Belém VIRUS Laboratory

eek agança ~~ lds, deed re ble 1er
44-
IABORATORY CONTAMINATION CFmCK
With the isolation and passage of so many strains of virus at the same time
in this laboratory, it is to be expected that cross-contamination will occur, and
!rom time to time isolations have been discounted when other evidence tended
to cast cloubt on their validityo But a useful check that cross-contamination is not
comm.:>n
be made by looking at the viruses isolated from sentinel mice in adjacent
boxes (Table 41) and from material inoculated L~ series 42)0 It is clear that
adjacent mouse groups do not yield the same vírus any more often than might be
expected by chance. There does not seem to be any frequent spread or infection
on the shelf or on the inoculation tableo
REroRTED EQUllm .ENCEPHALITIS ll.J BP..AOOJÇA
In 1960, EEE virus was isolated from horses and ~s ~e~or~ch~ mos qui toes
in the Bragança regiono
Intensive studies during 1961, 1962, and again L~ late 1963
the initial heavy rains each year, but no return oí EEJ activity was detected.
This year, after reports af equine encephalitis were received durin!
in I~rch, a field team went to Bragança to investigate.
the third
l~o encephali tio horses
'~ere faund in spi te af a hause to hause canvas by canoe over the recently flooded
however nW:1erous first-hand reports "lere received or equine deaths from
"mal de rodas" during the previous ~'1ree weekso Mosquitoes were said to have been
abunctant but to have disappeared coincident wi th the flooding and wi th the
disappearance af clinical disease in horses two weeks beforeo Almos t no mos qui toes
evident at the time of the investigationo
It was concluded that probably
equine encephali tis acti vi ty had returned after an absence af 5 years in the
region