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Besides culling, vaccination is the other method used to control the further widespread of influenza A H5N1; whether by human or even bird species. This action has been endorsed by experts from the UN's Food and Agriculture Organization (FAO), the World Organization for Animal Health (OIE), and the World Health Organization after several meetings in February 2004.[18,22]
Figure 3: Spreading mode of influenza A (H5N1) viruses and efforts to make better vaccines for potential pandemic. ARDS, acute respiratory distress syndrome. http://www.cdc.gov/eid/content/13/10/1512-G.htm
The common vaccine used prior to influenza season is inactivated influenza virus vaccine (dead vaccine). It is produced by using a strain of influenza B virus and two strains from influenza A virus subtypes; H1N1 and H3N2. Base on the antigenicity of influenza viruses monitored through the WHO surveillance network, the composition is determined annually. The common medium for the propagation of the virus before its inactivation and formulation for vaccination is fertilized chicken eggs. Before the viruses are inactivated with formalin or a-propialactone, they are replicated to high titers in allantoic fluid and then purified and concentrated by zonal centrifugation. Figure.
In 2003, live vaccine had been licensed in United States. Three different live flu viruses that are generated by cold attenuation are composed to manufacture this vaccine. Due to temperature factor, the viruses cannot replicate in the lower respiratory tract where but only can replicate in the nose and throat where the temperature is lower. Since fertilized eggs are not used for virus propagation, this approach becomes more practical for prevention of possible avian flu pandemic. For better results in generating an effective vaccine in a pandemic situation, it is advantageous to achieve attenuation in a single step by attenuating genes transfer.
The vaccines work by stimulating the body to increase the immune system against diseases. The viral haemagglutinins brought by the vaccine make the immune system of the body to respond against the foreign and antibodies will be produced faster when it is exposed to the virus again. For a better response, the vaccine is mixed with adjuvant-contained emulsion which brings out double stimulation to immune system.
Other method that available to prevent widespread of H5N1 is antiviral drugs. Uncoating inhibitors drugs like Adamantanes, amantadine and rimantadine are the earliest antiviral drugs described against influenza virus which are M2 ions channel blockers that inhibit the viral replication at the uncoating stage. neuro.jpg
Figure 4: Illustration of the inhibition of neuraminidase by the inhibitor. http://www.relenza.com/hcp/relenza-action-mechanism.htmlOther type of drug that is well used is neuraminidase inhibitors. Zanamivir and oseltamivir are examples of neuraminidase (NA) inhibitors which were synthesized when the influenza NA crystal complexes with sialic acid. According to infection mechanism, the viruses enable to dissolve chemically a pathway through the cell membranes of the human body cells through the neuraminidase coating so that it can invade the cells. It will then replicates in the cells forming many other virus molecules. Using the neuraminidase, the new viruses break through, out from the cell membrane and invade the next cells in the same way. As the membrane of the cell left behind is broken, the cell dies itself. This process is repeated and an efficient chain reaction is set up. The patient would begin to experience flu symptoms such as headaches and fevers. By taking oseltamivir, its phosphate inhibits the new viral particles ability to escape from the infected cell as it binds to the neuraminidase on the surface of the virus particles.
As the neuraminidase enzymatic active site seems to be highly conserved among all influenza viruses, this potentially offers protection against any influenza virus that might infect humans. Oseltamivir hold great potential for clinical use in a pandemic situation caused by H5N1 as it is effective against avian influenza virus. Nowadays, oseltamivir is well commercialized as Tamiflu tablet by Roche Pharmaceutical Company and in inhaler form named Relenza by GlaxoSmithKline Company.
Social and Economic Implications
(1058 words)To overcome the possibility of bird flu pandemic, there are several issues come out; either socially or even economically. About the vaccination, actually there are some countries have challenged vaccination as a control measure. Some studies have shown that some vaccines approved by OIE take time to confer immunity to vaccinated poultries and may not fully prevent birds from becoming infected virus.Â This has caused considerable controversy over the benefits and risks of vaccination. There is case where Thailand, which exports 30% of its poultry to the European Union, has refused to vaccinate its flocks and has ban the use of vaccine in the country due to concerning about the controversy.
