Mosquito odour-baited mass trapping reduced malaria transmission intensity: a result from a controlled before-and-after intervention study

BACKGROUND

Conventional vector control strategies have significantly reduced the malaria burden. The sustainability of these methods is currently challenged. Odour-based traps are emerging technologies that can complement the existing tools. Implementation of odour-based traps for mass trapping is limited due to the restricted range of vectors caught with available carbon dioxide-dependent lures, and the lack of comprehensive field studies. The objective of this study was to assess the impact of odour-mediated mass trapping targeting outdoor vectors, using a synthetic cattle urine lure that attracts a wide range of vector species in a variety of physiological states, on malaria prevalence and entomological parameters to determine malaria transmission intensities.

METHODS

A controlled before-and-after study was conducted in two rural communities in southern Ethiopia. Baseline monthly entomological and seasonal cross-sectional malaria prevalence surveys were conducted in both communities for a year. Then, mass trapping of mosquitoes was conducted in one of the villages, while the monthly entomological surveillance and seasonal malaria prevalence surveys continued in both villages. Generalised linear mixed models were constructed and tested to determine which factors were significantly affected by the intervention.

RESULTS

Mass trapping contributed to the reduction of the population of the principal malaria vector, Anopheles arabiensis, and the associated entomological indicators, the human bite rate (HBR) and the entomological inoculation rate (EIR), in the intervention village compared to the control village. The intervention village had an average HBR by An. arabiensis of 3.0 (95% CI 1.4-4.6) during the peak malaria transmission season, compared to 10.5 (95% CI - 0.5-21.5; P < 0.0001) in the control village. The intervention village (mean 0.02, 95% CI - 0.05-0.4.8) had a daily EIR eight times lower than the control village (mean 0.17, 95% CI), which likely contributed to the reduced malaria prevalence in the intervention community following its introduction by ca. 60% (95% CI 55-63).

CONCLUSIONS

The combined use of odour-based mass trapping and conventional control strategies coincided with a reduction of human-vector contact and malaria prevalence, providing support for odour-baited technologies as a viable option for next-generation vector control tools. Further cluster-randomised control studies are recommended in different eco-epidemiological settings with varying malaria transmission intensities.

Visual and thermal stimuli modulate mosquito-host contact with implications for improving malaria vector control tools

Malaria prevention relies on mosquito control interventions that use insecticides and exploit mosquito behavior. The rise of insecticide resistance and changing transmission dynamics urgently demand vector control innovation. To identify behavioral traits that could be incorporated into such tools, we investigated the flight and landing response of Anopheles coluzzii to human-like host cues. We show that landing rate is directly proportional to the surface area of thermal stimulus, whereas close-range orientation is modulated by both thermal and visual inputs. We modeled anopheline eye optics to theorize the distance at which visual targets can be detected under a range of conditions, and experimentally established mosquito preference for landing on larger targets, although landing density is greater on small targets. Target orientation does not affect landing rate; however, vertical targets can be resolved at greater distance than horizontal targets of the same size. Mosquito traps for vector control could be significantly enhanced by incorporating these features.

Aedes aegypti oviposition-sites choice under semi-field conditions

Vector control is still the recommended approach to avoid arbovirus outbreaks. Herein, we investigate oviposition preferences of Aedes aegypti (Diptera: Culicidae) females under a semi-field structure Rio de Janeiro, Brazil. For that, in Experiment 1, we used two settings: 'Single items', which included as containers drain, beer bottle, bucket, car tyre, water tank, and a potted Peace Lily (Spathiphyllum wallisii) in a saucer with water, or 'Multiple containers', as an urban simulation, in which one drain, two additional beer bottles, and an extra plant pot saucer were added. Experiment 2 (sensory cues) used five variations of potted plant, each one varying in the range of sensory cues known to attract gravid females to oviposition containers. Our results indicate that gravid Ae. aegypti prefer to oviposit close to the ground and in open water containers with organic compounds from plant watering. Domestic large artificial containers containing tap water received significantly fewer eggs, except for the car tyre, which exhibited as many eggs as the potted plant. We also show that visual (potted plant shape) and olfactory clues (odour of the plant or from water containing organic matter) were equally attractive separately as were these stimuli together.

The influence of manure-based organic fertilisers on the oviposition behaviour of Anopheles arabiensis

The rice agroecosystem provides suitable breeding habitat for many malaria vector species, and rice-adjacent communities are consequently exposed to a greater malaria transmission risk than non-rice-associated communities. As part of efforts to expand rice production in Africa, sustainable and climate-adapted practices such as the System of Rice Intensification (SRI) are being promoted. SRI encourages the use of organic fertilisers (OFs) such as cow and chicken dung, as opposed to inorganic industrially produced fertilisers, due to their lower resource cost, apparent benefit to the rice agroecosystem and as a means to reduce the greenhouse gas emissions associated with the production of industrial fertilisers. However, the impact of OFs on mosquito fauna is not well documented and may have knock-on consequences on malaria transmission risk. Here, we demonstrate, using dual choice egg count assays, that both cow and chicken dung modulate the oviposition behaviour of Anopheles arabiensis, a major malaria vector in Sub-Saharan Africa. A significantly reduced proportion of eggs were laid in water treated with either cow or chicken dung compared to untreated water, with higher dung concentrations resulting in further reduced proportions. When presented in competition, significantly fewer eggs were laid in water treated with chicken dung than with cow dung. Moreover, there was no evidence of egg retention in any experiment, including in no-choice experiments where only dung-containing dishes were available. These results suggest both cow and chicken dung may act as oviposition deterrents to malaria vector species and that the application of manure-based OFs in rice agriculture may modulate the oviposition behaviour of An. gambiae s.l. within agroecosystems. Quantification of the ammonia present in dung-infused water showed higher concentrations were present in the chicken dung infusion, which may be one contributing factor to the difference in observed deterrence between the two dung types. Deterrence of mosquito oviposition in OF-treated farms may potentially affect the overall production of malaria vectors within rice fields and their contribution to local malaria transmission.

Case closed - Wrappings and encasement delays and reduces fly presence on body parts

Homicide, particularly where a body has been concealed, is uniquely challenging for investigators to estimate the time of occurrence due to the methods employed by perpetrators to hide the body or its constituent parts from detection. The regularity of necrophagous insect lifecycles to determine minimum post-mortem interval (minPMI) is widely employed but remains an unreliable technique if used without a clear understanding of the factors that affect insect access and oviposition behaviour to concealed remains. The purpose of this study was to investigate the effect of wrapping body parts on fly colonisation and implications for minPMI calculations. Field studies were carried out using four treatments of pork (as surrogate body parts), in five replicates, one unwrapped, the other three wrapped in either a black plastic sack, a small-zipped wash bag (to simulate a suitcase), or a plastic sack further placed in a wash bag. Over a 48-h period all the methods of wrapping significantly disrupted the host-finding process of blowflies to dismembered carcasses, with a delay of initial contact and oviposition of 30+h (dependant on wrapping) and even more in wet conditions (48+ h). Egg numbers were also reduced by as much as 99.1% on wrapped samples compared to unwrapped. These new findings highlight the importance of applying adjustments to minPMI calculations when encountering wrapped remains. Advances in the accuracy of minPMI calculations will prevent the waste of valuable police time and resources and better focus the search for witnesses and suspects in homicide investigations.

