Simon Bahrndorff

Foodborne disease prevention and broiler chickens with reduced Campylobacter infection.

Studies have suggested that flies play a linking role in the epidemiology of Campylobacter spp. in broiler chickens and that fly screens can reduce the prevalence of Campylobacter spp. We examined the year-round and long-term effects of fly screens in 10 broiler chicken houses (99 flocks) in Denmark. Prevalence of Campylobacter spp.–positive flocks was significantly reduced, from 41.4% during 2003–2005 (before fly screens) to 10.3% in 2006–2009 (with fly screens). In fly screen houses, Campylobacter spp. prevalence did not peak during the summer. Nationally, prevalence of Campylobacter spp.–positive flocks in Denmark could have been reduced by an estimated 77% during summer had fly screens been part of biosecurity practices. These results imply that fly screens might help reduce prevalence of campylobacteriosis among humans, which is closely linked to Campylobacter spp. prevalence among broiler chicken flocks.

Bioinformatics and protein expression analyses implicate LEA proteins in the drought response of Collembola

Humidity has a large impact on the distribution and abundance of terrestrial invertebrates, but the molecular mechanisms governing drought resistance are not fully understood. Some attention has been given to the role of the heat shock response as a component of desiccation tolerance, but recent focus has been on the chaperone-like LEA (late embryogenesis abundant) proteins in anhydrobiotic animals. This study investigates the expression of putative LEA proteins as well as the heat shock protein Hsp70 during drought stress in soil and surface dwelling species of Collembola (springtails). In silico analysis of four EST candidates from two species of Collembola showed the presence of a Group 3 LEA protein in Megaphorura arctica. In common with other Group 3 LEA proteins, the new sequence is predicted to be 100% natively unfolded, with a strong degree of lysine and alanine periodicity and with a negative average hydrophobicity of -1.273. The sequence clusters with members of the Group 3 LEA in plants. Furthermore, cross-species Western blotting showed drought-induced expression of putative LEA proteins in six species of Collembola. In the surface dwelling species, Orchesella cincta, degree of dehydration and length of exposure correlated with level of putative LEA protein. Hsp70 was also found to increase in individuals of O. cincta and Folsomia candida that had been exposed to drought conditions for 6 days. These results show the presence of a LEA protein-coding region in Collembola, but also indicate that several proteins are involved in response to dehydration stress, including Hsp70.

The Microbiome of Animals: Implications for Conservation Biology

In recent years the human microbiome has become a growing area of research and it is becoming clear that the microbiome of humans plays an important role for human health. Extensive research is now going into cataloging and annotating the functional role of the human microbiome. The ability to explore and describe the microbiome of any species has become possible due to new methods for sequencing. These techniques allow comprehensive surveys of the composition of the microbiome of nonmodel organisms of which relatively little is known. Some attention has been paid to the microbiome of insect species including important vectors of pathogens of human and veterinary importance, agricultural pests, and model species. Together these studies suggest that the microbiome of insects is highly dependent on the environment, species, and populations and affects the fitness of species. These fitness effects can have important implications for the conservation and management of species and populations. Further, these results are important for our understanding of invasion of nonnative species, responses to pathogens, and responses to chemicals and global climate change in the present and future.

Plasticity in behavioural responses and resistance to temperature stress in Musca domestica

Organisms can respond to and cope with stressful environments in a number of ways including behavioural, morphological and physiological adjustments. To understand the role of behavioural traits in thermal adaptations we compared heat resistance, locomotor (walking and flying) activity, flight performance and morphology of three European populations of Musca domestica (Diptera: Muscidae) originating from different thermal conditions (Spain, Switzerland and Denmark) at benign and stressful high temperatures. Spanish flies showed greater heat resistance than Swiss and Danish flies. Similarly, at the stressful high temperature Spanish flies flew the furthest and Danish flies the shortest distance. Neither body size nor wing loading affected flight performance, although flies with narrower wings tended to fly further (wing shape effect). Swiss flies were most active in terms of locomotor activity at the benign temperature, whereas the Spanish flies were able to stay active for longer at the stressful temperature. Population differences in behavioural traits and heat resistance were obtained using flies held for several generations in a laboratory common garden setting; therefore we suggest that exposure to and avoidance of high temperatures under natural conditions has been an important selective agent causing the suggested adaptive differentiation between the populations.

