View report page

47
In consequence of their increased liability to develop the disease,
sewer workers (and those who may come into close contact with rats) should
be warned of the risk, as the disease comes under the Workmen's Compensation
Acts. Control of the disease depends on the efficiency of measures
taken for the reduction of rats, and the protection of workers exposed to
infection.
In addition to being the cause of leptospiral jaundice, rats are also to a
great extent responsible for the spread of such diseases as plague, rat-bite
fever, food poisoning, enteric fever, trichiniasis and round-worms in human
beings, and of foot and mouth disease and mange in the lower animals.
In order to ascertain the extent of the infection among the local rat
population, with the co-operation of Dr. J. C. Broom of the Wellcome
Research Institution, arrangements were made for the investigation by him
of rats caught in Leyton.
Although it is possible to get some idea of the degree of infection by
examining rats that have been poisoned or killed in traps, it is much more
satisfactory to conduct the pathological examination immediately after
death. For that reason only live rats were submitted for post-mortem
examination.
The catching of live rats is no easy task, and the 32 caught during the
winter of 1953-54 were regarded as quite a satisfactory and representative
sample of the rat population infesting the Borough.
Of six live rats submitted for examination on 4th January, four were
definitely established to be black or ''ship" rats (Rattus rattus). This catch
of six live rats—of which four were black and two brown"—was surprising
in two respects. Firstly, because we had believed that the black rat was
confined to ships, ports and wharves; secondly, because we had been taught
that the two species would not live together and that the brown rat exterminates
the black. It was therefore a matter of surprise when four black or
''ship" rats were caught in a house in Leytonstone High Road and even more
so when it was found that the four black rats and two brown rats had spent
a long week-end together in the same cage. The unreliability of the colour
of fur in identification of the species has been stressed, and it has been
pointed out that the black rat is often brown in colour, and the brown rat
often black. So now we know where we are.
Subsequent enquiries and investigations elicited the information that
the black or ship rat is by no means confined to Leyton, and that it appears
to be gaining a foothold in other parts of London.
Results of Pathological Investigation.