How to Deal With Internal Parasites in Livestock

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Tapeworms (Taenia and Dipylidium) are the largest internal parasites.

It’s very possible that a number of total strangers are
thriving on the food that you give to your livestock or
pets. These “freeloaders” may take many forms, but they
usually resemble white worms and could be either several
feet in length or microscopically small.
I’m talking, of course, about internal parasites. If your feed bills have been rising while the
general health and productivity of your animals have been
slipping, these pests are probably already well
established around your farm or home.
Internal parasites (commonly called worms) occur in every
part of the world, and each living creature (yes, even
humans) has its own particular worms. Worse yet, since
these parasites live (usually) in an animal’s belly or
intestines, you may not even know that your beasts are
infested with ’em! Of course, animals with severe worm
problems will display some of the classic symptoms–such as
weight loss, poor growth, low milk yields, weakness, or
white gums–but a critter <em>can</em> have parasites
without showing such drastic signs. For example, a recent
experiment conducted on healthy-<em>looking</em>
goats showed that milk production was increased by
17% after one dose of an effective worm medicine!
The Problem With Parasites
Before you can even begin a parasite elimination program,
though, you’ll have to realize that you are faced with more
than one form of pest. You see, most worms have several
stages in their life cycles. In order to
completely eradicate the freeloaders, you have to
attack each of those Individual stages separately.
In order to explain this difficulty, let’s look at the life
cycle of the common parasite, <em>Haemonchus</em>. The
adult worm thrives in the stomachs of sheep and goats, and
there, in its hiding place, the parasite lays tough-skinned
eggs. These are then passed In the host animal’s feces
(manure) and deposited in pastures, where they can lie for years unaffected by freezing cold or
intense heat just waiting for another animal to come
along and pick them up.
So, the first problem that confronts the “do it yourself”
parasite controller is that worm eggs can be almost
anywhere and are nearly impossible to destroy.
But, let’s continue with our “sample” parasite. The eggs in
that sheep or goat manure may, perhaps, be picked up by a
small snail who happens to be munching grass in the area.
Once inside the snail (which is referred to as the
parasite’s “intermediate host”), the egg will develop into
a larva. This is the second stage in the life cycle of
the <em>Haemonchus</em>.
The snail, however, crawls merrily around and hardly
notices the presence of the worm larva. Then along comes
your friendly lamb or kid–who isn’t a particularly
fussy eater–and he or she munches on the tasty grass
and inadvertently swallows the tiny snail.<br />
<br />
Now that the larva is back in the kind of critter that
makes it happiest (in this example the sheep or goat is the
final or ” definitive” host), it will do one of several
things. For instance, the larval worm may move into the
animal’s stomach, develop into an adult parasite, and begin
passing more eggs onto your pasture. Or, for some unknown
reason, the larva might decide to take a detour on the way
to its host’s stomach. This “side trip” is called larval
migration, and–since it could take the pest through
muscles, blood vessels, lungs, or liver–can be more
harmful to your animal than the adult worm would be. (This
is, of course, not a particularly appealing or appetizing
picture of the worm’s life cycle, but internal parasites
aren’t particularly appealing or appetizing creatures.)
On the other hand, the parasite larva may find the
environment inside your critter not to its liking. When
this happens, the larva will form a cocoon-like substance
around itself (this is called “encysting”) and can–in
this form–lie dormant until a change in the internal
environment causes it to emerge. Unfortunately, the
environmental changes that make life easier for the
encysted larva can further compound your parasite problems.
When your ewe or doe gets pregnant–for
example–its internal environment may change enough to
cause the parasite to emerge from its cyst and begin
another migration. If this happens, the traveling larva
might find its way directly into the unborn offspring or
into the mother’s milk … which explains why many
animals are infested with parasites at birth.
This example should convince you that worms are pretty
difficult to eliminate. You could, for instance, try to get
rid of all the eggs, but unless you’re capable
of (and interested in) picking up every little black sheep
or goat nugget in your pasture, this will be a nearly
impossible task.
Or, of course, you can try to kill the adult parasites by
giving your beast the proper medication, but the
medicine that will destroy the adults usually will not
kill the larvae. Because of this, you must administer worm
medicine at least twice (once to destroy the adults and
once to kill the larvae <em>after</em> they’ve become
adults), and it’s better still to administer wormers
periodically throughout the host critter’s lifetime.
