Jonathan Guy

The poultry red mite (Dermanyssus gallinae): a potential vector of pathogenic agents

The poultry red mite, D. gallinae has been involved in the transmission of many pathogenic agents, responsible for serious diseases both in animals and humans. Nowadays, few effective methods are available to control the ectoparasite in poultry farms. Consequently, this is an emerging problem which must be taken into account to maintain good health in commercial egg production. This paper addresses the vector capacity of the ectoparasite with special emphasis on salmonellae, pathogenic agents responsible for many of the most important outbreaks of food-borne diseases worlwide. It has been experimentally shown that D. gallinae could act as a biological vector of S. enteritidis and natural carriage of these bacteria by the mite on poultry premises has also been reported. It was also found that D. gallinae carried other pathogens such as E. coli, Shigella sp., and Staphylococcus, thus increasing the list of pathogenic agents potentially transmitted by the mite.

Immunisation with recombinant proteins subolesin and Bm86 for the control of Dermanyssus gallinae in poultry

Dermanyssus gallinae has a worldwide distribution and is considered to be the most serious and economically significant ectoparasite affecting egg-laying poultry in Europe. Recombinant Bm86 and subolesin proteins derived from Boophilus microplus ticks and Aedes albopictus mosquitoes were used to immunise poultry in an attempt to control D. gallinaein vitro. Immunisation with subolesin and Bm86 stimulated different profiles of IgY response, whilst Bm86 but not subolesin was recognized by IgY on western blots. Orthologues for Bm86 were not found in D. gallinae by PCR, but a 150 bp fragment aligned with mammalian akirin 1 and a 300 bp fragment aligned with Amblyomma hebraeum were amplified by subolesin PCR. D. gallinae mortality after feeding was 35.1% higher (P=0.009) in the Subolesin group and 23% higher (not significant) in the Bm86 compared to the Control group. Thus it can be concluded that immunisation with recombinant subolesin can stimulate a protective response in laying hens against D. gallinae.

Environmental interactions with the toxicity of plant essential oils to the poultry red mite Dermanyssus gallinae

The toxicity of a range of plant essential oils to the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), a serious ectoparasitic pest of laying hens throughout Europe and elsewhere, was assessed in the laboratory. Dermanyssus gallinae may cause losses in egg production, anaemia and, in extreme cases, death of hens. With changes in legislation and consumer demand, alternatives to synthetic acaricides are needed to manage this pest. Fifty plant essential oils were selected for their toxicity to arthropods reported in the literature. Twenty‐four of these essential oils were found to kill > 75% of adult D. gallinae in contact toxicity tests over a 24‐h period at a rate of 0.21 mg/cm2. Subsequent testing at lower rates showed that the essential oils of cade, manuka and thyme were especially toxic to adult D. gallinae. The toxicity of the seven most acaricidal essential oils was found to be stable at different temperatures likely to be encountered in commercial poultry housing (15°C, 22°C and 29°C), although results suggest that humidity and dust might influence the toxicity of some of the oils tested. The toxicity of clove bud essential oil to D. gallinae, for example, was increased at high humidity and dust levels compared with ambient levels. The results suggest that certain essential oils may make effective botanical pesticides for use against D. gallinae, although it is likely that issues relating to the consistency of the toxic effect of some oils will determine which oils will be most effective in practice.

Repellence of plant essential oils to Dermanyssus gallinae and toxicity to the non-target invertebrate Tenebrio molitor.

With changes in legislation and consumer demand, alternatives to synthetic acaricides to manage the poultry red mite Dermanyssus gallinae (De Geer) in laying hen flocks are increasingly needed. These mites may cause losses in egg production, anaemia and even death of hens. It may be possible to use plant-derived products as D. gallinae repellents, especially if such products have a minimal impact on non-target organisms. An experiment was conducted with D. gallinae to assess the repellence of a range of plant essential oils, previously found to be of varying toxicity (relatively highly toxic to non-toxic) to this pest. Experiments were also undertaken to assess the toxicity of these products to mealworm beetles (Tenebrio molitor L.), a non-target invertebrate typical of poultry production systems. Results showed that all seven essential oils tested (manuka, thyme, palmarosa, caraway, spearmint, black pepper and juniper leaf) were repellent to D. gallinae at 0.14mg oil/cm(3) (initial concentration) during the first 2 days of study. Thyme essential oil appeared to be the most effective, where repellence lasted until the end of the study period (13 days). At the same concentration toxicity to T. molitor differed, with essential oils of palmarosa and manuka being no more toxic to adult beetles than the control. There was neither a significant association between the rank toxicity and repellence of oils to D. gallinae, nor the toxicity of oils to D. gallinae (as previously determined) and T. molitor.

