746 



SCIENCE 



[N. S. Vol. XL. No. 1038 



QUOTATIONS 



FOOT-AND-MOUTH DISEASE 



In view of the recent outbreak of foot-and- 

 mouth disease in the Mississippi Valley, the 

 most extensive as yet in the United States, a 

 brief consideration of the principal features 

 of the disease may be of interest. It is an 

 acute, highly infectious disease, which occurs 

 chiefly in cattle, sheep, goats and swine, 

 though other animals such as the horse and 

 dog, as well as certain vrild animals are at- 

 tacked also, and it may affect human beings. 

 In animals it is characterized especially by 

 the eruption of vesicles in the mouth and on 

 the feet, in some species more in the mouth, 

 in others more on the feet. It cattle the incu- 

 bation period averages from three to five days, 

 whereupon a moderate fever with loss of appe- 

 tite and other general symptoms sets in. In 

 two or three days small blisters appear on the 

 lining of the mouth, and now the fever usually 

 subsides. At the same time one or more feet 

 may show tenderness and swelling of the skin, 

 soon vesicles form here also, and the animal 

 goes lame. In the mouth the blisters may 

 reach half an inch or more in diameter, but 

 usually they are smaller; the contents, at first 

 clear, become turbid, and as the covering 

 bursts, small painful erosions are produced 

 which either heal quite promptly or turn into 

 ulcers that heal more slowly. Usually the milk 

 is altered and reduced in quantity; blisters 

 and ulcers may form on the udder. There is 

 marked loss of weight, as the animals do not 

 eat because of the pain. In this, the ordinary 

 form, in which the death-rate is very small ex- 

 cept among the young, the symptoms fade away 

 in from ten to twenty days or so, except when 

 complicating local secondary infections delay 

 recovery, but there are also severe forms with 

 extensive infection of the respiratory tract and 

 gastro-intestinal inflammation, which fre- 

 quently end in sudden death. In such severe 

 cases ulcers are found in the stomach and in- 

 testines. In sheep and swine, lesions of the 

 feet predominate. The disease is transmis- 

 sible to the fetus in utero. 



The cause of the disease is present in the 

 contents of the vesicles, the discharges from 

 the ulcers, the saliva, the milk, the urine and 



feces, but as a rule not after the tenth day. 

 It is stated that animals having had the dis- 

 ease may carry the virus for months.^ Any 

 susceptible species may infect any other sus- 

 ceptible species. Infection occurs not only 

 through direct contact, but also indirectly, as 

 the virus retains its virulence for some little 

 time, at least outside the body. Contamina- 

 tion of fodder, of stalls, of feeding and drink- 

 ing troughs, of miUs and milk products and of 

 the hands and clothes of drovers serves to 

 spread the disease, which often travels over 

 wide stretches of country with remarkable 

 rapidity, as shown by the present outbreak. 

 As from 25 to 50 per cent, of the cattle ex- 

 posed to infection may become sick, there re- 

 sults great loss from fall in the production of 

 milk, from reduction of vitality and fecundity, 

 and from deaths as well as on account of the 

 measures adopted to stamp out the epizootic. 



The immunity produced by an attack seems 

 to be feeble, as animals are said to suffer some- 

 times more than one attack within a short 

 time. So far no practical method of protec- 

 tive inoculation has been developed. 



Our knowledge of the cause of foot-and- 

 mouth disease is limited to the fact that it 

 concerns a filterable virus, as yet invisible and 

 incultivable. It was in 1897 that Lo&er and 

 Frosch made their classical experiment, show- 

 ing that the disease is caused by a living, pro- 

 liferative virus that passes filters which do not 

 permit bacteria to go through, an experiment 

 that has served as a model for all the subse- 

 quent work on the many other forms of filter- 

 able virus recognized since then. Foot-and- 

 mouth virus may remain active for months if 

 kept cool and moist, but is destroyed rapidly 

 by drying, by heat at 60° 0. (140° F.) and 

 above, by formal dehyd and by phenol (car- 

 bolic acid). The wide range of virulence of 

 this virus among animal species has been indi- 

 cated, and as stated, the disease may affect hu- 

 man beings, especially children, being trans- 

 mitted by milk from diseased cows (experi- 

 mentally verified) and by butter and cheese 

 made from such milk as well as through 



1 Moore, ' ' The Etiology of Inf eetious Diseases 

 in Animals, ' ' 1906. 



