RESUMEN
The brown dog tick or Rhipicephalus sanguineus sensu lato is an ixodid tick, responsible for the dissemination of pathogens that cause canine infectious diseases besides inflicting the direct effects of tick bite. The hot humid climate of Kerala, a south Indian state, is favorable for propagation of tick vectors and acaricides are the main stay of tick control. Though the resistance against synthetic pyrethroids is reported among these species, the status of amitraz resistance in R. sanguineus s. l. in the country is uncertain due to the lack of molecular characterisation data and scarce literature reports. Hence the present study was focused on the phenotypic detection and preliminary genotypic characterisation of amitraz resistance in the R. sanguineus s. l. A modified larval packet test (LPT) on a susceptible isolate was performed to determine the discriminating dose (DD). Further LPT-DD on 35 tick isolates was carried out to detect amitraz resistance robustly, along with that full dose response bioassays on the resistant isolates were performed. The results indicated that amitraz resistance is prevalent with 49 per cent of the samples being resistant. Amplification of exon 3 of octopamine receptor gene from both the susceptible and resistant larval isolates was carried out. Amplicons of ten pooled amitraz susceptible and ten pooled amitraz resistant representative samples were sequenced and analysed, unveiling a total of three novel non-synonymous mutations in the partial coding region at positions V32A, N41D and V58I in phenotypically resistant larval DNA samples. In silico analysis by homology modelling and molecular docking of the mutated and unmutated receptors showed that these mutations had reduced the binding affinity to amitraz. However, lack of mutations in the octopamine receptor gene in three of the pooled low order resistant R. sanguineus s. l. larval samples could be suggestive of other mechanisms associated with amitraz resistance in the region. Hence, further association studies should be carried out to confirm the association of these mutations with target insensitivity in R. sanguineus s. l. ticks, along with exploring the status of metabolic resistance and other mechanisms of resistance.
Asunto(s)
Acaricidas , Receptores de Amina Biogénica , Rhipicephalus sanguineus , Toluidinas , Animales , Toluidinas/farmacología , Receptores de Amina Biogénica/genética , India , Rhipicephalus sanguineus/genética , Rhipicephalus sanguineus/efectos de los fármacos , Acaricidas/farmacología , Larva/genética , Larva/efectos de los fármacos , Resistencia a los Insecticidas/genética , Polimorfismo Genético , Genotipo , Perros , Femenino , Enfermedades de los Perros/parasitología , Simulación del Acoplamiento Molecular , Secuencia de Aminoácidos , BioensayoRESUMEN
Tanycytic ependymoma is an uncommon but well-recognized variant of ependymoma. Here we report a case of tanycytic ependymoma occurring at the region of filum terminale in a 44-year male who presented with low backache, bilateral lower limb weakness and urinary incontinence. MR imaging in this patient showed a lesion that was composed of solid and cystic components and was suggestive of ependymoma. The filum terminale region is an extremely unusual location for the occurrence of tanycytic ependymoma. To the best of our knowledge this is the third case of tanycytic ependymoma occurring in the filum terminale region.