David Harrington

Significance and Control of the Poultry Red Mite, Dermanyssus gallinae

The poultry red mite, Dermanyssus gallinae, poses a significant threat to poultry production and hen health in many parts of the world. With D. gallinae increasingly suspected of being a disease vector, and reports indicating that attacks on alternative hosts, including humans, are becoming more common, the economic importance of this pest has increased greatly. As poultry production moves away from conventional cage systems in many parts of the world, D. gallinae is likely to become more abundant and difficult to control. Control remains dominated by the use of synthetic acaricides, although resistance and treatment failure are widely reported. Alternative control measures are emerging from research devoted to D. gallinae and its management. These alternative control measures are beginning to penetrate the market, although many remain at the precommercial stage. This review compiles the expanding body of research on D. gallinae and assesses options for its current and future control. We conclude that significant advances in D. gallinae control are most likely to come through an integrated approach adopting recent research into existing and novel control strategies; this is being combined with improved monitoring and modeling to better inform treatment interventions.

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.

Use of Plant-derived Products to Control Arthropods of Veterinary Importance : A Review

The use of synthetic products in veterinary pest management is becoming increasingly problematic. Issues, including pest resistance, product withdrawal, undesirable environmental persistence, and high mammalian toxicity associated with synthetic pesticides, are driving research to identify new pest management approaches. One approach employs the repellent/toxic effects of plant‐derived products (PDPs). Several pesticides based on PDPs are already available in some areas of pest management. This review highlights instances in which such products have been used with success against pests of domestic animals, livestock, apiculture, and poultry.

The Poultry Red Mite Dermanyssus gallinae as a Potential Carrier of Vector‐borne Diseases

The poultry red mite Dermanyssus gallinae is an obligatory blood‐sucking parasite that is considered to be one of the most important ectoparasites in the poultry industry, mainly because it is responsible for important economic losses, leads to a reduction of welfare of laying hens, and may pose a disease risk to humans. As a result of these problems, much of the current research on this parasite targets new methods of control. Less attention has been paid to the importance of D. gallinae as a carrier of vector‐borne diseases. Some authors have mentioned the possible involvement of D. gallinae in the transmission (both in vitro and directly isolated from the mites) of viral and bacterial agents. Our research group has demonstrated the presence of Mycobacterium spp. within D. gallinae. DNA coding for Mycobacterium spp. was successfully amplified from unfed adult D. gallinae, larvae, and eggs by using reverse transcription‐polymerase chain reaction targeting the 16S rRNA gene. The results have suggested the possible transovarial and transstadial transmission of pathogens by D. gallinae.

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.

Opportunities for integrated pest management to control the poultry red mite, Dermanyssus gallinae

Dermanyssus gallinae is the most economically important ectoparasite of laying hens in Europe. Control of D. gallinae is already hampered by issues of pesticide resistance and product withdrawal. With the prohibition of conventional cages in 2012 and the resulting switch to more structurally complex housing which favours red mite, the importance of managing this pest is expected to increase. Integrated Pest Management (IPM), as often employed in agricultural pest control, may be a way to address these issues where a combination of different novel control methods could be used with/without conventional management techniques to provide a synergistic and more efficacious effect. Work at in our laboratory has shown that essential oils, including thyme and garlic, may act as effective D. gallinae repellents and acaricides, whilst preliminary vaccine studies have demonstrated a significant increase in mite mortality in vitro using concealed antigens. Work elsewhere has considered predators and fungi for D. gallinae control and other husbandry techniques such as manipulating temperature and lighting regimes in poultry units. This paper will review the available and emerging techniques for D. gallinae control and discuss which techniques might be suitable for inclusion in an integrated management programme (e.g. synthetic acaricides and diatomaceous earths).

Immunological control of the poultry red mite

In the current study whole poultry red mite antigens were extracted and birds were immunized subcutaneously with either antigen in adjuvant (antigen group) or PBS in adjuvant (control group). Immune responses of birds following immunization were investigated by ELISA and Western blotting, while vaccine efficacy was assessed by feeding of red mites on birds. Immunized birds showed a significant (P < 0.05) increase in IgY titers after immunization compared to controls, while immunoglobulin A (IgA) and IgM did not change significantly. However, the antigen group had a generally higher increase in all immunoglobulin titers compared to the controls. Western blotting identified a number of protein bands at different molecular weights, although these were not different between treatments. PCR analysis of whole mite protein identified bacterial DNA that might have confounded immunological data. In addition, there was a trend toward reduced survival rate of red mites feeding on antigen‐immunized birds, but the difference was not statistically significant compared to controls. This study demonstrates the potential for somatic red mite antigens to stimulate an antibody‐mediated immune response, although this response did not confer protection to birds.

