34 



ScHWELLENGREBEL (N. H.)- Vcrsuche und Beobachtungen uber die 



Biologic von Xenopsjjlla cheopis in Ost-Java. [Experiments and 



Observations on the Biology of Xenopsylla cheojyis in East Java.] 



—Cenlmlbl. Bakt., Parasit. und Infeklionskr.,Jena, Ite Abt. Orig., 



Ixxiv, nos. 5-6, 16th July 1914, pp. 456-466. 



■ Xenopsylla cheopis not being a very mobile species, individuals from 



plague-stricken rats are only likely to reach human beings hving in 



the same house. The various stages of this flea are considerably 



influenced by the hygroscopic condition of the surroundings and are 



also susceptible to changes in temperature. In Surabaya other as yet 



unknown factors unfavourably influence the development of this flea. 



In damp surroundings X. cheopis is better able to resist hunger than 



in dry ones, and this is probably one of the reasons why Surabaya has 



suffered so little from plague. Cajuput oil has proved a useful insecti- 



fuge against these fleas in Java. To destroy them on a small scale, 



carbon bisulphide or steam at 60° C. are recommended ; sulphurous 



acid is only useful on a large scale. The paper concludes with a 



bibliography of five works. 



SCHWELLENGREBEL (N. H.) & Otten (L.). Expedmentelle Beitrage 

 zur Kenntnis der Uebertragung der Pest durch Flo he und Lause. 



[Experimental contributions to the knowledge of plague trans- 

 mission through fleas and ]ice.]—Centralbl. Bakt., Parasit. und 

 Infektiomkr., Jena, Ite Abt. Orig., Ixxiv, no. 7, 25th July 1914, 

 pp. 592-603. 

 In Java, as in British India, Xenopsylla cheopis is able to transmit 

 plague from one animal to another. Once it has sucked infected blood 

 it is capable of transmitting plague by its bite for a period extending 

 up to 33 days. CUmatic variations only influence this power to a 

 slight extent. Transmission is not purely mechanical, and is only 

 really successful when the plague bacilh have increased in the intestine 

 of the flea [c/. this Review, Ser. B, ii, p. 60]. Transmission is not 

 possible if the fleas are parasitised by Tyroglyphine mites (probably 

 belonging to the genus Anoetus, Duj.) in the Hypopus stage. These 

 larvae prevent the fleas from moving and sucking freely. Pygiopsylla 

 ahalae is also able to transmit plague. The period of infectivity could 

 not be ascertained in vivo, but the bacilli were observed even after 

 the fourteenth day. Plague bacifli were transmitted by X. cheopis and 

 P. alialae in circumstances excluding infection through their faeces, or 

 any other way except through the proboscis. In nature, the louse 

 {Pediculus hominis) also proved a virus carrier. Experiments have 

 shown that up to now the immunity of house rats against plague is 

 but little developed in East Java. Schwellengrebel states that in a 

 recent paper [Centralbl. flir Bakt, etc., Abt. I., Kef. Ixi., p. 33] 

 Galli-Valerio criticises his findings as foUows : " On 56,790 people 

 of the infected district of Malang, Schweflengrebel has only found three 

 X. cheopis and on 1829 persons of the infected houses only seven 

 X. cheopis. Under such circumstances how is it possible to ascribe 

 to rat-fleas an important role in the transmission of plague to man ? " 

 Schwellengrebel repUes to this objection by pointing out that inan 

 is only a temporary host on which the flea does not remain after feeding. 

 The fact that the rat-flea is only very seldom found on man does not 

 militate against the hypothesis that it acts as the carrier of plague. 



