Trend of Changes in the Titer of Antibody against Avian Influenza Virus H9n2 during Raising Period in Vaccinated and Unvaccinated Broiler Farms in Qazvin Province, Iran: A Cohort Study.

Avian influenza virus (AIV) H9N2 is endemic in Iran and its large-scale circulation in the poultry industry of the country is devastating. This virus was first reported in the industrial poultry populations of Iran in July 1998. Some of the published studies showed that inactivated avian influenza (AI) vaccines are capable of inducing an immune response and providing protection against morbidity and mortality in different countries (Vasfi et al., 2002; Tavakkoli et al., 2011). Low pathogenicity avian influenza subtype H9N2 virus has been reported to have a zoonotic potential and widespread distribution in Iran. Therefore, water-in-oil emulsion vaccines are employed to control the disease in chickens (Nili and Asasi, 2003). This cohort study was conducted during July 2016-November 2017 in broiler chicken farms of Qazvin province, Iran to investigate the serological change trends in broiler chickens in this region. Level of immunity against the H9N2 virus was evaluated by hemagglutination inhibition assay. Fifteen farms out of thirty enrolled units used AI H9N2 killed vaccines. The minimum of mean antibody titers (MATs) was 4.54-2.42 and the maximum of MATs was 4.54+2.42 on day 3. In addition, the minimum and maximum MATs on day 50 were 0.4-0.64 and 0.4+0.064, respectively. The transfer rate of H9N2 AIV antibodies from the serum of breeders to the serum of chickens was calculated as 60.35% in our study. A significant difference was revealed between the maternal mean antibody titers (MMATs) and the MATs on day 3 (P<0.001). In addition, the difference between the MATs on day 3 and the MATs on day 10 was found to be significant (P<0.01). Moreover, MATs were significantly different between the vaccinated and unvaccinated herds on day 40 (P<0.05), while no significant difference was observed on days 3, 10, 20, and 30 (P>0.05). According to the results of this study, antibody titers in the vaccinated farms did not reach the protective level until the end of the rearing period. Most of the unvaccinated herds experienced a spurt in antibody titers due to exposure to the virus. Consequently, biosecurity measures must be implemented more seriously and strictly in broiler farms.

Serological Survey of Avian Influenza (H9N2) in Commercial Ostrich Farms in Iran, 2015.

The aim of this study was to determine the seroprevalence of avian influenzaH9N2 subtype in the industrial ostrich farms and its geographical distribution. This cross-sectional study was conducted from January to June 2015. A total of 40 farms were selected from different provinces of Iran, from each of which 11 ostriches (n=440) were sampled. The sera samples were examined using 4 hemagglutination units of H9N2 antigens. A frequency distribution was used to describe the responses to the survey questions. The mean titers between provinces were compared using one-way analysis of variance. According to the results, 21 (47.5%) out of 40 farms and 108 (24.5%) out of 440 ostriches tested positive in the HI-H9N2 test. There were statistically significant differences between the mean titers of samples in different provinces (P<0.001). The current study was conducted on unvaccinated ostriches. The results showed that H9N2 had a high seroprevalence at both farm and bird levels. The findings of this study can be for the further investigation of infection in ostrich farms in order to consider this species in the surveillance programs of the Iranian Veterinary Organization. The detection and isolation of viruses and epidemiological investigation are necessary for the persistent use of H9N2 vaccines in some ostrich farms.