A22—Lancaster Farming, Saturday, October 6,1984
Editor’s note: Johne’s disease is
of growing concern to more and
more dairy farmers, and is the
subject of much recent research.
This article is the first of a two
part senes to up-date farmers on
research progress and current
knowledge about Johne’s.
NEW BOLTON CENTER-Will
my cows Contract the debilitating
Johne’s disease’ How common is
it in Pennsylvania herds? Could
my cows already be harboring the
paratuberculosis organism that
causes Johne’s? And what are the
economic consequences pf Johne’s
if it’s already in my herd? You, as
a dairyman want to know the
answers to these questions.
In a few short months, the dairy
Dairy Exclusive
industry will be turning to Dr.
Robert Whitlock of the Univ. of
Pennsylvania’s New Bolton Center
for the answers to these questions.
As the coordinator of a three-year
collaborative project on Johne’s,
he has already collected a
significant amount of data on the
disease.
And collecting data has to be
step one in combating Johne’s
because so little is known about the
disease.
If you've had a positive Johne’s
cow in your herd, you know what a
threat the disease is. You probably
weren’t aware of the disease until
it reached it’s acute clinical stage,
when the cow had severe diarrhea
and became increasingly
emaciated, although she continued
to eat normally.
At that stage, and at any stage
for a cow that tests positive for
Johne’s, the only choice is to cull
her, because the disease which is
so difficult to diagnose also has no
known cure.
What members of the dairy
industry fear are the cow" who are
infected, but aren’t showing the
clinical signs of Johne’s disease.
These undetected cows are not
only transmitting the
paratuberculosis organism to
other animals, particularly yjung
stock, they are also an economic
liability because of resultant
decreased production, decreased
fertility, and increased suscep
tibility to mastitis.
To begin answering the ultimate
question of the economic
seriousness of Johne’s, at least two
things must first be achieved.
First, quick and reliable tests must
be developed to diagnose the
disease, and, secondly, a survey of
Pa cows must be undertaken to
get a figure on just how
widespread the disease is in the
16,000 dairy herds in the state
Three-year study
Achieving these two goals is the
. pi
tests being developed to diagnose Johne’s. More sensitive
and specific diagnostic tests are an important goal of the
lohne's research.
Johne’s Update:
primary concern of Dr. Whitlock
and the other members of the Pa.
Dept, of Agriculture funded
project. Other members of the
research group include Dr Larry
Hutchinson, extension
veterinarian from Penn State and
researchers at the National
Animal and Disease Laboratory in
Ames, lowa. Their three-year
study began in Oct. 1983.
With one year of the project
completed, Whitlock isn’t ready to
give definitive answers to the
plaguing questions about Johne’s,
but he is prepared to describe the
extensiveness of the research and
what this could mean for Pa.
dairymen.
“I’m not trying to be self
centered or anything, but we
seriously think our study is
probably the biggest and best, and
at the very least most com
prehensive, study on Johne’s
undertaken in the world to date,”
says Whitlock.
To understand the scope of the
research, consider the work that
has been completed in the first
year.
Phase one of the project was to
do a survey of cull cows in Penn
sylvania to try and get a handle on
the extent of the problem. To do
this they have gone to Taylor’s
Packing Plant in Wyalusing one
day a week for the past year to get
a random sampling of dairy cull
cows to test for Johne’s. Taylor’s
handles 10 percent of the cull cows
in the United States.
Now in the final weeks of this
phase, they have gathered feces,
blood, and tissue samples from
nearly 1500 slaughtered animals,
about half of which are from
Pennsylvania.
Numerous tests will be done on
the samples. The feces culture will
be done out at Ames and five blood
tests will done for each animal.
Three different tissue samples
were taken from each animal from
areas around the small intestine
where the paratuberculosis
organism grows. Three different
stains will be used on each of the
three tissue samples to identify the
orgamsm.
“Take 4500 tissue samples times
three different stains and you get
an idea of the number of slides that
have to be examined,” notes
Whitlock. And this doesn’t include
the fecal and blood cultures that
are done as well.
But it’s the tissue samples that
are a vital part of determining the
sensitivity and specificity of the
other diagnostic tests for Johne’s.
“Here we have a so-called ‘gold
standard’ to see if the culture is
positive or negative for Johne’s,”
explains Whitlock. Obtaining that
tissue sample is not possible with a
live animal, and that’s why it’s
Answers through research
crucial to develop these other
diagnostic tests.
Whitlock emphasizes sensitivity
and specificity as the important
characteristics of a diagnostic test.
Most dairymen are aware of the
drawbacks of the fecal culture that
is now used to diagnose Johne’s - a
lag time of several weeks is in
volved in obtaining results.
Whitlock explains why reliable
tests need to be specific, that is
able to show paratiiberculosis and
not mistakenly some similar
organism, and sensitive, that is
able to pick up Johne’s even if only
a small number of the organisms
are present in the animal.
“The fecal culture, for instance,
is specific - if the test comes out
positive then the paratuberculosis
organism really is there. But the
fecal culture is not a particularly
sensitive diagnostic test - it will
only detect Johne’s about one third
of the time,” comments Whitlock.
The blood, tissue, and fecal
samples from the 1500 cull cows
will give Whitlock and his fellow
researchers, which include two
full-time and one part-time
technician at New Bolton, an op
portunity to develop these new
diagnostic tests.
