The first diagnostic
tests for Johne's disease were created after the discovery of how to cultivate
M. paratuberculosis in the laboratory. Recognition of the disease in
the U.S. led to early warnings of its potential impact on animal agriculture.
By the early 1900's,
pseudotuberculous enteritis was well recognized as a new disease and one that
was widespread. Scientists proposed a variety of alternative names for the disease,
such as paratuberculosis and hypertrophic enteritis. In the Annual Report for
1906 of the Principal of the Royal Veterinary College, J. McFadyean coined the
term "Johne's disease". Most publications since then have used either Johne's
disease or paratuberculosis when referring to the disease. In 1908, L Pearson
published the first report of Johne's disease in the USA (Pennsylvania).
The 1910's witnessed
many discoveries about Johne's disease. In Denmark, O. Bang learned that animals
with Johne's disease responded weakly or not at all to intradermal injection of
antigens prepared from the tubercle bacillus (Mycobacterium bovis), but
responded well to avian tuberculin (antigens prepared from Mycobacterium avium).
On the basis of this observation, Bang suggested that avian tuberculin could be
used for diagnostic testing of animals. This was confirmed a year later in England
by G.P. Male. Thus, even before the bacterium that caused Johne's disease was
isolated, scientists believed it to be related in someway to the bacterium causing
tuberculosis in birds. A critical difference was that the organism causing avian
tuberculosis could be grown on laboratory culture but the organism causing Johne's
disease could not.
serendipitous observation by the British scientist F.W.Twort led to the isolation
of the etiologic agent during attempts to culture the Johne's disease bacterium.
Twort's failure to keep pace with cleaning laboratory glassware and his discriminating
eye enabled him to note small bacterial colonies growing like satellites around
larger colonies in old cultures he was preparing to discard. The larger colonies
were contaminants of the common hay bacillus, Mycobacterium phlei. Suspecting
that the M. phlei bacteria were providing some essential nutrient, Twort
incorporated a heat-killed preparation of M. phlei into his culture medium.
This new culture medium, he discovered, supported the growth of a new acid-fast
bacterium. He named it "Mycobacterium enteriditis chronicae pseudotuberculosae
bovis Johne". In 1912, H. Holth also reported successful isolation of the cause
of Johne's disease. Holth recognized the disease descriptions of Bang and simply
called the organism he isolated the paratuberculosis bacillus. He failed to receive
much recognition for his discovery.
After the etiologic agent could be cultivated in the laboratory, antigens
were obtained from it for diagnostic testing. They were used in skin testing
(as was done for tuberculosis), and for assays to detect antibodies in
serum samples using complement fixation and agglutination techniques.
The man who first referred to the disease as Johne's disease coined the
term "johnin" for the skin test antigen since the equivalent preparation
for skin testing for tuberculosis was called tuberculin. The next several
decades were devoted to evaluation of these and other diagnostic tests
and to improvements in methods for laboratory cultivation of the organism.
Early warnings in the USA
K.F. Meyer, in
a report to the Pennsylvania State Livestock Sanitary Board said:
loss will become one of a very serious nature if necessary steps for
the control of this disease, which has been brought to this country
by importation, are not taken."
In the 1920s, paratuberculosis was described in animals on the African and Asian
continents. Valle and Rinjard, recognizing that the subcutaneous injection of
M. paratuberculosis did not cause disease, evaluated vaccination as a means
to control spread of the Johne's disease. In 1923, the first edition of Bergey's
Manual of Determinative Bacteriology was published and officially named the causative
agent of Johne's disease Mycobacterium paratuberculosis (Bergey's Manual
is a catalogue of all bacteria and their characteristics and is considered "the
bible" of bacterial identification). Much energy was spent in the 1920s to find
a small laboratory animal model of Johne's disease. Although some investigators
will debate this conclusion, the goal of finding a small laboratory animal that
develops pathology and disease truly typical of Johne's disease after experimental
challenge with M.paratuberculosis remains elusive.
description of Johne's disease
343 from the University of Wisconsin Agricultural Experiment Station provides
a 22 page description of Johne's disease, complete with pictures of affected
animals, tissues and laboratory cultures of M. paratuberculosis.
In this publication, these astute scientists gave sound advice to farmers
that is still true today such as:
(of the infection from a herd) by elimination of those animals showing
symptoms would, in most instances, not be successful."
of all suspicious animals from the herd and care in the purchase of animals
will certainly do much to limit the continued spread of this disease."
"The prompt separation
of calf and dam will, undoubtedly, prevent the infection of the former,
as it does in tuberculosis."
Larson, Beach and
Wisnicky from the University of Wisconsin reported on the occurrence of
Johne's disease in Wisconsin dairy herds in the Journal of the American
Veterinary Medical Association and offered this advice:
"The disease has,
at present, a limited number of sources from which it can spread.....These
sources of infection will continually increase, unless agencies are operative
to offset the constantly increasing commerce in cattle."
It took another seventy years before any country began to develop systematic
methods to try and stop the spread of paratuberculosis among herds.
In this same article Larson et al. quoted other experts as saying:
position of Johne's disease is compared with that of bovine tuberculosis
60 years ago and, if not controlled, it may become a more troublesome
scourge for future generations than tuberculosis is for the present generation
of cattle owners."