Multimodal synergisms in host stimuli drive landing response in malaria mosquitoes

Anopheles mosquitoes transmit malaria, which affects one-fifth of the world population. A comprehensive understanding of mosquito behaviour is essential for the development of novel tools for vector control and surveillance. Despite abundant research on mosquito behaviour, little is known on the stimuli that drive malaria vectors during the landing phase of host-seeking. Using behavioural assays with a multimodal step approach we quantified both the individual and the combined effect of three host-associated stimuli in eliciting landing in Anopheles coluzzii females. We demonstrated that visual, olfactory and thermal sensory stimuli interact synergistically to increase the landing response. Furthermore, if considering only the final outcome (i.e. landing response), our insect model can bypass the absence of either a thermal or a visual stimulus, provided that at least one of these is presented simultaneously with the olfactory stimuli, suggesting that landing is the result of a flexible but accurate stimuli integration. These results have important implications for the development of mosquito control and surveillance tools.

Understanding mosquito host-choice behaviour: a new and low-cost method of identifying the sex of human hosts from mosquito blood meals

Background

Mosquito-borne diseases are a global health problem, causing hundreds of thousands of deaths per year. Pathogens are transmitted by mosquitoes feeding on the blood of an infected host and then feeding on a new host. Monitoring mosquito host-choice behaviour can help in many aspects of vector-borne disease control. Currently, it is possible to determine the host species and an individual human host from the blood meal of a mosquito by using genotyping to match the blood profile of local inhabitants. Epidemiological models generally assume that mosquito biting behaviour is random; however, numerous studies have shown that certain characteristics, e.g. genetic makeup and skin microbiota, make some individuals more attractive to mosquitoes than others. Analysing blood meals and illuminating host-choice behaviour will help re-evaluate and optimise disease transmission models.

Methods

We describe a new blood meal assay that identifies the sex of the person that a mosquito has bitten. The amelogenin locus (AMEL), a sex marker located on both X and Y chromosomes, was amplified by polymerase chain reaction in DNA extracted from blood-fed Aedes aegypti and Anopheles coluzzii.

Results

AMEL could be successfully amplified up to 24 h after a blood meal in 100% of An. coluzzii and 96.6% of Ae. aegypti, revealing the sex of humans that were fed on by individual mosquitoes.

Conclusions

The method described here, developed using mosquitoes fed on volunteers, can be applied to field-caught mosquitoes to determine the host species and the biological sex of human hosts on which they have blood fed. Two important vector species were tested successfully in our laboratory experiments, demonstrating the potential of this technique to improve epidemiological models of vector-borne diseases. This viable and low-cost approach has the capacity to improve our understanding of vector-borne disease transmission, specifically gender differences in exposure and attractiveness to mosquitoes. The data gathered from field studies using our method can be used to shape new transmission models and aid in the implementation of more effective and targeted vector control strategies by enabling a better understanding of the drivers of vector-host interactions.

Malaria hotspots explained from the perspective of ecological theory underlying insect foraging

Hotspots constitute the major reservoir for residual malaria transmission, with higher malaria incidence than neighbouring areas, and therefore, have the potential to form the cornerstone for successful intervention strategies. Detection of malaria hotspots is hampered by their heterogenous spatial distribution, and the laborious nature and low sensitivity of the current methods used to assess transmission intensity. We adopt ecological theory underlying foraging in herbivorous insects to vector mosquito host seeking and modelling of fine-scale landscape features at the village level. The overall effect of environmental variables on the density of indoor mosquitoes, sporozoite infected mosquitoes, and malaria incidence, was determined using generalized linear models. Spatial analyses were used to identify hotspots for malaria incidence, as well as malaria vector density and associated sporozoite prevalence. We identify household occupancy and location as the main predictors of vector density, entomological inoculation rate and malaria incidence. We propose that the use of conventional vector control and malaria interventions, integrated with their intensified application targeting predicted hotspots, can be used to reduce malaria incidence in endemic and residual malaria settings.

Long-term follow-up of two randomized trials comparing laparoscopic Nissen 360° with anterior 90° partial fundoplication

BACKGROUND

The side-effects of Nissen fundoplication have led to modifications, including partial fundoplications such as an anterior 90° wrap. Five-year follow-up of two randomized trials suggested fewer side-effects following anterior 90° partial fundoplication, but better reflux control after Nissen fundoplication. However, longer-term outcomes have not been reported. This study combined data from previous trials to determine 10-year outcomes.

METHODS

From 1999 to 2003, 191 patients were enrolled in two randomized trials comparing anterior 90° partial versus Nissen fundoplication. Trial protocols were similar, and data were combined to determine long-term clinical outcomes. Patients completed annual questionnaires assessing dysphagia, heartburn, medications, satisfaction and other symptoms. Visual analogue scales (0-10), a composite dysphagia score (0-45) and yes/no responses were used.

RESULTS

Of the 191 patients, 152 (79·6 per cent) were available for 10-year follow-up. After anterior 90° fundoplication, patients reported less dysphagia to solids (score 2·03 versus 3·18 for the Nissen procedure; P = 0·037). Heartburn scores were lower after Nissen fundoplication (1·90 versus 2·83 for anterior 90° fundoplication; P = 0·035) and fewer patients required proton pump inhibitors (PPIs) (22 versus 39 per cent respectively; P = 0·035). Satisfaction scores were similar for both anterior 90° and Nissen groups (7·45 versus 7·36 respectively; P = 0·566), and the majority considered their original decision for surgery to be correct (86 versus 84 per cent; P = 0·818).

CONCLUSION

After 10 years, both procedures achieved similar success as measured by global satisfaction measures. Patients who had a Nissen fundoplication reported more dysphagia, whereas more heartburn and PPI consumption were reported after anterior 90° fundoplication. Registration numbers: ACTRN12607000298415 and ACTRN12607000304437 (http://www.anzctr.org.au/).

Airflow limitation and survival after surgery for non-small cell lung cancer: Results from a systematic review and lung cancer screening trial (NLST-ACRIN sub-study)

OBJECTIVE

Lung cancer remains the single greatest cause of cancer mortality where surgery for early stage non-small cell lung cancer achieves the greatest survival. While there is growing optimism for better outcomes with screening using annual computed tomography, the impact of co-existing airflow limitation on survival remains unknown. To compare survival in non-small cell lung cancer patients undergoing surgery stratified according to the presence or absence of pre-surgery airflow limitation.

