Oct. io, 1913 
Cysticercus Ovis 
47 
The actual percentage of sheep infested with measles, at least in those 
sections of this country where a close relationship exists between sheep 
and dogs, probably approximates 5 per cent much more nearly than it 
does the very small percentage derived from the figures given in Table II. 
AGE OF INFESTED SHEEP 
Information as to the age at which sheep are most likely to be found 
infested with measles is meager. A priori it would be expected that 
rather young animals would most commonly show infestation. As a 
rule, young animals are more liable to infestation with tissue parasites 
than old animals, possibly because their tissues offer less resistance to 
the migration of the parasites than those of older animals. This greater 
susceptibility is offset to some extent by the fact that the longer an 
animal lives the more opportunity he has for becoming infested, other 
things being equal. 
Among a total of 189 infested sheep whose ages (approximate) were 
recorded by inspectors of the Bureau of Animal Industry at several 
stations, the distribution of cases according to age was as follows: 
6 months. 
Number 
of cases. 
. 20 
2 to 4 years. 
Number 
of cases. 
8 months. 
. 57 
3 to 5 years. 
. 14 
10 months. 
. 3 
4 years. 
. I 
1 year. 
. 4 
5 years. 
years. 
. 3 
6 years. 
2 years.... 63 
Owing to the lack of data as to the relative numbers of sheep of these 
various ages which are slaughtered, the figures in the above table do 
not prove anything. They seem to indicate, however, that Cysticercus 
ovis is more commonly met with in young than in old sheep. As one 
possible explanation of the apparent rarity of C. ovis in old sheep it is 
reasonable to suppose that as the animals grow older any parasites which 
they may have picked up in earlier life tend to disappear more or less 
completely as a result of degeneration and absorption by the surrounding 
tissues. Meanwhile with increasing age the susceptibility to infestation 
diminishes, and this, combined with the death and disappearance of 
the parasites acquired during youth, tends to result in freedom from 
infestation. 
ECONOMIC IMPORTANCE 
Sheep measles, instead of being as formerly considered a sort of zoo¬ 
logical or pathological curiosity, is a matter of great importance to the 
sheep grower, the butcher, and the consumer of mutton. Although the 
tapeworm cysts are not transmissible to man, mutton infested with them 
is not a desirable article of food, and modern ideas in meat inspection 
require that mutton infested with these parasites to any considerable 
7954 0 —13-4 