The Effects of Sex-Ratio and Density on Locomotor Activity in the House Fly, Musca domestica

Abstract Although locomotor activity is involved in almost all behavioral traits, there is a lack of knowledge on what factors affect it. This study examined the effects of sex—ratio and density on the circadian rhythm of locomotor activity of adult Musca domestica L. (Diptera: Muscidae) using an infra—red light system. Sex—ratio significantly affected locomotor activity, increasing with the percentage of males in the vials. In accordance with other studies, males were more active than females, but the circadian rhythm of the two sexes was not constant over time and changed during the light period. There was also an effect of density on locomotor activity, where males at intermediate densities showed higher activity. Further, the predictability of the locomotor activity, estimated as the degree of autocorrelation of the activity data, increased with the number of males present in the vials both with and without the presence of females. Overall, this study demonstrates that locomotor activity in M. domestica is affected by sex—ratio and density. Furthermore, the predictability of locomotor activity is affected by both sex—ratio, density, and circadian rhythm. These results add to our understanding of the behavioral interactions between houseflies and highlight the importance of these factors when designing behavioral experiments using M. domestica.

The effects of temperature and innate immunity on transmission of Campylobacter jejuni (Campylobacterales: Campylobacteraceae) between life stages of musca domestica (Diptera: Muscidae)

ABSTRACT The house fly (Musca domestica L.) is a well-established vector of human pathogens, including Campylobacter spp., which can cause infection of broiler chicken flocks, and through contaminated broiler meat can cause outbreaks of campylobacteriosis in humans. We investigated whether Campylobacter jejuni (Jones) could be transferred between life stages of M. domestica (larvae-pupae-adults) and determined bacterial counts of C. jejuni at different time points after bacterial exposure. C. jejuni was transmitted from infected larvae to pupae, but not to the adult stage. Infected larvae maintained at 25°C had mean bacterial numbers of 6.5 ± 0.2 SE log10 (colony forming units [CFU]/g) that subsequently dropped to 3.6 ± 0.3 SE log10 (CFU/g) 8 h after infection. Pupae originating from infected larvae contained mean bacterial numbers of 5.3 ± 0.1 SE log10 (CFU/g), and these numbers dropped to 4.8 ± 0.1 SE log10 (CFU/g) 24 h after pupation. The decline in C. jejuni numbers during pupal development coincided with increased expression of antimicrobial peptides, including cecropin, diptericin, attacin, and defensin, in the larva-pupa transition stage and a later second peak in older pupae (4 or 48 h). Conversely, there was a reduced expression of the digestive enzyme, lysozyme, in pupae and adults compared with larvae.

Design and data analysis of experimental trials to test vaccine candidates against zoonotic pathogens in animals: the case of a clinical trial against campylobacter in broilers

The development of effective vaccines against zoonotic pathogens represents a priority in public health protection programs. The design of clinical trials and appropriate data analysis of the experiments results are crucial for the assessment of vaccine effectiveness. This manuscript reviews important issues related to the assessment of the effectiveness of vaccines designed to obtain a quantitative reduction of the pathogen in animals or animal products. An effective vaccine will reduce the risk of human infections and therefore the number of human cases. Important considerations will be illustrated using a vaccination trial of a new campylobacter vaccine candidate developed to reduce the numbers of campylobacter in chickens and consequently the numbers of human campylobacteriosis cases. The design of the author’s vaccination trial was based on the use of isolators, a parallel group design and several rotations. The effect of clustering or design effect was considered in the sample size calculations. Chickens were randomly assigned to different isolators (treatments) and challenged with Campylobacter jejuni. Samples were obtained at different intervals and processed in the laboratory. C. jejuni counts were determined as colony-forming unit-per-gram of chicken cecum or fecal mass in order to assess vaccine effectiveness. A desired vaccine effect of 2 logs reduction on the numbers of C. jejuni recovered from vaccinated chickens was selected. Sample-size calculations, desired vaccine effect, biological and epidemiological aspects, experimental design and appropriate statistical analysis of data considering group or clustering effects will be the focus of this manuscript.

