732 IOWA DEPARTMENT OP AGRICULTURE 



on the comb, wattles, ear lobes, and less frequently on the skin of 

 other parts of the body. It Is more frequent and more malignant in 

 warm than in cold climates, but occurs in most parts of the world. 

 Recent investigations make it probable that it is caused by a filterable 

 virus which identical with that of diphtheria. As the symptoms of the 

 -two conditions are generally quite distinct they are here described sep- 

 arately. 



Causation. — Bird pox, so far as known, does not originate in any 

 other way than by contagion. It seems to be produced by virus from 

 fowls or pigeons affected with either the eruption of bird pox or the 

 false membranes of diphtheria. Experiments have shown that both 

 pox and diphtheria are easily inoculated from fowl to fowl and from 

 pigeons to fowl, but the inoculation of pox from fowl to pigeon has proved 

 very difficult and that of diphtheria impossible. The contagion is believed 

 to exist in the blood as well as in the nodules which appear upon 

 the skin. 



The disease is generally introduced by new birds which are put into 

 the flock or by exhibition birds which return infected. Probably it 

 is often brought by pigeons, sparrows, and other birds which fly from 

 one yard to another. The inoculation of the comb and wattles appears 

 to occur by rubbing these parts with the infected feet or by being 

 injured with the infected beaks of other birds. 



The virus is quite resistant and requires thorough disinfection for 

 its eradication. 



Symptoms. — The eruption appears as round, oblong, or irregularly 

 shaped nodules from the size of a pinliead to that of a pea or a hazel- 

 nut. They are seen especially about the beak and nostrils and on the 

 comb, the eyelids, and wattles, and the ear lobes. In some individuals, 

 and particularly in pigeons, the eruption is more generalized and is 

 found on the skin of other parts of the body, as the neck, under the 

 wings, on the rump, and about the cloaca. Here the nodules may 

 become larger than on the head. 



The nodules begin as small red or reddish-gray deposits with a 

 shiny surface and generally enlarge, while the color changes to a 

 yellowish, brownish, or dark brown and the surface dries and de- 

 come shriveled, uneven, and warty in appearance. Owing to the num- 

 ber of nodules and the extension of the inflammation, large patches 

 of skin become thickened and covered with hard, dry crusts, closing 

 the nasal openings or the eyelids and making it difficult even to open 

 the beak. 



In the milder cases the eruption is limited to the head, the nodules 

 are distinct and small, and the general health of the affected bird 

 does not suffer. The nodules soon dry, heal, and shrink; the crusts 

 become loosened and fall off, and there is rapid recovery. In the more 

 malignant cases the eruption is generalized over the surface of the 

 body, the nodules are larger, and there is a diffuse inflammation and 

 thickening of large areas of skin. If the crusts are rubbed or scratched 

 off by the fowls, there occurs from the ulcerous surface a discharge 

 at first watery, but later thick, yellowish, and viscid, which soils the 

 feathers and, if abundant, gives off a disagreeable odor. This typo of 



