5th ASM - Orals Detection & Control

Session 1: Wednesday 3 June, 17.00

Sally Cutler from The University of East London, UK, provided an interesting overview of Borrelial relapsing fever in Africa, transmitted by ticks. Recent developments in the sequencing of the genomes of Borrelia recurrentis and B. duttoni have provided insights into the evolutionary history and genetic relationships of these organisms, with possible implications for the identification of the role of new spirochetes in human disease.

A second presentation, delivered by Neil Leblanc of the National Veterinary Institute, Uppsala, Sweden, described a novel combination of a Taqman® RT-CR and a suspension microarray assay for the detection and speciation of pestiviruses. The new method overcomes problems associated with antibody cross-reactions, ELISA sensitivity and lack of the multiplexing capability of standard PCR-based tests. The novel platform includes a real-time (RT) PCR designed for the universal detection of pestiviruses combined with a microarray assay that can use the amplicon produced in the RT PCR to identify the specific pestiviruses. It is hoped that the test will be used in the field in the near future.

The theme of developing RT-PCR assays was continued in the following presentation, when Simone Caccio of ISS, Rome, Italy, described RT PCR assays for the simultaneous detection of assemblages A and B of the parasite Giardia duodenalis. Only assemblages A and B of G. duodenalis cause human disease and the test is based on primers for the detection of qPCR products for specific genes by melting point analysis. The possibility of detecting simultaneously and specifically DNA from both assemblages may find application in distinguishing between mixed infections and recombinants in field isolates, and also in their detection in food and water samples.

Finally, Baldissera Giovani of AFSSA LERPAZ, France, described the development of a new indirect ELISA test for the detection of Trichinella spiralis. This test is based on two previously-identified antigens, namely Nb1 and 411, expressed as recombinant GST‑fusion his-tagged proteins. It is hoped that the new test will overcome the lack of specificity of the current serological test for early detection of the organism in food animals.

Session 2: Thursday 4 June, 16.45

Yvonne van Duynhoven of CIDC, The Netherlands opened the session with an update of the outbreak of Coxiella burnetti (Q-fever) infection in The Netherlands, which has been on-going since 2005. The outbreak has caused abortion waves in over 20 goat farms and a human outbreak has been documented, as well as an overall increase in Q-fever infections in the general population. A large scale vaccination programme in small ruminants is underway, although the effectiveness of this is difficult to predict for a variety of reasons, including host factors and weather conditions.

The second presentation, by Joao Inacio of LNV-INRB, I, P, Portugal, described a novel gold-nanaprobe (AuNp) approach for the detection of members of the Mycobacterium tuberculosis complex (MTBC), and for the identification of M. bovis and M. tuberculosis. This approach, which relies on the colorimetric differentiation of specific DNA sequences induced by differential aggregation profiles in the presence and/or absence of specific hybridization. The method appears sensitive, specific and rapid and should be suitable for the routine diagnosis of tuberculosis in veterinary and human health settings.

Guiseppe Cacciatore of RnA BV, The Netherlands then presented details of microsphere-based flow cytometry for the direct and indirect detection of salmonella in food-producing animals. The method appears highly specific, and should have considerable applicability to the detection of salmonella organisms in the veterinary production chain.

Wim van der Poel from CVI-WUR, The Netherlands then presented the results of a nine-centre laboratory ring trial especially within WP31 participating laboratories for the evaluation of swine Hepatitis E virus (HEV) genotype antibody detection tests. Eight out of the nine participating laboratories were able to detect HEV antibody in an undiluted serum sample from an experimentally-infected pig, but at least two laboratories reported false positive test results. An important conclusion was that more extensive studies may need to be undertaken to elucidate whether there may be different serotypes of HEV.

This presentation was followed by an interesting paper delivered by Alia Yacoub of the NVI, Uppsala, Sweden, who described a new proximity ligation assay (PLA) for the detection of avian influenza viruses. Results showed that the method is comparable to the ‘gold-standard´ RT-PCR method for influenza gene detection, and presents a simple and rapid tool for influenza diagnosis.

The final presentation, by Monica Martinez-Martinez of ITACyL, Spain, provided an account the use of a real-time TaqMan® RT‑PCR method to detect HEV, norovirus, enteric coronaviruses, porcine adenoviruses and rotavirus in animal stools and by‑products in farms in the Castilla y León area of Spain. The method appeared robust, and demonstrated that adenoviruses rotaviruses were the most common viruses detected in pig faeces, whist rotaviruses were most common in bovine stools.

The two Detection and Control sessions provide examples of the development and validation of a wide range of new methods for pathogen detection, particularly in farm animals. Several Med‑Vet-Net WPs have contributed to such studies, and in many cases the methods developed will be taken forward outside the network in future years.

John Threlfall (HPA)