200 
The N.Z. Journal of Science and Technology. [July 
In the foregoing pages I have endeavoured to trace the birth and growth 
of the great frozen-meat industry of New Zealand. Some writers have 
stated that we have reached the maximum export of meat from this country, 
but I cannot believe that this is correct. While no doubt dairying has now 
taken up a very large area of land formerly used for breeding and fattening 
stock, still the millions of acres awaiting settlement and closer farming, 
and the greatly enhanced prices of meat (with the probability of it continu¬ 
ing), will result in much greater production. Every year will see an 
expanding demand for meat food among the nations of the Old World. 
North America is hardly producing sufficient for her own wants, so that 
the world’s supply must be looked for in the Southern Hemisphere. 
RAT TRYPANOSOMES IN NEW ZEALAND. 
Bv A. B. Dore. 
The blood-parasite Trypanosoma lewisi (Kent), discovered in 1877 by 
T. Lewis, has since been recorded from most parts of the world, but not 
from New Zealand. It is transmitted from host to host by fleas and lice, 
which, after sucking blood from an infected rat, inoculate the virus into a 
healthy one. 
Since the discovery of the parasite in the Auckland District in 1912 
the routine blood-examination of several hundred rats caught in various 
parts of the North Island has shown that many of them harbour trypano¬ 
somes the measurements of which correspond with those obtained elsewhere 
for Trypanosoma lewisi. The percentage of infected rats from various 
districts and places differs ; thus, of those caught in the neighbourhood of 
sewers 30 per cent, are affected, as against 12 per cent, for those captured 
on wharves and in grain-stores. The trypanosomes are often very numerous, 
and on one occasion there was one to every four of the host’s erythrocytes. 
As regards the pathological anatomy of the infected rodents, the only organ 
which evei* appears abnormal is the spleen, which is sometimes nearly 
doubled in weight. 
Regarding the degree of pathogenicity of this parasite in wild rats there 
is some controversy amongst authors. Rabinowitsch and Kempner* main¬ 
tain that, contrary to what they have found in the case of white rats, the 
infection is fairly severe in wild rats, and sometimes causes death. In view 
of the fact that the native rats introduced by the Maoris are rapidly dis¬ 
appearing it seems possible that this trypanosome may be the primary cause, 
as the native rat may not have the immunity which the European species 
probably possess. Rats are constantly arriving on these shores from oversea 
liners, and therefore several strains of this parasite are probably in New 
Zealand. Owing to the scarcity of the native rat it has so far been impossible 
to establish the theory put forward above. 
Further haematological investigations are being made in regard to 
various other animals, both native and imported, and it may be found 
possible to connect the comparatively rapid disappearance of New Zealand 
native birds with the introduction of exotic protozoa through the medium 
of the imported fauna. 
* Zeitschr. J. Hyg., Bd. 33, p. 444, 1900- 
