Avian Influenza Virus - Article Example

Avian Influenza Name Institution INTRODUCTION Avian influenza, which sometimes is referred to as bird flu, is a viral disease that affects poultry. It affects the respiratory, nervous or digestive system of birds. The disease occurs in almost all species of birds. This paper covers its epidemiology, causes, pathogenesis, diagnosis, clinical signs, transmission, prevention and treatment. EPIDEMIOLOGY Avian flu is severely contagious poultry disease that is transmittable to humans. In some instances, it causes deaths in patients. The cause of bird flu is a RNA influenza virus, specifically, type A. It belongs to a family called Orthomyxoviridae (Whitworth et.al 2007). Its genus is influenza virus A. Its impact to international trade and poultry production has been great. This is especially so with the subtype H5N1. This subtype was reported in 1997 for the first time when it caused human death (United States 1984). It then spread worldwide and caused serious outbreaks in many Asian countries. The disease has been listed in the diseases under the Animal Epidemic Act in Thailand. CAUSES In wild waterfowl, avian influenza occurs naturally. It can be spread to domestic poultry like chicken, geese, turkeys and ducks. Bird flu is transmitted through contact with infected faecal matter or nasal secretions or secretions from the mouth or eyes. Places where birds or their products are sold in unsanitary and crowded conditions are hotbeds of infections (Sshrijver et.al 2005). From these places, this disease can easily spread to the wider community. PATHOGENESIS When a bird contracts influenza virus into its body, the virus replicates itself in the respiratory system, mostly in the digestive track or in the nasal cavity before getting into the environment. Influenza virus that is highly pathogenic penetrates into sub mucosa and replicates itself in the sinusoidal endothelial cells (Swayne 2008). After influenza virus get out of the cells, they flow via the lymphatic as well as cardiovascular systems to other organs like the skin and the brain. Appearance of symptoms or death of the bird is due to the internal organs failing to function. The virus can survive in secretions, tissues and even the faecal matter of the infected birds, water and environment. Influenza virus gets inactive when exposed to a temperature of 60 °C for 30 minutes or 56 °C for three hours or when placed in certain acidic chemicals like, lipid solvents, iodine compounds, β - propiolactone, formalin sodium, oxidizing agents and dodecyl sulphate (Allegra 2008). DIAGNOSIS Diagnosis of avian influenza virus is done by following two steps. The first step is isolating the virus. A sample is inoculated in the hatching eggs of a chicken and by haemagglutination test in order to detect precipitation, a characteristic of the red blood cells. It is at this step that we identify that the virus is influenza type A. It can also be indicative of other pathogens having a similar characteristic. If this test turns out to be positive, we move to the next step. HA test showing positive results HA test showing negative results The second step is virus identification that goes through avian virus test of influenza type A as well as subtypes by Agar Gel Immunosorbent Assay (AGID) that is precipitation in Enzyme – Linked Immunosorbent Assay (ELISA) or by agar or by other recommended methods for confirmation of the type A influenza virus. If this test yields positive results, then a confirmation for subtypes by use of serum strictly for H7 and H5 for haemagglutination inhibition test that detects the inhibition of precipitation of red blood cells. SYMPTOMS Symptoms or clinical signs greatly vary and are subject upon many factors such as the inherent pathogenicity of the influenza virus strain, the age and species of birds affected and husbandry practices. Clinical signs of this disease are: feathers that are ruffled, droopiness, little appetite, swelling of head, discharge from nostrils, incoordination, including loss of ability to walk and stand, pin-point hemorrhages, cyanosis of comb and wattles, respiratory distress, increased deaths, egg production sudden drop, diarrhoea and eggs with a soft shell (Capua et.al 2009). TRANSMISSION Poultry that is infected sheds this virus in oculo-nasal as well as in fecal discharges. Even if recovered flocks do not shed off as much virus as flocks that are clinically ill, they will frequently shed the virus and are therefore considered to be infected throughout their lifetime (Bethe 2006). Waterfowl naturally has the virus that causes avian influenza. Wild waterfowl normally don’t show any clinical signs, they however are capable excreting the virus for a long time. Additionally, waterfowl is susceptible to infection by several types of influenza