6th International Conference on Typhoid Fever and Other Salmonelloses, Guilin, China, 12-14 November 2005

Abstract

The International Conference on Typhoid Fever and Other Salmonelloses is organized every two to three years and has usually taken place in Asia. The first meeting was held in Malaysia 15 years ago. The 6th international meeting, held in Guilin, China, in November 2005, was organized by the Guangxi Centre for Disease Prevention and Control, in collaboration with the World Health Organization (WHO), the International Vaccine Institute (IVI), and the American Society for Microbiology (ASM). Two hundred fifty participants from 27 countries, including Africa, participated. Nine sessions covering the major topics of interest provided the latest updated information on typhoid fever. These include: Epidemiology and disease burden; Molecular pathogenesis and genomics; Contemporary issues in vaccine development; Diagnostics in typhoid fever; Antimicrobial resistance in typhoid fever; Clinical and therapeutic aspects; Socio-behavioural research; Other salmonelloses-related contemporary issues; and a Roundtable on Expanding Vaccine Implementation in Developing Countries. Travel grants for participants from developing countries were supported by the WHO, IVI, and the ASM, and by the Conference Organizing Committee. Epidemiology and disease burden During the epidemiology session, general consensus was raised that typhoid fever remains an important, but under-estimated, disease which has high mortality in developing countries, particularly in Asia. However, there are extremely limited data from Africa, and the burden of disease is probably under-estimated in this region. Endemic disease in South-East Asia is observed to be high, although it varies greatly in different settings. In addition, disease in the paediatric population was higher than previously recognized. The latest published figure for the estimated number of cases is approximately 22 million per year, with an estimated 210,000 deaths (1). This number of deaths was calculated from a conservative figure using a case-fatality rate (CFR) of 1%. However, the reported CFR from presentations during the meeting was generally much higher than this in different studies, with the general agreement that this 1% estimate was under-estimated and that additional robust studies are required. It was suggested that WHO should convene a consultative meeting to resolve this during 2006. Second, the increasing number of Salmonella Paratyphi A isolates recovered in Asia, particularly in China and Pakistan, was noted with concern. In Guingxi province of China, 94% of Salmonella isolates are currently S. Paratyphi A. This situation raised the point of accelerating the development of S. Paratyphi A vaccine candidates. Molecular pathogenesis and genomics Developments in molecular pathogenesis and genomics highlighted the difficulties that surround the serotyping of Salmonella species and the classification of Salmonella strains. The full genome sequence of Salmonella strains indicates that the S. Typhi and S. Paratyphi A have a recent evolutionary history. Using this sequence data, a novel system based on multi-locus sequences typing (MLST) has been devised which should help type Salmonella strains in a more precise approach and could replace classical serotyping in future. New data from Viet Nam showed that a haplotype of the TNF region was associated with fever-clearance time in patients. Individuals who have the protective haplotype (*12*22**1) cleared their fever significantly faster than individuals who did not have this haplotype. Better understanding of the organization of Salmonella pathogenicity islands and diversity of Typhi flagellar antigen expression were presented. Finally, it was recommended that further research was required on (a) S. Typhimurium in Africa, (b) paediatric versus adult strains of S. Typhi, and (c) molecular epidemiology of outbreaks versus endemic strains. Contemporary issues in vaccine development Besides the currently-licensed and available vaccines (Vi polyssacharide and Ty21a), other candidate vaccines, consisting of either subunit vaccine or live-attenuated vaccines, were described. …