Item 11 – Persistent and subclinical infections – diagnostic and surveillance issues

consideration of “substances from animals for which there is a low probability that infectious substances are present, or where the concentration is at the level naturally encountered, not to be subject to these Regulations (2.6.3.2.3.2)” since these samples do not represent a risk to transport workers or to the environment.

1. The meeting endorsed and supported the actions taken by EUFMD /FAO and OIE on these subjects.

1. The actions taken by OIE to guarantee a realistic possibility for transport of samples should be supported. 2. Laboratories should improve their collaboration and information exchange, which will support global FMD control. 3. Close collaboration between the EUFMD Research Group and the OIE experts is essential for a coordinated improvement of the international standards.

Drs. Paul Sutmoller and John Bashiruddin discussed vaccinated carriers and recovered carriers, respectively. An account of the actual risks compared to the perceived risks of FMD carriage by vaccinated carriers was discussed by Dr Sutmoller and co-authors, who considered that based on historical data, the risk of transmission of FMDV from carriers after emergency vaccination is smaller than the risk of introduction of FMDV by illegally imported meat (Appendix 63). Further it was suggested that the risk of transmission of FMDV from carriers might be of the same magnitude as the risk of import of meat from animal populations in countries using vaccination against FMD. Dr Bashiruddin from experimental evidence concluded that there were differences in the rate of carriage and clinical presentation dependent on the age of the cattle at the time of infection (Appendix 64).

Drs. Franco De Simone and Kris De Clercq reported on the results of the validation exercise, undertaken as part of the EU ImproCon project, for various NSP-ELISA kit tests on sera from naïve, FMDV vaccinated, infected and vaccinated plus infected populations of cattle, sheep and swine (Appendix 6). Extensive analyses were shown and the workshop results were considered to have produced sufficient information to enable test comparison. However, they considered further analysis is needed before publication of the final report. Dr. Kitman Dyrting reported on the NSP-ELISA evaluation that is part of the Coordination Action of the IAEA/FAO, on pig sera from Hong Kong (Appendix 65). The sensitivity of NSP ELISA systems applied to the detection of exposed animals after outbreaks in pigs was reported to decrease with time subsequent to outbreaks.

Dr. Nesya Goris considered the validation and batch-to-batch consistency of commercial diagnostic kits and their testing to ensure consistency of test results (Appendix 66).

1. Experimental infection with the FMDV type O virus responsible for the outbreak in 2001 in the UK resulted in more carrier cattle in older than in younger cattle. 2. High specificities (CI lowest test, highest test system-prelim) with the current NSP ELISA systems were obtained in both unvaccinated and vaccinated, non-infected cattle. 3. The finding that samples from naive animals that scored false positive in one NSP tests often scored correctly in the other NSP tests may provide a basis for use of confirmatory tests to increase specificity. 4. Where there is no relevant national system, batch-to-batch testing is necessary when using diagnostic kits to ensure consistency of results; this could be organised internationally.

1. Science-based risk assessments should be made to compare the risk associated with persistent infections, and risks associated with different eradication methods of FMD and trade in animals and animal products. 2. The ability and likelihood of FMD carrier bulls to transmit disease by the sexual route should be investigated.