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and other property is in the majority of cases traced to defects in drainage systems
and sewers. When such evidence is found appropriate action is taken by the Public Health
Inspectorate under the Public Health Act to effect necessary repairs; meanwhile the
rodent operatives carry out disinfestation treatment.
By reason of its age, much of the drainage in Leyton does not conform to accepted
standards of design and construction. In those areas which contain aggregations of
obsolescent properties, drainage defects are invariably due to open clay joints or
subsidence and failure of pipes owing to inadequate concrete support; this accounts for
many surface infestations.
If it were possible to confine rats to sewers and drains the problem of surface
infestation would not be so acute. As it is, defective drains and sewers provide a
ready means of communication for rats migrating in search of nesting places and change
of diet; rats travel along working sewers when scavenging food, but they need dry,
undisturbed places for nesting.
The only practicable method available to the Local Authority for reducing the rat
population in sewers is by poisoning, and two such treatments are carried out each year.
Poison baiting of sewers is not expected to eliminate sewer rats completely, for the
impossibility of bringing all rats to feed at available baiting points, which are
necessarily limited to manholes suitable for the purpose, is evident; and the rat
population soon builds up again following disinfestation.
Technical officers of the Rodent Division of the Ministry of Agriculture, Fisheries
and Pood are confident, however, that poisoning campaigns carried out by adjoining
Local Authorities in the London area over the years have resulted in a reduction of
rats in the sewers and a proportionate decrease in surface infestation, but, as already
indicated, measures taken to destroy rats, however successful, have only a limited and
temporary effect.
The area of land comprising Auckland Road Depot and Destructor Works, Temple Mills
Railway Sidings, the Allotments, Marsh Lane Tip, and the open surface water sewer which
is referred to as the 'Dagenham Brook, provides a natural habitat for rodents,
preventing their complete eradication; all that we can hope to do with such reservoirs
of infestation is to keep the number of rodents down to reasonable proportions; this
is achieved by regular and systematic block treatment of the whole area. Hydrogen
cyanide gas is used wherever practicable as an alternative to solid poison baiting
treatment, especially in the region of the Dagenham Brook, but owing to the highly
lethal and dangerous character of this method of destruction its use is limited to open
land where there can be no possible danger to human life.
Conditions at the Auckland Road Depot are conducive to the propagation and sustenance
of rats; there is shelter and food and, by reason of the nature of the buildings,
favourable harbourage for nesting and breeding purposes. It is natural, therefore, that
during certain times of the year, especially in the winter, rats tend to leave the open
land and migrate to the depot. Such migration was evident during October and November,
when the level of the water in the Dagenham Brook and Lea Valley generally was exceptionally
high due to abnormal rainfall during that period.
To fully appreciate the extent of the problem, it should be realised that rats
are prolific breeders. Technical research has shown that a pair of rats and their progeny
may, in the course of twelve months, increase in number to well over one thousand, and,
whenever there is a marked reduction in the numbers of a rat colony, which occurs as a
result of disinfestation, there is a tendency for the colony to breed quickly in order
to restore its numbers. This emphasises the need for effective disinfestation at
regular intervals. Four block treatments are carried out at the Depot each year and
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