Abstract
The present research work was carried out to isolate and identify Newcastle disease virus (NDV) by using haemagglutination inhibition (HI) test and HA-HI virus isolation, embryonated eggs (EE) and chicken embryo fibroblasts (CEF). A total of 95 clinical (blood, tracheal and cloacal swabs) and post-mortem (brain, lung, colon and spleen) samples were collected from chickens of field outbreaks of suspected Newcastle disease virus (NDV). The HI and HA-HI were employed to detect NDV in tissue homogenates of all the clinical and post-mortem samples as well as laboratory samples (AF and ICF). Among the four different types of post-mortem samples, virus isolation rate was found to be low in body organs. In CEF cell culture system, the rate of virus isolation from all the aforesaid samples was found to be at 100% with the exception of serum samples; while in tracheal and cloacal swabs, it was at 90%; while in serum, it was at 10%, in all clinical cases. The isolation rate of NDV was higher in CEF culture system (66.7%) compared to that of avian embryos (33.3%). Samples were inoculated and the allantoic fluid (AF) of the dead embryos and the infected culture fluid (ICF) of the CEF were harvested at 24 to 96 hours of the post-infection, respectively, which revealed that the virulent strain of NDV is highly prevalent in the region. The prevalence of NDV was established at 1.1%, 2.1% and 4.2% using HA-HI, EE, and CEF methods. Rapid detection and identification of the virus are crucial for the effective control of the disease as conventional diagnostic methods such as virus isolation on embryonated eggs followed by serological identification in haemagglutination-inhibition test are laborious and time-consuming. The speed of the diagnosis can be considerably increased by using methods based on molecular biology, e.g. reverse transcription—polymerase chain reaction. However, the genetic variability of APMV-1 isolates should be considered carefully as the potential cause for false negative results of genetic-based laboratory tests.
Highlights
Newcastle disease virus (NDV), known as avian pneumoencephalitis, is an important production disease of poultry having a serious impact on national and international markets worldwide
The farmers came from central Uganda (Kampala, Mukono, Kayunga, Kiboga, Mpigi, Wakiso, Rakai and Kyankwanzi districts) and all chicken presented was screened for virus shadding and antibody titers by use of the HA-haemagglutination inhibition (HI) tests followed by virus isolation from the tissues using 11-day-old chick embryonated eggs and chicken embryonated fibroblasts (CEF)
Clinical cases were submitted to the central diagnostic laboratory (CDL) from which postmortem (PM) chicken samples were collected for ND virus isolation whenever judged appropriate by the pathologists CoVAB
Summary
Newcastle disease virus (NDV), known as avian pneumoencephalitis, is an important production disease of poultry having a serious impact on national and international markets worldwide. Cause a severe respiratory and neurologic disease in poultry worldwide and naturally occurring avirulent NDV strains have been successfully used as vaccines for more than 70 years [1]. A prospective study of risk factors associated with outbreaks of Newcastle disease (ND) in indigenous freerange chickens was carried out in three agro-ecological zones in eastern Uganda. Multivariate survival analyses were performed to identify the risk factors for Newcastle disease outbreaks. Purchasing of restocking chickens [11] from the market and neighborhood (hazard ratio [HR] = 1.79; 95% confidence interval [CI] 0.89 - 3.60), the presence of migratory wild birds (HR = 1.70; 95% CI 0.65 - 4.48) and being in agro-ecological zone 1 (HR = 1.48; 95% CI 0.66 - 3.36) showed a positive but non-significant association with risk for ND [11]. The benefits and adaptability of these poultry health interventions are discussed in view of the rural poultry management system in Uganda [12]
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