88 i'kesidential address section d. 



Strongyloides Infections. 



St roii(jij}t)i<lc6 tiiercoralis or intcstinalis, as is well known, has 

 a complicated lile-liistory somewhat resembling that of Ancylo- 

 stoma or Necator. The adult worms are small, being about '2-2 

 nun. long. A sinnmary of its life-history is as follows: — A form 

 occurs in the liinnan intestine which is asexual and gives rise 

 parthenogenetically to eggs. The eggs hatch sometimes in men, 

 but more often extracorporeally, into the first rhabditiform larvae. 

 At a temperature from 15°C. to 18°C., after a first moult, the 

 rhabditiform larvae become strongyloid larvae. If, however, the 

 temperature is raised from 20°C to 25°C., the rhabditiform larvae 

 develop into definite free-living males and females. These mate, 

 and the female then lays eggs that develop into the second, 

 rhabditiform larvae. After a moult these larvae become 

 strongyloid or filariform, penetrate into the skin or enter the 

 vertebrate host by way of the mouth, and eventually become the 

 asexual intestinal form with which the story of the life-cycle 

 commenced. 



Kocently some most interesting results have accrued from 

 work by Brumpt* in connection with Strongyloides papiUosus 

 of sheep, which can also develop in the rabbit. Brumpt (1921) 

 has found that in the sheep the parthenogenetic worm gives rise 

 to eggs which develop in the proportion of 2,000 females to 1 

 male, and yield from 200 to 100,000 larvae by direct development. 

 On the other hand, when the infection is produced in rabbits, the 

 asexual or parthenogenetic worm gives rise to sexual worm's in 

 tlic ])roportion of 287 males to 409 fertile females, and yields 

 1.2;J() larvae by direct development. This striking contrast is 

 attributable, perhaps, to the environments — that is, to the 

 influence of the hosts. 



AiiTiiRoPODs AS Transmitters of Disease. 



The study of Arthropods in connection with disease is an 

 enoiinous subject. The relation of insects and ticks to disease- 

 has already been discussed in former Addresses delivered before 

 this Association, and such grovmd need not be traversed again. 

 It will suffice to give outlines of a few interesting items, some 

 entomological, some dealing with Arachnids. 



That the housefly, Mufica do)}icstica, is a jiest to man by 

 transmitting ty]ihoid bacilli, tuberculosis, cysts of Enfania;ba 

 histoliitica, Giardia [Lniiihlin) intcstiindis and other Protozoa is 

 well recognised. A new way in which the housefly affects man 

 and his stock lias recently been shown by L. B. Bullf iu 

 Australia. This worker finds that Mu>ica domestica acts as the 

 intermediate host of species of Habronema. a Nematode whose 

 larvae cause a granulomatous condition of the exteraal mucous 

 membranes of horses in South Australia, while the adult worms 

 are parasitic in the intestines of horses. The lai'vae reach the 

 horse by way of the housefly and destioy the skin and submucosa. 

 The suggested remedies are to destroy all adult worms found, and 



* (\ 1!. Sor. Biol.. Ixxxv. pp. 149—152. 

 t TrauK. ii'iii/nl Soc. S. Aiistrafid. xliii. pp. 85 — 131. 



