| Psoroptic mange is a chronic, intractable, contagious and infectious disease caused by Psoroptes which survive on the skins of mammals and fed with the body fluids, lymph and exudate of the hosts. The common clinical symptoms include extreme itch, scab, depilation and pachyderma and then lead to emaciation or death caused by secondary infection as feeding and rest are influenced. To date, the control strategies are mainly based on chemical pharmacotherapy. Selection of various drugs and doses according to the route of administration and endemic tolerance is the key to the method. But its inevitable disadvantages such as expensiveness, resistance and drug residue are emerging. Therefore, novel control methods are required, for example plant extract, biological acaricide and vaccination. Vaccine which represents one of the most promising candidates is the hardest and least developed, and it is also the focus of the scholars all over the world in recent years. At present, diagnosis of P. cuniculi is currently based on conventional clinical methods that possess numerous disadvantages, including their failure to diagnose sub-clinical infections and time-consuming. Hence, alternative measures are required, and dot-ELISA is one of the most promising strategies.First, we cloned and expressed the recombinant P. cuniculi actin gene (rPc-act). Antiserum levels against rPc-act in rabbits were used to locate actin distribution in mite sections. Challenge trials were carried out to evaluate the immunity protection of rPc-act in rabbits, with antibody levels determined by ELISA. Sequence analysis of this gene fragment showed 89.26% and 84.91% identity to Sarcoptes scabiei and Mayetiola destructor sequences, respectively. Immunohistochemistry showed rPc-act to locate widely throughout the mites, especially in feet and muscle tissues. Recombinant P.cuniculi actin with QuliA adjuvant was used to immunize six rabbits. Each animal was challenge-infested with 25-50 adult mites. Although IgE levels showed no significant difference to controls, IgG levels were significantly higher, and clinical development showed no significantly different severity of lesions in vaccinated rabbits than in the controls. This study showed that rPc-act is a muscular isotype actin and has no clinical protective efficacy against P. cuniculi. The results still remain valuable for further investigations, which may concentrate on the development of optimal applications of allergens or immunogens as vaccines to prevent P. cuniculi infection.Second, we cloned and expressed the recombinant P. cuniculi troponin C gene for use as a basis for novel dot-ELISA assay to detect P. cuniculi infections in rabbits. Results showed that this novel assay had more than 90% sensitivity but low specificity in distinguishing infections with P. cuniculi or Sarcoptic scabiei, despite very high agreement between observers (97% to 99%; Kappa values ranged from 0.95 to 0.98 for inter- and intra-observer variability test). Hence, this study showed that this novel method, at present, lacks diagnostic utility. Nevertheless, we suggest that with further refinement, this dot-ELISA assay based on troponin C will offer a promising way forward for rapid, inexpensive field diagnosis of mite infestations. |
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