The efforts done also give great impact in economy. All of the methods used actually used huge cost. Vaccination had used big financial to make several experiments for confirmation of the effective vaccines. While usage of antiviral drugs also use much money as they are commercialized averagely in high price. About the culling, actually it give big loss to the farmers, wholesalers and also poultry retailers as over 200 million of poultry had been culled all over the world.[24,25] Although the impact of bird flu prevention and treatment are obviously big, it seems to be worth as the infectivity rate of the avian flu has statistically decreased nowadays.
Benefits and RisksCapture2.JPG
Table 1: Cumulative number of confirmed cases of avian influenza reported to WHO. http://www.who.int/csr/disease/avian_influenza/country/cases_table_2010_03_16/en/index.html
Generally, the solutions that have been explained before have give a great improvement in the prevention of the further widespread of avian influenza. Based on statistics, globally, total cases including deaths that caused by bird flu overalls decreased after peaked in 2006 until today.[16,19] This shows that the efforts that had been done by the specialists and government have contribute to the decreases in the flu transmission and infection thus the global community become healthier.
However, there are risks detected from the efforts that had been done. Besides economical issue, vaccination and use of antiviral drugs also lead to the conflict of side effects. FDA investigations show that neuraminidase inhibitor drugs used can give central nervous system (CNS) side effects such as nervousness, anxiety, difficulty concentrating, and lightheadedness, and gastrointestinal side effects like nausea, vomiting and loss of appetite. Well known oseltamivir, Tamiflu also had been warned to be used by children as it is not effective for them and also can lead to other health problems.
Besides culling, vaccination and drugs treatment, authorities suggest several practices that should be considered to minimise avian flu infection and transmission. This is because most of the influenza cases actually have resulted from direct contact with the infected poultry or surfaces that contaminated with secretions and excretions from the birds. Following are some of the precaution steps suggested:[18,22]
Keep poultry in closed poultry houses.Â
Keep wild birds and their faeces away from poultry and poultry feed.Â
Seal poultry house garrets and cover ventilation openings with screens.
Before and after coming into contact with poultry, thoroughly and routinely clean all equipment, vehicles, clothing and footwear
Ensure proper hygiene practices for all persons coming into contact with poultry.
Maintain high sanitation standards in and around poultry houses.
Avoid introducing new unknown health status birds into existing poultry flocks.
Ensure complete cleaning and disinfecting for all cages transporting birds.
Log all visitors coming into contact with poultry.
Other than that, the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) stated that proper cooking would kill H5N1 viruses even if poultry and eggs were to be contaminated with the virus. Below are some cooking skills suggested:
For at least 20 seconds, wash hands with soap and warm water before and after handling raw poultry and eggs.
Clean cooking utensils with soap and hot water.
Ensure poultry is cooked to a temperature of at least 75 Â°C by using a food thermometer.
Ensure whites and yolks of cooked eggs are really firm.
The three methods; culling, vaccination and antiviral drugs treatment had been found helping in overcome the transmission of H5N1 influenza virus all over the world. Averagely, most of the references for the solution of this problem state the three methods together, starting with culling of infected birds and followed by vaccination and drugs treatment. As an example, reference [7,http://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H5N1]. This source explained briefly about the prevention steps for bird flu which mainly about the three methods, relevant with source  and . These sources also agreed by following extract, "Together steps are being taken to minimize the risk of further spread in animal populations, reduce the risk of human infections, and further support pandemic planning and preparedness.", stated by United States Agency for International Development (USAID) (http://www.usaid.gov/our_work/global_health/home/News/news_item/ai_activities.htm).
Another reference that I found
Basically, most of the references that I used give information based on the view of trusted international health organisation such as WHO, FDA, and CDC. Therefore the information obtained is said to be reliable as the studies are made based on large global human population and updated frequently. However, there are several references that are obtained from individual or small researcher group views. The source is considered to be reliable as well as the information is given by experts in this influenza case which have made a lot of investigation and observation following the sequences of the influenza globally.
(Total = 1924 words)