HISTORY OF AVIAN INFLUENZA (BIRD FLU) IN PAKISTAN

Investment in poultry sector in Pakistan is about one billion dollars. Every family in rural areas and every fifth family in urban areas is associated directly or indirectly with poultry production activities in one way or the other (Sadiq., 2000). Poultry industry in Pakistan and all over the world is a major contributor of animal proteins substitute. Pakistan poultry industry is facing various managemental problems along with infectious diseases including avian influenza avian influenza (Alexander., 2000). Economics losses from avian influenza have varied depending on strain of virus, species of bird infected, number of farms involved, control methods used, and speed of implementation of control or eradication strategies. Direct losses in HAPI outbreak have included disposal costs, high mortality and morbidity losses, quarantine and surveillance costs and indemnities paid for elimination of marketing birds (Swayne., 2003).

In Pakistan outbreak of AI was first recorded in October 1994. The disease affected broiler breeder in Mansehra, Abbotabad, Rawalpindi and adjoining areas, killing approximately one million birds. The causative agent was confirmed as avian influenza a virus H7N3 (Naeem and Hussain.,1995).

In 1996, outbreak of AI broiler breeder and commercial layer was suspected in various areas of the Punjab. This outbreak did not cause considerable loss but was responsible for low production and immunosuppression. The causative agent was isolated and characterized as avian influenza virus H9N2. Keeping in view the virulence of this virus for poultry, this was also included in locally prepared vaccine. The AI vaccines containing locally isolated H7N3 have been extensively used since 1996 (Muhammad et al., 1997).

However, due to poor bio security and congested poultry colonies, the problem of AI started reappearing in Karachi in 1999 mainly in broilers. The disease was controlled by vaccination and strict bio security measures. However, later on due to poor bio security and no usage of vaccine the avian influenza was endemic in Karachi by the end of 1999 (Naeem et al.,1999).

In 2001, outbreak of a respiratory syndrome in broiler and layer, in Karachi and Abbotabad was recorded. The morbidity upto 100 percent and mortality was upto 50 percent. The HA agent was confirmed as avian influenza (H9 subtype) by using HI with AIV-H9 specific antis era (Muhammad et al., 2001). In 2003, the occurrence of avian influenza virus (AIV) infection in broiler, layer and broiler breeder flocks were reported in |Southern Pakistan. Data from this survey showed high levels of AIV antibodies, indicating unrecognized AIV infection occurring in these flocks. Based on this information, a second investigation was undertaken in selected broiler breeder, broiler and layer flocks. In this investigation, nine H9N2 AIV isolates were recovered. Chicks with the previous history of respiratory tract infection and some without overt clinical respiratory signs, had seroconverted to H9N2 (Naeem et al., 2003).

Production of recombinant fowl pox vaccine expressing Haemagglutinin of Avian Influenza H5N1

Introduction:

Avian influenza (AI) is an infectious disease caused by Avian Influenza virus (AIV), which is divides in to 16 Heamagglutinin (HA) subtypes and 9 Neuraminidases (NA) subtypes on the bases of antigenicity of HA and NA surface glycoprotein. H5 and H7 may cause High Pathogenic Avian Influenza (HPAI). Out breaks of severe disease caused by influenza virus have been reported frequently in the recent years, leading to substantial economic losses. H5N1 strain can de transmitted directly from birds to human (1-2) H7 and H9 AIV have been identified from humans and other mammals. These facts have made clear the zoonotic importance of the Avian Influenza virus. Presently H5 and H7 (HPAI) remain active in the south Asia and other part of the world (3-4). From Pakistan H9N2 (5), H7N3 have been isolated a no of time and in 2006 H5N1 was reported. Now in 2007 there is a severe outbreak of H5N1 in Islamabad and different districts of Punjab.

Objectives:

To produce avian influenza H5 vaccine, recombinant with Fowl Pox virus (FPV). Currently, inactivated whole vaccines are used which are creating problems in Epidemiological studies and it is difficult to differentiate between vaccinal response and outbreak from serological studies (6).

Methodology:

Avian Influenza virus will be isolated from field or RNA will be isolated from inactivated whole H5 subtype vaccine, cDNA encoding whole H5 genes of H5N1 subtype will be cloned and introduce into expression vector plasmid. The plasmid will be introduced in Fowl Pox virus attenuated strain; the recombinant Fowl pox virus will be propagated in Chicken Embryo Fibroblast (CEF) to produce vaccine. Expression of H5 gene in the virus will be detected by PCR using specific primers. Immunity produced in the experimental birds will be titrated by Haemagglutination Inhibition (HI) test and experimental inoculation of H5N1 virus to the birds.

References:

1. Subbarao K, Klimov A, Katz J, Regnery H, Lim W, Hall H, et al. Characterization of an avian influenza A (H5N1) virus isolated from a child with a fatal respiratory illness. Science 1998; 279:393–6.

2. Claas EC, de Jong JC, van Beek R, Rimmelzwaan GF, Osterhaus AD. Links Human influenza virus A/Hong Kong/156/97 (H5N1) infection. Vaccine 1998; 16:977–88.

3. Spackman E, Senne DA, Davison S, Suarez DL. Sequence analysis of recent H7 avian influenza viruses associated with three different outbreaks in commercial poultry in the United States. J Virol 2003; 77:13399–402.

4. Fouchier RAM, Schneeberger PM, Rozendaal FW, Broekman JM, Kemink SAG, Munster V, et al. Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome. PNAS 2004; 101:1356–61.

5. Naeem, K., A. Ullah, R. J. Manvell and D. J. Alexander, 1999. Avian influenza A subtype H9N2 in poultry in Pakistan. Vet. Rec., 145: 560.

6. Beard CW, Schnitzlein W, Mand Tripathy DN. Protection of chickens against highly pathogenic avian influenza virus (H5N2) by recombinant fowlpox viruses. Avian Diseases 1991; 35:356–9.