Bird Flu: Everything You Need to Know
Syed Muhammad Ali Shah1 and Asim Shamim2
1,2 Faculty of Veterinary and Animal Sciences, University of Poonch Rawalakot.
Abstract:
Bird flu, also known as avian influenza, is caused by a type A influenza virus that belongs to the orthomyxoviridae family of viruses, which is a group of single-stranded minus-sense RNA viruses. This virus primarily affects poultry birds but is of public health importance because of its zoonotic transmission from poultry birds to humans, which raises concern for farmers, consumers, and wild birds’ health. It is time to break the transmission cycle of this disease for the reduction of both bird-to-bird and bird-to-human transmission of bird flu. This chapter will comprehensively focus on a brief introduction of avian influenza, its symptoms, mode of transmission, treatment regimes, control, and one health and global health perspective for the development of effective treatment and control of this highly contagious disease in both humans and birds.
- Introduction:
Bird flu is a highly contagious viral disease of not only domesticated and commercial but also wild poultry birds (Proença-Módena et al., 2007). The virus also affects a number of mammalian species including humans. It is caused by influenza type A virus that is a virus of orthomyxoviridae family of virus. The virus is a single stranded RNA virus which is roughly spherical shaped virus (Dires, 2020; Nayak, 2014). Bird Flu virus is classified into different subtypes on the basis of two antigenic proteins i.e. hemagglutinin and neuraminidase (Böttcher-Friebertshäuser et al., 2014; Suarez, 2016). These proteins classify influenza A virus into 18 different HA subtypes and 11 different NA subtypes (Byrd-Leotis et al., 2017; Khaliq et al., 2015). Subtypes are named by combining the H and N numbers such as A(H1N1), A(H3N2) depending upon which antigenic protein is present on the virus (Nuwarda et al., 2021; Wu & Wilson, 2020). There are five types of influenza A virus that are regarded to affect human population including H5, H6, H7, H9, and H10 viruses (Bi et al., 2020; Patil et al., 2020). Among these serotypes H5, H7 and H9 viruses are mostly isolated from avian influenza infected individuals (Sun et al., 2020).
- Transmission:
Bird flu affects a wide range of species, from birds to other birds, wild mammals, and even humans (Lycett et al., 2019). The most common sources of infection are the feces, feathers, and respiratory secretions of infected birds (Dhama, 2013; Miskiewicz et al., 2018). Wild, watery birds such as geese and doves play an important role in the transmission of this disease from wild to domesticated birds (Shriner & Root, 2020). The major routes of transmission are direct contact with respiratory secretions and the oro-fecal route of transmission from the feces of infected birds via contaminated feed and water (Malik et al., 2016). The virus gets into the host body through these contaminations, resides in the upper respiratory system of host birds, and starts multiplying (Umar, 2017). Hence, major factors contributing to the transmission of avian influenza include the movement of infected birds, the farming and sale of live birds, and the movement of wild or migratory birds (Health et al., 2017). The virus is resistant to low temperatures and can survive on surfaces for a long period of time, making its transmission easier through farm equipment. The other notable reasons for the massive and extensive transmission of this disease are the typical characteristic of influenza. A virus is in two main ways, i.e., antigenic drift and antigenic shift (Berhanu, 2021; Treanor, 2023).
- Clinical Findings:
The symptom of avian influenza varies from individual to individual depending on the immune status of birds (Van Dijk et al., 2020). In some birds, it acts as a career, showing no signs or symptoms to mild and even severe symptoms. Most Avian Influenza viruses are low pathogenic (LPAI), including serotypes H1–H16, while H5 and H7 are highly pathogenic (HPAI) for birds (Verhagen et al., 2021). It is important to understand the symptoms and clinical findings of the disease for early detection of disease and to prevent loss at the farm (Swayne & Sims, 2021).
LPAI can cause mild symptoms or no symptoms in poultry birds, including sneezing, coughing, ocular and nasal discharge, swollen infraorbital sinuses, sinusitis, and decreased feed consumption (Saif & Toro, 2021). It also causes decreased egg production in layers or breeding birds. Mortality and morbidity are rarely seen in LPAI-infected flocks.
