Introduction: Newcastle disease virus (NDV) cultures held in the isolate collections in Ethiopia between 1976 and 2008 were not characterized using biological and molecular techniques. The already characterized NDV isolates belonged to genotype VI but the genetic nature of previously collected isolates, which could shade light on the history of introduction into the country and their evolutionary relationships, were not established. Methods: A total of 14 NDVs (11 obtained from outbreak cases in chickens and three commercial vaccinal strains used in the country) were inoculated into specific pathogen free (SPF) embryonated chicken eggs (ECE). Allantoic fluids harvested from grown SPF ECE were tested by heamagglutination (HA) and heamagglutination inhibition (HI) tests. Partial F gene sequences were generated for all samples and molecular evolutionary relationships were reconstructed together with reference sequences freely available online. The pathogenicities of the isolates were assessed in vivo by determining their intracerebral pathogenicity index (ICPI) in day-old chicks and molecularly by determination of F gene cleavage sites. Results: Of these, 12 viruses (two vaccines and 10 outbreaks) were successfully propagated as evidenced by a positive heamagglutination (HA) test. These 12 propagated viruses were further characterized by heamagglutination inhibition (HI) test, of which only three viruses reacted with monoclonal antibody (MAb 617/616) specific for pigeon paramyxovirus-1. In addition, all 14 viruses were characterized by partial fusion (F) gene sequencing and phylogenetic tree reconstruction. The Ethiopian NDV isolates clustered with genotype VI viruses, forming two clades (groups 1 and 2) that have ancestral relationships with Egypt-1990 and Sudan-1975 like viruses. Discussion: The characterized genotype VI NDVs were genetically similar to currently circulating NDVs in Ethiopia. The isolates had cleavage sites consistent with mesogenic/velogenic NDV with a mean ICPI value of 1.76, indicating that the isolates were velogenic. Two and four highly virulent viruses were thermostable at 56°C for 2 hours and 1 hour, respectively. To reduce chicken mortality and production losses, proper control of the disease should be instituted using high quality and protective vaccines together with strong biosecurity measures.

Introduction: Infectious bursal disease virus (IBDV) is an avian viral pathogen that causes infectious bursal disease (IBD) of chickens. The disease has been endemic in Ethiopia since 2002, and vaccination has been practiced as the major means of disease prevention and control. An IBD vaccine is produced in Ethiopia using primary chicken embryo fibroblast (CEF) cell, which is time-consuming, laborious, and uneconomical. The present study was carried out to develop cell-based IBDV LC-75 vaccine using Vero cells and to evaluate the safety, immunogenicity and protection level. Methods: Identity of the vaccine seed was confirmed with gene-specific primers using reverse transcription polymerase chain reaction (RT-PCR). Confluent monolayer of Vero cells was infected with vaccine virus and serial passage continued till passage 10. A characteristic virus-induced cytopathic effect (CPE) was observed starting from passage 2 on the third day post-infection. The infectious titer of adapted virus showed a linear increment along the passage level. The virus-induced specific antibody was determined using indirect ELISA after vaccination of chicks through ocular route. Results: The antibody titer measured from Vero cells vaccinated chicks revealed similar level with the currently available CEF cell-based vaccine, hence no significant difference. Chicks vaccinated with Vero cell adapted virus showed complete protection against very virulent IBDV, while unvaccinated group had 60% morbidity and 25% mortality. Conclusion: It is concluded that the IBDV vaccine strain well adapted on Vero cells and found to be immunogenic induces antibody development and successfully protects chicks against challenge with the circulating field IBDV isolate. Hence, it is recommended to produce IBD vaccine using Vero cell culture at the industrial scale to conquer the limitations caused by using CEF cells and thus to vaccinate chicks population to protect against the circulating IBDV infection.

