The indirect immunofluorescence assay using cardiac tissue from chickens, quails and ducks for identification of influenza A virus during an outbreak of highly pathogenic avian influenza virus (H5N1): A rapid and simple screening tool for limited resource settings

Here we describe the diagnostic utility of the indirect immunofluorescence assay (IFA) during a recent outbreak of highly pathogenic avian influenza (HPAI) subtype H5N1 virus in southern Thailand and demonstrate the usefulness of the cardiac tissue from infected chickens, quail, and ducks for diagnosis. The most reliable sample for IFA diagnosis of influenza A virus was cardiac tissue (83.0%; 44/53) which when divided by species (chicken, quail and duck cardiac tissues) gave respective positivity rates of 88% (22/25), 88.9% (16/18) and 60.0% (6/10). Cardiac tissue also gave the highest IFA intensity for the three species. We believe that the IFA method has wide applicability in developing countries or remote settings where clinically similar avian diseases with high morbidity and mortality such as Newcastle disease and fowl cholera are common and could be rapidly excluded thereby conserving valuable reference laboratory capacity for true HPAI outbreaks.

Tissue tropism of a Thailand strain of high-pathogenicity avian influenza virus (H5N1) in tissues of naturally infected native chickens (Gallus gallus), Japanese quail (Coturnix coturnix japonica) and ducks (Anasspp.)

The tropism of a Thailand strain of highly pathogenic avian influenza H5N1 virus was demonstrated on tissues (lung, trachea, heart, liver, spleen, pancreas, rectum, kidney, brain, skeletal muscle, duodenum, and oviduct) from naturally infected native chickens (Gallus gallus), Japanese quail (Coturnix coturnix japonica) and ducks (Anas spp.) by indirect immunofluorescence assay. In chickens and quail, the distribution and localization of nucleoprotein viral antigen was similar and detected at the highest level in cardiac myocytes, at 88% (chickens) and 89% (quail), and respiratory, digestive and urinary systems all showed high levels of antigen. Antigen in duck tissues were detected at significantly lower levels (P < 0.05) with the exception of brain and skeletal muscle samples. In most cases, antigen in duck tissue was absent in the digestive organs but present in respiratory organs, which supports the hypothesis that aerosol and oral-oral transmission are the main method of highly pathogenic avian influenza virus transmission from this species.

Isolation of Avian Influenza Virus A Subtype H5N1 from Internal Contents (Albumen and Allantoic Fluid) of Japanese Quail (Coturnix coturnix japonica) Eggs and Oviduct during a Natural Outbreak

Avian influenza virus (AIV) was recovered from the internal contents of eggs, including mixture of albumen and allantoic fluid, and from the oviduct of naturally infected Japanese quail (Coturnix coturnix japonica) flocks in the southern part of Thailand. The virus titers of 10(4.6)-10(6.2) ELD(50)/mL were directly measured from the internal content of infected eggs. The virus was isolated by chorioallantoic sac inoculation of embryonating chicken eggs. Infected allantoic fluid was identified as hemagglutinating virus and then was indicated the presence of H5 hemagglutinin. The virus was confirmed to be H5N1 subtype influenza A virus by reverse transcriptase-polymerase chain reaction. Additionally, real-time reverse transcriptase-polymerase chain reaction assay could specifically detect influenza virus subtype H5. Furthermore, indirect fluorescent antibody (IFA) test by using specific anti-influenza A monoclonal antibody indicated that virus antigens were detected in the parenchyma of multiple tissues. Systemic localization of viral antigen detected was certainly considered to be viremic stage. In addition, influenza virus antigen was also detected by IFA in allantoic fluid sediments isolated from internal content of egg or oviduct. The conclusion of isolated AIV type A subtype H5N1 from these two infected materials was correlated to the viremic stage of infection because the virus antigens could be observed in almost all tissues. Conclusively, the need for adequate safeguards to prevent contamination and spread of the virus to the environment during movement of eggs--including hatching eggs, cracked eggs, and other relevant infected materials-- or egg consumption from area of outbreak is emphasized and must not be ignored for the reasons of animal, public, and environmental health.