Some General Recommendations</h2>
<p>There is, however, no need to throw your hands up in
despair. You can do many things to ease your animals’ parasite problems. Fortunately, a number of these preventive measures
are easy enough for anyone to undertake.
In the case of the sheep and goat parasite, for instance,
there are several simple courses of action that could help
break the egg-larva-adult life cycle.
You could, perhaps, allow your animals to use a large
pasture rather than cramping them together in a small pen.
This would insure that the critters had less exposure to
their own manure and would also lessen the chance that any
wandering snails (or other intermediate hosts) would pick
up parasite eggs. Also, if the pasture is thick and lush,
your beasts are less likely to gulp down one of those
snails because the little shelled critters like to
stay hidden in moist places <em>beneath</em> the grass
And, of course, you’ll want to keep your animals’ “living
quarters”–whether these are in the barn or
shed–scrupulously clean. Daily manure removal is a
must with most farm beasts … and don’t forget that the
manure is “organic gold” for your compost pile. Remember,
too, that many worm eggs won’t attain their effective stage
until after they’ve matured on the ground for a few days,
so–by consistently removing the animal
droppings–you can actually break the parasite’s life
cycle! (The rule around the Kidd house is: “If a stall
isn’t clean enough to sit down in, it’s time to get the
pitchfork out.” This attitude has helped us keep our
worm–and rusty pitchfork–problems to a
If you have two or more pasture areas, it’s wise to rotate
your grazing livestock so the animals will only be pastured
on a particular piece of land every two (or, better yet,
three) years. This pasture rotation gives Mother Nature a
chance to help you eliminate your parasites by either
covering the eggs with dirt or killing them–over a
period of time–with sun and frost. Also, the majority
of the snails, etc. that might have ingested a larva will
have disappeared after a span of a year or two.
As you can see, simple good husbandry can go a long way
toward breaking the life cycles of most parasites. And you
have another ally in your fight against worms, too:
the natural resistance to parasites that your animals can
develop. A beast’s ability to resist parasitic infestation
<em>can</em> be compared to your ability to “throw off” a
cold. While you’ll likely never completely avoid colds,
your body may–as you grow older–become less and
less susceptible to these minor illnesses. So it is, too,
with animals and their parasites. As the beast matures,
it becomes at least partially resistant to some worms.
But–just as our resistance to the common cold can be
lowered if we become “run down” or exposed to unhealthy
environmental conditions–a weary, unsheltered, or
poorly fed animal will be much less likely to develop an
immunity to parasites.
Do Your Animals Have Parasites?
At this point you’re probably scratching your head and
wondering if your beasts might, indeed, have parasites.
Unfortunately, there’s no way for you to tell by looking at
the animals. A dog who eats grass may have worms, or he or she might just like eating grass. A goat
who chews on the manger may carry parasites, too, or
perhaps be simply bored. Unless animals are heavily
infested, they won’t likely show the classic “symptoms.”
The beasts may just not be as “vital” as they would be if
they were completely healthy.
Most worms that could infect your pets or barnyard beasts
are far too tiny to be detected with the naked eye. The
tapeworm, however, is the exception to this rule. If you
notice small, white, worm-like things crawling around in
fresh manure (or small, white, dried-up objects that
resemble rice grains) chances are that your critter has
tapeworms. The “ricey” looking objects are actually
segments, or proglottids, of what may be a very long
parasite. Each of these sections is a “packet”
that contains many tapeworm eggs.
The only way to discover whether or not your critters have
the smaller worms, though (or to tell which <em>kinds</em>
of worms they’re harboring), is to have your vet check the
animals out. To do this, the veterinarian will mix a sample
of the beasts’ manure in a special solution that causes fecal matter to sink and parasite eggs to float to the top. By
examining these eggs under a microscope, the vet will be
able to tell what kinds of worms are present and can then
determine the best methods to control the pests. (Having a
fecal sample analyzed for parasite eggs shouldn’t run you
more than a few dollars; unchecked worms could
cost you more than that in no time!)
