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Twenty-nine distinct epizootics of high-pathogenicity avian influenza (HPAI) have occurred since 1959. The H5N1 HPAI panzootic affecting Asia, Africa and Eastern Europe has been the largest among these, affecting poultry and/or wild birds in 63 countries. A stamping-out programme achieved eradication in 24 of these epizootics (and is close to achieving eradication in the current H5N2 epizootic in South African ostriches), but vaccination was added to the control programmes in four epizootics when stamping out alone was not effective. During the 2002 to 2010 period, more than 113 billion doses of avian influenza (AI) vaccine were used in at-risk national poultry populations of over 131 billion birds. At two to three doses per bird for the 15 vaccinating countries, the average national vaccination coverage rate was 41.9% and the global AI vaccine coverage rate was 10.9% for all poultry. The highest national coverage rate was nearly 100% for poultry in Hong Kong and the lowest national coverage was less than 0.01% for poultry in Israel and The Netherlands. Inactivated AI vaccines accounted for 95.5% and live recombinant virus vaccines for 4.5% of the vaccines used. Most of these vaccines were used in the H5N1 HPAI panzootic, with more than 99% employed in the People's Republic of China, Egypt, Indonesia and Vietnam. Implementation of vaccination in these four countries occurred after H5N1 HPAI became enzootic in domestic poultry and vaccination did not result in the enzootic infections. Vaccine usage prevented clinical disease and mortality in chickens, and maintained rural livelihoods and food security during HPAI outbreaks. Low-pathogenicity notifiable avian influenza (LPNAI) became reportable to the World Organisation for Animal Health in 2006 because some H5 and H7 low-pathogenicity avian influenza (LPAI) viruses have the potential to mutate to HPAI viruses. Fewer outbreaks of LPNAI have been reported than of HPAI and only six countries used vaccine in control programmes, accounting for 8.1% of the total H5/H7 AI vaccine usage, as compared to 91.9% of the vaccine used against HPAI. Of the six countries that have used vaccine to control LPNAI, Mexico, Guatemala, El Salvador and Italy have been the biggest users. In countries with enzootic HPAI and LPNAI, development and implementation of exit strategies has been difficult.

The panzootic of the H5N1 strain of highly pathogenic avian influenza has become an international crisis. All parts of the world are now considered at risk due to trade globalisation, with the worldwide movement of animals, products and humans, and because of the possible spread of the virus through the migration of wild birds. The risk of introducing notifiable avian influenza (NAI) through trade depends on several factors, including the disease status of the exporting country and the type of products. The highest risk occurs in the trade of live birds. It is important to assess and manage these risks to ensure that global trade does not result in the dissemination of NAI. However, it is also important that the risk of infection is not used as an unjustified trade barrier. The role of the regulatory authorities is thus to facilitate the safe trade of animal products according to international guidelines. Nevertheless, the balance between acceptable risk and safe trade is difficult to achieve. Since the movements of poultry and birds are sometimes difficult to trace, the signature or 'identity card' of each isolated virus can be very informative. Indeed, sequencing the genes of H5N1 and other avian influenza viruses has assisted greatly in establishing links and highlighting differences between isolates from different countries and tracing the possible source of introduction. Recent examples from Asia, Europe and Africa, supported by H5N1 molecular fingerprinting, have demonstrated that the sources of introduction can be many and no route should be underestimated.

The evolution of influenza is a continuing process involving viral and host factors. The increasing frequency of emergence of the highly pathogenic H5N1, H7N3 and H7N7 influenza viruses and the panzootic spread of H9N2 influenza virus, all of which can be potentially transmitted to humans, are of great concern to both veterinary and human public health officials. The question is how soon the next pandemic will emerge. A convergence of factors, including the population densities of poultry, pigs and humans, are likely factors affecting the evolution of the virus. Highly concentrated poultry and pig farming, in conjunction with traditional live animal or 'wet' markets, provide optimal conditions for increased mutation, reassortment and recombination of influenza viruses. Strategies to reduce the evolution of influenza and the emergence of pandemics include the separation of species, increased biosecurity, the development of new vaccine strategies and better basic knowledge of the virus. More effective co-operation between scientists and veterinary and public health officials is required to achieve these goals.

Summary : The recorded foot and mouth disease ouibreaks in Zambia are confined to three zones. The disease is caused by SAT 1 and SATc2 virus in the two zones A and B. In national game parks close to Zone B, all three SAT types have been isolated from wildlife. In Zone C (close to the Tanzanian border) outbreaks of FMD were caused by virus type O. In the latest recorded outbreaks in zones B and C the virus strains have behaved mildly. It is believed that the rinderpest panzootic of 1896, which wiped out a large part of the ruminant population, probably also eliminated foot and mouth disease (FMD) in the Southern African territories (Condy, 1979). This may be the reason why no outbreaks of the disease were reported in cattle in Zambia during the first third of this century. FMD has been seen in the country from 1933 and since then it has been recorded during 29 of the 50 subsequent years. Four virus types have been isolated : SAT 1, SAT 2, SAT 3 and O of which SAT 3 has been found in game animals only. FMD outbreaks up to 1974 have been reported before (Zyambo, 1975). This paper deals with the latest surveys and reports on FMD in Zambia.

Summary: Rinderpest is still the greatest scourge of domestic cattle and buffaloes in tropical Africa and Asia. Despite large-scale mass vaccina­ tion campaigns, outbreaks of the disease continue to spread to countries from where it was once eradicated. During the past few years an increased incidence of the disease has affected several countries in West, East and Central Africa, the Middle East and South-East Asia. The Sahelian drought this year might force large-scale migration of cattle from Chad and Mali, and thereby increase the spread of the disease to countries south of Sahara. Currently a panzootic of rinderpest is sweeping across tropi­ cal Africa, and an epidemiologist has already claimed that a million cattle have died or been emergency slaughtered. This calamity coupled with drought, famine and political strife has resulted in a disaster of the century. Global eradication of smallpox has shown that it is possible to eradic­ ate a disease by human endeavour. Rinderpest is also a severe disease of domestic cattle and is of great economic significance. It does not pro­ duce persistent, recurrent and subclinical infection, and a safe and effec­ tive cell-culture vaccine is available. With international financing and organisation, global eradication of rinderpest should be possible within a period of a few years. The paper describes the present situation of the disease, efforts made to control and eradicate it in the recent past, and suggests ways and means to achieve these goals.