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From 1982 to 1987 a total of 4,371 dairy cattle in Saitama Prefecture, were examined for levels of hemagglutination inhibition (HI) antibody to Japanese encephalitis virus (JEV) and the correlation with meteorological factors and an antibody positive rate was studied. Positivity rates of HI antibody from July to October each year (Yi) ranged from 58.8 to 88.0% with a considerable annual variation. Simple regression analysis of Yi with the comparative meteorological value (Xi) was determined from mean temperatures (Ti, j-1), rainfalls (Ri, j-1) for 10-day-periods each, and the number of days showing 25 degrees C or above (ti, j-1) from June to September, which yielded a correlation coefficient of 0.8147 (p less than 0.05) and an equation for estimated HI antibody positivity rate: Yi = -0.04Xi+79.9 (p less than 0.05). Multiple regression analysis with the power values of three meteorological parameters as independent variables and Yi as the dependent variable, showed a multiple correlation coefficient of 0.987 (p less than 0.05) and a multiple regression equation: Yi = -3991T1/13-0.0035R-12+1978t1/9+4187 (p less than 0.05), giving estimated positivity rates almost equal to the values from the observations. Therefore, a predictive equation was formulated reflecting positive and negative correlations of sero-positivity with the temperature and the precipitation, respectively.

Serum samples were collected from 55 pairs of calves that had not passed the first summer and their dams reared in Kagoshima from 1983 through 1985. They were investigated for the HI antibody to Japanese encephalitis virus (JEV) in calves and for the correlation of antibody levels between calves and their dams. The maternally derived antibody was detected in 35 of 55 calves (63.6%), showing the mean antibody titer of 12.4. A significant negative correlation (p<0.01) was noted between the age of calve and titer of passively acquired antibodies. The regression equation suggested that the maternal antibody disappeared from the calf serum at about 3 months of age. On the other hand, 37 of 55 dams (67.3%) were positive for HI antibody to JEV, and the mean titer of the antibody was 12.7. There was a significant correlation (p<0.01) in serum antibody titers between dams and their calves.

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