Sero-epidemiological study of Avian Influenza (H9N2) in South Khorasan poultry farms in 1396

Introduction and Objectives: The H9N2 avian influenza virus has been identified for the first time in 1998 in the of Tehran and Qazvin provinces. Although this virus isolate is known as a low pathogenic isolate, it has led to heavy losses and a sharp drop in production. The mortality rate is 20-60%. The aim of this study was to determine the prevalence and mean antibody titer against the virus in poultry farms in South Khorasan province.Material and Methods: During the implementation of this study, which was conducted in 1396, samples from 227 poultry and other avian farms in south khorasan province were investigated for antibody titers by hemagglutination inhibition test. Poultry farms with high or low losses and different age groups were randomly selected each months for sampling. The tests was done using PASOUK Company antigens under CVL SOP suggested method. The obtained results were analyzed using SPSS software from various aspects.Results and Discussion: The mean titer of HI was 4.1 for broiler farms and 6.5 for layer farms. The highest titers of broiler farms were found in Khousf district with an average of 5.2, which did not show significant differences with other districts (p> 0.05). Also, the mean titer in broiler chickens with more than 10% losses during breeding time was not different significantly with other units. There was no significant difference in the comparison of the titers of broiler farms older than 30 days and less than 30 days. The mean titer in the broiler herds was unlikely lower than non-vaccinated herds, but again, their difference was not significant. Comparing the CVs of the titers showed that the results with a CV higher than 30% were significantly lower than the results below 30%. (2.6 versus 4.8, respectively) (P <0.05). Due to the small number of samples (33 units of 227 units), it was not possible to compare and analyze the data in layer farms. The results of the analyzes indicated that the population is not uniformly sampled and that there was several confounding factors. Given the fact that in South Khorasan province vaccination against poultry influenza in broiler farms is mostly not carried out, or is incomplete, the results of this study show that farms with more than 10% losses, are not infected with influenza in most cases. On the other hand, the presence of a mean titer of 4 in broiler farms and a high number of results with a CV above 30% indicates the presence of the virus in farms and the fragile protective titer, so high risk of immunity defeat and losses due to the disease.