtained clearly demonstrate that yeast-baited traps are effective for capturing triatomine bugs. Floor traps, when baited, captured significantly more bugs than their controls (t-test, P = 0.0008, k = 10). In addition, wall traps were also more effective, when compared to their controls (t-test, P = 0.011, k = 10). The maximum capture by a single yeast-trap was 39 bugs in one night, while for the same period the maximum capture by a control-trap was two bugs. Traps captured significantly more bugs at nights when maximum temperature was above 18 degrees C (t-test, P = 0.0002). Results indicate that yeast traps are capable of capturing significant numbers of free insects in one night. The potential use of yeast- traps for the detection of triatomine bugs is discussed.

Activity pattern in relation to refuge exploitation and feeding in Triatoma infestans (Hemiptera: Reduviidae)

The pattern of locomotion activity was studied in Triatoma infestans, in relation to the use of an artificial refuge offered to the bugs in an experimental arena. In assays performed with insects that had a post-ecdysis starvation period of 1 week, the activity was low and mainly related to refuge leaving or entering. Insects that had gone through a longer period of starvation (6 weeks) exhibited a high locomotory activity throughout the night. Specific temporal windows were detected for refuge leaving and entering after dusk and before dawn, which were not modified by different levels of starvation of the insects. T. infestans exhibits a higher motivation for feeding during the first night hours, in comparison to that observed at the end of the scotophase. The activity peaks previously reported for T. infestans are therefore related to host and refuge search.

Baker's yeast, an attractant for baiting traps for Chagas' disease vectors

We tested the attraction of volatile compounds, produced by the aerobic growth of Saccharomyces cerevisiae on saccharose for Triatoma infestans. For these tests, we exploited the behavioural characteristic of these haematophagous insects of dropping when searching for food. In olfactometer assays, yeast cultures activated and attracted bugs as effectively as a mouse. The attraction of the cultures was significantly reduced when the carbon dioxide released was partially eliminated using potassium hydroxide. Yeast cultures were also tested as lures in a novel trap device. A baited device for trapping Chagas' disease vectors using the behavioural peculiarities of T. infestans and this simple attractant is described.