
On the prevention of foot and mouth disease 
by 
Dr. HENRIQUE MARQUES LISBOA e Dr. ARMANDO ALVES DA ROCHA. 

In a paper on the prevention of foot 
and mouth disease published in KOLLE and 
WASSERMANN ’s treatise, M. CASPER sta- 
tes that immunity follows an attack of this 
disease, but mentions that opinionson the 
duration of immunity vary. 
We have had the opportunity to make 
observations in many foci of aphthous fever 
and have also been making an experimental 
study of this disease for over six years, so 
that we feel justified in giving our opinion 
on the subject. 
‘The average duration of iaa after 
aphtous fever is about one year and we be- 
lieve that the divergence of opinions on 
this point is due tothe varying intensity of 
infection and to the degree of individual re- 
sistance. If an animal has a slight attack 
of foot and mouth disease it may be 
liable to another benign attack at the end 
of some six months, though this is very 
exceptional. The shortest period of immunity 
we observed lasted only four months and oc- 
curred after avery slight infection, following 
experimental inoculation of the disease. These 
cases were found among a herd of Devon- 
shire cattle imported by the State of Minas 
Geraes. Four months after benign experi- 
Te. 

mental inoculation wiht eigth bladed scari- 
fiers, to test the vaccinating power of Cow- 
pox, a pig with foot and mouth disease was 
put in the pen where this herd was kept. 
Other pigs in the same pen were contami- 
nated and boils appeared on the skin of 
three head of cattle, accompanied by a slight 
rise of temperature. After two daysthe fever 
and the boils disappeared leaving no traces. 
lf the animals had not been under observa- 
tion, it is probable that the outbreak would 
not even have been noticed. 
The longest period of immunity which 
came under our notice lasted for two years 
and occured after a virulent attack. 
We have never met with complete 
immunity though we have heard of it; 
but we were not given sufficiently con- 
vincing proofs of the positive risk of in- 
fection to which the supposedly immune 
herd was exposed. The fact that the disease 
be found in neighbouring ranches is not 
enough as one may only be sure of conta- 
gion when there has been promiscuity of 
healthy and sick cattle. It is well known 
that calves born of cows which had the dis- 
ease in an advanced state of pregnancy, 
without miscarrying, are very refractory and 