There are five blood serum tests
that they are using on the blood
samples and Whitlock is hopeful
that one or a combination of these
will have the necessary specificity
and sensitivity for use by
veterinarians to test animals
suspected of Johne’s.
Economic consequences
Of those 1500 slaughtered cull
cows, how many were Johne’s
positive?
“We found the paratuberculosis
organism in about 10 percent so
far,” says Whitlock. But more
information about the prevalence
of the disease will be gathered in
the continuing phases of the
project, which focus on learning as
much as possible about the disease
so that the question of total
economic loss can be dealt with.
Whitlock emphasizes that this is
not merely the problem of
economic loss from the cows that
show clinical signs of the infection
and must therefore be culled.
They’re just as concerned in their
study with the economic con
sequences of the sub-clinical cases.
It’s apparent, explains Whitlock,
that many cows are carriers of
Johne’s yet never develop into
acute cases with the resulting
diarrhea, emaciation, and even
tual death. Previous studies have
shown that these subclmical
carriers of Johne’s may have in
creased susceptibility to mastitis,
decreased fertility, and lowered
milk production.
■ To gam more definitive answers
about the economic consequences,
extensive information is being
gathered in this three-year study
In the just-completed phase one,
the researchers were able to
identify each of the 1500 cows and
are following up on the 600 or so
that are from Pa. by sending out
questionnaires to the former
owners of the slaughtered animals.
They are gathering information
about all of the cows, whether
positive or negative Johne’s
The questionnaires’ ask all sorts
of questions about the cow, about
age, production and breeding
records, health and management
conditions, and other items about
the herd that she came from To
date they’ve had about a 60 percent
rate of return on the questional res.
Dairymen can help
“If anyone has received one of
these questionnaires, it will be a
tremendous help to us if you do
take the time to fill it out and
return it.” reminds Whitlock.
“Even five or six more forms that
we get back will help us a lot in
evaluating the problem.” And he
reminds farmers that they’ll .be
helping themselves by helping the
dairy industry.
examines a Johne's infected heifer. Johne’s
disease usually doesn’t appear clinically until after two years
of age, but this 16-month-old heifer is severely emaciated.
Plasma will be taken from the animal to be put in an antibody
bank that is used for Johne's research at the Animal and
Disease Laboratory in Ames.
The purpose of gathering in
formation on both the positive and
negative testing animals is to
compare the two groups. If'
significant differences are
discovered on one or more items,
such as body weight, for instance,
or occurrence of mastitis, this may
be a clue to other effects of Johne’s
and will deserve more research.
The information gathered in
phase one is only the beginning.
Dairylea renames directors
SYRACUSE Five area
dairymen have been re-elected to
the board of directors of Dairylea
Cooperative, the Northeast’s
largest farm-to-consumer dairy
marketing cooperative.
The dairymen directors re
elected to the cooperative’s board
include; David Hardie, Lansing,
N.Y.; Peter Schuyler, Jr.,
Cobleskill, N.Y.; Beriah Willson,
Vernon Center, N.Y.; Duane
Hartzel, Slippery Rock, Pa.; and
August Kmspel, Pittstown, N. J
Hardie is Director of Dairylea's
District 4. He was a subdistrict
president for six years before
joining Dairylea’s Board, and was
also a member of Dairylea’s
director on the O-AT-KA Board in
Batavia, New York and is a
Batavia, New York and is a
director of Dairy, Food and
Nutrition Council. He is a Farm
Bureau member and has been a
county Farm Bureau president.
Hardie farms 600 acres with his
son in Lansing.
Schuyler, Director of District 13,
was first elected a Dairylea
director 21 years ago. He is a
director on the Syracuse-based
American Dairy Association and
Dairy Council and is also a director
of the National Milk Producers
Federation. He has served as
president of the Schoharie County
Farm Bureau and president of
Schoharie County DHIA. Schuyler
farms 500 acres in Cobleskill and
has a herd of purebred Ayrshires.
Willson has served as District 10
Phase two, which has already
begun, is to do herd studies to
gather even more information that
might prove useful in determining
the incidence and spread of
Johne’s.
Next week read about phase two
of the Johne’s research project,
about finding Johne’s positive
animals, and about management
practices that can be undertaken
to help curtail the spread of the
disease.
Director since 1975. He was elected
to Dairylea’s Executive Com
mittee last year and was recently
appointed to the New York Dairy
Promotion Advisory Board. He has
served as director and president of
the Vernon local cooperative as
well as sub-district president, and
was recently honored as Farmer of
the Year in Oneida County. Willson
and his sons farm 500 acres and
milk more than 100 Holstems.
Hartzell has been Director of
Dairylea’s District 1 since 1969. He
has served as a member of the
Resolutions Committee and as sub
district president. He was recently
appointed to the 15-member Ad
visory Board for the Pennsylvania
Milk Promotion and Marketing
Program, and is also a member of
the Pennsylvania Farmers
Association. In partnership with
his sons, Stephen and George, Mr
Hartzell farms 378 acres in the
Slippery Rock area.
Knispel, who became a Dairylea
member in 1962, is Director for
Dairylea’s District 7. He has
served as sub-district president as
well as president and secretary
treasurer of the Pittstown local.
Knispel was recently elected
president of the Garden State Milk
Council and participates in the
newly developed “Agriculture In
The Classroom” project. He also
serves as mayor of the Franklin
Township and sits on the New
Jersey Dairy Industry Advisory
Council. Knispel still runs the 30C
acre farm on which he was raised.