Affiliations: *Virus Reseach Institute, Department of Medical Sciences
Source: Bulletin of Department of Medical Sciences 1996; 38(1): 45-58
Language: Thai with English abstract
A study on intratypic differentiation of 52 poliovirus strains isolated in Thailand during 1992 and 1993 was carried out, using ELISA and nucleic acid probe hybridization. The hybridization yielded obvious results in all the strains, whereas ELISA gave indeterminate results in 11 strains (15.4%). Form hybridization assay showed that eleven strains of poliovirus type 1 isolated from acute flaccid paralytic (AEP) patients in 1992 were wild or non-Sabin-like (NSL) strains. From 14 strains of polioviruses isolated from AFP cases in 1993, it was found that 9 were wild strains (P1-6;P3-3) and 5 were Sabin-like (SL) strains (P1-2, P2-1, P3-2). One (P3) of the 5 SL strains was excluded, as a final diagnosis of one of the patients showed she had brain tumour. The 2 SL strains of this isolates (P2 and P3) gave double reactive results with ELISA.
From polioviruses isolated from contacts in which stools were correctly collected (before mop-up immunization) all 6 strains were wild poliovirus type 1; this result was used to confirm the diagnosis of 2 AFP cases for poliomyelitis by epidemiological linkage (one of the patients had a negative isolation result while the stool of the other had not been submitted for testing). From 21 strains of polioviruses isolated from contacts after mop-up immunization, it was found that 16 were SL (P1-9 ; P2-4 ; P3-3) and 5 were NSL strains (P1-2; P2-1; P3-2) This shows that there is still a transmission of 3 types of wild polioviruses circulating in the community.
Of 24 poliomyelitis patients, 13 were Thai and 11 were foreigners. Of the 13 Thai patients, 5 were< 1 - 4 and 8 were 5-14 years old. Eight among 13 had received 3 or more doses of oral polio vaccine (OPV).Of the foreign patients, who were all younger than 4 years, 8 had never been vaccinated while the remaining 3 had received less than 3 doses of OPV.
It can be concluded that poliomyelitis still occurred sporadically in the country. The people in the bordering provinces, immigration camps and foreign children enterring the country are high-risk groups of the circulating transmission of wild polioviruses.