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Ohservations on British Rat-feas 
T. REPORT ON RAT-FLEAS IN SUFFOLK ANU 
NORTH ESSEX. 
By C. STRICKLAND, M.A., B.C., 
Assistant to the Quick Professor, Cambridge; 
AND G. MERRIMAN, F.E.S., F.Z.S., 
Student in Medical Entomology, Quick Laboratory, Cambridge. 
(With 3 Charts.) 
The investigations herewith reported upon were undertaken at the 
instance of the Local Government Board in connection with an enquiry 
in relation to rats and plague in East Anglia. We were commissioned 
to study the rat-fleas in the suspected plague area, determining more 
especially their species and the numbers in which they occurred. 
In India, the evidence brought by the Indian Plague Commission 
has proved that fleas are the active agents in transmitting plague from 
rat to rat: the number of fleas which occurs on rats in India bears 
a direct relation to' the plague incidence among these rodents. The 
established connection between rat plague and human plague incidence 
and the fact that Xenopsylla cheopis, the common Indian rat-flea, 
readily attacks man have led to the now generally-accepted conclusion 
that fleas play an important part in the epidemiology of human plague, 
especially in India. 
In England, Martin and Rowland (1910) found that rat plague 
prevailed chiefly in those parts of Suflblk where fleas were most 
numerous on rats. They moreover found B. pestis-like organisms in 
the gut of fleas removed from plague rats. We find that British rats 
are infested mainly by two species of flea, Ceratophylhis fasciatus and 
Ctenophthalmus agyrtes, of which the former only has been proved by 
experiment to be capable of transmitting plague from rat to rat in India. 
In that country X. cheopis is, however, chiefly concerned in the spread 
of rat plague. Experimental evidence is still wanting to prove that 
C. fasciatus is capable of transmitting plague from rat to rat under the 
conditions prevailing in England. It is the only species of rat-flea in 
this country which has been found to attack man readily under ex¬ 
perimental conditions; consequently, if evidence is forthcoming that it 
serves as a vector of B. pestis from rat to rat in England this Hea would 
also have to be regarded as a potential transmitter of the plague 
bacillus from the rat to man. 
