650 DISEASES OF SWINE 



opening thus made the newly hatched parasite comes out and 

 attaches itself to the hair of the animal, or may drop to the 

 ground and wait for a favorable opportunity to attach itself to a 

 host. 



It is not difficult, as a rule, to find lice on hogs if they are 

 present. The size of the parasite and the thin hair possessed by 

 the hog make it a rather easy matter to locate them. There are 

 some parts of the body where they are particularly common, and 

 where they can be found very easily. The favorite place is in the 

 grooves or folds of the skin back of the ears. Here the louse and 

 the nits are especially common. The inner side of the hind legs 

 is also a common location for the louse. The reason that Hce 

 choose these locations for attachment is that the skin here is thin, 

 and it is easy for the parasites to pierce through and obtain the 

 blood upon which they live. 



Lousiness is a very widely distributed affection among hogs 

 in the United States. In recent serum injection work I have found 

 about 80 per cent, of the herds treated to be lousy. In serum 

 injections it is very easy to notice lice if present, for the favorite 

 seats of injection of serum are also the favorite locations for attach- 

 ment of the hematopinus. 



There are a number of causes which may explain the presence 

 of lice in a herd. Animals that are kept in poorly ventilated, 

 tumble-down, dirty sheds and pens are almost certain to become 

 the hosts of large numbers of these lice. Unclean, badly drained 

 feed lots and old dirty, mud-hole wallows are favorable factors in 

 the breeding of the hog-louse. Unthrifty animals, such as those 

 which suffer from chronic digestive disturbances and a chronic 

 cough, are particularly Hkely to become victims of the blood-suck- 

 ing louse. They are in a naturally weakened condition and offer 

 but little resistance to attack by the parasites. Healthy, clean 

 animals are not often found to be favorable hosts by the louse, and, 

 even though they may become affected, the parasites do not seem 

 to find conditions suitable for their existence, and they drop off and 

 look for a more desirable victim. 



Bringing in of new hogs from an affected herd and adding them 

 to the home feed lots without first inspecting them for lice and dip- 

 ping them, if any are present, is a common means of scattering the 



