|
Vet-Varsity Scientists Discovered a solotion for Bird FLU
Dr. M. M. Mukhtar
Dr. Masood Rabbani
Dr. Khushi Muhammad
Department of Microbiology, University of Veterinary & Animal Sciences, Lahore
Bird flu is a disease caused by type A influenza virus. It is a disease of many species of poultry affecting the respiratory, enteric, and nervous systems. Influenza viruses are responsible for major disease problems in birds, as well as humans and lower mammals.
Acute form of the disease in chickens, caused by highly virulent serotypes, is characterized by sudden onset of high mortality, cessation of egg laying, respiratory signs, rales, excessive lacrimation, sinusitis, oedema of the head and face, cyanosis of the unfeathered skin, especially combs and wattles, and diarrhoea. It is the condition formerly termed as 'fowl plague' and it may be noted that one of the reasons for the suggested abandonment of the term is the extreme variability of the signs seen in outbreaks of the highly pathogenic serotypes of avian influenza virus.
Sub acute form of the disease caused by mesogenic serotypes of the virus may cause drop in egg production which can result in complete cessation of eggs, respiratory distress, anorexia, depression, sinusitis and low rate of mortality. In complicated form, the birds are under stress due to adverse environmental conditions, mortality may rise to as high as 70 per cent in the affected flocks and the birds from these affected flocks display severe form of clinical signs.
Gross lesions in several avian species extremely vary with regard to their location and severity. Petechial haemorrhages and ecchymoses may be seen throughout the body but especially in the proventriculus in the inner surface of the sternum and abdominal fat. The most severe and consistent lesions include splenomegaly, pulmonary oedema and congestion and haemorrhages in enteric lymphoid areas, or serosal surfaces.
An outbreak of avian influenza was diagnosed in layer, broiler and breeder flocks in suburban areas of Islamabad, Murree and Abbotabad, Pakistan in 1994 and 1995. The clinical signs, postmortem lesions, and serological tests confirmed that the cause of the disease was H7 type influenza virus. This outbreak has resulted in heavy economic losses to the poultry industry.
In USA, the avian influenza viruses have caused considerable economic losses. The U.S. government expended over $60 million in 1983-84 to eradicate a highly pathogenic H5N2 virus in poultry. Consumers paid an estimated additional $349 million to cover losses passed on by the producers. More limited outbreaks of avian influenza are also quite costly. For example, on one chicken farm in Australia in 1985, an outbreak involving a highly pathogenic virus cost over $2 million to eradicate.
To save these losses, there are following methods 1) biosecurity measures, 2) use of chemotherapeutics, 3) active immunization, and 4) passive immunization. Biosecurity measures are not very effective in Pakistan due to social interactions of the poultry workers. However, some of the countries like USA, UK, etc. have promulgated the legislation aimed at preventing introduction and spread of the highly pathogenic avian influenza viruses. Slaughter policies were implemented in Great Britain in 1963 and 1979 and in Australia in 1975. On all three occasions, no subsequent spread of highly pathogenic viruses was seen.
The major problem faced in considering vaccination against avian influenza is the antigenic diversity, which exists among these viruses. Generally, the vaccines have been of some success in reducing the severity of disease and the economic losses.
Management can play an important role in preventing both the introduction and the spread of avian influenza. Wild birds have been implicated in both primary infection and secondary spread. The solution for poultry appears to be confinement in bird-proofed buildings. When disease outbreaks have occurred, procedures of depopulation, cleaning, disinfections, leaving the premises empty for two to four weeks before restocking and controlling the movement of personnel and equipment have been successful in preventing
reinfection.
Active immunization is very effective way of immunoprophylaxis of the disease but in case of an outbreak, effective remedy to cure the infected birds is not available for the treatment of the avian influenza disease. Vet-varsity scientists for the 1st time discovered the solution for this disease. In this project, commercial chicken layers have been vaccinated against H7 type of AIV. This vaccination induces specific antibodies in blood. The antibodies are secreted in yolk of the eggs laid by these birds. In this case, there is no need to collect blood from the vaccinated birds, as is the routine practice in mammals to separate serum for therapeutic use in foot and mouth disease. These antibodies in the yolk are titrated and haemagglutination inhibition (HI) units of these antibodies are determined. It is observed that 1ml of 128 HI units of antibodies against avian influenza virus is able to give 100 per cent protection of the challenged birds. It is necessary to
injec!
t 1ml of 128 HI units of antibodies before, simultaneously or even during incubation period of the disease in experimentally infected broilers with the virulent virus. If it is injected on the onset of clinical signs then the chances of recovery decrease from 100% to 75% according to the condition of the bird. In this case, serum and yolk antibodies are found equally effective against avian influenza virus (H7 type). This crude extract of antibodies is no much costly. A poultry producer can easily afford this treatment for commercial broiler, layer and breeder farms.
It is concluded that crude extract of yolk antibodies can effectively be used to cure the avian influenza virus infected commercial broiler, layer, breeder or other precious birds. For the information of the farmers it is noteworthy that such antibody containing preparations / products are available in the market for commercial use.
|
Pakissan.com;
|
