PREVENTIVE MEDICINE 341 



" verminous bronchitis " in the different domesticated animals are 

 as follows : In calves, Strongylus micrurus; in lambs, S. filaria 

 and S. rufescens (the latter first described in this country by 

 M'Fadyean) ; in pigs, S. paradoxus; in horses S. arnfeldi. Infec- 

 tion is believed to occur usually by ingestion, the larval worms 

 after reaching the stomach travelling to the lungs during rumin- 

 ation. In the lungs they arrive at sexual maturity and lay eggs, 

 which are passed out on to the land during the paroxysms of 

 coughing. According to Miessner the first signs of illness in cattle 

 appear 6 to 10 weeks after they have picked up the worms, but the 

 time is variable and is more or less dependent upon weather 

 conditions. 



PREVENTIVE MEASURES. As before. Affected animals should 

 be housed or at any rate segregated so that the worms or ova coughed 

 up are not scattered over a wide area. If housed, the litter can 

 be collected and destroyed. It is probable that the eggs and larvie 

 are very resistant to adverse conditions. Since humidity and 

 warmth are favourable to the development of the worms, pastures 

 should be drained and low-lying areas should be avoided if possible. 

 Stagnant pools and ditches should be filled up and a supply of good 

 pure water provided. 



HELMINTHIASIS OF THE ALIMENTARY CANAL. Ascariasis 

 due to A. megalocephala is not in the horse of great clinical import- 

 ance, though cases have been recorded where large numbers of these 

 parasites have, by bunching, occluded the lumen of the gut. It 

 is known that ascarides produce a toxin which has been shown to 

 be capable of producing nervous disturbances. Ascarides are also 

 found in the intestines of calves (A. vituli), sheep (A. ovis), pig 

 (A. suUa), dog (A. marginata), and cat (A. mystax). 



Oxyuriasis. The Oxyuridse are not considered to be of great 

 clinical importance in the horse. 



STRONGYLOSIS. This very serious condition is caused by a 

 variety of parasites, notably Sclerostomum equinum (Strongylus 

 armatus"), Sclerostomum tetracanthum (Strongylus tetracanthus), 

 Sclerostomum vulgare and Sclerostomum edentatum. 



PREVENTIVE MEASURES. As with other intestinal parasitic 

 diseases attempts should be made to keep infected dung off the 

 pastures. Fresh, clean water for horses at grass is imperative, 

 and animals should not be allowed to drink from dirty pools. 

 Grazing fields on the outskirts of towns set apart for the running 

 of horses at grass are often very badly infected, and it must be 

 remembered that horses carry the various helminthces in their 

 intestines for years and so convey the disease to any pastures on 



