Paris

Simple tests for foot-and-mouth disease that differentiate between vaccinated, infected and 'carrier' livestock could become available quickly if international agreement was reached on sensitivity and specificity, a meeting in Paris was told last week.

The International Scientific Conference on Foot-and-Mouth Disease brought together representatives of the UN Food and Agriculture Organization (FAO) and the main intergovernmental animal-health organization, the Office International des Epizooties (OIE), which covers 157 countries.

Under examination: vaccination against foot-and-mouth disease could become more common. Credit: CORBIS

Delegates heard that such tests would be highly valuable to countries that want to maintain disease-free status and export livestock or meat after a vaccination programme or epidemic. The tests would make it far easier for countries to vaccinate animals, rather than slaughter them, as Britain has done, in response to outbreaks of the disease.

The diagnostic tests in question are based on enzyme-linked immunosorbent assay techniques. These can differentiate between antibodies in the blood against structural proteins found in whole viruses and against non-structural proteins, which are produced as the virus replicates. Because the vaccines tend to be produced from inactivated viral particles, vaccinated animals do not usually generate antibodies against the non-structural proteins and so can be identified by the assays.

“The tests are proving useful but they aren't yet 100% perfect,” said Tony Garland, of Britain's Institute for Animal Health (IAH) in Pirbright, Surrey. “They are currently only suitable for diagnosis at herd level, not at the individual level.” The IAH and the Istituto Zooprofilattico Sperimentale in Brescia, Italy, in collaboration with the Dutch vaccine company Intervet, hope to have their test on the market in September. Another commercial test has been produced by United Biomedical, a pharmaceutical company based in New York state.

But before they can be produced in sufficient quantities for mass screening or be accepted by the World Trade Organization as proof of disease-free status for export purposes, the tests need to be harmonized against a set of standard varieties of the disease virus. The complexity of the foot-and-mouth virus and its wide range of hosts makes this standardization hard to achieve.

The process could take between one and three years, according to Bernard Vallat, director-general of the OIE. Another problem is that the OIE's general assembly, which has the final vote on such standardization, meets only once a year.

At last week's conference, experts called for international concerted action to speed up the process. They proposed a list of recommended actions on foot-and-mouth disease to be put before the OIE's annual meeting in May.

“Steps should be taken on preventative measures in areas where the virus is endemic,” said John Crowther, a member of a Vienna-based collaboration between the International Atomic Energy Agency and the FAO animal-health division.

The meeting also recommended special provision for emergency vaccination of endangered species and those carrying rare genetic material, without prejudice to the disease status of the host country, provided that the animals are physically separated from other populations. But little research has been done on the effectiveness of vaccines in rare and exotic species.

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