Control and prevention of avian influenza in an evolving scenario.

Continuing outbreaks of highly pathogenic avian influenza (HPAI) across Eurasia and in Africa, caused by a type A influenza virus of the H5N1 subtype appear out of control and represent a serious risk for animal and public health worldwide. It is known that biosecurity represents the first line of defence against AI, although in certain circumstances strict hygienic measures appear to be inapplicable for social and economic conditions. The option of using vaccination against AI viruses of the H5 and H7 subtypes, has made its way in recent times--primarily as a tool to maximise the outcome of a series of control measures in countries that are currently infected, but also as a means of reducing the risk of introduction in areas at high risk of infection. In developing countries vaccination programmes in avian species have been recommended recently, however it will require concurrent management of local husbandry practices and industry compliance to eradicate the disease rather than the establishment of an endemic situation. Other key deliverables expected for this control strategy include maintaining a major source of food for rural communities and the preservation of the commercial viability of the local poultry industry. In developed countries vaccination is being used as a means of increasing resistance of susceptible animals to reduce the risk of introduction from the reservoir host or to reduce secondary spread in densely populated poultry areas. The recent joint OIE/FAO summits recommended applying vaccination, using the differentiating infected from vaccinated animals (DIVA) strategy when there is risk of major spread and depopulation is not feasible or desirable. Particularly in developing countries, stamping out of infected animals does not seem to be an appropriate means of reducing the spread of infection, if food supplies are to be guaranteed and economic consequences minimised. Crucial points to the success of a vaccination campaign are the implementation of complex territorial strategy involving upgraded biosecurity, monitoring vaccine efficacy, identification of field exposure and the appropriate management of infected flocks, regardless of vaccination status. Granting financial support for the compensation of farmers is also a key part of this strategy. Poultry veterinarians working for the industry or for the public sector represent the first line of defence against the pandemic threat and for the prevention and control of this infection in poultry and in wild birds.