Parasitic Bronchitis in Cattle. 
79 
are severe, and difficult breathing is much marked. The 
paroxysms probably depend on movement of the bunches 
of worms in the bronchi, which are dislodged by the cough, 
and then inhaled into a tube, blocking it. Sometimes under 
these circumstances the animal may appear as though choked. 
Mucus is often discharged through the nostrils and may contain 
the parasite or its embryos, or both. In severe cases there 
may be great depression and a high temperature indicating 
inflammation of the lungs ; but in milder cases, which are 
commonest, the young animal’s general health and appetite are 
not much affected. In a certain proportion of cases diarrhoea 
is present, emaciation is very marked, and the course of the 
disease is rapid and fatal. This we take to be evidence of 
the co-existence of minute strongyles in the stomach and of 
the Strongylus micrurus in the bronchi. When there are 
only a few worms in the air passages recovery usually takes 
place in the winter. 
Concerning the development of the Strongylus micrurus 
little is definitely known. The females are seen to contain 
immense numbers of living embryos and worms, and embryos 
are found free in the bronchial tubes. There is every reason for 
supposing that the embryos do not develop into worms within 
the “ host,” for if large numbers of embryos, taken from the 
lungs, are given to cattle or injected into the windpipe, no 
worms are to be found in the bronchial tubes afterwards. It 
is assumed that the embryos and those of other strongyles 
pass out of the animal’s body into some soft-bodied animals 
as worms, or snails, and there undergo some essential change 
rendering them fit to live in the bronchi of cattle. Experi- 
ment shows that the embryos live in moisture for months, and 
after having been dried, resuscitate on being placed in water ; 
also that embryos coughed up and discharged in dry weather 
may remain dormant in the dry condition for weeks and 
revive after rain. 
Prevention . — In the absence of knowledge of the life-history 
of these worms, measures of prevention cannot be adopted 
with the precision desirable. The results of common obser- 
vation, however, indicate certain lines which are likely to be 
followed by a degree of success. Calves and yearlings should 
not be turned on to pastures suspected of being infested ; indeed, 
when practicable they should be kept on young grass which 
has not been depastured with cattle. Land holding water, 
flooded land, dirty pools, &c., should be avoided. It is deemed 
advisable to keep young cattle housed at night, turning them 
out only after the dew has gone, and to give some dry food 
before turning out. Shelter from cold and a liberal diet are 
important, and the admixture of common salt with manger 
