Yamamoto, Hideki

We estimated the number of stray dogs in Kathmandu, Nepal, where human rabies cases still occur, and in Shimotsui, Okayama Prefecture, Japan. In Kathmandu, the stray dog density was 2,930 stray dogs/km2, and the ratio of stray dogs to humans was 1:4.7. In Shimotsui, the density was 225 stray dogs/km2, and the ratio was 1:5.2. Since the stray dog population in Nepal is very large, one of the measures used to prevent dog bites and dog-acquired infections such as rabies is an effort to capture stray dogs. Another such measure is an effort to decrease the availability of food for stray dogs. We also organized health education programs in both Nepal and Okayama Prefecture, Japan, which involved a course on the prevention of dog bites and subsequent infections. After each course, a questionnaire survey was conducted. The results suggest that the course participants understood these important preventive methods. In addition to the measures mentioned above and the routine vaccination of dogs, this health education course is recommended as a long-term preventive program

In order to elucidate the role of erythrocyte catalase in the accumulation of mercury in erythrocytes, labeled erythrocytes and plasma were prepared by exposing normal and acatalasemic mice to radioactive mercury vapor (203Hg0: 6.8mg/m3) for 30 min. Labeled erythrocytes (or plasma) were mixed with unlabeled plasma (or erythrocytes) of normal or acatalasemic mice and incubated at 0 degrees C for 1 h. After incubation, the radioactivity of mercury in the erythrocytes and the plasma was measured by a gammascintillation counter. When labeled erythrocytes were incubated with unlabeled plasma, the ratio of mercury transferred from acatalasemic erythrocytes to normal plasma (11.6%) or to acatalasemic plasma (13.3%) were significantly higher than that from normal erythrocytes to normal plasma (1.8%) or to acatalasemic plasma (2.2%). When labeled normal (or acatalasemic) plasma was incubated with unlabeled normal or acatalasemic erythrocytes, the uptake of mercury by acatalasemic erythrocytes from normal plasma was 2.0%, and 1.2% from acatalasemic plasma, which tended to be lower than that by normal erythrocytes from normal plasma (3.4%) or from acatalasemic plasma (2.2%). The results indicated impaired accumulation of mercury in acatalasemic erythrocytes, suggesting the importance of catalase in taking up mercury in erythrocytes and protecting other organs from toxic effects of metallic mercury.

A sharp rise in the number of patients with infectious gastroenteritis was observed in the 25th week of year 1996 in the Takahashi-Ashin district by researchers with the Infectious Disease Surveillance Program for tuberculosis and other infectious diseases in the Okayama Prefecture. This sharp rise occurred coincidentally with an outbreak of enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) infection in Niimi City of the Takahashi-Ashin district. However, this phenomenon of coincidental outbreaks was not observed during the outbreak of EHEC O157 infection in Oku Cho. By reviewing outpatients' charts in a sentinel hospital in Niimi City for the Infectious Disease Surveillance Program, it was noted that patients with acute gastrointestinal infection visiting the hospital during the increased incidence of infectious gastroenteritis may have been included as misclassified cases of EHEC O157 infection. On the other hand, the exponential probability plotting of symptomatic patients with EHEC O157 infection in Niimi City revealed a breaking point which suggested a dual exposure to contaminated food or an overlap with other acute gastrointestinal infections. The latter possibility was discounted, because stool culture-positive patients with EHEC O157 infection also exhibited a similar breaking point, and furthermore, the coincidental increase in infectious gastroenteritis in the same area was attributable to the EHEC O157 infection. The present study demonstrates the association between the sharp rise in gastroenteritis and the outbreak of EHEC O157 in the Takahashi-Ashin district. A careful analysis of the cases of infectious gastroenteritis by the Infectious Disease Surveillance Program would have predicted the outbreak of EHEC O157.

