COMPARISON OF NEURAMINIDASE ACTIVITY OF INFLUENZA A VIRUS SUBTYPE H5N1 AND H1N1 USING REVERSE GENETICS VIRUS

Abstract. Neuraminidase (NA) is an envelope surface glycoprotein of influenza A viruses. It cleaves α-(2,3) or α-(2,6) glycosidic linkage between a terminal sialic acid residue of the host cell receptor and hemagglutinin of the viral envelope, thus releasing viral progeny from the infected cell. In this study, a reassortant virus (H1N1-NA-H5N1) containing the NA gene from A/duck/Phitsanulok/ NIAH6-5-0001/2007 (H5N1) virus and seven remaining genetic segments from A/ Puerto Rico/8/1934 (H1N1) was constructed using reverse genetic technique. NA activity of H1N1-NA-H5N1 virus was lower than that of A/Puerto Rico/8/1934 (H1N1), and NA activity of A/duck/Phitsanulok/NIAH6-5-0001/2007 study (H5N1) was the lowest among them (p < 0.05). To our knowledge, this is the first comparative study of NA activity of H1N1 and H5N1 virus using reverse genetic technique. It also indicates that the NA gene may be expressed at a higher level in the H1N1 infected cell than the H5N1 infected cell

An investigation of 11 outbreaks of foot-and-mouth disease in villages in northern Thailand

The results of investigations of 11 outbreaks of foot-and-mouth disease in villages in northern Thailand are described. The causative virus was Asia in one in seven outbreaks, Type O in two outbreaks and unknown in two outbreaks. The most probable sources of the outbreaks were co-mingling of cattle and/or buffalo with livestock from an infected neighbouring village (four) and recent introductions of infected cattle from a public livestock market (two) while the probable source could not be determined in five outbreaks. Attack rates in cattle and buffalo ranged from 0.28% to 50.9% but no pigs became sick during any of the outbreaks. Most outbreaks lasted 4 weeks or less. Adult cattle and buffalo were at higher risk of becoming a case when compared with work cattle. Beef cattle were at higher risk than buffalo and adult cattle and buffalo were at higher risk than calves less than 1 year of age. There was significant clustering of cases within households. Serological investigations indicated that many unaffected animals were probably not exposed to virus during the outbreaks. We concluded that close contact between animals was the main method of spread and that differences in attack rates between animal classes reflected differences in animal management. We further concluded that simple quarantine of early cases during outbreaks is likely to be effective in reducing spread within and between villages

Village level risk factors for foot-and-mouth disease in northern Thailand

A study was undertaken in northern Thailand to identify factors which put some villages at higher risk of foot-and-mouth disease (FMD) outbreaks than others. The number of FMD outbreaks experienced in the previous 5 years and data on 145 putative risk factors were obtained by interview from 60 villages during 1991–1992. Univariable analyses identified 27 factors for further investigation using logistic regression. When villages were classified into three FMD frequency groups of zero to one, two to three or four or more outbreaks in the last 5 years, the important factors explaining the differences in risk were the total number of cattle and buffaloes purchased in the previous year, the number of neighbouring villages which shared a common water source and whether agriculture was the most important source of cash income for the village. These factors were also the most important variables in explaining the difference in risk when comparing villages with zero or one outbreak with those having four or more. We concluded that the greatest impact on reducing spread of FMD among villages would be obtained through the development of strategies to reduce the likelihood of introduction through livestock purchases and for villagers to take greater care when livestock are grazed with those from neighbouring villages and when sharing common water supplies