130 ANNUAL KEPORTS OF DEPARTMENT OF AGRICULTURE. 

 ZOOLOGICAL DIVISION. 



The Zoological Division, under Dr. B. H. Ransom, chief, has con- 

 tinned the investigation of parasitic diseases of animals, and tlie 

 study, collection, and determination of animal parasites. 



ROUNDWORMS OF SHEEP. 



At the bureau farm near Vienna, Ya., experiments to determine 

 methods of rearing lambs free from parasites, or as nearly free as 

 practically possible, have been continued. Successful results ha\e 

 been obtained repeatedly by dosing the ewes with 1 per cent copper- 

 sulphate solution in the spring before turning them out to pasture 

 with their lambs, after which the lambs with or without the ewes are 

 changed every two weeks to fresh pasture. If kept on separate pas- 

 tures from the ewes the lambs until weaning are alloAved in the stable 

 with the ewes at niglit and during a period in the middle of the day. 

 For pastui-e, fields of appropriate size planted in various forage 

 crops are used; also, when available, fields from which crops have 

 been removed in the course of regulai' farming operations. No fields 

 are used that have been occupied b}^ other sheep since cultivation 

 unless at least a year has elapsed since such occupancy. During the 

 fall and winter the lambs may be allowed to remain on the same field 

 for longer periods one or two months or even longer and during 

 the next spring and summer they are also moved to fresh pasture only 

 occasionally. This method does not entirely prevent infection, but 

 the number of stomach worms and other roundAvorms is kept down 

 to such an extent that they cause no apparent injury. Experiments 

 are now in progress relating to a method under which the lambs are 

 changed to fresh pasture only every three wrecks during the summer. 

 Tlie question of preventing or minimizing tapeworm infestation is 

 also being studied. 



ROUNDWORMS OF HOGS. 



Investigations on the common intestinal roundworm of hogs (Asca- 

 ris lumtricoides or A. suum) have been continued. Supplementing 

 laboratory experiments, a study of conditions in the field has been 

 made. It has been found that ascariasis in pigs is of great im- 

 portance as a cause of death and stunting of growth. Invasion of the 

 lungs by the larvse of Ascaris commonly causes pneumonia, the symp- 

 toms of which are popularly known as "thumps." Even if a pig 

 survives the invasion of the lungs by the young parasites he receives 

 a setback from which he never fully recovers, but remains in poor 

 condition, fails to grow at the normal rate, and at an age when he 

 should weigh 100 pounds may weigh less than 50 pounds, sometimes 

 less than 20 pounds. Under the usual conditions under which hogs 

 are kept a considerable proportion of the young pigs die from ascari- 

 asis and many others are stunted in growth, so that the sum total of 

 loss throughout the country is enormous. Methods of management 

 to prevent losses from this cause are under investigation, and suf- 

 ficient progress has been made to justify the belief that with com- 

 paratively simple precautions the damage caused by Ascaris can be 

 reduced on any farm to an inconsequential amount. Several papers 

 reporting the results of investigations on Ascaris have been pub- 

 lished during the year. 