All you have to do to prepare for one of these tests is
collect a sample of fresh manure–a lump about half
the size of a horse chestnut will do–and whisk it off
to your vet. You will, of course, need a separate example
for each kind of animal that you have, but if you
keep a number of one kind of critter in one
area you’ll only need a single sampling because all of
the sheep, cows, etc. In that pasture or barn will probably
be hosting the same parasites.
Remember that the samples (you can carry ’em in an old baby
food jar or the like if your vet doesn’t provide a
container) should be fresh. If the manure sits for too
long, the eggs may hatch into larvae; these won’t
necessarily be found by a vet who’s looking for eggs.
Tapeworm segments won’t show up in a flotation test, either. But, of course, you’ll be able to spot those worm
“indicators” yourself.
If, for some reason, you have to wait a day or two between
the time that you collect the samples and your trip to the
vet, put the manure (safely sealed in its jar, of course)
in the refrigerator. When kept cool in this way, the
samples will be “good” indefinitely.
Once you and your vet have determined what kind of
parasites (if any) your animals have, you can decide what
sort of worm medicine will most effectively eliminate the
Worm Medicines (Anthelmintics)
There are several things to consider before you choose the
kind of wormer (these medicines are called anthelmintics: anti = against, helmins = worm) you want to use.
The anthelmintic that you select (with your veterinarian’s
help) should, of course, kill the particular worms that
your critter has without harming the host
animal. Piperazine, for example, is an anthelmintic that is
used in a number of worm preparations, and it’s an
extremely safe medication for almost all critters. However,
while piperazine is effective against round-worms, it will
kill few–if any–hook-worms, tapeworms, or
So, ideally, the medication that you administer should be
highly effective against <em>many</em> kinds of worms.
Several recent anthelmintics have been developed that can
destroy a variety of parasites, and some of ’em will kill
nearly all of the worms that are commonly found in
critters. These medicines are the broad-spectrum
And, since these broad-spectrum anthelmintics allow you to
use one medication for almost all of your parasite problems
(some of ’em even destroy migrating parasitic larvae!),
they can really simplify a do-it-yourself worm elimination
Finally, the anthelmintic you choose should be both
economical and easy to administer. Most of the newer worm
medications come either in powder or granular forms (which
can be sprinkled on feed) or in a paste or liquid (that can
be squirted directly into the animal’s mouth).
Remember, though, that any anthelmintic should be
administered in the prescribed manner. In many
cases wormers should be used at a particular time of year.
Anthelmintics for bots (a horse parasite), for example,
should–in most parts of the U.S.–be given at
least once after the first frost. There also seems to be a
seasonal increase in the release of parasite eggs, so
your control program had best include a treatment that
correlates with this stepped-up egg “production.”
And, of course, there are certain specific precautions that
should be taken when using anthelmintics. PLEASE TAKE THE
Caution No. 1: <em>Know what you’re doing!</em> Before
using an anthelmintic (or any type of medication), read the
directions on the label … and then reread them until
you understand everything that they recommend!
Caution No. 2: <em>Use the correct dosage</em> .
Anthelmintics are meant to eliminate parasites without
harming the host animal. Overdoses of wormers can make an
animal sick, or even kill the beast. Do <em>not</em> assume
that a double dose of worm medicine will be twice as
effective as the recommended quantity. Overdosing is
an often fatal mistake.
And, since many of these medicines are administered
according to the “patient’s” weight, be sure that you
<em>know</em> how much your critter weighs or that you at
least have a knowledgeable person do the estimating for
you. (Sale barns or county fairs are good places to learn
weight estimation since the animals are all weighed
before the sale or show.)
Caution No. 3: <em>Be extremely careful when using
anthelmintics on sick animals, young animals, pregnant
animals, or lactating animals (critters giving milk)</em>.
It is always potentially dangerous to give <em>any</em>
medicine to a sick animal, and anthelmintics are no
exception to the rule. The same warning applies to young
beasts, too, and some worm remedies should <em>never</em>
be used until a critter reaches a prescribed age.
Pregnant animals should only be medicated under a vet’s
supervision. Some of the older wormers acted by increasing
the muscle activity of the intestines in order to
shake the worms loose and flush them out. This kind of
medication could also cause muscular activity in the uterus
(or womb), resulting in an aborted offspring.
