Since 2002, the South African poultry industry has experienced outbreaks of Newcastle disease (ND) caused by a newly introduced virus (NDV) strain belonging to lineage 5d/VIId (“goose paramyxovirus” - GPMV). Control of the disease has proved difficult with commercially available vaccines appearing ineffective. In the first of two studies, broilers chicks were vaccinated with VG-GA vaccine (lineage II), then challenged with both GPMV and a “classic” challenge virus (RCV) of lineage 3d/VIII to compare the efficacy of the vaccine against both strains. In the second study, commercial and SPF hens in lay were vaccinated with La Sota vaccine and challenged with GPMV isolate, and immunohistochemistry staining used to determine the distribution pattern of viral antigen in the oviduct of the hens. The second study also compared the efficacy of cloacal and ocular routes of vaccination. The first study did not detect any statistically significant difference in protection offered by the vaccine against the GPMV strain in comparison to the RCV strain. The protection offered by the vaccine against challenge with both viruses was found to be dosedependant with 106.0 EID50 producing a 100% protection and 94.44% and 13.89% for 104.5 EID50 and 103.0 EID50 vaccination doses respectively. Protected birds did not manifest clinical signs, but still had macropathological lesions in some organs at necropsy. The computed protective doses (PD50 and PD90) for the VG-GA vaccine were 103.51 and 104.38 for GPMV and 103.79 and 104.43 for RCV. Results from the second study showed no clear difference in the protection of the oviduct from challenge with GPMV by either the cloacal and ocular routes of vaccination. Vaccinated birds were fully protected (100%) against challenge by La Sota vaccine, but not against infection and replication of the virus, as birds showed varying degrees of macropathology with numerous stained viral antigens in the oviducts demonstrated by immunohistochemistry. The susceptibility and colonisation of the oviduct of laying hens by both the lentogenic La Sota and the virulent NDV isolates was confirmed, with the uterus being more susceptible than magnum and isthmus. Necrosis and apoptosis of cells of the oviduct were not detected but cellular infiltration, gland dilatation and interstitial oedema were observed. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2009. / Production Animal Studies / unrestricted

The specific objectives of this study were to determine the Newcastle disease virus (NDV) antibody titres from the chicken sera collected from various districts and provinces of Zambia and to determine the seroprevalence of ND in Zambian backyard chickens. Results showed that 73.9 % of the birds sampled tested positive for Newcastle disease (ND) antibodies. The seroprevalence of Newcastle disease virus (NDV) in Zambian backyard chicken flocks varied among the five provinces sampled, ranging from 82.6 % in Eastern Province to 48.3 % in Luapula Province. The seroprevalence of the virus also varied among the 11 districts sampled, ranging from 91.3 % in Monze District of Southern Province to 22.8 % in Mufulira District of the Copperbelt Province. The results indicated that the seroprevalence of ND in Zambia has increased since the last survey conducted in 1994. The data generated is expected to contribute towards a more clear understanding of the epidemiology of NDV that would ultimately contribute towards an improved ND control programme to benefit all stakeholders in Zambia. An improved ND control programme is expected to enhance flock numbers and ultimately improve the dietary requirements and income needs of many poor households in the country. / Dissertation (MSc)--University of Pretoria, 2012. / Veterinary Tropical Diseases / unrestricted