Endosymbiotic bacteria living inside the poultry red mite (Dermanyssus gallinae)

This study investigated the endosymbiotic bacteria living inside the poultry red mite collected from five samples of one commercial farm from the UK and 16 farms from France using genus-specific PCR, PCR-TTGE and DNA sequencing. Endosymbiotic bacteria are intracellular obligate organisms that can cause several phenotypic and reproductive anomalies to their host and they are found widespread living inside arthropods. The farm sampled from the UK was positive for bacteria of the genera Cardinium sp. and Spiroplasma sp. From France, 7 farms were positive for Cardinium sp., 1 farm was positive for Spiroplasma sp., 1 farm was positive for Rickettsiella sp. and 2 farms were positive for Schineria sp. However, it was not possible to detect the presence of the genus Wolbachia sp. which has been observed in other ectoparasites. This study is the first report of the presence of endosymbionts living inside the poultry red mite. The results obtained suggest that it may be possible that these bacterial endosymbionts cause biological modifications to the poultry red mite.

Toxicity of plant essential oils to different life stages of the poultry red mite, Dermanyssus gallinae, and non‐target invertebrates

Seven essential oils with potential as acaricides for use against the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), were selected for study. These products (essential oils of manuka, cade, pennyroyal, thyme, garlic, clove bud and cinnamon bark) were deployed against different life stages of D. gallinae in laboratory tests at the (lethal concentration) LC50 level for adult mites. For all essential oils tested, toxicity to D. gallinae juveniles was as high as toxicity to adults, if not higher. However, at the LC50 level determined for adults, some oils were ineffective in preventing hatching of D. gallinae eggs. The essential oils were also tested under laboratory conditions at their LC90 levels for D. gallinae adults on two model non‐target species, the brine shrimp, Artemia salina (L.), and the mealworm beetle, Tenebrio molitor (L.). Results showed that not all essential oils were as toxic to A. salina and T. molitor as they were to D. gallinae, suggesting that it may be possible to select certain oils for development as acaricides against D. gallinae that would have minimal impact on non‐target organisms. However, the level of toxicity to A. salina and T. molitor was not consistent across the selected essential oils.

Lack of prolonged activity of lavender essential oils as acaricides against the poultry red mite (Dermanyssus gallinae) under laboratory conditions

Managing the poultry red mite, Dermanyssusgallinae (De Geer) by conventional means (i.e., synthetic acaricides) has become increasingly problematic. As a possible alternative, research has identified several plant essential oils that are toxic to D. gallinae. However, essential oils are highly volatile and any acaricidal effect they exert could be short-lived in practice. This study investigated the short-lived toxicity of six lavender essential oils to D. gallinae. In sealed Petri-dishes, mites were exposed to filter papers impregnated with essential oil at a concentration of 0.14mg/cm(3). When filter papers were used immediately after impregnation, 66-90% D.gallinae mortality was observed after 24h, depending upon the essential oil used. If impregnated filter papers were left in a fume cupboard for 24h prior to use, mortality rates of D.gallinae fell to 11% or less.

Characterization of the immune response of domestic fowl following immunization with proteins extracted from Dermanyssus gallinae

Dermanyssus gallinae is the most significant ectoparasite of European poultry egg laying production systems due to high costs of control and associated production losses as well as adverse effects on bird welfare. In this study, soluble proteins were extracted from unfed D. gallinae (DGE) using a urea-based detergent and ultra-filtration, passed through a 0.22 microm filter and blended aseptically with adjuvant. One group of laying hens was immunized with DGE and adjuvant (Montanide ISA 50 V) whilst another group (Control) received physiological saline and adjuvant. All birds were immunized on two occasions, 21 days apart. Antibody response to immunization was determined by ELISA and western blotting using immunoglobulins (Igs) extracted from egg yolk. DGE immunization of hens resulted in a significant (P<0.05) IgY response compared to controls, although there was no significant difference in IgM response between treatments. A number of proteins were identified by western blotting using IgY antibodies from DGE immunized birds, most prominently at 40 and 230kDa. Analysis of proteins from approximately corresponding bands on SDS-PAGE confirmed the identity of tropomyosin, whilst other proteins showed high sequence homology with myosin and actin from other arachnid and insect species. Immunization of hens with DGE resulted in a 50.6% increase in mite mortality (P<0.001) 17h after feeding when tested by an in vitro mite feeding model. Data in this study demonstrate that somatic antigens from D. gallinae can be used to stimulate a protective immune response in laying hens. Further work is needed to identify other proteins of interest that could confer higher protection against D. gallinae, as well as optimization of the vaccination and in vitro testing protocol.

