Diagnosis and histopathological study of avian influenza virus-H5 (AIV-H5) in broiler farms

Fanar A Isihak,Abed Alwaheed A Wahid,Hana Kh Ismail

doi:10.33899/ijvs.2019.125646.1120

Abstract

This study was conducted for diagnosis and description of the pathological changes of AIV-H5 as the causative pathogen in Iraqi broiler farms. The current study was carried out on 84 broiler farms. Infected birds were tested for detection of the AIV infection from the tracheal swabs by rapid chromatographic AIV type A and H5 test kits. In RRT-PCR 8 samples (8 farms) of Trachea were selected to be tested by this assay. Samples of trachea, lung, and spleen from the dead birds with natural AIV-H5 infection were submitted for histopathological examination. seventy-two out of 84 farms tested for AIV-Type A gave positive results, and 58 out of 72 positives for type A-AIV gave a positive result for H5 antigen in a rapid chromatographic strip. The main gross lesions in the trachea of infected birds were severe congestion and hemorrhage. In the RRT-PCR assay, 8 out of 8 samples gave a distinct positive result for this test. The microscopic histopathological examination of infected tracheas showed obvious desquamation of lining epithelium with complete loss of cilia associated with congestion of blood vessels in lamina properia. Infected lungs revealed diffuse alveolar damage and severe multifocal vascular congestion. There was deposition of fibrinous material in the splenic tissue associated with the disappearance of the germinal centers. Thus, we concluded that AIV-H5 infection causes severe pathological and histopathological changes as a result of systemic infection. The RRT-PCR assay was highly sensitive and specific for the detection of highly pathogenic avian influenza virus subtypes.

Highlights

The highly pathogenic avian influenza virus (AIV) subtype H5N1 is considered one of the important pathogens that lead to severe respiratory disease with high morbidity and mortality in poultry industry
Rapid chromatographic strip Seventy two out of 84 farms tested for AIV were positive (Table 1, Figure 1a) and 58 out of 72 positives for type A-AIV gave positive results for H5 antigen in rapid chromatographic strip (Figure 1b)
There has been a noticeable increase in the occurring of highly pathogenic avian influenza virus (HPAI) outbreaks and in the numbers of avian species infected in those outbreaks [11]

Summary

Introduction

The highly pathogenic avian influenza virus (AIV) subtype H5N1 is considered one of the important pathogens that lead to severe respiratory disease with high morbidity and mortality in poultry industry. Since 1996, H5N1 subtypes undergone significant antigenic drift phenomena and these viruses have been classified into different clades according to phylogenetic features depended on hemagglutinin (HA) gene [2].The rapid diagnostic kits for detection of H5 subtypes are necessary for the control of infection with influenza viruses and these kits are affordable in the market for detection of specific nucleoprotein (NP) of this virus. Virus cultivation on embryonated eggs is currently performed for tracheal and cloacal samples from avian spp. are considered as standard diagnostic procedure for isolation, detection and subtyping of influenza A viruses [4]. RRT-PCR technique provides advantages of rapidity, viral loading analysis, sensitivity and specificity in comparison with standard protocol of RT-PCR

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