View report page

41
were obtained. The Sanitary Inspector in charge of the district made a careful
inspection of the premises and also prepared a plan of the warehouses. This inspection
failed to reveal any local nidus which might, on account of its nature, provide
harbourage and favourable breeding facilities for Xenopsylla cheopis.
Observations on Pleas.
The average number of fleas per rat for the whole period was 2'49, the number
increasing from 1.00 per rat in April to 4.02 per rat in August; after which there was a
gradual monthly decline up to November. December, however, showed an increase
to 3.80 fleas per rat, but this figure was not maintained during the following cold
period.
Ceratophyllus fasciatus was again found to be the predominant rat flea, its
numbers representing 85.11 per cent. of all fleas examined during the period under
review. Its incidence, as represented by the C. fasciatus index, reached its zenith
in December with a figure of 3.52. The next highest figure was recorded during the
month of August. The lowest figure, 0.9, is shown for the month of April, but if the
small number of rats (11) examined during this month be considered, the figure may
lose some of its significance.
Leptopsylla musculi.—Next to C. fasciatus this was the flea most frequently
encountered. It represents 14.11 per cent. of the total fleas examined. During
August its numbers represented 23 per cent. of the total fleas. September showed a
rise to 43 per cent. and October a drop to 26 per cent. In November a maximum
percentage of 46 was reached. Occasional specimens were met with during the
winter months.
Ctenocephalus felis.—This species is represented by three specimens which were
obtained from two rats at different times and from different zones.
XenopsyUa cheopis.—Two specimens were encountered under the circumstances
already detailed.
Pulexiritans and Ceratophyllus londiniensis.—No specimen of either was met with
in the course of the survey.
All fleas examined were submitted to the Department of Entomology, London
School of Hygiene and Tropical Medicine, for confirmation of the identifications.
Ship Eats.
Since the inception of the rat flea survey, attention has been paid to ship rats
in order to determine their degree of flea infestation and also the variety of fleas
harboured. With this in view, rats from ships whose ports of call included actual
or potential Plague areas were periodically taken and examined. In all cases where
rats were taken in traps only those trapped singly were examined, and their attendant
fleas were obtained as in the manner adopted for the shore rats. In some cases when
a ship had undergone Cyanide fumigation the dead rats were collected, the near vicinity
of the dead rat being carefully searched for fleas which might have fallen from the
dying rat. The rat was afterwards examined in the usual way and any fleas which
had been found in the vicinity were added to those obtained by combing.
During the year ended January, 1933, twenty black rats and one brown rat were
trapped singly in different ships. Of this number, 16 rats were found to be free
from fleas. The remaining 5 rats yielded altogether 13 fleas, all C. fasciatus.
During the year ended January, 1934, 68 black rats and one brown rat were taken
from ships and examined. Of these 69 rats, only 5 were found to be harbouring fleas.
The total number of fleas obtained from them was 39, of which 21 were found to be
X. cheopis and 18 C. fasciatus.