RESUMEN
The accurate and early diagnosis of rabies is critical for undertaking public health measures in animals. The aim of the current study was to identify the molecular characterization of the circulating rabies virus (RABV) among camels (Camelus dromedaries) in Oman and to evaluate the efficacy of the histopathology and reverse transcription polymerase chain reaction (RT-PCR) as diagnostic tools of acute rabies encephalitis in camels in comparison with direct fluorescent antibody test (dFAT). Of the forty-five brain samples from suspected camels submitted to the Animal Health Research Center in Oman (2009-2013), 22 cases were positive by dFAT and RT-PCR. Two positive samples were subjected for N gene nucleotide sequencing and phylogenetic analysis (accession numbers GU353156 and KC883998 for brain samples collected in 2009 and 2011, respectively). The specificity and sensitivity of histopathology were 100% and 81%, respectively, while in RT-PCR were 100% and 100%, respectively. The neuropathological changes were presence of intracytoplasmic inclusions (Negri bodies) in the pyramidal neurons of the hippocampus beside prominent cerebral and cerebellar congestion and hemorrhage. Neuronal necrosis with satellitosis and neuronophagia were also noticed in the cerebrum of affected brains. Conclusively, there was one genetic group of RABV with 99% homology circulating in Omani camels. Also, it is concluded that histopathological examination is a safe and reliable diagnostic tool when only formalin-fixed and paraffin-embedded material is available, but the negative results should be reaffirmed by dFAT or RT-PCR.
Asunto(s)
Camelus , Virus de la Rabia/genética , Rabia/veterinaria , Animales , Omán , Filogenia , Rabia/diagnóstico , Rabia/prevención & control , Estudios Retrospectivos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/veterinariaRESUMEN
A low pathogenic avian influenza virus was identified from free-living birds (mynah, Acridotheres tristis) of the starling family. Virus was isolated by inoculation of homogenized suspension from lung, tracheal, spleen, and cloacal swabs into the allantoic cavity of embryonated chicken eggs. Subtype of the isolate was characterized as H9N2 by hemagglutination inhibition test using monospecific chicken antisera to a wide range of influenza reference strain. Pathogenicity of the isolate was determined by intravenous pathogenicity index. The virus was reisolated from experimentally infected chicken. Additionally, the isolate was subjected to reverse transcriptase PCR using partial hemagglutinin (HA) gene-specific primers and yielded an amplicon of 487 bp. HA gene sequence analysis revealed 99% sequence homology among mynah and chicken isolates from Oman. On phylogenetic analysis, isolates from mynah (A/mynnah/Oman/AIVS6/2005) and chicken (A/chicken/Oman/AIVS3/2006; A/chicken/Oman/AIVS7/2006) clustered together tightly, indicating these free-flying birds may be a source of introduction of H9N2 subtype in poultry bird in Oman. Moreover, the HA gene of H9N2 isolates from Oman resembled those of viruses of the G1-like lineage and were very similar to those from United Arab Emirates.