Finally, almost all medicines given to a milking animal
will be passed into the milk,
and–again–anthelmintics will follow this
pattern. Of course, the quantity of medication that is
passed into the milk–and the length of time during
which it will show up–varies from one drug to
Dairy farmers refer to the time period during which a
medicine can be detected in milk as the “withdrawal time”
for that medication. No milk should be used for human
consumption during this withdrawal time, although some
of it may be safe for animal use. There is also evidence
that several wormers will cause a milking cow or goat to
dry up (quit producing milk).<br />
When you’re in doubt about using a particular anthelmintic
on any sick, young, pregnant, or lactating animal, always
consult your vet <em>before</em> administering the
In Conclusion …
If you’ve been listening closely up to this point, you’re
probably anxious to begin your own worm elimination
program. So, let’s take a look at Dr. Kidd’s Famous Five
Point Parasite Control Course (well … maybe
<em>someday</em> it’ll be famous).
POINT 1: <em>There is a wealth of wisdom in keeping your
critters healthy</em>. Give your animals all of the aid
you can in their battles against internal parasites. This
help should include a wholesome diet, a fresh water supply,
clean and adequate shelter and bedding, and–once in a
while–a little bit of affection to keep the critters
content. A healthy, happy animal is much more likely to be
able to develop its own resistance to internal parasites.
POINT 2: <em>Graze your grass graciously</em>. If
possible, rotate your animals annually to a completely
fresh pasture (that is, a piece of land that hasn’t had
beasts on it for at least a year). A three-year pasture
rotation, of course, would be even better. (Remember, too,
that adequate pasture space helps avoid dense accumulations
of potentially egg-bearing manure.)
POINT 3: <em>Manage your manure</em> . Animals that are
confined in pens, sheds, stalls, or kennels should have
their manure removed daily. In addition, the barnyard or
feedlot should be cleaned periodically.
<em>(No parasite control program is complete UNTIL you
practice–religiously–these first three
POINT 4: <em>Pickle those parasites with the proper
parasiticide</em>. Identify the parasites that are
infecting your animals, and then attack the squirmy
villains with the best ammunition that you have:
consistent and routine use of an effective anthelmintic.
POINT 5: <em>Analyse your efforts</em>. Always have your
vet run fecal checks <em>at least</em> once a year. These
tests should be performed at a time two to three months
after you last administered worm medication. Since the
maximum effectiveness of most anthelmintics only lasts for
60 to 80 days, this delay will allow your animals to show
signs of any <em>new</em> parasites the critters might have
picked up in your pasture.
You may never be able to completely eliminate parasites
from your animals, but don’t let this fact discourage you. The main aim of parasite control is to keep the levels
of infestation as low as possible.
Of course, the alternative to parasite control is–in
most cases–letting the worms take over. If you allow
this to happen, you could end up feeding more food to your
parasites than you do to your pets or barnyard animals!
<hr />
More Home Veterinary Care Information</h2>
<p>Further information about how you can keep your farm
animals and house pets healthy can be found in the
following sources:
1. “<a title=”The Home Herdsman’s Guide to Parasite Detection, Parasite Control, and Parasite Prevention in Livestock” href=””>The Home Herdsman’s Guide to Parasite Detection, Parasite Control, and Parasite Prevention in Livestock</a>”</p>
2. “<a title=”Natural Dewormer for Livestock ” href=””>Natural Dewormer for Livestock </a>”</p>
3. <a title=”” how=”” to=”” give=”” a=”” horse=”” that=”” first=”” injection”=”” href=””>”How to Give a Horse That First Injection</a>”</p>
4. “<a title=”Animal Restraint Techniques” href=””>Animal Restraint Techniques</a>”</p>
5. “<a title=”You Can Too Give That Animal an Injection” href=””>You Can Too Give That Animal an Injection</a>”</p>
6. “<a title=”Be Your Own Animal Medicine Man” href=””>Be Your Own Animal Medicine Man</a>”</p>
7. “<a title=”Horse Care: Restrain and Medicate Your Horse” href=””>Horse Care: Restrain and Medicate Your Horse</a>”</p>