174 



A list is given of the known forms of trypanosomiasis and their 

 insect earners from the tropical regions of the world. 



Flu (P. C). Enkele epidemiologische Waarnemingen over Pest. 



[Some epidemiological Observations on Plague.] — Geneesk. 

 Tijdschr. Ned.- Indie, Batavia, Ixii, no. 3, 1921, pp. 263-287. 



Numerous epidemiological observations on rat-plague were made 

 at Batavia and other places where an outbreak occurred in 1920. 



Xenopsylla cheopis was found in storehouses, sometimes in important 

 numbers. ' These fleas are to be found at all times, but especiall}/ 

 when rat-plague is present. They are most abundant in stores 

 containing goods attractive to rats, especially rice. 



The importance of rice in the spread of plague has long been known 

 in Java, but hitherto rats were considered to be chiefly responsible 

 by being transported with their nests, which were supposed to be 

 inside the rice-bags. The author found that if dead plague rats were 

 seen in a rice-store it was sufficient to take up the flooring to find large 

 numbers beneath in various stages of decomposition. Their fleas 

 must attempt to escape and some of them infest the fabric of the bags, 

 or work their way into the mass of rice. The weight of a pile of bags 

 tends to force apart the threads of the fabric, so that entry is easy. 

 It was found that individuals of A', cheopis do occur on the floor and 

 among the stacked goods, having probably come from infested rats. 

 They are able to remain at least three days in a gunny bag. Fleas 

 are therefore quite as important as rats in the spread of plague. The 

 author is indeed inclined to think them of greater importance, as 

 living rats "seldom harbour fleas infected with plague. 



The pi-ospects of an effective quarantine against plague are not 

 promising in view of the author's reseaich on the killing power of 

 SO2 on fleas in rice-bags. At present the most powerful weapon in 

 plague quarantine is fumigation with this gas, but it appears that 

 reliance solely on this method may be mistaken. It has been found 

 that rice weevils are able to avoid the effects of sulphurous acid fumes 

 or of steam at 60°C. [140°F.] by burrowing into the mass of the grain. 

 When native dwellings are fumigated with sulphur dioxide, the 

 fleas (which are more resistant to the fumes than are their rat -hosts) 

 abandon the rats and burrow into the sand covering the floor. 



Using hermetically sealed jars it was ascertained that if the enclosed 

 air contained | per cent, of SOg, about 40 minutes elapsed before all 

 the fleas within were motionless ; on opening the j ars two hours after- 

 wards the fleas appeared to be dead. At a strength of 4 per cent, 

 immobility ensued immediately. 



In another test a pound of rice in a gunny bag was placed with 

 about 100 fleas in a jar into which air containing 2\ per cent, of SOg 

 was introduced. After a few minutes all the visible fleas were 

 motionless. The jar was opened two hours later, when a number of fleas 

 were found alive beneath the bag and on its fabric. The rice was 

 then spread out and all the weevils and other insects present were 

 found to be alive. 



These results do not inspire confidence in the method of burning 

 sulphur in open containers with a view to destroying the ectoparasites 

 of rats, though it is an excellent method of killing the rats themselves. 



In experiments with Clayton gas on fleas on and in sacks of rice 

 in a specially sealed native boat it was found that when 3 per cent, 

 of SO2 was registered at the inlet the strength at the outlet was less 



