Complex genetic structure of the rabies virus in Bangkok and its surrounding provinces, Thailand: implications for canine rabies control.

Dog vaccination and population management have been suggested as priorities in attempts at disease control in canine rabies-endemic countries. Budget limitations and the complexity of social, cultural and religious variables have complicated progress in the developing world. In Bangkok, Thailand, an intensive canine vaccination and sterilization programme has been in place since November 2002. Our objective was to determine if the rabies virus could be mapped according to its genetic variations and geographical location on the small localized scale of Bangkok and its surrounding provinces. Phylogenetic characterization of 69 samples from Bangkok and five neighbouring and two remote provinces, by limited sequence analysis of the rabies virus nucleoprotein gene, distinguished six different clades. Rabies viruses of four clades were intermixed in Bangkok and in the surrounding highly populated regions whereas the other two clades were confined to rural and less populated provinces. Such a complex pattern of gene flow, particularly in Bangkok, may affect the outcome of canine control programmes.

Transmission dynamics of rabies virus in Thailand: implications for disease control.

BACKGROUND: In Thailand, rabies remains a neglected disease with authorities continuing to rely on human death statistics while ignoring the financial burden resulting from an enormous increase in post-exposure prophylaxis. Past attempts to conduct a mass dog vaccination and sterilization program have been limited to Bangkok city and have not been successful. We have used molecular epidemiology to define geographic localization of rabies virus phylogroups and their pattern of spread in Thailand. METHODS: We analyzed 239 nucleoprotein gene sequences from animal and human brain samples collected from all over Thailand between 1998 and 2002. We then reconstructed a phylogenetic tree correlating these data with geographical information. RESULTS: All sequences formed a monophyletic tree of 2 distinct phylogroups, TH1 and TH2. Three subgroups were identified in the TH1 subgroup and were distributed in the middle region of the country. Eight subgroups of TH2 viruses were identified widely distributed throughout the country overlapping the TH1 territory. There was a correlation between human-dependent transportation routes and the distribution of virus. CONCLUSION: Inter-regional migration paths of the viruses might be correlated with translocation of dogs associated with humans. Interconnecting factors between human socioeconomic and population density might determine the transmission dynamics of virus in a rural-to-urban polarity. The presence of 2 or more rabies virus groups in a location might be indicative of a gene flow, reflecting a translocation of dogs within such region and adjacent areas. Different approaches may be required for rabies control based on the homo- or heterogeneity of the virus. Areas containing homogeneous virus populations should be targeted first. Control of dog movement associated with humans is essential.

[Rabies control in Thailand].

Two governmental sectors, Department of Livestock Development, Ministry of Agriculture and Cooperatives and Department of Disease Control, Ministry of Public Health, have been jointly responsible for rabies control in Thailand. The aim is to have the rabies situation controlled both in humans and animals. Strategies included promotion of collaboration among governmental agencies, private sectors and publics in carrying out activities. Public campaigns are continually undertaken to raise public awareness, understanding and participation in rabies prevention and control. Providing education to the general public on appropriate self care after rabies contact is also one of their tasks. Another important mission aims to enhance a wider coverage of rabies vaccination in dog population in order to create and expand rabies free territories.

[Rabies situation in Thailand].

Rabies statistics have been officially recorded since 1929 and rabies became a notifiable disease in Thailand in 1980. The direct fluorescent antibody test is the test most frequently used to diagnose rabies. Although rabies incidence has been declining, animal specimens submitted for testing have been inadequate and it is not justifiable to conclude that the rabies situation is controlled. Laboratory confirmation of rabies in man relies on demonstration of rabies antigen on brain impression smear or RNA in secretions and hair follicles. Nevertheless, almost all specimens belonged to patients who manifested as furious rabies only. Reliability of the reporting system needs improvement in public understanding and close cooperation between public and government sectors.