CHAPTER XX 

 NEMATODA. FAMILY IV. FILARIID^ 



The Thread-like Worms 



Nematoda (p. 217). — The nematodes of this family have the body 

 long and filiform (Figs. 127 and 129). The shape of the mouth varies; 

 it may be provided with lips or it may be surrounded with papillae. 

 The esophagus is slender, without posterior bulb. The males may have 

 one spicule or two unequal spicules, and the tail is generally spirally 

 rolled. The females have two ovaries; vulva usually anterior to the 

 middle of the body. The embryonal development is usualty within the 

 body of the female. 



Parasitism. — The filarise live as parasites chiefly in serous cavities 

 of the body, blood and lymph channels, and in the submucous and sub- 

 cutaneous connective tissues. They may be found in most any part of 

 the body, but do not commonly inhabit the lumen of the alimentary 

 canal. 



The parasitism of the filariae produces a condition in their hosts known 

 as filariasis. 



FiLARIID.E OF THE HORSE 



1. Setaria labiato-papillosa (Filaria equina). Fig. 127. Filariidse 

 (p. 244). — ^The Iwdy is long, white, filiform, and attenuated at both 

 ends. The integument has fine transverse striations. The mouth is 

 small, circular, and provided with a chitinoiis ring, the border of which 

 is divided by four salient papilla?. Outside of this on each side are two 

 small papillae in the form of small spines. The tail of the male is rolled 

 up spirally and presents on each side four preanal and four or five 

 postanal papilla?. There are two spicules. The tail of the female is 

 slightly spiral and is terminated by a papilla. The vulva is situated 

 near the anterior extremity. 



Length of female, 9-12 cm. (3 1/2-4 3/4 inches); male, 6-8 cm. 

 (2 3/8-3 1/8 inches). 



Newly hatched embryos are about 280 microns long by 7 microns in 

 breadth. The embryonic development is within the body of the female. 



Occurrence. — This species is most often met with in the peritoneal 

 cavity — more rarely in the pleural cavity of the horse, ass, and mule. 

 The worms are especially fitted for migrations by their slender and 

 attenuated bodies, and, from their location in serous cavities, may pass 