Characterization of the immunological response to Dermanyssus gallinae infestation in domestic fowl.

Dermanyssus gallinae is a haematophagous ectoparasite of birds, which adversely affects both production and welfare of commercial poultry. Poultry in commercial production systems chronically exposed to D. gallinae do not appear to develop immunity to the mite. The objective of the current study was to determine the initial immune response of domestic fowl following exposure to D. gallinae. Two groups of birds (11 birds/group) had mite chambers secured to their backs. Controls received no mites, while infested birds received 200 unfed female D. gallinae on day 0 which were then removed on day 1 or 2. Spleen samples were collected on days -1, 1, 2 and 5. The expression of Th1 (IFNgamma, CXCLi2, IL6 and IL18), Th2 (IL4, IL10 and IL13) cytokines/chemokines normalized against a reference gene, GAPDH, were determined by semi-quantitative RT-PCR. Although there were no significant differences between treatments, numerical trends were observed. Th2 cytokine expression was not detected in any birds on any day. IL6, CXCLi2, IFNgamma and IL18 expression was increased on day 1 in the infested group, while on day 2 CXCLi2 and IFNgamma were lower and IL6 and IL18 levels were similar between treatments. The IL18 expression was similar between treatments on day 5, while IL6 and IFNgamma levels were increased and CXCLi2 expression was decreased in the infested group. Data suggest that D. gallinae feeding stimulates Th1 and pro-inflammatory cytokines/chemokines initially (day 1) followed by their subsequent down regulation. This study is the first report of the characterization of the immunological response of the domestic fowl to controlled numbers of D. gallinae.

Comparison of synthetic membranes in the development of an in vitro feeding system for Dermanyssus gallinae

Although artificial feeding models for the poultry red mite (Dermanyssus gallinae) most frequently use biological membranes consisting of day-old chick skin, there are ethical considerations associated with the use of skin. The few studies reported in the literature that have investigated the use of synthetic membranes to feed D. gallinae in vitro have reported limited success. The current study describes an investigation into the use of synthetic membranes made from either Nescofilm or rayon and silicone, used either alone or in combination with different feather or skin extracts, as well as the use of capillary tubes. In all, 12 different treatments were used, and the feeding rate of D. gallinae was compared to that of day-old chick skin. Allowing mites to feed on a membrane consisting of Nescofilm with a skin extract resulted in the highest proportion of mites feeding (32.3%), which was not significantly different to the feeding rate of mites on day-old chick skin (38.8%). This study confirms that synthetic membranes can be used to feed D. gallinae artificially. Further optimization of the membrane and mite storage conditions is still necessary, but the study demonstrates a proof of concept.

Immune cellular response to Dermanyssus infestation in poultry birds

CD200 is a cell-surface glycoprotein that is normally expressed in tissues of the immune system, where its role is to protect immune privileged sites. We previously established CD200 to be frequently over-expressed and associated with poor AML patient outcome. In this study, we investigated the possibility that CD200 expression may mediate suppression of T-cell function in this disease. Using multiparameter flow cytometry, we compared PMA/ionomycin stimulated CD8+ T-cell cytotoxic potential (CD107a expression) and the frequency of intracellular TNFa, IL-2 and IFNc producing CD4+/CD8+ memory T-cells between CD200hi and CD200lo patients. We demonstrated that both the magnitude of the CD8+ memory cytotoxic T-cell response and the Th1 cytokine producing CD4+ memory helper T-cells was significantly inhibited in CD200hi AML patients (P < 0.05). Further, using ELISPOT assays to measure IFNg release we showed that the Th1 memory response to common viral antigens was significantly reduced by 75% in CD200hi versus CD200lo AML patients(P < 0.05). Recovery of IFNc release in response to recall antigens was observed in CD4+ memory T-cells incubated with a blocking antibody to CD200R. In conclusion, this study shows a correlation between T-cell dysfunction and expression of CD200 which suggests targeting this axis could be therapeutically beneficial for AML CD200hi patients.