MATERIALS AND METHODS

We undertook a systematic literature search of non-screen lung cancer that encompassed studies reported between January 1946 and January 2017. Full-text articles were identified following eligibility scoring, with data extracted and analysed using a standardised analytical method (PRISMA). The results of this systematic review in non-screen lung cancers were compared to real-world results from a lung cancer screening cohort (N = 10,054), where outcomes following surgery could be compared after stratification according to pre-surgery airflow limitation.

RESULTS

In the systematic review, 6899 subjects were included from 10 studies; 7 were retrospective, 3 were prospective. Overall survival was 950 (44%) in 2144 people with COPD and 2597 (55%) from 4755 controls (unadjusted P value <0.001). However, the overall meta-analysed random effects odds ratio for overall survival (N = 10) and 5-year survival (N = 4) comparing those with and without COPD was 0.91 (95% CI = 0.84-1.00) and 0.99 (95% CI = 0.79-1.24) respectively. There were no signs of significant heterogeneity (I² = 19.1%, P = 0.27) nor publication bias as assessed by funnel plot and Egger's test (P = 0.19). In the lung cancer screening sub-study of 10,054 screening participants we found no difference in 5-year survival in those with and without airflow limitation (84% and 81% respectively, P = 0.64).

CONCLUSION

Survival after surgery for non-small cell lung cancer is comparable between those with and without spirometry evidence of airflow limitation. This finding was replicated in lung cancer diagnosed during screening.

Thus far but no further: predatory mites do not migrate effectively into strawberry plantations

Enhancing the performance of predatory mites is often regarded as the best biological control approach towards the spider mite Tetranychus urticae, the main pest of strawberry plantations. Optimizing the colonization of plantations by predators from adjacent areas such as field margins is seen as an important component of conservation biocontrol. We have investigated the factors contributing to enhancing the numbers of predatory mites (Acari: Phytoseidae), such as management of the field margins, vegetation composition and the effect of the presence of woody species. We also tested the penetration of the phytoseiids from the field margins into the crop. In a study carried out in 14 open-field extensively managed strawberry plantations in Poland we found phytoseiids to be abundant in field margins; 14 taxa were discovered. However, only two species Amblyseius andersoni and Euseius finlandicus dispersed a modest distance into the crop. We found that the diversity and densities of the predatory mites were enhanced somewhat by the management type of the field margins; especially the spontaneous vegetation favoured the presence of phytoseiids. However, despite the predatory mites being rather retained in the field margins also significant reduction in numbers of their prey T. urticae was recorded over the course of the year. The low penetration of predatory mites into the main part of the field, indicates that conservation biological control measures in the field margin might not be sufficient on their own to enhance the impact of predatory mites within the main part of the fields.

Shady business: understanding the spatial ecology of exophilic Anopheles mosquitoes

Background

Understanding the ecology of exophilic anophelines is a key step toward developing outdoor control strategies to complement existing indoor control tools against malaria vectors. This study was conducted to assess the movement pattern of exophilic Anopheles mosquitoes between blood meal sources and resting habitats, and the landscape factors dictating their resting habitat choice.

Results

Resting clay pots were placed at 5 m, 25 m, 50 m, 75 m and 100 m away from isolated focal houses, radiating from them in four directions. The locations of the clay pots represent heterogeneous land cover types at a relatively fine spatial scale in the landscape. The effect of the landscape characters on the number of both female and male anophelines caught was modelled using zero-inflated negative binomial regression with a log link function. A total of 420 Anopheles mosquitoes (353 females and 67 males) belonging to three species; Anopheles arabiensis, Anopheles pharoensis, and Anopheles tenebrosus were caught in the resting clay pots, with An. arabiensis being the dominant species. Canopy cover, distance from the house, and land cover type were the significant landscape characters influencing the aggregation of resting mosquitoes. Both the count and binary models showed that canopy cover was the strongest predictor variable on the counts and the presence of Anopheles mosquitoes in the clay pots. Female Anopheles were most frequently found resting in the pots placed in banana plantations, and at sampling points that were at the greater distances (75 m and 100 m) from the focal house.

Conclusions

This study showed that exophilic Anopheles mosquitoes tend to rest in shaded areas some distance away from human habitation. These findings are important when targeting mosquitoes outdoors, complementing the existing effort being made to control malaria vectors indoors.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2499-7) contains supplementary material, which is available to authorized users.

Parasitism of Two Spodoptera spp. by Microplitis prodeniae (Hymenoptera: Braconidae)

Early instar larvae of the tobacco cutworm Spodoptera litura (Lepidoptera: Noctuidae) and the beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae) are recognized hosts of the parasitic wasp Microplitis prodeniae Rao and Kurian (Hymenoptera: Braconidae), although M. prodeniae has previously been regarded as monophagous. In this study, we found the immature period and longevity of M. prodeniae developing in S. exigua was similar to that in S. litura. It was shown that the development time of M. prodeniae in S. exigua was 15.1 ± 0.3 d, not significantly different from 15.0 ± 0.2 d in S. litura. The parasitism rate of M. prodeniae attacking S. exigua was significantly lower than on S. litura (65.48 ± 2.29 and 43.83 ± 2.20%, respectively), whilst the female ratio of the wasp's offspring was not significantly different when developing on the two species. M. prodeniae females prefer to oviposit on the second- and third-instar host larvae of S. exigua, rather than other instars. The effects of development of M. prodeniae on two important lepidopterous pests are discussed.

Correcting transmission losses in short-wave infrared spatially offset Raman spectroscopy measurements to enable reduced fluorescence through-barrier detection

Spatially offset Raman spectroscopy (SORS) is a proven technique for sub-surface detection. SORS is able to separate Raman signals from a container and its contents, thereby demonstrating application to through-barrier detection for defence and security. Whilst SORS has been demonstrated to reduce fluorescence from the barrier (or surface), fluorescence from the sample (or sub-surface) can still be problematic for some materials when using Raman excitation wavelengths typical in commercially available instrumentation (e.g. 785 nm). Previous work has demonstrated that short-wave infrared (SWIR) excited SORS (e.g. 1064 nm) can reduce fluorescence from the sample and barrier, thereby providing the potential to detect a wider range of materials through a wider range of barriers. In this paper we highlight an additional challenge for detection through some plastic container materials (e.g. high density polyethylene (HDPE) and other opaque plastics) that absorb and scatter both incident and Raman scattered photons in the SWIR band, leading to distortion of the resultant SORS spectrum. The existence of this effect and its impact is explored, along with a potential solution to overcome this challenge that uses multi-wavelength Raman excitation to avoid the detrimental HDPE absorption region.

