a similar method of growing foot-and-mouth disease 
virus in cultures of swine and cattle kidney cells. Foot- 
and-mouth disease virus previously had been grown 
experimentally in other types of tissue by European 
research scientists. But the new method further devel- 
oped and applied at the Plum Island Laboratory pro- 
vides a lower cost method and uses material that is 
readily available. Therefore, it is an important step 
toward large-scale production of the virus for funda- 
mental studies. 
FACTS ABOUT FOOT-AND-MOUTH 
DISEASE 
Foot-and-mouth disease is a highly contagious 
vesicular disease (characterized by vesicles or blisters) 
affecting cloven-footed animals almost exclusively. 
These include, among farm animals, 
sheep, and goats; 
cattle, swine, 
and, among wild animals, deer, 
buffalo, antelope, etc. It is caused by a virus of which 
there are at least 7 recognized types and variants within 
types. 
Visible symptoms of the disease appear first as 
blisters on such tissues as the tongue, lining of the 
mouth, and between and around the top of the claws. 
In milk cows, the blisters may appear on the teats 
and udder. The blisters soon break, leaving a raw 
eroded surface. In cattle there is excessive salivation, 
causing the animal to drool. When the feet are af- 
fected, the animal limps painfully or lies down. 
Mortality varies widely. Generally it is less than 5 
percent, occurring especially in young animals. More 
virulent forms have caused death losses of 30 to 50 
percent. 
Greatest damage to herds, however, comes from loss 
in condition and permanent impairment such as loss of 
fertility. Recovered animals seldom regain produc- 
tion efhciency. Meat animals lose weight. Dairy 
stock lose condition rapidly and milk production often 
drops to almost nothing. It has been estimated that 
if the disease ever became firmly established in the 
United States, the combination of death losses and 
damage to affected animals could cost this country up 
to one-fourth of its production of meat, milk, and other 
animal products. 
Nine outbreaks of foot-and-mouth disease have 
occurred in this country—from 1870 to 1929. The 
United States Government worked closely with Mexico 
to eradicate the disease there during the years 1947-52 
and 1953-54. Specialists from this country were 
invited to observe the eradication program in Cana 
in 1952. 
SAFETY PRECAUTIONS | 
The safety precautions enforced at the Plum Island 
Laboratory are geared to control the highly contagious: 
foot-and-mouth disease virus. The two research struc- 
tures, with similar safety features, are considered the 
safest in the world for work on animal viruses. 
Among the safety precautions are the following: 
1. Isolation on an off-shore island as required by 
law.—The location—on an island controlled by the. 
Federal Government and with no normal traffic facili- 
ties connecting with the mainland—makes it possible te 
control movement to and from the island and on it. 
2. Controlled movement of vehicles ——Vehicles mov- 
ing to and from Plum Island (by water transport) are 
restricted to a few Government-owned trucks, allowed 
only as far as the fenced-in dock area. Government 
vehicles operated beyond the fenced dock area are 
restricted to the island. Personally owned automobiles 
are not permitted on Plum Island. 
3. Careful introduction of experimental animals.— 
Only healthy animals are selected for experiments. On 
the way to Plum Island they are kept in strict isolation. 
The animals are transferred to Government trucks at an 
isolated point on Long Island. These trucks are then 
allowed to proceed only as far as the fenced-in area at 
the Plum Island dock. Here the animals are trans- 
ferred to island trucks on the other side of the dock-area 
fence by means of unloading and loading ramps that 
are disinfected after each transfer. 
Beef kidney is used in one method for tissue culture of | 
foot-and-mouth disease virus developed at the Plum 
Island Laboratory. This method is a major contribu- 
tion in providing an efficient and inexpensive means of 
producing large quantities of virus for continuing 
studies of the disease and methods of combating it. | 
