Newcastle disease (ND) is an OIE listed viral infection that has spread throughout developed and underdeveloped countries, either as an endemic or epizootic disease. ND has been endemic in several developing countries in non-integrated poultry production systems. Serological baselines of poultry diseases can be established and monitored as a useful and reliable tool to design effective strategies for prevention and control of infectious diseases, yet almost no comprehensive report on serological baseline values is yet available. This review covers the situation of ND in northeast Iran during 2009–2018, and ND serological baselines of layer flocks in Khorasan-e-Razavi Province in Iran are presented for the first time. The mean haemagglutination inhibition (HI) titres for NDV throughout the production cycle of layer flocks in the two periods 2009–2015 and 2016–2018 were around 9.5 Log2 (range 7.9 to 11.4) and 7 Log2 (range 6 to 9.1), respectively. In addition to a 2.5 Log2 decrease in HI antibody titres, a significant decline was seen in the rate of incidence, mortality and clinical manifestations of respiratory diseases, especially ND. Interestingly, layer flocks reached a significant milestone in the adoption of biosecurity practices during the first emergence of highly pathogenic avian influenza in the early months of 2016. It was concluded that increased application of biosecurity in non-integrated poultry production systems of developing countries may take priority over the other control/preventive measures against ND. There is a need for other control and prevention studies to be promoted in developing countries, empowering them to formulate and adopt strategies that move beyond the conventional approaches and aim at international health and trade.

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