Affililations: *Virus Research Institute, National Institute of Health, Department of
Medical Sciences, Ministry of Public Health, Nonthaburi11000,
Source: Journal of Infections Diseases and Antimicrobial agents
1997; 14(2): 79-86
Twenty years ago, poliomyelitis was one of the main health problem in Thailand and most cases are associated with type 1. Since the reception of the Expanded Program on Immunization in 1977, the incidence has been dropping dramatically. In the last 4 years, number of confirmed indigenous polio cases were under 10 per year. Most of them lived in bordering provinces and some of them in refugee camp. To trace the source of reserviors and transmission in Thai children and the distribution of wild poliovirus type 1, the molecular epidemiological studies were used. A total of 25 strains of wild type 1 poliovirus isolated from patients were studied. Among these, 12, 6, 2, 1 and 4 strains were isolated from patients living in Thailand, hill tribe, Cambodia, Myanmar and Nepal respectively and were analyzed by partial genomic sequencing of viral genome. One hundred fifty bases of genomic sequence which encoding parts of the capsid protein VP1 and noncapsid protein 2A at position 3,508 - 3,527 were analyzed. The result of genomic sequencing dendrogram showed that these strains could be grouped into 2 genotypes. The first genotype included 9 strains most of which were isolated from patients in the eastern provinces of Thailand and their genetype were closely related to strains recently isolated from Cambodian and hill tribe patients living in provinces near eastern border of Thailand. Another independent genotype, 16 strains, were related to strains found in Myanmar Nepal patients. These genotypes were found in Thai patients living in other regions in the years later which started from 1992 - 1995. The study indicated that the primary source of cases - associated viruses imported into Thailand must be from these neighboring countries. The combination of surveillance and molecular epidemiological studies are useful to attain more effective eradication of poliomyelitis in Thailand.