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Eco-epidemiology and pathogenesis of Newcastle disease in ostriches (Struthio camelus)

SUMMARY The first documented outbreaks of Newcastle disease virus (NDV) in ostriches were reported in zoo birds in the 1950s. Newcastle disease (ND) causes economic losses in the form of morbidity and mortality as well as expenses incurred for vaccination, diagnosis and disease treatment. Avian paramyxovirus type 1 causes lethal disease in ostriches with morbidity and mortality >50% and 80–85%, respectively. The most vulnerable age of ostriches for ND infection is 3–6 months. Symptoms include facial oedema and persistent nervous behaviour, followed by death. Adoption of best biosecurity measures, vaccination of chicks and monitoring antibody titres at regular intervals can reduce ND incidence significantly. It has been proven that higher doses of commercially available vaccines are required to produce protective antibody titres in ostriches against a field challenge. Control programmes in the ostrich should be started at <3 months of age, primarily in regions where NDV is prevalent. The eye drop immunisation method provides 80–90% protection; as compared to drinking water at 50–60%, but eye drop administration is difficult in older ostriches. Different serological and molecular tests have been developed for the detection of ND in ostrich samples. The enzyme-linked immunosorbent assay is more specific and sensitive (91–96%) than the haemagglutination inhibition test (86–87%) to determine anti-NDV antibodies in ostrich sera. To understand the disease, the history of ND in the ostrich, along with aetiology, epidemiology and genomic sequence of NDV is required. The prevention and control of the disease through vaccination and measures to prevent transmission to other ostrich birds is important.