THE RAT PROBLEM. 
1. Spirochetal Jaundice occurs in most parts of the world, but most 
commonly in Japan. It was frequently met with amongst the allied 
troops in France, the trenches being infested with rats. -Although this 
disease has been conveyed to man by rat-bites, it is probable that con- 
taminated food and water is the most important source of infection. 
2. Rat-bite Fever has been known for a long time in Japan, and cases 
of similar illness have been described in this country, the United States 
of America, and elsewhere. During 1918, rats caught in and about the 
city of London were examined by Alexander Foulerton, F.R.C.S., for 
the presence of parasites causing these diseases. Of 101 rats examined, 
four brown rats were found affected with Spirocheta icterohemorrhagiv, 
whilst of six rats examined for Spirochela morsus muris, none were 
found affected. Whilst it has been clearly proven that rats capable of 
conveying spirochetal jaundice have been found within this country, 
it would be unwise, on the other hand, to conclude that rats capable of 
conveying rat-bite fever do not exist, simply because six were examined 
for that disease with negative results. 
3. Plague is a specific and infectious disease affecting man and some 
of the lower animals. Between the year 1896 and the beginning of 1905, 
no fewer than 3,150,000 persons died from plague in India. With the 
ending of the great outbreak of plague in 1664-1679, this country was 
free for more than 200 years. According to a memorandum issued by 
the Local Government Board, outbreaks of plague have occurred periodi- 
cally during the past twenty years at several of our ports, and, in view 
of these facts, sanitary authorities are advised to be always on the alert, 
and especially for ascertaining the cause of any recognised excessive 
sickness in rats, or of human illness of a doubtful nature associated with 
sickness or mortality in rats in the same district. 
As rats are subject to plague, and are often killed by it in great num- 
bers, they are the most dangerous of all animals so far as the spread of 
the disease and the creation of new centres of infection are concerned. 
It should be remembered, however, that fleas form the intermediaries 
between the diseased rat and man. When rats are dying of plague their 
blood is literally swarming with the bacilli of that disease. Fleas feeding 
on plague-infected rats get plague bacilli on to their mouth parts, and 
myriads of them are, of course, sucked up into the stomach with the 
blood. ‘Those on the proboscis may ‘be transferred directly to the next 
victim that it is thrust into, and those in the stomach may be carried 
for some time, and finally liberated when the flea is feeding again, or 
when it is crushed by the annoyed host. In fact, the latter is probably 
a common method of infection, for the bacilli that are liberated when the 
flea is crushed may readily be rubbed into the wound made by. the flea- 
bite, or into abrasions of the skin due to the scratching. A useful hint 
to remember would therefore be—Kill the flea, but don’t “rub it in.” 
The rat flea (Ceratophyllis fasciatus) occurs on both the brown and 
the black rats, on the house mouse, and frequently on man. 
The common human flea (Pulex irritans), although regarded pri- 
marily as a pest of human beings, often occurs very abundantly on cats, 
dogs, mice, and rats, as well as on some wild mammals, and occasionally 
on birds. 
C.7745.—4. 289 
