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bug may escape to—to the roof space, to adjoining rooms or adjoining houses—and
to take appropriate measures to deal with this situation. But one of the most valuable
details is a careful search afterwards by trained disinfectors.
(c) Subsequent Action.
Ten days later the Inspector in charge of disinfection visits the house. If he
is satisfied that there are no bugs, an order is given to the builder to replace the
woodwork and to distemper. Ten days later a further visit is paid by the Inspector
in order to satisfy himself that the de-bugging is complete. If he is not satisfied,
the disinfestation is done again, but no articles are removed. If he is satisfied that
the room appears to be free from bugs, the "verminous" card is handed to the
woman sanitary inspector who makes a visit once a month for the first three months
or until she gets three successive negative examinations, and then once every two
months for the next six months, and it is proposed that she will continue to visit
once a quarter until two years are complete.
This scheme was started in August and, up to the end of the year, 172 rooms
had been so disinfested.
In actual practice it has been found that with the high concentration of sulphur
dioxide used, a second disinfestation, except in rare instances, has been unnecessary.
It looks, therefore, as if this high concentration killed eggs, but this observation is
subject to the reservation that most of this work was done in the latter part of the
year after the normal breeding season was over, and it may be that these results
may not appear so satisfactory when the rooms are examined in the summer of 1933;
or it may be that the results of disinfestation will not be so good in the early summer
months.
The life history of the bug is briefly as follows: the female lays eggs; these eggs
hatch out and after five successive moultings the adult bug attains its being.
Recent scientific thought seems to indicate that it is comparatively easy to kill the
egg and that the bug is most difficult to kill in the stage just before it becomes an
adult bug. If this is correct it means that in actual practice, in any form of gaseous
disinfection, careful search of the premises has to be made by skilled observers
immediately afterwards in order that any survivors may be dealt with.
The present methods of getting rid of bugs are expensive and cumbersome, and
a great deal of research work is necessary in order to discover some simple and
economic method of dealing with the problem.
It is not simply a question of adding a given amount of disinfectant to the
air of a room, as there are two very variable factors in any operation—the extent and
rate of leakage is never known and difficulties are experienced in getting an equal
distribution of disinfectant throughout the air of the room. The temperature of the
air of a room has to be taken into account, and the extent of penetration into walls,
crevices and articles is not known. It is because of these variants that the room has
to be specially inspected after disinfestation.