HPAI-infected birds may show symptoms of diarrhea, gasping, swelling around the eyes, head, and neck, purple discoloration of the head and legs, and even sudden death. Some birds may exhibit neurological symptoms such as lethargy, tremors, head tilting, and incoordination (Reperant et al., 2012). HPAI is highly fatal, and even a 100% mortality rate has been observed (Seneviratna, 2013).
- Diagnosis:
Clinical signs alone are not reliable enough to confirm a diagnosis. In cases of suspected disease outbreaks, the veterinarian should recommend lab tests. Samples for lab diagnosis can be collected via swabbing at the trachea, oropharyngeal, and cloacal regions of suspected birds (Crespo & Shivaprasad, 2021).
For the detection of avian influenza, serological tests, including ELISA and AGID, can be performed along with hemagglutination inhibition and neuraminidase inhibition (Gashaw, 2020; Spackman & Killian, 2020). A PCR test can be requested for rapid identification of the virus if required (James et al., 2022). Virus isolation can also be performed but is not used in practice because it requires more time to produce results than the other tests available (Hood et al., 2021).
- Treatment:
There is no known effective treatment for avian influenza infection (Chaudhary & Pahwa, 2013). Birds affected with LPAIs can be treated with broad spectrum antibiotics to prevent secondary infection by other pathogens and supportive fluid therapy can be administered if required. Increase in temperatures at the sheds can decrease the morbidity and mortality rates. Recovery of birds infected from HPAI viruses is extremely rare. Poultry birds that are diagnosed with HPAIs are culled and poultry products are discarded to reduce transmission (He & Kam, 2024).
- Prevention and Control:
Biosecurity measures can be regarded as the most effective measures for controlling this disease. It is recommended to use personal protective equipment (PPE) if necessary under the circumstances of handling infected birds (Morishita & Derksen, 2021). Culling of infected birds is also the most renowned method of treatment and control in developed countries (Parvin et al., 2020). The workers should be properly trained to deal with the potential risk of the disease. There should be proper disinfection of the farm after the marketing of each flock. Fecal waste from the birds should be disposed- of properly (Msami, 2020). There should be proper ventilation to reduce contamination after culling the diseased flock. The poultry farm should be properly fenced to restrict the entry of infected wild birds. The feed and drinking water should be free from any contamination. If an outbreak is suspected, regulatory authorities should be informed immediately (Simancas-Racines et al., 2023).
- Zoonotic Risk:
In normal cases, the Avian Influenza virus is not transmitted to humans, but in rare cases, transmission of bird flu from infected birds to humans is seen on close contact with affected birds (European Food Safety Authority et al., 2020; Tang & Chen, 2013). It is advised to handle the carcasses of infected birds with precautions to avoid disease because, at the onset of disease, viruses can produce mild to severe symptoms (Kozdruń et al., 2015).
The meat of an infected bird is safe to eat after cooking at high temperatures, as cooking temperatures are high enough to kill the virus present in the meat (Marmion et al., 2021; Swayne, 2016). The United States Department of Agriculture recommends that a temperature of 165 degrees Fahrenheit be maintained during cooking in order to successfully kill viruses that may be present in meat (Owusu-Apenten & Vieira, 2022).
- Future Perspectives:
Avian influenza poses significant economic challenges worldwide. There is a need of working of professionals from multidisciplinary areas specially veterinarians and human physicians for developing effective treatment regimens and control strategies against this contagious disease. There is no effective vaccine of avian influenza is available for commercial use. Further research is required for development of vaccine for control and prevention of avian influenza. This chapter has highlighted the current status of disease and contributed toward the way for formation of effective treatment plans for treatment and development control strategies to combat with this economically affecting poultry disease.
- Conclusion:
Avian influenza is highly contagious disease of poultry birds. It is also a public health risk to some context. It is crucial to adapt preventive measures for effective control and ultimate eradication of this disease.
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