240
Respiratory Diseases of the Horse
demonstrated partial or complete auricular-ventri-
cular heart block.
The nervous and psychic disturbances which
may occur during the course of respiratory diseases
have been noted by most authors. Bemelmans
[ 1921 ] attributed many of the primary disease
symptoms to nervous derangement, and Steffan
[ 1941 ] has made a special study of the subject.
There can be little doubt that there is a relationship
between the neural damage caused and the subse-
quent onset of roaring, stringhalt and the other
nervous affections of the horse. Ebberbeck's [ 1940 ]
pathological investigations have provided much
evidence in support of this view, but it is probable
that nutrition [ Mitchell, 1936 ] and heriditary
disposition also play their part.
DISCUSSION
The four respiratory diseases have been described
as though they were separate entities, and some of
their main features are summarized in Table I, but
it must be admitted that, whilst the typical diseases
can be recognized, there are many outbreaks whi ch
even experienced workers are unable to classify
[ Theiler, 1918 ].
TABLE I
—
Incubation period
Infectivity . .
Symptoms
Action of neosalvarsan
Mortality
Contagious
pneumonia
Long, up to 40 days .
Low, only by direct contact.
Spread is irregular and the
duration of an outbreak in
a group of horses is much
longer than with the other
diseases.
Primary fever with regular
temperature curve may
pass almost
unnoticed.
Pneumonia
may
then
develop, accompanied by
a
secondary
rise
of
temperature.
A yellow
discharge from the, nose is
said to be pathogomonic.
Effective
....
Higher than in the other
diseases 10-20 per cent.
Influenza
Short
High, by direct and indirect
contact. May assume very
severe epidemic propor-
tions.
Primary fever with larger
diurnal
variations
of
temperature marked de-
pression,
cardiac
and
muscular
weakness.
Reddening
of
mucous
membranes and swelling
of subcutaneous tissues.
Severe intestinal, or less
often respiratory involve-
ment may follow.
Not effective
Usually low
Infectious
respiratory
catarrh
Short
....
High, by direct and indirect
contact.
Fever,
purulent
rhinitis,
coughing and occasional-
ly swelling of the sub-
maxillary
lymphnodes.
Pneumonia
may occur
under adverse conditions.
Not effective
Low
....
Strangles
Short.
High, by direct and
indirect contact.
Fever,
early rhinitis
followed by marked
swelling
and often
abscess formation of
the
sub-maxillary
lymphnodes.
Pneu-
monia
may occur
under adverse condi-
tions.
Presumably
not
effective
Usually low.
It would appear that infectious pneumonia can be
differentiated from the other diseases by its longer
incubation period and lower infectivity; the clinical
observation that there is no cross-immunity between
infectious pneumonia and influenza supports this
view. Bemelmans [ 1932 ] wrote a long review
comparing human influenza, brustseuche and canine
distemper. Many of his views can no longer be
accepted, but the review is valuable in that there
are 345 references to the older literature. Lührs
[1933] commented on Bemelmans' article. They
both agreed that brustseuche and influenza were
distinct diseases, but it is probable that Bemelmans
[ 1933 ] described infectious catarrh as ' abortive
brustseuche,' and other writers have stated that
outbreaks of catarrh predispose to brustseuche.
Lührs [ 1933 ], however, is quite definite that they
are separate diseases: the whole course of an out-
break of infectious catarrh is much shorter and
neosalvarsan exerts no therapeutic action.
Discussing strangles, Percival [1834] said: 'I
now begin to doubt whether any tumour or abscess
at all is absolutely necessary
I believe most
horses to have sooner or later in life, strangles fever;
but I doubt that everyone that has that fever has
it demonstrated or accompanied by local tumour or
abscess
Of the many young three to four
year-old horses which have in the course of years
passed under my medical superintendance, I shoul d
say that not have above one in four of them had
undergone regular strangles, though very many of
them at one time or the other had sickened
Let other veterinarians turn their attention to t hese
interesting points: we shall then probably, ere
many years pass over our heads, elicit .some curious
if not valuable addition to our present stock of