Editor’s note: Johne’s disease is
0 f growing concern to more and
more dairy farmers, and is the
subject of much recent research.
This is the conclusion of a two-part
article about research progress
and current knowledge about
Johne’s.
BY WENDY WEHR
NEW BOLTON CENTER-
Phase two of the Johne’s research
project, which is being conducted
by the University of Pennsylvania
School of Veterinary Medicine and
Penn State, with funding from the
Pa. Department of Agriculture, is
to complete herd studies of 24
Pennsylvania dairy herds. As with
phase one of the project, the ob
jective is to collect as much data as
possible, to establish a base of
information that might give some
clues to solving the Johne’s
problem.
The 24 herds, all on the DHIA
program, are a stratified random
sample of the dairy herds in
Pennsylvania. They are
distributed geographically across
the state, and represent all sizes of
herds. Animals in these herds may
or may not be carrying the
paratuberculosis organism that
causes Johne’s. That’s one part of
the testing in the herd studies.
Dr Robert Whitlock, coor-
R
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Johne’s Update
dinator of the project, and his
fellow researchers recently
completed the sixth herd study.
The first herd study was done in
July. Whitlock explained that it
takes five or six people a full day
on each farm to gather all the
information they think might
pertain to Johne’s.
“In each of the 24 herds, every
animal from six months of age and
up is tested for Johne’s,” said
Whitlock. In addition, each animal
is classified according to body
condition, and information is
gathered about her breeding
records, lifetime production,
health, and feeding programs. The
DHIA records enables them to
gather much of this related in
formation.
Management practices are also
noted because this may give the
researchers clues about the spread
of the disease between animals in
the herd. Because most animals
that contract Johne’s are infected
at a very young age, calf housing
and contact between young stock
and cows is of particular concern.
Knowing whether the dairyman
raises his own replacements or
does a lot of buying and selling of
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Answers through research
cattle might also indicate how the
disease spreads.
One of the questions that the
researchers are particularly
curious about, said Whitlock, is at
what age an infected calf will show
positive on the diagnostic tests.
Collecting soils samples on the
farms, another part of the herd
studies, may shed some light on
how long the paratuberculosis
organism lives outside of an in
fected animal.
Johne’s positive
Of course all of the information
that is gathered in the herd studies
will be valuable to the Johne’s
research. Important answers to
the questions about economic
consequences of both the sub
clinical and clinical occurrence of
Johne’s may be found.
But what about the animals that
test Johne’s positive during the
herd studies?
Any animal that is found to have
Johne’s in Pennsylvania must be
reported to the Bureau of Animal
Industry. As long as she remains
in the herd, the dairyman cannot
obtain certain health charts, so
there is little choice but to cull the
animal.
The BAI does pay an indemnity
under certain conditions to
dairymen who lose animals to
Johne’s. Whitlock explained, “The
state will pay 90 percent of the
appraised value of the cow, less the
meat value when the cow is culled,
if the dairyman agrees to continue
cooperating by testing for Johne’s
at regular intervals and culling
any additional animals that test
Johne’s positive.”
“Several hundred farmers have
taken advantage of the indemnity
program to date,” says Whitlock,
“and as far as I know Penn
sylvania is the only state that has
initiated such a program.”
But the indemnity program
hardly covers the threat of Johne’s
for some diarymen. Whitlock
explained why a few of the
dairymen contacted for herd
studies refused to become part of
the research.
“If you’ve got an extremely
valuable animal, or a registered
herd with terrific genetic potential,
finding Johne’s in the herd would
be really unfortunate.”
Interestingly, there are a few
options, with considerable
drawbacks, that owners of par
ticularly valuable cows can
choose.
One option is the Johne’s vac
cine, which is only available on a
strictly controlled basis. Five or
six years ago the vaccine was used
experimentally in three or four
herds, and four new herds have
been approved for its use recently,
commented Whitlock.
But the drawbacks of the vaccine
are many. Calves must be vac
cinated before 35 days of age, and
often a large lump occurs at the
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site of the injection. And although
this vaccine may prevent the
clinical disease, it is not known
whether it prevents infection.
“Furthermore,” says Whitlock,
“use of the vaccine means that the
herd is then Johne’s infected.”
Even so, some dairymen would
prefer to buy a vaccinated animal.
Another even lesser known
option for valuable Johne’s in
fected cows is an experimental
treatment. Whitlock mentioned its
successful use recently on an
animal that was worth at least
$200,000. The only reason to use it
is if a cow has terrific genetic
potential, because once she
receives the treatment the cow
may never be used for milk or
meat again.
“The treatment is a drug called
Lamprene, which is actually used
as a treatment for human leprosy
in other countries, but it is so rare
and unusual that for all uses in the
United States it is only used ex
perimentally.
Lamprene does not cure Johne’s,
it merely arrests it. Three cows
that received the treatment did
respond, but they continued to shed
the paratuberculosis organism.
Several embryos were obtained
from the valuable cow mentioned
above, before she had to be
destroyed.
Managing Johne’s
Obviously the vaccine and
treatment are of very limited use
to most dairymen. But until the
results of the three-year Johne’s
research project begin to yield
some solutions, what can
dairymen do about Johne’s?
(Turn to Page A3B)
Student
S-15