Grass Pollen Affects Survival and Development of Larval Anopheles arabiensis (Diptera: Culicidae)

Nutrients in breeding sites are critical for the survival and development of malaria mosquitoes, having a direct impact on vectorial capacity. Yet, there is a limited understanding about the natural larval diet and its impact on the individual fitness of mosquitoes. Recent studies have shown that gravid Anopheles arabiensis Patton (Diptera: Culicidae) are attracted by and oviposit in grass-associated habitats. The pollen provided by these grasses is a potential source of nutrients for the larvae. Here, we assess the effect of Typha latifolia L. (Poales: Typhaceae), Echinochloa pyramidalis Lamarck, Pennisetum setaceum Forsskål, and Zea mays L. pollen on larval survival and rate of development in An. arabiensis under laboratory conditions. In addition, we characterize the carbon to nitrogen ratio and the size of pollen grains as a measure of diet quality. Carbon-rich pollen with a small grain size (T. latifolia and P. setaceum; 9.7 ± 0.3 × 103 and 5.5 ± 0.2 × 104 µm3, respectively) resulted in enhanced rates of development of An. arabiensis. In contrast, the larva fed on the nitrogen-rich control diet (TetraMin) was slower to develop, but demonstrated the highest larval survival. Larvae fed on carbon-rich and large-grained Z. mays pollen (4.1 ± 0.2 × 105 µm3) survived at similar levels as those fed on the control diet and also took a longer time to develop compared with larvae fed on the other pollens. While males and females did not appear to develop differently on the different pollen diets, males consistently emerged faster than their female counterparts. These results are discussed in relation to integrated vector management.

A Place to Grow? Host Choice and Larval Performance of Microplitis similis (Hymenoptera: Braconidae) in the Host Spodoptera litura (Lepidoptera: Noctuidae)

Host selection is a key stage in the lifecycle of parasitoids, and is critical to both their function in control and to the maintenance of their population. The solitary endoparasitoid Microplitis similis (Hymenoptera: Braconidae) is a potential biological control agent of Spodoptera litura (F.) larvae (Lepidoptera: Noctuidae). In this study, we examined the preference M. similis exhibits for different instars of the host, host instar effects on parasitoid development, and the weight gain and food consumption of different instars of parasitized larvae. In no-choice tests, parasitization rates were highest in second- and early third-instar larvae, and no fourth- or fifth-instar hosts were parasitized. When provided with a choice of first- to late third-instar host larvae, M. similis preferred to parasitize early third-instar host larvae (41%) with a selection coefficient of 0.37. All morphometric features of wasp offspring increased with increasing age of the host at parasitization. A lower proportion of females emerged from first-instar larvae than any other instar. Parasitized S. litura larvae showed a pronounced reduction in food consumption and weight gain. Microplitis similis may have the potential to significantly suppress population growth and the damage caused by S. litura.

The role of grass volatiles on oviposition site selection by Anopheles arabiensis and Anopheles coluzzii

Background

The reproductive success and population dynamics, of Anopheles malaria mosquitoes is strongly influenced by the oviposition site selection of gravid females. Mosquitoes select oviposition sites at different spatial scales, starting with selecting a habitat in which to search. This study utilizes the association of larval abundance in the field with natural breeding habitats, dominated by various types of wild grasses, as a proxy for oviposition site selection by gravid mosquitoes. Moreover, the role of olfactory cues emanating from these habitats in the attraction and oviposition stimulation of females was analysed.

Methods

The density of Anopheles larvae in breeding sites associated with Echinochloa pyramidalis, Echinochloa stagnina, Typha latifolia and Cyperus papyrus, was sampled and the larvae identified to species level. Headspace volatile extracts of the grasses were collected and used to assess behavioural attraction and oviposition stimulation of gravid Anopheles arabiensis and Anopheles coluzzii mosquitoes in wind tunnel and two-choice oviposition assays, respectively. The ability of the mosquitoes to differentiate among the grass volatile extracts was tested in multi-choice tent assays.

Results

Anopheles arabiensis larvae were the most abundant species found in the various grass-associated habitats. The larval densities described a hierarchical distribution, with Poaceae (Echinochloa pyramidalis and Echinochloa stagnina)-associated habitat sites demonstrating higher densities than that of Typha-associated sites, and where larvae were absent from Cyperus-associated sites. This hierarchy was maintained by gravid An. arabiensis and An. coluzzii mosquitoes in attraction, oviposition and multi-choice assays to grass volatile extracts.

Conclusions

The demonstrated hierarchical preference of gravid An. coluzzii and An. arabiensis for grass volatiles indicates that vegetation cues associated with larval habitats are instrumental in the oviposition site choice of the malaria mosquitoes. Identifying volatile cues from grasses that modulate gravid malaria mosquito behaviours has distinct potential for the development of tools to be used in future monitoring and control methods.

Plant-Mediated Effects on Mosquito Capacity to Transmit Human Malaria

The ecological context in which mosquitoes and malaria parasites interact has received little attention, compared to the genetic and molecular aspects of malaria transmission. Plant nectar and fruits are important for the nutritional ecology of malaria vectors, but how the natural diversity of plant-derived sugar sources affects mosquito competence for malaria parasites is unclear. To test this, we infected Anopheles coluzzi, an important African malaria vector, with sympatric field isolates of Plasmodium falciparum, using direct membrane feeding assays. Through a series of experiments, we then examined the effects of sugar meals from Thevetia neriifolia and Barleria lupilina cuttings that included flowers, and fruit from Lannea microcarpa and Mangifera indica on parasite and mosquito traits that are key for determining the intensity of malaria transmission. We found that the source of plant sugar meal differentially affected infection prevalence and intensity, the development duration of the parasites, as well as the survival and fecundity of the vector. These effects are likely the result of complex interactions between toxic secondary metabolites and the nutritional quality of the plant sugar source, as well as of host resource availability and parasite growth. Using an epidemiological model, we show that plant sugar source can be a significant driver of malaria transmission dynamics, with some plant species exhibiting either transmission-reducing or -enhancing activities.

Daytime shelter use of individually kept horses during Swedish summer

In Sweden, no provision for summer shelter to protect horses from heat and insects is required, although access to shelter for horses kept outdoors 24 h during winter is a requirement. This study investigated horses' daytime shelter-seeking behavior in relation to weather conditions and insect activity during a 2-wk period in summer. Eight Warmblood riding horses had access to 2 shelters of different design to test which shelter design is preferred by horses. Furthermore, rectal and skin temperatures and insect-defensive behavior were measured to test whether horses would benefit from the provision of shade. The horses were kept alone in paddocks for 4 d. During 2 d, horses had access to 2 shelters: 1) open shelter with roof and uncovered sides and 2) closed shelter with roof, wind nets on 2 sides, and opaque plastic opposite the entrance. Weather conditions (ambient temperature, relative humidity, solar radiation, wind speed) were recorded every 10 min. The number of insects (flies, mosquitos) was counted from insect traps placed in each shelter and outside. Behavior (shelter use, insect-defensive behavior, locomotion, grazing) was recorded at 5-min intervals between 0900 to 1200 h and 1300 to 1600 h and rectal and skin temperatures were measured at 0800 h, 1200 h, and 1600 h. Data were analyzed with PROC MIXED and GLIMMIX procedure for Generalized Linear Mixed Models. Ambient temperature ranged from 16 to 25°C (average temperature humidity index 65.7 ± 1.4). Five horses preferred the closed shelter and were observed inside up to 2.5 h continuously. Greater wind speed decreased the likelihood of observing horses inside the shelter ( < 0.001), as did lower numbers of flies ( < 0.001). The insect-defensive behaviors, skin shiver and ear flick, were performed less frequently when horses were using the closed shelter ( < 0.001), indicating that they were less disturbed by insects. Thirty-minute shelter use had no effect on rectal and skin temperatures ( > 0.05). Results showed that horses made use of shelters during the summer even when weather conditions were moderate. A shelter with roof and covers on 3 sides was preferred over a shelter with roof only and can reduce insect-defensive behavior.

