Okayama Igakkai Zasshi (Journal of Okayama Medical Association)

Seasonal level of hemoagglutination inhibiting antibody and its 2-mercaptoethanol sensitive antibody in the sera of animals, inhibitants and patients; Comparison of results in 1969 with those in 1965-1968

Epidemiological study on Japanese encephalitis 27

Masana Ogata, Yutaka Nagao, Shinsaku Watanabe, Katashi Hitomi, Fumihik ...

1970 Volume 82 Issue 1-2supplement Pages 1-7
Published: February 28, 1970
Released on J-STAGE: March 30, 2009

DOIhttps://doi.org/10.4044/joma1947.82.1-2supplement_1

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The Japanese encephalitis patients of Okayama Prefecture in 1968 and 1969 were less, and the median date of epidemic time curve in 1968 and 1969 was later in coming than in 1965-1967. In order to clarify this fact, variation of the level of HI and 2-ME sensitive antibodies in the sera of swine, canine, and inhabitants were measured every week in summer of 1969, and the relationship between these seasonal variation of antibody level and the seasonal outbreak of patients were examined. By comparing these findings with those in 1965-1968, the following results were obtained.
1) In both norhtern and southern parts of Okayama Prefecture in 1969 year, the respective date showing 50 per cent positive HI reaction and 2-ME sensitive reaction (D, 50% pos. HI and D, 50% 2-ME in short) in swine was 10 days later than in 1965-1967 and 10 days earier than in 1968.
2) In inhabitants also, of both parts of the prefecture, D. 50% pos. 2-ME was more later in coming, and the positive rate of 2-ME sensitive reaction was also lower than in 1965-1967, that is, inhabitants received inapparent infection later and the rate of receiving inapparent infection was lower than in 1965-1967. And D. 50% pos. 2-ME was 10 days earier than that in 1968.
3) In the case of blood taken from the same out-patient successively, 2 out of 10 person shows 2-ME positive reaction in August in Kurashiki district and 2 out of 13 person in Tsuyama district.

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Vaccination with complete adjuvant-added inactivated virus vaccine of Japanese encephalitis to swine for preventing viremia

For specific reference of detecting viremia; epidemiological study on Japanese encephalitis 28

Masana Ogata, Yutaka Nagao, Fumihiko Jitsunari, Naoji Kitamura, Tokio ...

1970 Volume 82 Issue 1-2supplement Pages 9-18
Published: February 28, 1970
Released on J-STAGE: March 30, 2009

DOIhttps://doi.org/10.4044/joma1947.82.1-2supplement_9

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We divised the vaccination with formalin inactivated virus of Japanese encephalitis mixed with complete adjuvant to the swine for inducing high titer of hemoagglutinin inhibition (HI in short) and neutralizing antibody which could prevent viremia, when swine were bitten by hazardous mosquitoes.
The results obtained were as follows.
1) The higher titer (1; 810) of HI antibody was induced by three times injections of 6 ml, 6 ml and 8 ml of inactivated Japanese encephalitis vaccine with complete adjuvant than that without adjuvant, and titer of HI antibody (1:400) showed itself 84 days after 1st injection with complete adjuvant.
2) The neutralizing antibodies obtained by the vaccination were almost proportional to HI antibodies.
3) HI antibodies of swine were increased by natural infection in 22nd of August. And it was recognized that 2-mercaptoethanol resistant antibodies were produced by vaccination with complete adjuvant as well as vaccination without complete adjuvant. However 2-mercaptoethanol sensitive antibodies were produced in swine of the non-vaccinated group by natural infection.
4) Viremia could be detected in 2 out of 4 swine in the non-vaccinated group, but could not be detected in the vaccinated group in Takahashi district.
5) In order to know that Japanese encephalitis viruses are spread or not through mosquitoes in a swinery where swine are vaccinated with the Japanese encephalitis virus mixed with the complete adjuvant, above vaccination was conducted.
And rabbits decoied for mosquitoes' attacks were set in a swinery of Yoshinaga district as well as of Wake district as a non-vaccinated control and the HI titer, in rabbit' blood was tested, and the next results were obtained.
a) The rabbits set in the swinery in Yoshinaga district where all eight swine received the vaccination of formalin inactivated virus mixed with the complete adjuvant, showed the negative HI reaction.
b) In Wake district where only six swine among forty ones received the above vaccination at the swinery, one out of three rabbits showed the positive HI reaction in the rabbit serum.
6) Piglets were born from 5 swines out of 10 received inactivated vaccine alone at Bisei Town situated in southern part in Okayama prefecture, and it is suggested that viremia was induced in swine innoculated with inactivated virus alone, by natural infection.

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Forecasts on date of prevalence of Japanese encephalitis

