Prevent
kets, by their nature, are not under any form of control, although there may be customary informal regulation by the community. From a disease management point of view, the ideal is that all live animal markets and slaughter places are licensed and that all sales be recorded by the veterinary authority to ensure health status. But this requires a considerable infrastructure to create and enforce regulations. This is possible in circumstances where markets are well-identified and small in number and where effective measures are available against those who break the law. But in many countries, the locations are numerous, access is frequently difficult and veterinary services are overstretched, so this is not possible. Even where it is possible, overzealous enforcement of regulations without the support of traders will create parallel trading systems which may create a greater problem. Markets should also be seen as a potential source of information on trading patterns and disease reports, and as concentration sites where diseases can be detected. Gaining the cooperation of market traders can perhaps be as important as controlling their activities. Trading patterns change, and unless there is close contact with traders, entire parallel trading systems may grow up outside the purview of the veterinary or other authorities. Nonetheless, a degree of control is necessary and must be sustainable. It is important to understand the entire production and marketing network in order to identify the most important nodes where the use of resources will be most likely to detect problems early and where enforcement is most likely to prevent spread through the system.
Live bird marketing systems The wide spread of H5N1 HPAI in domestic poultry (commencing in the late twentieth century) highlighted the role of selling live birds in markets in the spread and maintenance of the infection. Likewise, this may be a source for spread of other diseases such as Newcastle disease. Healthy birds come in close contact with potentially infected birds, and birds that are not sold for immediate slaughter are taken back home, thus spreading infection. The live bird marketing system is complex and each stage often has links to another. While it is often thought that the poultry sold in live markets is from small-holder or backyard farms, in some countries many of the birds come from large-scale, commercial farming systems. The term “live bird markets” is frequently used, but most of the markets where live birds are sold are daily general markets, often in urban areas ranging from villages to cities. Many of the large specialist live bird markets may be held weekly at any one location but can be effectively a daily market held in a different location each day, moving around a regular circuit of locations, with a wide area of supply and a carryover of birds from day to day and location to location. Specialist wholesale poultry sellers are commonly found, usually in urban areas, supplying large areas or regions. This complex marketing system is a difficult challenge for disease management, not capable of easy resolution. Bans or strict limitations on the selling of live birds may be applied, but these are unlikely to be effective unless they can be properly enforced and may lead to the emergence of further, less formal but equally risky marketing practices. Restrictions are likely to be more effective if supported by public awareness campaigns, and
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