Gene by Environment Interaction Linking the Chromosome 15q25 Locus With Cigarette Consumption and Lung Cancer Susceptibility--Are African American Affected Differently?

The majority of lung cancer cases result from complex interactions between smoking exposure, genetic susceptibility and a person's immune response to chronic inflammation or lung remodelling. Epidemiological studies confirm that susceptibility to developing chronic obstructive pulmonary disease (COPD), especially emphysema, is also closely linked to lung cancer susceptibility. Genetic epidemiology studies have consistently reported associations between the chromosome 15q25 locus with lung cancer and COPD. In addition, studies show this locus to be independently associated with cigarette consumption and nicotine addiction in a dose-response manner, primarily at lower levels of cigarette consumption. Studies that measure both cigarette consumption and lung function, together with extensive genotype analysis, will be needed to further unravel these complex relationships.

Clinical applications of gene-based risk prediction for lung cancer and the central role of chronic obstructive pulmonary disease

Lung cancer is the leading cause of cancer death worldwide and nearly 90% of cases are attributable to smoking. Quitting smoking and early diagnosis of lung cancer, through computed tomographic screening, are the only ways to reduce mortality from lung cancer. Recent epidemiological studies show that risk prediction for lung cancer is optimized by using multivariate risk models that include age, smoking exposure, history of chronic obstructive pulmonary disease (COPD), family history of lung cancer, and body mass index. It has also been shown that COPD predates lung cancer in 65–70% of cases, conferring a four- to sixfold greater risk of lung cancer compared to smokers with normal lung function. Genome-wide association studies of smokers have identified a number of genetic variants associated with COPD or lung cancer. In a case–control study, where smokers with normal lungs were compared to smokers who had spirometry-defined COPD or histology confirmed lung cancer, several of these variants were shown to overlap, conferring the same susceptibility or protective effects on both COPD and lung cancer (independent of COPD status). In this perspective article, we show how combining clinical data with genetic variants can help identify heavy smokers at the greatest risk of lung cancer. Using this approach, we found that gene-based risk testing helped engage smokers in risk mitigating activities like quitting smoking and undertaking lung cancer screening. We suggest that such an approach could facilitate the targeted selection of smokers for cost-effective life-saving interventions.

Chromosome 4q31 locus in COPD is also associated with lung cancer

Chronic obstructive pulmonary disease (COPD) is the single greatest risk factor for lung cancer in smokers and is found in 50-90% of lung cancer cases. The link between COPD and lung cancer may stem in part from the matrix remodelling and repair processes underlying COPD, and the development of epithelial-mesenchymal transition (EMT) that underlies lung carcinogenesis. The Hedgehog-interacting protein (HHIP), which mediates the epithelial response (EMT) to smoking, has been implicated in COPD and lung cancer. Recent genome-wide and candidate gene studies of COPD implicate genetic variants on the chromosomal 4q31 (HHIP/glycophorin A (GYPA)) locus. In a case-control study of smokers with normal lung function, COPD and lung cancer (subphenotyped for COPD), we show the GG genotype of the rs 1489759 HHIP single-nucleotide polymorphism (SNP) and the CC genotype of the rs 2202507 GYPA SNP confers a "protective" effect on COPD (OR 0.59, p = 0.006 for HHIP and OR = 0.65, p = 0.006 for GYPA) and lung cancer (OR = 0.70 (p = 0.05) for HHIP and OR 0.70 (p = 0.02) for GYPA). This study suggests that, in smokers, genetic variants of the 4q31 locus conferring a protective effect for COPD are also protective in lung cancer. We conclude that genetic susceptibility to lung cancer includes COPD-related gene variants.

A gene-based risk score for lung cancer susceptibility in smokers and ex-smokers

BACKGROUND

Epidemiological and family studies suggest that lung cancer results from the combined effects of age, smoking and genetic factors. Chronic obstructive pulmonary disease (COPD) is also an independent risk factor for lung cancer and coexists in 40-60% of lung cancer cases.

METHODS

In a two-stage case-control association study, genetic markers associated with either susceptibility or protection against lung cancer were identified. In a test cohort of 439 Caucasian smokers or ex-smokers, consisting of healthy smokers and lung cancer cases, 157 candidate single nucleotide polymorphisms (SNPs) were screened. From this, 30 SNPs were identified, the genotypes (codominant or recessive model) of which were associated with either the healthy smokers (protective) or lung cancer (susceptibility) phenotype. After genotyping of this 30-SNP panel in a second validation cohort of 491 subjects and using the same protective and susceptibility genotypes from our test cohort, a 20-SNP panel was selected on the basis of independent univariate analyses.

RESULTS

Using multivariate logistic regression, including the 20 SNPs, it was also found that age, history of COPD, family history of lung cancer and gender were significantly and independently associated with lung cancer.

CONCLUSIONS

When numeric scores were assigned to both the SNP and demographic data, and sequentially combined by a simple algorithm in a risk model, the composite score was found to be linearly related to lung cancer risk with a bimodal distribution. Genetic data may therefore be combined with other risk variables from smokers or ex-smokers to identify individuals who are most susceptible to developing lung cancer.

Lung cancer gene associated with COPD: triple whammy or possible confounding effect?

Recently, several large genome-wide association studies have identified a putative "lung cancer" locus in the nicotinic acetylcholine receptor subunit genes (nAChR) on 15q25. However, these findings may be confounded by the presence of chronic obstructive pulmonary disease (COPD), which is also strongly associated with smoking exposure and lung cancer. This is likely as the prevalence of COPD in lung cancer cohorts is as much as two-fold greater than that reported in smoking control populations (50 versus 20%). The present authors compared the genotype frequencies of the most strongly associated single nucleotide polymorphism (rs16969968) in the alpha5 subunit of the nAChR gene cluster between three matched smoking cohorts. The AA genotype was found to be more frequent and was seen in 437 (16%) lung cancer cases and 445 (14%) COPD cases compared with 475 (9%) healthy smoking controls. More importantly, when 429 lung cancer cases were divided according to spirometry results (performed within 3 months of diagnosis, prior to surgery and in the absence of effusions or collapse), the AA genotype was present in 19 and 11% of cases with and without COPD, respectively. These findings suggest that the association between the alpha5 subunit nicotinic acetylcholine receptor single nucleotide polymorphism and lung cancer may, in part, be confounded by chronic obstructive pulmonary disease.

