Summary
Since
September 2001, Japan has reported to the World Organisation for
Animal Health (OIE: Office International des Epizooties) 31 cases
of typical bovine spongiform encephalopathy (BSE) and two atypical
cases. There were at least two major exposure episodes in Japan.
The first, attributed mainly to imported contaminated feed ingredients,
occurred between 1995 and 1996 and 13 affected Holstein cows
(Group A) were detected in different parts of Japan. The second
exposure occurred in Hokkaido, the northernmost island of Japan,
between 1999 and 2000. To date, 14 BSE cases (Group B)
have been found there. All positive cases of Groups A and B
were Holstein cows. The remaining four cases (Group C) were
of various ages, including one atypical case of 169-month-old native
beef cattle, but the sources of infection are not yet known. Two
young (21- and 23-month-old) Holstein steers are also included
in Group C, but the transmissibility of these cases has not
been confirmed. It appears unique that all confirmed typical BSE
cases in Japan have been in Holstein cows, and it could be suggested
that future surveillance of BSE in Japan should be focused solely
on Holstein cows. It is also suggested that Japan be divided into
two zones; Hokkaido zone and the rest. In this way, different strategies
could be implemented to achieve eradication within shorter periods
of time in respective zones. Since the youngest typical BSE case
confirmed in Japan was a 48-month-old cow belonging to Group B,
it is suggested that the age of the cattle to be tested at abattoirs
be raised from 20 months to 30 months and older. So far,
two so-called atypical cases of BSE have been found
in Japan, and the author proposes that it is necessary to demonstrate
the transmissibility of these cases in order to confirm that they
are indeed transmissible spongiform encephalopathies. Further, the
author considers it necessary to compare the standards of the national
diagnostic laboratory that tests healthy cattle in Japan with those
of other OIE BSE reference laboratories in order to demonstrate
that current Japanese diagnostic practices meet international standards.
Keywords
Atypical
cases, Bovine spongiform encephalopathy, Exposure, Japan, Pithing,
Risk communication, Surveillance, Transmissible spongiform encephalopathies,
Zoning. |