virus. Influenza virus has been discovered in organic material and water from lakes and ponds that have been used by ducks that are infected. This mingling of the flock with others is a contributing factor in many outbreaks. Influenza virus has the ability to remain alive for quite long under normal temperatures (Spackman 2008). The virus can as well survive in frozen material indefinitely. Improper disposal of carcasses that are infected, manure or by-products can therefore further spread the disease. This disease can also be spread with ease by human beings and equipment that are contaminated with the virus. The influenza virus can as well be transmitted on shoes, or other equipment that are contaminated. Anything within the infected poultry farm is deemed to be contaminated and must be cleaned completely and disinfected before it is removed from that farm house (Klenk et al 2008). Clothes worn while in the infected farm must be properly laundered. Rodents and insects may carry the virus mechanically from infected birds to susceptible ones. The virus of influenza has been isolated from eggs of turkey, which suggests a transmission that is vertical, even though the virus kills the embryo typically. There is scanty evidence of egg-borne infection of birds (Bethe 2006). However, surfaces of an eggshell can be contaminated with virus. This virus has been isolated frequently from healthy, exotic birds that are imported. This infected flock is a potential threat to wild birds, cage birds and poultry. Markets for live birds are a potential reservoir of the disease. These markets act as a focal point from which many species of birds are gathered and housed many. Neither are these facilities cleaned nor disinfected. TREATMENT Avian flu has no particular treatment. A broad spectrum antibiotics however, good nutrition as well as good husbandry might decrease losses from other infections. It is worth noting that birds that have recovered continuously shed this virus intermittently. Cleaning and disinfection of all poultry houses must be done after removing flock that is infected. The bird’s manure or litter should be composted prior to application on land (Bethe 2006). PREVENTION Control of mild avian influenza can be done using a program of vaccination, coupled with imposition of quarantine that is very strict. This is effective in commercial turkey and chicken flocks. Lethal forms of the disease can be controlled by rapid depopulation and strict quarantine. All efforts must be made to ensure there is no contact between domestic birds and wild waterfowl. This is because of wild waterfowl being a reservoir for the virus. People that handle wild waterfowl should completely change clothes and bathe before entering poultry houses. CONCLUSION Avian Flu has been identified as one of the most dangerous diseases in poultry. It can however be managed by good animal husbandry practices such as maintaining cleanliness of poultry houses and isolation of infected birds from healthy ones. References Allegra, E. P. (2008). Avian influenza research progress. New York: Nova Biomedical Books. Bethe, M. R. (2006). Global spread of the avian flu: Issues and actions. New York: Nova Science Publishers. Capua, I., & Alexander, D. J. (2009). Avian influenza and Newcastle disease: A field and laboratory guide. Milan: Springer. International Symposium on Avian Influenza, & Animal Health and Veterinary Laboratories Agency (Great Britain). (2012). 8th International Symposium on Avian Influenza: Avian influenza in poultry and wild birds, Royal Holloway, University of London, UK, 1-4 April, 2012. London: the Symposium. Klenk, H.-D., Matrosovich, M. N., & Stech, J. (2008). Avian influenza. Basel: Karger. Schrijver, R. S., & Koch, G. (2005). Avian influenza: Prevention and control. Dordrect ; New York: Springer. Spackman, E. (2008). Avian influenza virus. Totowa, NJ: Humana Press. Swayne, D. E. (2008). Avian influenza. Oxford, UK: Blackwell Pub. United States. (1984). Effect of avian influenza outbreak on the poultry industry: Hearings before a subcommittee of the Committee on Appropriations, United States Senate, Ninety- eighth Congress, second session : special hearing. Washington: U.S. G.P.O. United States. (1984). Review of the effects of avian influenza on Maryland's poultry industry: Hearing before the Subcommittee on Livestock, Dairy, and Poultry of the Committee on Agriculture, House of Representatives, Ninety-eighth Congress, second session, February 21, 1984, Wye Mills, Md. Washington: U.S. G.P.O. Whitworth, D., Newman, S., Mundkur, T., Harris, P., & Food and Agriculture Organization of the United Nations. (2007). Wild birds and avian influenza: An introduction to applied field research and disease sampling techniques. Rome: Food and Agriculture Organization of the United Nations. Read More