COPD prevalence is increased in lung cancer, independent of age, sex and smoking history

Chronic obstructive pulmonary disease (COPD) is a common comorbid disease in lung cancer, estimated to affect 40-70% of lung cancer patients, depending on diagnostic criteria. As smoking exposure is found in 85-90% of those diagnosed with either COPD or lung cancer, coexisting disease could merely reflect a shared smoking exposure. Potential confounding by age, sex and pack-yr smoking history, and/or by the possible effects of lung cancer on spirometry, may result in over-diagnosis of COPD prevalence. In the present study, the prevalence of COPD (pre-bronchodilator Global Initiative for Chronic Obstructive Lung Disease 2+ criteria) in patients diagnosed with lung cancer was 50% compared with 8% in a randomly recruited community control group, matched for age, sex and pack-yr smoking exposure (n = 602, odds ratio 11.6; p<0.0001). In a subgroup analysis of those with lung cancer and lung function measured prior to the diagnosis of lung cancer (n = 127), we found a nonsignificant increase in COPD prevalence following diagnosis (56-61%; p = 0.45). After controlling for important variables, the prevalence of COPD in newly diagnosed lung cancer cases was six-fold greater than in matched smokers; this is much greater than previously reported. We conclude that COPD is both a common and important independent risk factor for lung cancer.

Role of glucosinolates in insect-plant relationships and multitrophic interactions

Glucosinolates present classical examples of plant compounds affecting insect-plant interactions. They are found mainly in the family Brassicaceae, which includes several important crops. More than 120 different glucosinolates are known. The enzyme myrosinase, which is stored in specialized plant cells, converts glucosinolates to the toxic isothiocyanates. Insect herbivores may reduce the toxicity of glucosinolates and their products by excretion, detoxification, or behavioral adaptations. Glucosinolates also affect higher trophic levels, via reduced host or prey quality or because specialist herbivores may sequester glucosinolates for their own defense. There is substantial quantitative and qualitative variation between plant genotypes, tissues, and ontogenetic stages, which poses specific challenges to insect herbivores. Even though glucosinolates are constitutive defenses, their levels are influenced by abiotic and biotic factors including insect damage. Plant breeders may use knowledge on glucosinolates to increase insect resistance in Brassica crops. State-of-the-art techniques, such as mutant analysis and metabolomics, are necessary to identify the exact role of glucosinolates.

Role of glucosinolates in insect-plant relationships and multitrophic interactions

Glucosinolates present classical examples of plant compounds affecting insect-plant interactions. They are found mainly in the family Brassicaceae, which includes several important crops. More than 120 different glucosinolates are known. The enzyme myrosinase, which is stored in specialized plant cells, converts glucosinolates to the toxic isothiocyanates. Insect herbivores may reduce the toxicity of glucosinolates and their products by excretion, detoxification, or behavioral adaptations. Glucosinolates also affect higher trophic levels, via reduced host or prey quality or because specialist herbivores may sequester glucosinolates for their own defense. There is substantial quantitative and qualitative variation between plant genotypes, tissues, and ontogenetic stages, which poses specific challenges to insect herbivores. Even though glucosinolates are constitutive defenses, their levels are influenced by abiotic and biotic factors including insect damage. Plant breeders may use knowledge on glucosinolates to increase insect resistance in Brassica crops. State-of-the-art techniques, such as mutant analysis and metabolomics, are necessary to identify the exact role of glucosinolates.

The effect of repellents Ocimum forskolei and deet on the response of Anopheles stephensi to host odours

The behavioural response of Anopheles stephensi Liston (Diptera: Culicidae) to incubated host odours (from human and goat) and to human odour in combination with a repellent plant, Ocimum forskolei (Labiatae), or deet (N, N, diethyl-toluamide) (20%) was tested in a dual-port olfactometer. An. stephensi was significantly attracted to both host odours compared with air alone, but showed no preference when given a choice between both host odours simultaneously. In choice tests, the addition of deet to human odour did not significantly divert mosquitoes to human odour alone, but did divert them to goat odour. O. forskolei combined with human odour diverted mosquitoes to goat or human odour alone. Combinations of human odour and O. forskolei, and human odour and deet were both as unattractive as air alone, and attracted mosquitoes equally when offered simultaneously. The results indicate that use of O. forskolei as a repellent would be beneficial in reducing vector biting if used in communities in areas with partially zoophilic mosquito species such as An. stephensi, and where animals are present.

Frequency of venous thromboembolism in low to moderate risk long distance air travellers: the New Zealand Air Traveller's Thrombosis (NZATT) study

BACKGROUND

The frequency and role of risk factors for venous thromboembolism related to air travel is uncertain. We aimed to establish the frequency of this disorder in a group of long distance air travellers and to investigate the role of potential risk factors.

METHODS

We designed a prospective study into which we recruited individuals aged between 18 and 70 years, travelling for 4 h or more by aircraft. D-dimer measurement was done before and after travel. Participants with a negative D-dimer (<500 ng/L) before travel were included in the study. Those who became D-dimer positive or developed high clinical probability symptoms during the 3 months after travel were investigated with bilateral compression ultrasonography and CT pulmonary angiography. Suspected clinical and thrombophilic risk factors, and use of prophylactic measures, were assessed.

FINDINGS

1000 individuals were recruited, with 878 meeting inclusion criteria and completing the study. All participants travelled at least 10 h, with a mean total duration of air travel of 39 h (SD 12.5). 112 patients underwent radiological assessment on return. Frequency of venous thromboembolism associated with travel was 1.0% (9/878, 95% CI 0.5-1.9), which included four cases of pulmonary embolism and five of deep venous thrombosis. Six patients with venous thromboembolism had pre-existing clinical risk factors, two had a recognised thrombophilic risk factor, two travelled exclusively in business class, five used aspirin, and four wore compression stockings.

INTERPRETATION

Our results suggest an association between multiple long distance air flights and venous thromboembolism, even in individuals at low to moderate risk. The role of traditional risk factors and prophylactic measures in air travel-related venous thromboembolism needs further investigation.

Helicobacter pylori and early duodenal ulcer status post-treatment: a review

BACKGROUND

Data submitted to the FDA were reviewed to analyze the relationship between Helicobacter pylori infection and the incidence of early duodenal ulcers, within 6 weeks, following treatment.

MATERIALS AND METHODS

Retrospective analyzes were performed on data from three H. pylori development programs submitted to the FDA: ranitidine-bismuth-citrate (RBC), lansoprazole (L) and omeprazole (O). Efficacy assessments for the RBC, L and O programs were made at end of a 4-week treatment period, 4-6 weeks following the end of a 14-day treatment period, and 4 weeks following the end of a 4-week treatment period, respectively.

