Detection of target-site and metabolic resistance to pyrethroids in the bed bug Cimex lectularius in Berlin, Germany

Knockdown-resistance (kdr) against pyrethroids in bed bugs (Cimex lectularis) is associated with the presence of several point mutations in the voltage-sensitive sodium channel alpha-subunit gene and/or an increased metabolic detoxification by cytochrome P450 monooxygenases (CYPs). In the present study, pyrosequencing assays were developed to quantify the presence of the kdr substitutions (V419L or L925I substitution) in bed bugs in Berlin, Germany. In 14 of 17 bed bug field strains, pymsequencing revealed the presence of the substitution L925I with allele frequencies between 30% and 100%. One field strain additionally carried the substitution V419L with allele frequencies of 40% in males and 96% in females. In seven of the 17 field strains, mRNA levels of four CYP genes were examined using RT-qPCR. Relative to a susceptible laboratory reference strain, five field strains showed significantly higher mRNA levels of cyp397a1 with 7.1 to 56-fold increases. One of these strains additionally showed a 4.9-fold higher mRNA level of cyp398a1 compared to the reference strain, while cyp4cm1 and cyp6dn1 showed no significant differences. Our findings indicate that multiple resistance mechanisms are present in German C. lectularius populations simultaneously

Effect of Addition of Artificial Flavour on Rodent Bait Attractiveness

Some ready-to-use rodenticide baits against synanthrophic mice and rats exhibit an intense scent of vanilla, chocolate, peanut, or hazelnut. The effects of these additives on bait palatability are unclear. The aim of this study was to test whether flavoured food is more attractive to naïve rodents than natural (untreated) food. The attractiveness of flavoured against natural oat flakes was tested on wild strain groups of rodents. We tested vanilla, chocolate, hazelnut, and peanut flavour. House mice (group size 13 to 23 mice), roof rats (group size 5 to 8 rats) and brown rats (group size 5 to 7 rats) were introduced to test chambers (rats: 6.2 m², mice: 5 m²) for choice experiments. Flavoured and natural food as well as water was offered ad libitum for 12 days. Each day, the amount of consumed food was determined by weighting the remaining food, and food and water were replenished. All flavours that were tested on house mice had a positive effect on bait uptake, and the mice took up more flavoured than untreated food (hazelnut 57.7%, chocolate 61.2%, peanut 62%, and vanilla 73.1% of total food uptake). The effect on food uptake was not significantly different between flavours. Roof rats were repelled by chocolate and hazelnut (7.2% and 30.4% of total food uptake, respectively), whereas vanilla flavour had no clear effect on food consumption (51.6% of total food uptake). Similar effects were observed for bait consumption of brown rats, where chocolate flavour had a negative effect on food uptake (28.2% of total food uptake) and hazelnut flavour was neutral in terms of bait attractivity (50.0% of total food uptake). We conclude that the addition of an artificial flavour may increase the attractiveness of rodent baits to house mice, whereas it can reduce bait uptake in both rat species and has thus a detrimental effect on bait attractiveness. The different reaction of mice and rats to flavoured food is explained by the fact that house mice are neophilic, whereas both rat species avoid new stimuli and are neophobic

The energy and nutritional demand of the parasitic life of the mite Varroa destructor

The energy metabolism and nutritional demand of the ectoparasitic mite Varroa destructor Anderson and Trueman was investigated by calorimetry, respirometry and resource utilization rate. Mites from different sexes and developmental stages of the western honeybee Apis mellifera were monitored in the absence of the host. Energy metabolism of the mites, calculated from the rate of heat production, was an insignificant factor in the cause of honeybee colony death. The metabolic rates of mites ranged from 1.1% to 2.4% of that of the bee pupa depending on the infestation level. But the nutritional demand of the mites was very high, owing to their inefficient metabolic machinery, utilizing up to 25% of the nutritional reserves of the pupae accumulated in tissue during the larval stage. The feeding of the mites contributes to the malformation and weakening of the bees and eventually of the colony

The varroacidal action of propolis: a laboratory assay

The action of propolis (bee glue) against the ectoparasitic mite Varroa destructor Anderson and Trueman has been investigated and showed narcotic and lethal effects. Length of narcosis and rate of mortality depended on the extraction procedure, concentration of propolis and contact time. Propolis extracted with 70% ethanol was found to be highly toxic, a 10% (w/v) propolis resulting in 100% mortality with a brief contact time of 5 s. In addition, the effect of propolis on the metabolic rate of the mites has been investigated calorimetrically. Even sublethal propolis concentrations without varroacidal effects and of only short lasting narcotic effects resulted in a significant reduction in the heat production rate, indicating weakening of the mites

Cuticular lipids as trail pheromone in a social wasp.

We investigated the origin and composition of the chemical trail of the common yellow jacket Vespula vulgaris L. (Vespidae) and found that an artificial trail made from an extract of cuticular lipids from V. vulgaris foragers was biologically as active as a trail laid naturally by the foragers. Chemical analysis of natural trail extracts and the behaviourally active cuticular extracts by coupled gas chromatography-mass spectrometry revealed that the majority of cuticular hydrocarbons were also present in the trail extract at similar ratios. Thus, bioassay data and chemical analysis provide strong evidence that these cuticular hydrocarbons act as a trail pheromone in V. vulgaris

Rating the risks of anticoagulant rodenticides in the aquatic environment: a review

Anticoagulant rodenticides are used worldwide to control commensal rodents for hygienic and public health reasons. As anticoagulants act on all vertebrates, risk is high for unintentional poisoning of terrestrial and aquatic wildlife. Causative associations have been demonstrated for the unintended poisoning of terrestrial nontarget organisms. However, behavior and fate of anticoagulant rodenticides in the aquatic environment have received minimal attention in the past despite considerable acute toxicity of several anticoagulants to aquatic species such as fish. In light of recent regulatory developments in the European Union concerning rodenticides, we critically review available information on the environmental occurrence, fate, and impact of anticoagulant rodenticides in the aquatic environment and identify potential risks and routes of exposure as well as further research needs. Recent findings of anticoagulant rodenticides in raw and treated wastewater, sewage sludge, estuarine sediments, suspended particulate matter, and liver tissue of freshwater fish in the low ng/L and µg/kg range, respectively, demonstrate that the aquatic environment experiences a greater risk of anticoagulant rodenticide exposure than previously thought. While the anticoagulant’s mechanism of action from the molecular through cellular levels is well understood, substantial data gaps exist regarding the understanding of exposure pathways and potential adverse effects of chronic exposure with multiple active ingredients. Anticoagulants accumulating in aquatic wildlife are likely to be transferred in the food chain, causing potentially serious consequences for the health of wildlife and humans alike