Sir

Your welcome News report on 12 April (Nature 410, 727; 2001), that the UK foot-and-mouth disease epizootic may be slowing, referred to an article two weeks earlier (Nature 410, 501; 2001). This reported that three independent groups of researchers had told the UK government that rapid slaughter of infected animals was the best way to slow the outbreak.

Without wishing to detract from the valuable contributions being made by epidemiologists, most veterinary clinicians and pathologists dealing with farm animals were aware of this need even before the outbreak started. The need for rapid diagnosis and speedy implementation of control measures for diseases of this type is part of their basic training.

Early delays in dealing with the current outbreak were significantly influenced by owners of diseased animals not requesting veterinary advice quickly enough, possibly because the clinical signs of foot-and-mouth disease, particularly in sheep, can be difficult even for a responsible and observant owner to detect. Another cause of early delay was the requirement to have animals produced for commercial purposes valued — not an issue when dealing with an epizootic in laboratory mice.

At the beginning of an epizootic it is essential to diagnose the disease correctly and identify the causal agent by laboratory tests, to provide epidemiologists with accurate information for mathematical models. In some cases it can take as long as four days to declare a sample positive for foot-and-mouth disease virus.

Once the aetiology of the disease is known, control procedures can be implemented more quickly by relying on diagnosis based on clinical signs, and laboratory tests are not needed. The effectiveness of this approach depends on the diagnosis being made by people who, in the case of foot-and-mouth, can distinguish between the lesions of this disease and those of the other enzootic diseases prevalent in the United Kingdom such as mucosal disease, bovine papular stomatitis, contagious pustular dermatitis, foot rot and laminitis.