Intestinal colonization of broiler chickens by Campylobacter spp. in an experimental infection study

Consumption of poultry meat is considered as one of the main sources of human campylobacteriosis, and there is clearly a need for new surveillance and control measures based on quantitative data on Campylobacter spp. colonization dynamics in broiler chickens. We conducted four experimental infection trials, using four isolators during each infection trial to evaluate colonization of individual broiler chickens by Campylobacter jejuni over time. Individual and pooled faecal samples were obtained at days 4, 7 and 12 post-inoculation (p.i.) and caecal samples at day 12 p.i. There were large differences between broiler chickens in the number of C. jejuni in caecal and faecal material. Faecal samples of C. jejuni ranged from 4·0 to 9·4 log c.f.u./g and from 4·8 to 9·3 log c.f.u./g in the caeca. Faecal c.f.u./g decreased with time p.i. Most variation in c.f.u. for faecal and caecal samples was attributed to broiler chickens and a minor part to isolators, whereas infection trials did not affect the total variance. The results showed that pooled samples within isolators had lower c.f.u./g compared to the arithmetic mean of the individual samples. There was a significant correlation between faecal c.f.u./g at days 4 and 7 p.i., days 7 and 12 p.i. and for caecal and faecal c.f.u./g at day 12 p.i.

Temperature and Population Density Effects on Locomotor Activity of Musca domestica (Diptera: Muscidae)

ABSTRACT The behavior of ectotherm organisms is affected by both abiotic and biotic factors. However, a limited number of studies have investigated the synergistic effects on behavioral traits. This study examined the effect of temperature and density on locomotor activity of Musca domestica (L.). Locomotor activity was measured for both sexes and at four densities (with mixed sexes) during a full light and dark (L:D) cycle at temperatures ranging from 10 to 40°C. Locomotor activity during daytime increased with temperature at all densities until reaching 30°C and then decreased. Highdensity treatments significantly reduced the locomotor activity per fly, except at 15°C. For both sexes, daytime activity also increased with temperature until reaching 30 and 35°C for males and females, respectively, and thereafter decreased. Furthermore, males showed a significantly higher and more predictable locomotor activity than females. During nighttime, locomotor activity was considerably lower for all treatments. Altogether the results of the current study show that there is a significant interaction of temperature and density on daytime locomotor activity of M. domestica and that houseflies are likely to show significant changes in locomotor activity with change in temperature.

Bacterial Communities Associated with Houseflies (Musca domestica L.) Sampled within and between Farms

The housefly feeds and reproduces in animal manure and decaying organic substances and thus lives in intimate association with various microorganisms including human pathogens. In order to understand the variation and association between bacteria and the housefly, we used 16S rRNA gene amplicon sequencing to describe bacterial communities of 90 individual houseflies collected within and between ten dairy farms in Denmark. Analysis of gene sequences showed that the most abundant classes of bacteria found across all sites included Bacilli, Clostridia, Actinobacteria, Flavobacteria, and all classes of Proteobacteria and at the genus level the most abundant genera included Corynebacterium, Lactobacillus, Staphylococcus, Vagococcus, Weissella, Lactococcus, and Aerococcus. Comparison of the microbiota of houseflies revealed a highly diverse microbiota compared to other insect species and with most variation in species richness and diversity found between individuals, but not locations. Our study is the first in-depth amplicon sequencing study of the housefly microbiota, and collectively shows that the microbiota of single houseflies is highly diverse and differs between individuals likely to reflect the lifestyle of the housefly. We suggest that these results should be taken into account when addressing the transmission of pathogens by the housefly and assessing the vector competence variation under natural conditions.