RESULTS

Overall, there was a 15%, 21% and 23% decrease in the number of patients in the RBC, L and O programs, respectively, with ulcers among H. pylori cleared/eradicated patients post-treatment compared with patients with persistent infection. Among patients who did not have cleared/eradicated H. pylori in the RBC and O programs, where antisecretory agents were continued beyond the antimicrobial treatment period, the number of ulcers was lower in the antisecretory plus antimicrobial subgroups compared with the antimicrobial alone subgroups (37% vs. 46% for RBC and 33% vs. 42% for O). Among patients with cleared/eradicated H. pylori, the number of patients with ulcers in the antimicrobial alone subgroups and antisecretory plus antimicrobial subgroups were similar within each program. Antimicrobials alone had significantly lower rates of ulcers among patients with cleared/eradicated H. pylori as compared with patients without clearance/eradication.

CONCLUSIONS

The early incidence of duodenal ulcers is significantly decreased in patients with H. pylori clearance/eradication.

In search of the Holy Grail of Heliocobacter pylori remedies

In this issue, Gisbert et al. (pp. 157-62) present the results of a noncomparative study evaluating a twice daily, 5-day regimen of ranitidine bismuth citrate, amoxicillin, clarithromycin and metronidazole twice daily for Helicobacter pylori cure. This study is one of a few stuides that evaluate a 5-day triple antimicrobial regimen in combination with a antisecretory agent. Although the study design precludes making any definite conclusion, it does encourage additional investigation of these types of regimens. Randomized controlled trials (RCTs) using regimens containing multiple agents should consider both standard-of-care comparator regimens and comparator regimens that will provide a better understanding of why regimens are more effective or better tolerated. The goal of treatment should be to maintain a lower bound 95% confidence interval (CI) of the point estimate of greater than 80% and a 'delta' (lower bound 95% CI of the difference in rates) of less than 10%. All RCTs should conduct susceptibility testing to evaluate the impact of resistance on efficacy and explain eradication failures. Finally, consideration should be given to the inclusion of patients with functional dyspepsia in H. pylori studies evaluating H. pylori cure since patients with peptic ulcer disease are becoming harder to find.

Loss of Helicobacter pylori hemagglutination with serial laboratory passage and correlation of hemagglutination with gastric epithelial cell adherence

Adherence of Helicobacter pylori to gastric epithelial cells is thought to be important in the pathogenesis of infection and may be essential to maintain lifelong colonization. However, the factors responsible for adherence to gastric epithelial cells in vivo have not been characterized, and the significance of adherence to standard epithelial cell lines is unclear. Hemagglutination is also thought to be important in H. pylori adherence. However, no studies have clearly linked H. pylori hemagglutination or adherence to cultured epithelial cells to primary gastric epithelial cell adherence. Furthermore, it is not clear whether laboratory strains which have undergone multiple passages lose potential colonization factors. In this study, we examined the effect of serial laboratory passage on hemagglutination and correlated the hemagglutination characteristics of H. pylori strains to primary gastric cell adherence. Variable expression of hemagglutination was seen with serial laboratory passage of 15 strains. After 100 serial laboratory passages, all strains had lost hemagglutination activity. Hemagglutination was seen in association with adherence to primary gastric cells in vitro isolated from 2 patients. An association with ultrastructural intimate adherence was seen with HEp-2 cells, but not with gastric adenocarcinoma cells. Ultrastructural adherence was seen in corresponding antral biopsies of patients whose strains were hemagglutination positive, but hemagglutination was not associated with gastric inflammation. These data indicate that H. pylori hemagglutination is lost with serial passage and that hemagglutination may play a role in the attachment of H. pylori to gastric epithelial cells, but the role of adherence to chronic gastric inflammation is unclear.

The pollen beetle, Meligethes aeneus, changes egg production rate to match host quality

Motivation-based models dominate current theory concerning host plant selection for oviposition by herbivorous insects. A female searching for a host plant will be more likely to accept a host which is of inferior quality for her offspring if motivation is high, e.g. a large eggload or long time since last oviposition. This implies that insects will accumulate eggs if exposed to hosts of low acceptability and after a time lay eggs on such hosts. An alternative strategy for insects when exposed to less acceptable hosts is to stop producing, instead of accumulating, eggs. Thus, resources would be saved until a more acceptable host is found. If this hypothesis is true, a herbivorous insect would cease egg production when exposed to hosts of low acceptability and resume egg production when exposed to hosts of high acceptability. Previous exposure should not affect oviposition rate when an insect encounters a new host of a different quality. In an earlier study pollen beetles, Meligethes aeneus (F.) (Coleoptera: Nitidulidae), did not accumulate eggs in the absence of high quality hosts. In this study we monitored the daily oviposition rate of female pollen beetles on hosts plants of low (Sinapis alba L.), intermediate (Brassica nigra Koch) or high (B. napus L.) acceptability over a 5-day period. Individuals were then switched to an oviposition resource of a different acceptability. Beetles moved from high- to low-acceptability plants reduced their oviposition rate considerably. In the opposite case, low to high acceptability, the rate of oviposition increased markedly after the switch. When M. aeneus were moved from the high-acceptability host to that of intermediate acceptability oviposition rate was modified accordingly. However, when moved to the intermediate host from a host of low acceptability oviposition on B. nigra was much less than would normally be expected. A possible mechanism for this finding is discussed. M. aeneus, by adjusting oviposition rate to host acceptability, maximizes the average host quality for offspring, even at the cost of a lower egg-laying rate.

Has the impact of Helicobacter pylori therapy on ulcer recurrence in the United States been overstated? A meta-analysis of rigorously designed trials

OBJECTIVE

The aim of this study was to assess the effect of H. pylori eradication on ulcer recurrence in North American duodenal ulcer patients by examining only treatment studies that met rigorous methodologic criteria.

METHODS

Data sources were computerized bibliographic searches from 1983, review of reference lists, communication with companies that manufacture medications used for H. pylori therapy in the U.S., and H. pylori investigators, review of open presentations to the Food and Drug Administration, and review of abstracts from annual scientific meetings. Criteria for study inclusion were double blind, randomized North American trials of H. pylori therapy for duodenal ulcer, scheduled endoscopic follow-up exams for > or = 6 months, and H. pylori cure documented > or = 4 wk after completion of therapy by at least two endoscopic biopsy tests. Seven relevant trials were identified. Data were abstracted independently and disagreement was resolved by consensus. We obtained missing data and identified erroneous assessments through contact with an author or sponsor of all studies.

RESULTS

The common odds ratio for ulcer recurrence was 0.20 (95% CI, 0.13-0.31) and 2.8 patients would need to be successfully treated to prevent one ulcer recurrence at 6 months. The pooled ulcer recurrence rate at 6 months in patients with H. pylori eradication was 20%.

CONCLUSION

Results of North American studies of highest methodological quality confirm that H. pylori eradication markedly decreases ulcer recurrence. Nevertheless, 20% of patients in these studies had ulcer recurrence within 6 months, despite successful cure of infection and no reported use of NSAIDs. Non-H. pylori, non-NSAID ulcers may be more common in the U.S. than previously believed.

