Fig. 18,!. STROiVOTLUS TULGARIt: 



Verminous aneuvvstns jiffecting the anterior mesentei'ic 

 Foster & Clark, 1937. .\i>i. J. Tniii. Med. v. 17 (1). 



artery. After 



Strongj/lus larvae migrate via the hiiigs and trachea, but under- 

 go tlieir whole dfveloptueut within tlic abdominal cavity. 



S. edentatus larvae penetrate the walls of the intestine and 

 the majority come to rest under the peritoneum, though the 

 route followed in reaching this location has not been traced. 

 Some, probably carried by the blood stream, reach the liver 

 and lungs. After about 3 months, during which they grow 

 much larger, the larvae migrate to the roots of the mesenteries 

 and travel between the laminae to the walls of the cecum and 

 colon. Here they become lodged for about a month in large 

 subserous liemorrliagic nodules wliich eventually open into the 

 lumen of the intestine. 



S. equiniis larvae penetrate the walls of the intestine and 

 make their way to the liver and pancreas. It has generally 

 been assumed that they arrive in these places via the blood 

 stream, but Wetzel's observations (I.e.) throw doubt on this. 

 After development to the fourth larval stage they return to the 

 walls of colon and cecum, again by an undetermined route, and 

 continue their growth in nodules in the walls of these organs. 

 After reaching the final stage of development by a fourtli molt 

 they pass into the lumen. 



The Trichoneminae of horses are believed not to migrate out 

 of the intestine at all. Many of them, jierliaps all, penetrate 

 into the walls of the mucosa where they develop in nodules. They 

 undergo the tliird molt when about 1 mm long, becoming what 

 Ihle and Ocirdt (1923) call "Triehonema" larvae, provided 

 witli a provisional moutli capsule. Tlie final molt occurs in the 

 lumen of the intestine. 



Trioilontopliorus tcnuicolUs- is believed by Ortlepp (102.T) to 

 develop directly in the lumen of the cecum and colon, without 

 even temporarily burying itself in the mucosa. He was never 

 able to find larvae of this species in nodules. However, only 

 fourtli stage larvae were found, and there is nothing in Ort- 

 lepp 's observations to preclude a hookworm-like migration via 

 lungs and trachea on the part of the third-stage larvae. 



The Oesoidiagostomiuae have a life cycle in the host essen- 

 tially the same as that of the Trichoneminae, the young worms 

 tending to Ijuvy themselves in the mucosa, where tliey cause the 

 formation of cysts or nodules. Here thej- undergo their devel- 

 opment to the final stage, emerging into the lumen of the intes- 

 tine at about the time of the final molt, or in some cases even 

 later, when they have grown to a length of 4 or 5 mm. 



According to Spindler (1933), Oexophagostomnm quadrix- 

 plmilatum (= loiigicaudiim) of pigs produces inflamed liipiefy 

 ing cysts within 4.S hours after infection, and the larvae begin 

 escaping into the Inmen after aliout 17 days. Similar inflamed 

 cysts are produced by most other species of oesophagostomes, 

 but Goodey (1924) failed to observe tlieiu in experimental in 

 feetions with 0. dcntatiim and Schwartz (1931) saw onl}' small 

 noninflamcd nodules at the site of attachment of adult worms 

 of this species in contrast to the inflamed lesions caused by 

 quadrispiniilatum. Chabcrtia oviniis, though nearly related to 

 Oesophagostotniim, also fails to develop in submucous nodules. 



Stephaiturus diniatiis, (see Schwartz and Price, 1932; Ross 

 and Kauzal, 1932) whether entering by skin or mouth, migrates 



Fig. 184. OESOPHAGOSTOMVU BIFVKCUM AND 

 METASTRONaTLUS S'ALMI 



A — Nodules of Oesophagoatomum. bifurcum in the large intestine of 

 an African (after Brunipt). B-E — Metnstrongylns salvii (B — Egg with 

 fully developed embryo; C — Newly hatched first stage larva; D — First 

 stage larva undergoing first molt; E — Second stage larva undergoing 

 second molt while still enclosed within the cuticle of first molt). A. after 

 Chandler. 1940 (fig. 146) Int. to Parasit. B-E, after Alicata, 1!):!5, 

 U.S.D.A. Tech. Bull. 489. 



to the liver via the blood stream. The third molt occurs about 

 70 hours after infection, and the larvae have a provisional 

 mouth capsule. Normally such larvae escape from the capil- 

 laries in the liver and wander in the hepatic parenchyma until 

 they reach the surface capsule. They wander under this for a 

 time but eventually, 3 months or more after infection, break 

 free into the body cavity and make their way to the perirenal 

 fat tissue, perforating the walls of the ureters to establish con- 

 nection with the outside world. They tliemselves become en- 

 closed in capsules of host tissue. 



II. METASTRONGYLOIDEA 



In this supeifamily of the Strongylina the early development 

 follows somewhat different patterns from that of the other 

 members of the suborder, except in a few instances (e.g., 

 Strongijlacaniha resembles Dictyocaidus in hatching and then 

 reaching the infective stage without feeding or growing, and 

 the Sj'ugamidae also resemble Dicti/ocaulus in having optiiuial 

 transport hosts). 



Three principal types of development occur among the Mcta- 

 strongyloidea : (1) the Dicfi/ocaidus type, in which the larvae 

 go through two molts and reach the infective stage, surrounded 

 by one or both shed cuticles, without feeding or growing; (2) 

 the Metastrongylus type, in which the first-stage larvae con- 

 tinue their development after ingestion by earthworms, and 

 (3) the Prutostrongylus type, in which the first stage larvae, 

 attracted by the mucus of snails or slugs, continue their devel- 

 opment after entering the slime glands in the foot of these 

 molluscs, and becoming encapsulated in the muscular connec- 

 tive tissue under the epithelium. 



