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

Document Type: Original Articles


1 Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

2 Department of Poultry Diseases, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran

3 Department of Avian Diseases, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran


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. 


Article Title [French]

La Tendance des Changements dans le Titre d'Anticorps Contre le Virus de la Grippe Aviaire H9N2 durant la Période d'Élevage chez les Poulets de Chair Vaccinés et non Vaccinés de la Province de Qazvin, Iran: Une Étude de Cohorte

Abstract [French]

Le virus de l'influenza aviaire (VIA) du sous-type H9N2 est endémique en Iran et sa circulation est dévastatrice à grande échelle dans l'industrieaviaire. Ce virus a été signalé pour la première fois dans l'aviculture industrielle iranienne en juillet 1998. Certaines études publiées ont montré que les vaccins inactivés contre IA sont capables d'induire une réponse immunitaire et de fournir une protection contre la morbidité et la mortalité dans différents pays (Vasfi et al., 2002; Tavakkoli et al., 2011). Il a été signalé que VIA H9N2, virus d’une faible pathogénicité, a un potentiel zoonotique et une distribution répandue en Iran. Par conséquent, des vaccins en émulsion eau-dans-huile sont utilisés pour contrôler la maladie chez les poulets (Nili et Asasi, 2003). Cette étude de cohorte a été étudiée de juillet 2016 à novembre 2017 parmi les élevages de poulets de chair de la province de Qazvin, en Iran, afin d’étudier les tendances des changements sérologiques chez les poulets de chair de cette région. Le test d'inhibition de l'hémagglutination a été utilisé pour évaluer le degré d'immunité contre le virus H9N2. Les vaccins tués de l'IA H9N2 ont été utilisés dans quinze fermes sur trente unités inscrites. La valeur minimale des titres moyens d'anticorps (TMAs) était de 4.54-2.42 et le maximum de TMA était de 4.54+2.42 au troisième jour. De plus, les TMAs au jour 50 étaient de 0.4 ±0.64. Dans cette étude, le taux de transmission des anticorps VIA H9N2 du sérum des reproducteurs au sérum des poulets a été estimé à 60.35%. Une différence significative existait entre les titres moyens d'anticorps maternels et les TMA au troisième jour (P<0.001). De plus, il y avait une différence statistiquement significative entre les TMAs des troisième et dixième jours (P<0.01). En outre, les TMAs étaient significativement différents entre les troupeaux vaccinés et non vaccinés au quarantième jour (P<0.05), tandis qu' aucune différence significative n'a été observée aux jours 3, 10, 20 et 30 (P>0.05). Selon nos résultats, les titres d'anticorps dans les fermes vaccinées n'ont atteint le niveau de protection qu'à la fin de la période d'élevage. La plupart des troupeaux non vaccinés ont une augmentation des titres d'anticorps en raison de l'exposition au virus. Par conséquent, les mesures de biosécurité doivent être mises en œuvre plus sérieusement et strictement dans les élevages de poulets de chair.

Keywords [French]

  • Titre d'anticorps
  • Élevages de Poulets de Chair
  • Virus de La grippe Aviaire H9N2
  • Iran
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