To better understand the spread of hepatitis C virus (HCV) infection, we studied the association of HCV infection with similarly transmissible hepatitis B virus (HBV) infection and with hepatitis A virus (HAV) infection, which is supposed to be related to a nosocomial transmission of HCV. This was done by studying the presence or absence of antibodies to these viruses, as well as hepatitis B surface antigen, in a population of 1,398 inhabitants with abnormal liver function tests or history of liver disease and/or blood transfusion. This group was drawn from a group of 7,905 examinees screened for liver disease in 26 districts of Okayama prefecture, Japan. The prevalence of antibody-positive cases increased with age for those viruses. Small but significantly increased odds ratios were obtained among anti-HCV antibodies (HCVAb), anti-hepatitis B core antibodies (HBcAb) and anti-hepatitis A antibodies (HAVAb). After adjusting odds ratios by logistic regression analysis, a significant association was present only between HCVAb and HBcAb. The distribution of age-adjusted prevalences (AAP) of HCVAb in 26 districts was significantly wider than those of HBcAb or HAVAb. The district-based AAP of HCVAb, but not of HBcAb and HAVAb, correlated significantly with the district-based prevalence of infectious hepatitis having a tendency of chronicity reported in 1953-1955. Adjusted odds ratios calculated by logistic regression analysis of the virus markers showed that HCVAb was significantly associated with a past history of blood transfusion. Thus, the spread of HCV infection is speculated to have been triggered by blood transfusion, particularly from paid donors initially, followed by transmission by nosocomial or close person-to-person contact.

With advances in lectin affinity electrophoresis of alpha-fetoprotein (AFP), the detection of significant changes in serum AFP at low levels in cirrhotics has become important for early detection of hepatocellular carcinoma. Serum AFP levels of 616 healthy individuals without abnormal liver function tests or virus markers of hepatitis B and C were determined by enzyme immunoassay with IMx-AFP Dainapack using automated IMx apparatus set at twice the ordinary sensitivity and compared with those of 241 individuals with abnormal liver function tests and/or positive hepatitis virus markers. The coefficient of variation in this assay was less than 10% at AFP levels as low as 0.2 ng/ml with a lower detection limit of 0.1 ng/ml. The AFP level of healthy population showed a Gaussian distribution curve after logarithmic transformation with a median and 2.5-97.5 percentile reference range of 2.2 (0.6-5.6) ng/ml. There was no significant difference in the AFP level between males and females. Individuals with abnormal liver function tests alone showed no significant increase in serum AFP unless they were associated with positive hepatitis virus markers.

An exposure to GB virus C/hepatitis G virus (GBV-C/HGV) was studied among populations at risk for blood and sexual exposure to analyze risk factor of the transmission of the virus. Blood samples were drawn from 98 intravenous drug users (IVDU), 100 female high-class commercial sex workers (CSW) and 50 male outpatients (MOP) at a sexually transmitted diseases (STD) clinic in Chiang Mai, Thailand. These blood samples were analyzed for GBV-C/HGV RNA; antibodies against second envelope protein of GBV-C/HGV (anti-E2); anti-hepatitis C virus antibody (HCV-Ab); hepatitis B core antibody (HBcAb); and antibodies against human immunodeficiency virus (HIV-Ab). Prevalences of GBV-C/HGV RNA, anti-E2, HCV-Ab, HBcAb and HIV-Ab were 27.6%, 16.3%, 84.7%, 76.5% and 45.0% in IVDU; 0%, 21.5%, 2.0%, 72.0% and 11.0% in CSW; 6.0%, 13.6%, 0%, 64.0% and 14.0% in MOP. While the prevalence of GBV-C/HGV RNA was higher in IVDU than in CSW and MOP, comparable prevalences of anti-E2 among the three populations were found. Intravenous drug injection showed association with GBV-C/HGV RNA, while history of STD associated with anti-E2. In conclusion, intravenous drug injection and STD were found to be risk factors for the previous exposure to GBV-C/HGV, but STD did not increase the risk of the GBV-C/HGV viraemia.