Developing A Strategic Parasite Control
Dr. David Griswold
PADLS Field Investigation
There is no single, effective
parasite control program that
fits all animal groups. Control
measures vary according to age
the species of animal, species of
parasite (or parasites) and hus
bandry methods involved. As a
result, it is crucial to identify the
parasites infesting a particular
group of animals so that deci
sions can be made concerning
selection of appropriate anti
parasitic drugs and timing of
treatment.
Parasite identification is
often accomplished by micro
scope examination of manure
samples, looking for the para
site’s eggs. These eggs have
characteristic shapes, sizes and
contents which allow species
recognition. Timing of sample
collection can also be critical
because some parasites become
dormant and stop shedding eggs
during certain months or do not
produce eggs until they reach a
certain stage of development.
Internal Parasites:
In general, young animals are
more susceptible to infection
and show more severe effects of
infection than do adults. In fact,
adults often show no outward
signs of internal parasitism. The
highest risk groups for round
worm or nematode infections are
usually those animals grazing
pastures and the lowest risk
comes to animals in confinement
housing. The opposite is general
ly true for protozoal parasitisms
such as coccidia or Cryp
tosporidia.
Some general considera
tions for pasture manage
ment should be:
1. The safest pastures are
areas not previously grazed or
grazed by species that do not
share the same parasites.
2. Rapid drying and sunlight
will kill most parasite eggs and
larvae.
3. Some parasite larvae can
survive winter weather in a dor
mant state but will die after the
first 4 to 6 weeks of warm
weather in the spring. So infec-
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tion is more likely on spring pas
ture grazed the previous fall
than fall pasture grazed the pre
vious spring.
4. Overgrazing will force cat
tle to eat plants closer to the
ground, thus increasing their
chances of contacting and
ingesting infective larvae.
5. The higher the animal den
sity on a pasture, the heavier the
parasite load tends to be.
Guidelines for Pastured
Animals:
1. Animals should be wormed
as they come off pasture in the
fall or after a hard frost if they
are left on pasture during the
winter.
2. Potentially infected adults,
calves or youngstock should be
wormed prior to being placed on
pasture, especially in the spring,
to reduce the chance of pasture
contamination.
3. Pastured animals should
be wormed approximately 4 and
8 weeks after going onto pasture
to control infections from newly
ingested larvae and prevent sub
sequent egg shedding onto the
pasture.
Animals in Confinement
Housing: In general, animals
raised in confinement are at low
risk for nematode infections, but
can be exposed to high levels of
coccidia and other protozoal
organisms. Young animals
should be closely monitored
through fecal exams for these
parasites and placed on preven
tion or control programs as
needed. In addition, control of
animal densities and manure
contamination/build-up
often essential elements in
reducing infection rates.
Ecto (External) Para
sites: There are a number of
external parasites which can
create significant problems for
livestock. Here again, accurate
identification of the parasite or
parasites is essential in order to
determine which agent will be
most effective for treatment as
well as what schedule of treat
ment is required. In some cases,
a drug can be selected which will
be effective against both the
internal and external parasites
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affecting the animals and a sin
gle, well-timed, dosing will effec
tively deal with both groups of
organisms.
A relatively large number of
anti-parasitic drugs are current
ly available. Not only are there a
variety of chemical composi
tions, abut delivery forms as
well. Oral, injectable and topical
(surface application) agents are
available for many species.
Some agents remain active in
the body for weeks following a
Rebate
HARRISBURG (Dauphin
Co.) - Agriculture Secretary
Samuel E. Hayes Jr. reminded
eligible Pennsylvania farmers
that the deadline to claim hay
assistance rebates is April 28.
“Gov. Ridge created this pro
gram to help our farmers recov
er some of the devastating losses
brought on by the drought of
1999,“ Hayes said. “These funds
will ease the strain and offer
some relief to Pennsylvania’s
farm families and help to pre
serve and protect Pennsylvania
agriculture’s ability to produce
food and fiber. But eligible farm
ers must claim their rebates by
April 28.”
Gov. Ridge created the $5 mil
lion Livestock Hay Assistance
Program in response to last
year’s drought, eligible dairy
and livestock producers already
are
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single administration while
some require daily dosing for
continued protection. Some
agents are available in a slow
release bolus form, which can
provide protection for months.
Consultation with your veteri
narian will help you decide on
the most effective and economi
cal choice for the parasites of
concern in your operation.
In summary, strategic para
site control cannot be planned
without knowing which para-
have been notified that they
meet the following hay-assis
tance requirements:
•Be Pennsylvania residents
with farms in Pennsylvania
•Be livestock producers with
dairy cows, beef-breeding cows
or mature breeding ewes
•Have lost a minimum of 30
percent of the crops intended for
livestock feed (including pas
ture) because of the drought of
1999.
Notified farmers are encour
aged to claim their rebates by
mailing purchased-hay receipts
to the Pennsylvania Department
of Agriculture, c/o Hay
Assistance, 2301 North
Cameron St., Harrisburg, PA
17110-9408. Receipts must be
postmarked no later than April
28.
Eligible farmers who pur-
Lancaster Farming, Saturday, April 8, 2000-C3
Plan
sites are involved. This requires
a monitoring system to identify
and quantify parasite problems
as well as measure response to
treatment. Control often
requires management changes
as well as use of anti-parasitic
drugs in order to break parasite
life cycles and reduce levels of
infection in the environment.
Close co-operation between pro
ducer and veterinarian can
improve the effectiveness of any
parasite control program.
April 28
chased hay in Pennsylvania can
receive $6O rebates per ton. This
includes hay purchased from
Pennsylvania dealer/brokers If
an invoice is payable to a
Pennsylvania entity, it is consid
ered Pennsylvania hay, even if it
came originally from outside
Pennsylvania
Farmers who purchased hay
in New York, New Jersey,
Delaware, Maryland, Virginia,
West Virginia, or Ohio are eligi
ble for rebates of $5O per ton If
hay was purchased from a state
outside of those listed above,
farmers are eligible for long
haul assistance
Long-haul assistance pays
eligible applicants a rebate of
$5O per ton of hay, plus an addi
tional $25 per ton of hay to cover
transportation cost. Reimburse
ment for long-haul assistance
will be made only upon submis
sion of documentation verifying
the state of purchase and the
number of tons of hay purchased
from outside those states listed
above.
More than 1,500 eligible
dairy and livestock producers
already have submitted their
receipts. The first hay-assis
tance rebates were received by
farmers last December, with an
average rebate of approximately
$1,200
For more information about
the program, call the
Agriculture Department at (717)
787-4737 or visit Pennsylvania’s
homepage at www.state.pa.us
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