Epidemiological study on Japanese encephalitis 29

Masana Ogata, Hirokazu Osaki

1970 Volume 82 Issue 1-2supplement Pages 19-25
Published: February 28, 1970
Released on J-STAGE: March 30, 2009

DOIhttps://doi.org/10.4044/joma1947.82.1-2supplement_19

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For the purpose of forecasting the date of prevalenc of Japanese encephalitis in Japan, we estimated the median date of this epidemic time curve of the prevalence from the regression equation of one variable and multiple regression equation from the above factors using an electronic computer. And the following results were obtained.
1) To estimate median date (y) and mode (z) of the epidemic curve of the prevalence, we can use the next equation:
The regression equation to estimate y or z from T. 6, 7 (x₁) is as follows.
y=3.75x₁+144.47 σ₀=12.4……(1)
z=-3.80x₁+157.26 σ₀=14.9 ……(1)'
The regression equation from D. pos. swine (x₂) is as follows.
y=0.68x₂+31, 82 σ₀=9.7 ……(2)
z=0.76x₂+40.71 σ₀=12.0……(2)'
The multiple regression equation from T 6, 7 and D. pos. swine is as follows.
y=1.07x₁+0.62x₂+59.37 σ₀=9.7……(3)
z=-0.79x₁+0.71x₂+61.02 σ₀=12.0……(3)'
The multiple regression equation from T 6, 7 D. pos. swine, latitude and longitude is as follows.
y=1.01x₁+0.58x₂-0.26x₃+0.37x₄+18.50 σ₀=9.8……(4)
z=-0.32x₁+0.52x₂+2.05x₃+0.54x₄-87.81 σ₀=11.8……(4)'
These factors (x₁, x₂)were obtained as the results from 1965 to 1967.
2) We got the estimated value of median and mode in 18 prefectures in 1968 and 14 prefecture, in 1969 in Kyushu, Chugoku, Shikoku, Kinki and Kanto provinces from (1) or (2) or (3) or (4) equation. Ten prefectures out of 17 prefectures by equation (1), 12 out of 18 by (2), 13 out of 18 by (3), and 13 out of 18 by (4) could be estimated with about 10 days (σ₀) error or less in 1968. And in 1969, 9 out of 14 by (3). 7 out of 13 by (4) could be estimated. In the case of mode, 10 out of 18 by equation(1)', 6 out of 17 by (2)', 8 out of 17 by (3)', 12 out of 18 by (4)' could be estimated with about 12 days (σ₀) error or less in 1968, and 9 out of 14 by equation (3)' and 9 out of 13 by equation (4)', in 1969.
3) For the estimation of median and mode of prevalence of Japanese encephalitis two new factors; the date when the numbers of caught mosquitoes (Q. t.) were found to be maximum, and the date when hazardous mosquitoes were found at first, were added to above four factors (T. 6, 7 and D. pos. swine, latitude and longitude) by the data on multiple regression equation. But accuracy of estimation did not increase significantly.

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Forecasts on degree of prevalence of Japanese encephalitis and period of cycle of incidence in various prefectures of Japan

Epidemiological study on Japanese encephalitis 30

Masana Ogata, Hirokazu Osaki

1970 Volume 82 Issue 1-2supplement Pages 27-35
Published: February 28, 1970
Released on J-STAGE: March 30, 2009

DOIhttps://doi.org/10.4044/joma1947.82.1-2supplement_27

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For the purpose of forecasting cn the degree of prevalence of Japanese encephalitis in Okayama Prefecture, we estimated the incidence rate of the prevalence from the regression equation of one variable and multiple regression equation from the various factors using an electronic computer. And the following results were obtained.
1) On regression equation, estimation of incidence rate from the number of Cuiex tritaeniorhychus from May to July (C. t. 5-7 in short) is most correct. And the average atmospheric temperature from June to July (T. 6-7 in short) and vaccinated rate of inhabitants can also be useful for estimation.
2) On multiple regression equation, incidence rate can be estimated correctly in the descending order from (1) duration of sunshine in July, rainfall volume and Trit. 5-7, <(2) added vaccination rate of inhabitants to the above factors (1)<(3) added T. 6-7 and median date of epidemic time curve to the above factors (2).
3) In all Japan, presence of period of cycle, of 7 or 8 years, was recognized to be significant from 1954 to 1961. To each prefecture, period of cycles were detected to be various periods; 3 or 4 year's period to Nagasaki Prefecture, 6 or 7 year's to Okayama and Hyogo, 7 or 8 year's to Osaka, 5 year's to Kyoto, every second year's to Nagano by 1959, every year's by 1962 to Kanagawa, 2 or 3 year's from 1952 to Gunma and every second year's by 1958 to Ibaragi.

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The Seasonal Distribution of Mosquitoes and the Incidence of Japanese B Encephalitis in Okayama Prefecture during 1969

Seiiti Inatomi, Kazuo Itano, Setsuo Suguri, Daigoro Sakumoto, Yasumasa ...

1970 Volume 82 Issue 1-2supplement Pages 37-58
Published: February 28, 1970
Released on J-STAGE: March 30, 2009

DOIhttps://doi.org/10.4044/joma1947.82.1-2supplement_37

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In our study this year (1969) just as in the preceding years, we selected 12 sites, i.e. 3 sites in the northern region 2 in the central region and 7 in the southern region of Okayama Prefecture. At these spots we caught mosquitoes by light-traps, twice a week, starting 30 minutes before sunset till the following morning over the period of 6 monthes from April to September, and compared the number of mosquitoes with the incidence of Japanese B encephalitis. The results are briefly presented as follows.
1. The number of mosquitoes collected by the light-trap in 1969 at all spots in southern region, was less than that in 1968.
2. The number of patients of Japanese B encephalitis was less in 1969 than in 1968 when the number of mosquitoes collected was greater. The correspondence in the number of mosquitoes and the incidence of Japanese B encephalitis was found in the regional differences in 1969.
3. Compared to the results in 1968, the mean temperature of the day was a little higher and Culex tritaeniorhynchus appeared at southern sites 1 or 2 weeks earlier.
4. The number of Culex tritaeniorhynchus showed maxima in every sites after July 13th when the mean temperature exceeded 25°C.

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