EPIZOOTIC SITUATION OF FOOT-AND-MOUTH DISEASE IN KAZAKHSTAN AND CHINA: A COMPARATIVE ANALYSIS, CROSS-BORDER INTRODUCTION AND CONTROL MEASURES

Abstract

This article provides a comprehensive comparative analysis of the FMD epizootic situation in Kazakhstan and China in the period 2020-2026. In a study in Kazakhstan, out of 1007 serum samples with a positive reaction to ELISA, 88 samples were selected for in-depth analysis - 11 from each of the 8 districts. In DIVA testing (to 3ABC), a positive reaction was detected in only 7 samples. Upon subsequent RT-qPCR analysis of these 7 samples, the results were negative for the FMD virus genome of serotypes A, O, Asia-1 and SAT. This dissociation of markers can be explained by several factors: the presence of post-vaccination antibodies to NSP due to insufficient purification of the inactivated vaccines used, the peculiarities of the kinetics of antibody formation, or a low viral load below the limit of PCR detection. At the same time, a comprehensive assessment of the suitability of the strain of FMD virus Re-A/WH/09 for vaccine production was carried out in China. The strain was stably reproduced in the BHK-21 cell line with a characteristic cytopathic effect. The titer of infectious activity was 7.5lg TCID₅₀/ml. The LD₅₀ value of 4.5lg indicates the attenuated properties and relative safety of the strain. We obtained an antigen titer of 1:3200, which indicates that the key antigenic determinants are preserved. Molecular genetic verification confirmed that the isolate belongs to serotype A and that there is no contamination with extraneous genetic materials. The study confirms the need to switch to DIVA-compatible vaccines according to WOAH standards, as diagnostics show a distortion of monitoring due to NSP in poorly purified vaccines. As part of the development of an inactivated vaccine, cultivation conditions in the BHK-21 line were optimized, a technological base for antigen purification was created, and validation of the series in preclinical trials is planned.