Authors

D Price¹; T Kuester³; A J Nisbet¹; O Oines²; D P Blake³; F Tomley³;  ¹ Moredun Research institute;  ² Norwegian Veterinary Institute, Norway;  ³ Royal Veterinary College

Discussion

Dermanyssus gallinae is the most important ectoparasite affecting egg-laying chickens. Infested birds may suffer from anaemia, dermatitis, weight loss and decreased egg production. The scarcity of effective pesticides has contributed to a significant problem for the layer industry. Commercially available acaricides are not effective in the control of poultry red mite infestations due in part to increased parasite resistance. Additionally, acaricide use is gradually being discontinued as a consequence of public awareness and legislation against chemical residues on food products, and chemical release and accumulation in the environment. The development of an effective vaccine can decrease the occurrence and impact of D. gallinae, thereby improving the general health and welfare of layers without the use of acaricides.
Currently, prototype vaccines against D. gallinae have been delivered intramuscularly using adjuvants designed to produce high circulating IgG against the co-delivered antigen in mammals. Longevity of protection is particularly salient in the egg-laying sector where protection would need to be effective throughout a full laying cycle (ca. 1 year) following vaccination of immature birds.
Transfection vectors have been developed for genetic complementation of Eimeria tenella, prompting the notion that live-attenuated coccidial parasites could be used as effective vectors for the oral delivery of heterologous vaccine antigens to poultry. In cooperation with two PARAGONE partners - Norwegian Veterinary Institute and Moredun Research Institute - we propose to compare the delivery of a defined prototype D. gallinae antigen (cathepsin D1) in three systems, namely DNA vaccination, recombinant protein formulation in montanide and cytosolic, secreted, or membrane-tethered antigen expressed by the Eimeria vector. The immune responses, efficacy, and endurance of the effect of vaccination are being currently investigated.