Isolation and Molecular Detection of Newcastle Disease Virus From Outbreak Cases in Selected Areas of Northern and Western Oromia, Ethiopia

Newcastle disease (ND) is a commonly fatal viral disease that has been reported to affect a wide range of avian hosts, irrespective of their age and sex. It is reported to be a major constraint to the development, survival, and productivity of poultry in Ethiopia. Despite its significant effect, limited studies were conducted regarding the current situation of ND in different parts of Ethiopia, particularly in the Western Oromia region. Thus, an outbreak-based study was carried out from November 2020 to June 2021 in selected areas of northern and western Oromia with the aim of virus isolation and molecular detection from Newcastle disease suspected outbreak cases in chickens. A total of 98 samples (77 swabs and 21 pooled postmortem tissues) were purposively collected from clinically suspected chickens and examined for the presence of NDV by a one-step real-time polymerase chain reaction (real-time RT-PCR) test targeting a conserved region of the Matrix gene. From the clinical samples tested based on the one-step real-time RT-PCR, 25 (25/98) samples were positive for the NDV. From these, 22 of the positive samples were obtained from swabs, and the other 3 positive samples were from pooled postmortem tissue samples. Furthermore, among the 22 positive swab samples, 14 of the positive samples were of tracheal origin. ND-positive samples were further subjected to cell culture for isolation of the NDV. All 25 real-time RT-PCR-positive samples were inoculated into DF-1 cells for virus isolation, of which 18 of them were able to show CPE on the cell line. The other seven samples remained negative up to the third passage. Regular vaccination with further genetic analysis of the virus should be carried out to understand the specific genotype of the virus.