FURTHER INVESTIGATIONS OF INFECTIOUS EQUINE 
ANEMIA IN NEVADA 1 
By Lewis H. Wright 
Nevada Agricultural Experiment Station 2 
INTRODUCTION 
Infectious equine anemia was first 
reported in Nevada by Mack (5, 6, 7, 
8 ), in 1909; (9) 3 in 1909. He made ex¬ 
tensive observations on the pathology, 
bacteriology, and symptomatology of 
the disease, but with one possible excep¬ 
tion was unable to transmit it to other 
horses, and so failed to arrive at any 
positive conclusion as to its etiology. 
All of Mack’s material came from one 
portion of the State, the region of the 
south fork of the Humboldt River in 
Elko County, where the disease had 
been prevalent and had caused exten¬ 
sive losses periodically for a number 
of years. 
Since this first report the disease has 
been found and studied around Fallon 
in Churchill County, near Washoe in 
Washoe County, and along the north 
fork of the Humboldt River. There 
have been reports of its having occurred 
around Yerington, Pahrump, Lovelock, 
and Battle Mountain, but these reports 
have not been confirmed. 
It is especially interesting to note 
that all of the infected areas are a 
considerable distance from one another, 
and, as far as can be ascertained, there 
has been little or no interchange of 
animals among them. In fact, many 
of the infected animals had never left 
the ranch where they were raised. 
From 1909 until 1918 the disease 
was apparently quiescent and caused 
very little loss. In fact, material for 
experimental purposes was at times 
unprocurable and very little work was 
done during this period. In Septem¬ 
ber, 1917, material was procured from 
Antelope Valley and some experiments 
were undertaken. This outbreak sub¬ 
sided, however, and the experimental 
virus was lost, owing to its lack of 
pathogenicity. 
In September, 1918, material was 
obtained from natural field cases at 
Fallon. Most of this report is based on 
experimental work done with virus 
from this source. 
In this report it is intended to touch 
some phases of the disease not solved 
by Mack, such as transmissibility, 
differential diagnosis, etc. Mack’s (6, 
7, 8, 9) observations on the pathology 
and symptomatology of the disease 
are sufficiently complete to need little 
repetition here. If the form of anemia 
with which Mack worked is identical 
with that reported from other States 
and foreign countries, the thing that 
stands out conspicuously in his experi¬ 
ments is the great difficulty which he 
encountered in transmitting the disease. 
This may have been due to the fact 
that he inoculated only animals in 
districts where the disease was preva¬ 
lent. In other words, he may have 
used no really susceptible animals. 
His fear of introducing the disease in 
new areas caused him to refrain from 
inoculation experiments at Reno. 
If the disease upon which the present 
investigations are based is the form 
of anemia usually found, this work will 
present very little that is wholly new. 
However, this report may establish 
some new facts concerning the local 
disease, especially its transmissibility, 
and may add others to show that it is 
the same disease encountered else¬ 
where. 
EXPERIMENTAL DATA 
The observations of the writer agree 
with those of Mack (6) in this, that there 
are three types of the disease, namely, 
acute, subacute, and chronic. Al¬ 
though distinct, the three types are 
separated by no hard and fast line, and 
a case that is thought to be acute may 
develop into subacute or chronic, or 
vice versa. Ranchers have reported 
some acute fatal cases, but there is con¬ 
siderable evidence to support the be¬ 
lief that the cause of death in these 
cases was not infectious anemia. No 
opportunity was offered to check. up 
on these cases by animal inoculation. 
In these later observations the blood 
examinations were made in the chronic 
field cases to exclude intestinal para- 
1 Received for publication June 11,1924; issued June, 1925. 
2 Resigned June 1, 1920. 
3 Reference is made by number (italic) to “Literature cited,” p. 692. 
Journal of Agricultural Research, 
Washington, D. C. 
( 683 ) 
Vol. XXX, No. 7 
Apr. I, 1925 
Key No. Nev.-3 
