THE GUINEA WORM 63 







Strongyloides stercoralis. Parasitic female (Plate VI, Fig. 

 5), length about 2.2 mm.; width 0.037 mm. to 0.07 mm.; 

 cuticula with fine transverse striations; mouth surrounded 

 by four lips; esophagus cylindrical, filariform, one-third 

 body length; anus just in front of pointed posterior extrem- 

 ity; vulva at posterior limit of middle third of body; eggs 

 50ju to 58/-1 in length and 30ju to 34/z in width; usually lie in 

 chain and hatch in small intestine into rhabditiform larvae 

 (Plate VI, Fig. 8) ; eggs probably produced by parthenogenesis ; 

 rhabditiform larvae develop at high temperature (26 to 

 35C.) in about 30 hours into free living rhabditiform 

 generation of males and females (Plate VI, Figs. 6 and 7); 

 these produce eggs about 70ju by 45ju which hatch into a new 

 generation of rhabditiform larvae; these larvae grow in about 

 eight days into the filariform infective larva (Plate VI, 

 Fig. 9) ; infects man through the skin or mouth and develops 

 into the parasitic filariform female in small intestine; at 

 lower external temperature the free, living generation may 

 be omitted and infective larvae develop from first brood 

 of rhabditiform larvae; when present in large numbers 

 produces intestinal catarrh leading to anaemia and intermit- 

 tant diarrhoea; found everywhere in tropics and sub-tropics 

 where there is sufficient moisture for development of larvae; 

 distribution coincides with that of hookworm but incidence 

 much less. 



C. Family Dracunculidae 



Long threadlike nematodes; male very small in proportion 

 to female; anus absent; ovo viviparous; aquatic crustacean 

 intermediate host necessary for development. 



Dracunculus medinensis or the guinea worm. Females, 

 length 50 cm. to 80 cm., width 1.5 mm. to 1.7 mm.; color 

 whitish or yellowish; anterior extremity rounded and bears 

 a cuticular thickening or shield; alimentary canal below 