Introduction: In 2017 infectious bursal disease viruses (IBDVs) were reclassified into genogroups based on nature of clustering on a phylogenetic tree constructed using VP2 gene sequence data rather than according to their pathotype and/or antigenic types. Ethiopian IBD viruses were not reclassified according to the proposed genogrouping. Methods: In order to genogroup the Ethiopian IBDVs, available VP2 gene sequences data together with reference strain sequences were retrieved from GenBank and genogrouped as recently recommended based on evolutionary tree reconstruction and determination of their clustering on the phylogenetic tree. Results: The Ethiopian IBDVs were grouped into genogroups 1 and 3 that antigenically represent classically virulent and very virulent IBDVs, respectively. The genogroup 1 IBDVs were clustered with the vaccine strain while the genogroup 3 viruses were clustered with four known viruses belonging to sub-genogroup 3a and sub-genogroup 3b. Almost half of the Ethiopian IBDVs reported did not cluster with the specific sub-groups of genogroup 3; rather, the isolates were clustered differently suggesting they deserve a different sub-genogroup tentatively proposed as 3d. The two genogroups observed based on clustering on a phylogenetic tree were supported by corresponding deduced amino acid changes in similar positions in VP2 sequences. In addition, virulence marker amino acid genes coupled with second major hydrophilic region (amino acid positions 314– 325) were predicted in these sequences that could be responsible for the occurrence of IBD outbreaks. Conclusion: A new sub-genogroup of IBDVs, 3d, were observed in the sequences that could be one of the reasons for the frequent occurrence of IBD outbreaks and questions the protective potential of the existing vaccine. To institute disease control in the country, the effectiveness of the vaccine in use needs to be assessed in vivo against both genogroups 1 and 3 viruses and all three sub-genogroup 3 viruses circulating in the country.

Peste des Petits Ruminants (PPR) is a severe, contagious, and transboundary viral disease of goats, sheep, camels, and wild small ruminants in more than 70 countries, including Ethiopia. Hence, a cross-sectional study was conducted from September 2023 to June 2024 to assess the seroprevalence of PPR and investigate risk factors of the disease in the West Arsi and West Hararghe zones. A total of 751 serum samples were collected from 398 goats and 353 sheep of 422 flocks found in six districts of the two zones that had not a history of PPR vaccination. A hemagglutinin-based blocking enzyme-linked immunosorbent assay was used to test the serum for antibodies against PPR. A structured questionnaire survey was used to determine potential risk factors of the disease. The overall PPR seroprevalence in the West Arsi and West Hararghe zones was 9.7% at the flock level (95% CI: 7.1-12.9) and 5.9% at the animal level (95% CI: 4.4-7.8). At the species level, the seroprevalence of PPR was found to be 5.3% in goats (95% CI: 3.5-8.0) and 6.5% in sheep (95% CI: 4.4-9.6). Multivariable logistic regression analysis indicated that a geographic zone was a significant predictor of PPR infection in goats and at the flock level. Flocks in the West Hararghe Zone were 4.5 times more likely to be seropositive than those in West Arsi (95% CI: 2.0-9.8, p < 0.001). Age was a significant predictor of PPR exposure in both goats and sheep, whereas altitude was specifically a risk factor in sheep. The present study findings indicate a generally low PPR seroprevalence in both goats and sheep in the study areas. However, the disease was present in 20 out of the 26 kebeles (wards) surveyed, showing ongoing circulation. Therefore, vaccination campaigns should be expanded to cover both zones, with emphasis on West Hararghe. A further study is recommended to identify the influence of agroecology on PPR persistence and transmission.

An outbreak investigation of camelpox in dromedary camels (Camelus dromedarius) was conducted from October 2024 to May 2025 in Borena Zone, Ethiopia, with the aims of isolating, confirming the etiology and molecular characterization of camelpox virus from outbreak cases. The study integrated clinical assessment, virus isolation using Vero cell lines, and molecular characterization using conventional PCR, real-time PCR, sequencing and phylogenetic analysis. Clinically affected camels manifested typical pox-like lesions, fever and swollen lymph nodes, with a morbidity rate of 33.8% (24/71) and a case fatality rate of 4.2% (1/24). The virus was successfully isolated showing typical cytopathic effects of rounding of cells, syncytia, giant cell formation, aggregation and detachment. Conventional PCR targeting A-type inclusion protein (ATIP) gene amplified the expected 881 bp fragment with 26.3% positivity in both skin scab and nasal swab samples. Real-time PCR employing high-resolution melting curve analysis detected the viral DNA in 52.6% of samples with a melting temperature of 73.00 ± 0.20 °C for CMPV. Sequencing of the ATIP gene showed 100% nucleotide similarity with reference CMPV strains of CMPV M-96, CMPV CMS, strain 0408151v and CMPV genome (NC_003391), although a single nucleotide variation was noted when compared to the previously reported Ethiopian isolates (KU705085-KU705110) and Israeli isolates (MK910851 and MZ300856), and two nucleotide mismatches were observed with Sudanese isolates (KT931624 and KT931625). Phylogenetic analysis revealed that the current isolates clustered with CMPV strains of CMPV M-96, CMPV CMS, strain 0408151v and others but were distinct from previously reported Ethiopian isolates. This study provides significant insights on early diagnosis and control strategies.