Has the impact of Helicobacter pylori therapy on ulcer recurrence in the United States been overstated? A meta-analysis of rigorously designed trials

OBJECTIVE

The aim of this study was to assess the effect of H. pylori eradication on ulcer recurrence in North American duodenal ulcer patients by examining only treatment studies that met rigorous methodologic criteria.

METHODS

Data sources were computerized bibliographic searches from 1983, review of reference lists, communication with companies that manufacture medications used for H. pylori therapy in the U.S., and H. pylori investigators, review of open presentations to the Food and Drug Administration, and review of abstracts from annual scientific meetings. Criteria for study inclusion were double blind, randomized North American trials of H. pylori therapy for duodenal ulcer, scheduled endoscopic follow-up exams for > or = 6 months, and H. pylori cure documented > or = 4 wk after completion of therapy by at least two endoscopic biopsy tests. Seven relevant trials were identified. Data were abstracted independently and disagreement was resolved by consensus. We obtained missing data and identified erroneous assessments through contact with an author or sponsor of all studies.

RESULTS

The common odds ratio for ulcer recurrence was 0.20 (95% CI, 0.13-0.31) and 2.8 patients would need to be successfully treated to prevent one ulcer recurrence at 6 months. The pooled ulcer recurrence rate at 6 months in patients with H. pylori eradication was 20%.

CONCLUSION

Results of North American studies of highest methodological quality confirm that H. pylori eradication markedly decreases ulcer recurrence. Nevertheless, 20% of patients in these studies had ulcer recurrence within 6 months, despite successful cure of infection and no reported use of NSAIDs. Non-H. pylori, non-NSAID ulcers may be more common in the U.S. than previously believed.

Current FDA-approved treatments for Helicobacter pylori and the FDA approval process

U.S. Food and Drug Administration (FDA) approval of new drugs expands treatment options and serves as a "safety net" of well-documented efficacy and safety. The information provided in the package insert facilitates physician education and provides some assurance that marketing information is accurate. As of February 1997, three Helicobacter pylori regimes have been FDA-approved for eradication of H. pylori in infected patients with active duodenal ulcers. Regimen 1, omeprazole + clarithromycin (O/C), was supported by two multicenter, controlled studies with a 6-month follow-up. Eradication rates were 74% (n = 53; 95% confidence interval [CI], 62-85) and 64% (n = 61; 95% CI, 52-76). Twenty-five of 26 patients with failed eradication therapy who were taking O/C with clarithromycin-susceptible strains before treatment and who had pretreatment and posttreatment susceptibility tests performed developed clarithromycin resistance after treatment. Regimen 2, ranitidine-bismuth-citrate + clarithromycin, was supported by two multicenter, placebo-controlled studies with a 6-month follow-up. Eradication rates were 84% (n = 19; 95% CI, 60-96) and 73% (n = 22; 95% CI, 50-88). Insufficient pretreatment and posttreatment susceptibility data were collected to assess antimicrobial resistance. Regimen 3, bismuth subsalicylate + metronidazole + tetracycline + an H2-receptor antagonist, was supported by two pivotal literature-based studies. Eradication rates in patients with duodenal ulcer were 82% (n = 51; 95% CI, 70-92) and 77% (n = 39; 95% CI, 61-89), respectively. When extrapolating the results of these three FDA-approved regimens to the clinical setting, particular aspects of the clinical trial should be kept in mind. These include the type of controls, primary end points used, population studied, and number and type of dropouts.

Relationship between Helicobacter pylori eradication and reduced duodenal and gastric ulcer recurrence: a review

BACKGROUND & AIMS

The aim of this study was to determine whether the current literature supports the use of Helicobacter pylori cure as the primary efficacy end point in peptic ulcer clinical trials. This could potentially reduce the complexity of future trials.

METHODS

Published articles containing information on both H. pylori eradication and ulcer recurrence were searched with MEDLINE. Abstracts were found by reviewing references from both primary and review articles.

RESULTS

Fourteen duodenal ulcer and five gastric ulcer studies satisfied requisite inclusion criteria. Ulcer recurrence was significantly less common among H. pylori-cured patients vs. noncured patients (6% vs. 67% for patients with duodenal ulcers; 4% vs. 59% for patients with gastric ulcers). For H. pylori-cured patients, duodenal ulcer recurrence was higher in studies using two endoscopic tests compared with three tests (9% vs. 3%) and higher in abstracts compared with published articles (14% vs. 4%). Timing of H. pylori eradication (4 weeks vs. < / = 12 weeks) and ulcer recurrence assessment (6 months vs. < / = 12 months) was not significantly related to duodenal ulcer recurrence.

CONCLUSIONS

The current literature strongly suggests that H. pylori eradication 4 weeks after therapy should be used as the primary efficacy end point for reduced gastric and duodenal ulcer recurrence for the purpose of clinical trial design.

Cerebral mucormycosis associated with intravenous drug use: three case reports and review

We describe three cases of cerebral mucormycosis in intravenous drug users and review 22 previously reported cases. Involvement of the basal ganglia was demonstrated in all but two cases. Seven of the 10 patients tested for antibodies to the human immunodeficiency virus (HIV) were seronegative. Eight of the 25 patients survived and were discharged from the hospital; for 7 of 10 patients, cultures of brain lesions yielded Rhizopus arrhizus. The radiographic findings varied, and in most cases, no or minimal contrast enhancement was seen in the initial computed tomography scans. Although uncommon, the diagnosis of cerebral mucormycosis should be considered when basal ganglia lesions are present in an intravenous drug user, regardless of previous exposure to HIV.

Helicobacter pylori: the missing link in perspective

Helicobacter pylori, an organism responsible for a common human infection, may act as a cofactor to produce gastrointestinal disease in a significant minority. The exact mechanisms of transmission are still unclear, but likely involve direct person-to-person spread and fecal-oral or waterborne/environmental transmission. Infection is a necessary condition for the development of duodenal ulcers and chronic nonspecific gastritis. It also likely contributes to the development of gastric ulcers, and the intestinal-type gastric carcinoma, but further studies are needed to confirm these hypotheses. Multiple effective treatment regimens currently exists. We recommend using bismuth, metronidazole, and tetracycline as the initial regimen of choice. Unfortunately, the relative importance of bacterial virulence factors is still unclear when compared with host susceptibility factors, and much knowledge needs to be gained about pathogenesis before vaccine development can proceed.

Serologic response to Helicobacter pylori among children and teenagers in northern Chile

The serologic response to Helicobacter pylori was determined in 388 children and teenagers living in Iquique, Chile by using an IgG enzyme-linked immunosorbent assay. Serum antibody levels, as measured by optical density, correlated strongly with age. Increases in the mean antibody level were seen primarily after age five, with rates of seropositivity increasing to > or = 70% among teenagers. The reasons for this age-related pattern of acquisition of infection remain to be determined.

Seroprevalence of Helicobacter pylori in Chile: vegetables may serve as one route of transmission

Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans < 35 years of age. Seropositivity was > 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.