Antibody responses to La Sota strain vaccines of Newcastle disease virus in ostriches (Struthio camelus) as detected by enzyme-linked immunosorbent assay

Because of the fact that South Africa is a Newcastle disease virus (NDV)-en demic country, major concerns exist that the export of ostrich meat could t ransmit velogenic strains of this disease. The ability to transmit the viru s could be reduced by effective vaccination of South African ostriches. In this study, two vaccination trials were conducted to assess serum antibody production in response to vaccination with La Sota strain NDV vaccines. To this end, a commercially available chicken anti-NDV enzyme-linked immunosor bent assay (ELISA) was modified fur the detection of anti-NDV antibodies in ostrich serum. The results obtained with this ELISA were verified by compa rison with an indirect ELISA. In the first trial, ostriches were immunized subcutaneously four times with different volumes of an inactivated vaccine and their immune response was determined from 2.5 mo up to the ideal slaugh ter age of 14 mo. Results indicated that ostriches responded in a dose-depe ndent manner and gave support for the vaccination schedule currently recomm ended to South African farmers. In a second trial, immunization by eyedrop with a live La Sota vaccine of 5-wk-old ostriches did not elicit a humoral immune response. The results indicate that it is highly unlikely that ostri ches that have been vaccinated according to the recommended vaccination sch edule can transmit the virus.