Economic evaluation of high welfare indoor farrowing systems for pigs

New livestock housing systems designed to improve animal welfare will only see large-scale commercial adoption if they improve profitability, or are at least cost neutral to the farm business. Economic evaluation of new system developments is therefore essential to determine their effect on cost of production and hence the extent of any market premium necessary to stimulate adoption. This paper describes such an evaluation in relation to high welfare farrowing systems for sows where any potential system needs to reconcile the behavioural needs of the sow with piglet survivability, acceptable capital and running costs, farm practicality and ease of management. In the Defra-sponsored PigSAFE project, a new farrowing system has been developed which comprises a loose, straw-bedded pen with embedded design features which promote piglet survival. Data on this and four other farrowing systems (new systems: 360° Farrower and a Danish pen; existing systems: crate and outdoor paddock) were used to populate a model of production cost taking account of both capital and running costs (feed, labour, bedding etc). Assuming equitable pig performance across all indoor farrowing systems, the model estimated a higher production cost for non-crate systems by 1.6, 1.7 and 3.5%, respectively, for 360° Farrower, Danish and PigSAFE systems on a per-sow basis. The outdoor production system had the lowest production cost. An online survey of pig producers confirmed that, whilst some producers would consider installing a non-crate system, the majority of producers remain cautious about considering alternatives to the farrowing crate. If pig performance in alternative indoor systems could be improved from the crate baseline (eg through reduced piglet mortality, improved weaning weight or sow re-breeding), then the differential cost of production could be reduced. Indeed, with further innovation by pig producers, management of alternative farrowing systems may evolve to a point where there can be improvements in both welfare and pig production. However, larger data sets of alternative systems on commercial farms will be needed to explore fully the welfare/production interface before such a relationship can be confirmed for those pig producers who will be replacing their units in the next ten years.

Validity of the Microsoft Kinect sensor for assessment of normal walking patterns in pigs

Validity of Kinect for assessment of normal walking patterns in pigs was confirmed.Kinect neck elevation trajectories agreed well with a gold standard.The Kinect has potential to be developed into an automated lameness-detection tool. Lameness is a major problem affecting pigs and its detection is subjective and challenging on large farms. Previous research using advanced kinematic gait analysis (Vicon) has established that abnormality in the movement of the axial body during walking is associated with lameness in pigs. Vertical excursion of head and neck was most affected, and increased by +15-58mm in lame compared to normal pigs. However, simpler technology is required to automate lameness detection. In this experiment, walking trajectories of mid-line dorsal body regions of seven normal pigs varying in size were filmed repeatedly within day and between days on two or three occasions within one week. Trajectories were tracked simultaneously using both a 6-camera Vicon system, set up in an array flanking a walkway and detecting reflective markers, and a Microsoft Kinect motion sensor, mounted above the walkway. Four pigs wore a large (height 30mm) reflective marker in the mid-neck region, detectable by both Kinect and Vicon during two days. Two custom-written computer algorithms using the Kinect developer toolkit were produced to (1) follow the large neck marker and (2) enable marker-free tracking of other body regions. Reversed depth data from the Kinect and vertical position data from the Vicon were compared to assess agreement. There was a high positive correlation between the Kinect and Vicon trajectory means of the large neck marker (P<0.001; r=0.994). The Kinect neck marker trajectory mean was generally higher than the Vicon trajectory mean, therefore a positive difference of 4mm?4.2mm (LoA) was noted. There was no pig effect on trajectory differences, but a pig effect on trajectory mean which reflected the size of the pig (P<0.001). The mean?SD of continuous differences between corresponding Kinect and Vicon neck marker trajectories amounted to 5?1.5mm. The mean of vertical displacement amplitudes was 5?2.8mm, and hence the minimum difference of +15mm in lame animals should be detectable in more than 99% of cases. Trajectories of neck, back and pelvis generated by a marker-free Kinect application showed less similarity to corresponding Vicon trajectories. It was concluded that the Kinect device could distinguish sound from lame pigs by tracking neck region elevation during walking; however, markerfree tracking algorithms need refinement and further development to become sensitive and reliable.