Abstract
Background Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide. It infests the hens during the night where it causes irritation leading to restlessness, pecking and in extreme cases anaemia and increased cannibalism. Due to an increase in the occurrence of acaricide-resistant D. gallinae populations, new control strategies are required and vaccination may offer a sustainable alternative to acaricides. In this study, recombinant forms of D. gallinae tropomyosin (Der g 10) and paramyosin (Der g 11) were produced, characterised and tested as vaccine candidate molecules.MethodsThe D. gallinae paramyosin (Der g 11) coding sequence was characterised and recombinant versions of Der g 11 and D. gallinae tropomyosin (Der g 10) were produced. Hens were immunised with the recombinant proteins and the resulting antibodies were fed to D. gallinae and mite mortality evaluated. Sections of mites were probed with anti- Der g 11 and Der g 10 antibodies to identify the tissue distribution of these protein in D. gallinae. ResultsThe entire coding sequence of Der g 11 was 2,622 bp encoding 874 amino acid residues. Immunohistochemical staining of mite sections revealed that Der g 10 and Der g 11 were located throughout D. gallinae tissues. In phylogenetic analyses of these proteins both clustered with orthologues from tick species rather than with orthologues from astigmatid mites. Antibodies raised in hens against recombinant forms of these proteins significantly increased D. gallinae mortality, by 19 % for Der g 10 (P < 0.001) and by 23 % for Der g 11 (P = 0.009) when fed to the mites using an in vitro feeding device.ConclusionsThis study has shown that Der g 10 and Der g 11 were located ubiquitously throughout D. gallinae and that antibodies raised against recombinant versions of these proteins can be used to significantly increase D. gallinae mortality in an in vitro feeding assay. When comparing archived data for all recombinant and native proteins assessed as vaccines using this in vitro feeding assay, Der g 10 and Der g 11 ranked highly and performed better than some of the pools of native proteins.
Highlights
Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide
The sequence with highest homology to Der g 11 was from another member of the order Mesostigmata, M. occidentalis with an amino acid identity of 95 %
The predicted protein, Der g 11, had homologues in the tick species R. microplus, H. longicornis and Ixodes scapularis, with amino acid identities of 84, 84 and 82 %, respectively whereas the amino acid identities of Der g 11 with the orthologous proteins from astigmatid mites were lower at 76 % for Sarcoptes scabiei and 75 % for P. ovis (Fig. 1)
Summary
Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide It infests the hens during the night where it causes irritation leading to restlessness, pecking and in extreme cases anaemia and increased cannibalism. The poultry red mite (PRM), Dermanyssus gallinae (De Geer), is a blood-feeding ectoparasite that infests many bird species From both an economic and welfare perspective, PRM is the most important ectoparasite affecting egg-laying hens worldwide [1, 2]. In 2005 it was estimated that €130 million was lost annually due to PRM in Europe [3] and it is likely that losses far exceed that level These mites reside in crevices of the furniture and machinery in the poultry house and emerge in darkness to feed, for short periods of time, on the blood of hens [4, 5]. Several alternative methods of control are available or are in development, for example plant or fungal extracts, essential oils and vaccination [8]
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