Headlines around the world suggest that avian flu could become the next flu pandemic. Therefore, it is essential to understand that risks and precautions are implemented.
To that end, Global Access Diagnostics discusses why there is a need to worry about avian influenza and what the world is doing to develop rapid antigen testing (RAT) that supports early diagnosis and surveillance.
Types of avian influenza virus
Influenza viruses (also known as avian influenza) can be divided into four types: A, B, C, and D. Both A and B are associated with a global pandemic in which both A and B are circulating widely within human populations, causing seasonal influenza, and type A is associated with a global pandemic.
Influenza type C, characterized by a single primary surface glycoprotein, is considered antigenically stable, frequently detected, and usually causes mild infections. In contrast, influenza D mainly affects cows and is not known to infect or cause disease in humans.
Further evolution of influenza A and b
Influenza B (IBV) is divided into two phylogenetic strains that do not have known animal reservoirs and cocirculate within the population, causing approximately 25% of cases of seasonal avian influenza.
Influenza A circulates worldwide in both avian and mammalian hosts. This extensive gene pool has resulted in the identification of combinations of 130 influenza A virus (IAV) subtypes.
Highly pathogenic AIV (HPAIV) can pass species barriers from birds to mammalian species, causing sporadic human infections and/or death.
However, to date, they have not been shown to have the ability to communicate continuously from person to person. However, in some cases, variant subtypes can cross from pig to human.
Human preparation for the global influenza pandemic
As a cross-border zoonotic disease, HPAI impacts not only poultry, animal and human health, but also broader communities around the world by threatening livelihoods, agricultural productivity, economy and ecosystems.
Among the most concerning AIV HP subtypes are the H5NX and H9N2 AIV. These are widely common in bird production and are thought to have the greatest potential to trigger a global influenza pandemic as they exhibit receptor binding shifts towards human-like preferences.
The World Health Organization maintains a list of all candidate vaccines for the Panzootic bird flu. Currently, there is no indication that the currently circulating avian influenza virus is antigenically different from the candidate vaccine virus proposed to prepare for the pandemic.
Vaccination strategies to control panzic outbreaks
While some countries such as China and France are vaccine-connected chicken, the USDA has approved field safety studies of vaccine candidates designed to protect dairy cows from H5N1. However, many countries, including the UK, follow non-vaccination policies regarding disease prevention or control.
The reason why there are disadvantages to the currently available vaccines is that while mortality can be reduced, some vaccinated birds can transmit positively and have a negative impact on export trade.
Vaccination alone is not a sufficient strategy, but a integrated approach that involves surveillance. Here, practical, accessible, affordable and rapid antigen testing will identify a) PAN AIV infection and determine if it is H5N1 clade 2.3.4.4b or other H5, H7, H9 subtypes, if present.
Farm Outer Flow Test for Avian Influenza
Enzyme-linked immunosorbent assays (ELISA) and transverse immunochromatography assays (LFIA) can be developed for both AIV viral antigens and seropositive tests.
ELISA requires a laboratory processing environment with specialized equipment and operational level technical skills, but allows for screening of many samples simultaneously.
Some large poultry producers recognize the value of routine screening for antibody immune responses against infectious diseases and vaccinations, and are investing in facilities to deploy ELISA tests with trained staff. However, most of the time, this technique is not available.
Meanwhile, LFIA is accessible, affordable and easy to use, allowing users to employ on farms and test poultry on individual levels or on large scales by using or using scientific expertise.
Although ELISA and LFIA cannot provide RTPCR specificity and sensitivity for the diagnosis of avian influenza infections, they can provide producers with affordable, accessible tools for farm monitoring of herd health.
The challenges facing the development of AIV testing on sustainable farms: can they be overcome?
LFIAS for the detection of avian influenza can be used in a variety of poultry samples, including charcoal dorsal secretion, fecal, and tracheal/oropharyngeal samples.
However, there are many restrictions on use, and there may be cases where the national law surrounding its use cannot be distinguished between HP and LP AIV, or the subtype cannot be determined.
Furthermore, there is limited understanding of end-user knowledge about sample types for testing the poultry species involved, the effects of environmental parameters, the persistence of the virus in the sample, and the performance of diagnostic tests.
Although LFIAs claiming to identify PAN AIV infections are in the market, those that distinguish between H5, H7, and H9 subtypes are thought to lack the desired sensitivity required for early intervention as part of disease management strategies.
In collaboration with the Pirbright Research Institute, Global Access Diagnostics has developed a suite of first generation rapid LFIA tests to mitigate this issue and detect AIVs in sample matrices described by the poultry industry, and is developing a detection limit (LOD) in the region of <1000 AIV plaquefumming units/ml.
Selectively identify whether H5, H7, or H9 AIV is present, if present. The H5 test is specially designed to include recognition of circulating HP H5NX subtypes containing H5N1.2.3.4b. A second-generation test incorporating Diva H5 AIV and other poultry diseases, including Newcastle disease virus (NDV) and infectious bronchitis.
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