Studies Of COⅠ Gene Of Rhinoestrus Sp.(Diptera: Oestridae) And Immunology On The Horse Nasal-myiasis Fly,from Mongolian Horse

Rhinoestrus sp.(Diptera: Oestridae)is one kind of parasite in pathogen in horse.The reindeer infected nasal cavity,sinuses,pharyngeal mucosa and adjacent cavities in equids that causes injure and inflammatory reactions at the site of parasites and can causes weight loss and poor disease resistance in horses,leading to decreased production performance of horses.At present,there are relatively few studies on horse nasal-myiasis fly,therefore,this study investigated the pathogenic species and changes in the body after infection,provide data for the prevention and treatment of parasitic diseases.1.The study of the ultrastructure of Rhinoestrus.larval instars from Mongolian horse was examined by light and scanning electron microscopy.The cephalopharyngeal skeleton of Rhinoestrus sp.from Mongolian horse at immature stages was composed of “H”-shaped hypopharyngeal sclerites and “Y”-shaped pharyngeal sclerites.The posterior spiracular discs had incomplete peritremes.A row of spines was observed adjacent to the posterior spiracular discs in the first and second instars,and there were more spines in the third instar.Pairs of papillary sensillae in the cephalic region maintained the same number and location in all three instars,but the third instar additionally included two pairs of verruciform sensillae.2.The study of molecular characteristics of Rhinoestrus sp.larval instars from Mongolian horse by polymerase chain reaction(PCR).Partial sequencing of the mitochondrial cytochrome oxidase subunit I(COⅠ)gene was performed.With MEGA6 and Clustalx to achieve Phylogenetic relationships for Rhinoestrus sp.from Mongolian horse were reconstructed based on COⅠ gene from oestrid species available in GenBank,and inter-and intraspecies variations in nucleotide sequences were analyzed.COⅠ sequences of Rhinoestrus sp.larvae collected from Mongolian horses were collected with Rhinoestrus but separated from R.phacochoeri and R.usbekistanicus.3.The immunohistochemical examination from Mongolian horses infected with Rhinoestrus sp.in pharyngeal samples,retropharyngeal lymph node samples,guttural pouch samples tonsil samples,oral mucosa samples,ocular mucosa samples.Immunohistochemical results showed that Cellular counts showed significant differences(p <0.001)in the number of T and B lymphocytes and macrophages in the,tonsil and retropharyngeal lymph nodes between the groups of infected and control horses.Cellular counts showed differences(p < 0.01)in the number of overall T and B lymphocytes and macrophages in pharynx and guttural pouch,between the groups of infected and control horses.The immunohistochemical results suggest that antigens and enzymes excreted or secreted by the larvae into the mucosa induced the pathogenesis of Rhinoestrus sp.infection.The local inflammatory infiltrate contributed significantly to the production of antibodies,and cellular response occurred to isolate and destroy the larvae.Increased numbers of T and B lymphocytes in infected horses indicated the development of adaptive immunity and the production of specific anti-Rhinoestrus sp.immunoglobulins.Increased numbers of macrophages suggest that macrophages were important in antigen presentation to T helper lymphocytes.In conclusion,our COⅠ sequence analyses demonstrate that all samples greatly resembled Rhinoestrus purpureus but were not Rhinoestrus purpureus.The Rhinoestrus sp.from Mongolian horse maybe a new species.Immunohistochemical results showed that the presence of larvae induced a profound local recruitment of T and B lymphocytes and macrophages in the pharynx,retropharyngeal lymph nodes,guttural pouch,tonsil.