Gastrointestinal Parasite Management of Meat Goats

[Guest guest]

(There is a lot more information about paraites in animals than there

is about parasites in humans. Reading about parasites in general will

broaden your education about parasites as most act similarly.)

 

 

 

 

Gastrointestinal Parasite Management of Meat Goats

J-M Luginbuhl

 

Infection with parasites, especially those of the gastrointestinal

tract can, and in some circumstances do, cause substantial losses to

goat owners. These range from decreased utilization of feed in

unthrifty animals to death. The most important of the gastrointestinal

parasites include roundworms and coccidia. An effective control of

these two groups of parasites will make a significant contribution to

your goats's health and well-being.

 

Eradication of these parasites is impossible, but the simple presence

of a parasite in an animal does not indicate disease. An animal will

show the symptoms of disease only when parasite loads become excessive

or when an animal's natural immunity to disease becomes suppressed. A

certain amount of understanding about the life cycle of these

parasites is necessary to control them most effectively using

anthelmintics or other means of parasite control.

 

ROUNDWORMS

 

Of the family of roundworms, the really important ones are the barber

pole worm (Haemonchus contortus) and the brown stomach worm

(Ostertagia circumcincta). The barber pole worm is by far the most

significant parasite in this region of the country. According to the

Rollins Animal Disease Diagnostic Laboratory in Raleigh, autopsies

performed on goats indicate that barber pole worms are the most

prevalent cause of goat deaths. Other species can and occasionally do

cause economic loss to goat producers but they are of lesser

significance compared to the barber pole worm.

 

Symptoms

 

As a bloodsucking parasite the barber pole worm causes anemia. One

thousand barber pole worm larvae can suck up to 800 cc of blood per

day. The prime symptom, along with blood loss and gut damage, anemia

can be detected as paleness around the eyes, inside the mouth, or

inside the edge of the rectum or vagina. You may also detect swelling

under the jaw (bottle jaw) or low on the abdomen. Diarrhea may occur

but sometimes the goat dies before diarrhea can develop. Other

symptoms include loss of weight, poor growth, unthriftiness, and a

marked decrease in milk production.

 

The facts about the life cycle of which are important to understand

are the following:

 

1. Adult female barber pole larvae have a tremendous egg laying

potential (5,000 to 10,000 eggs or more per day) . Eggs are passed in

the feces and contaminate the environment.

 

2. Eggs hatch and pass through three larval stages, the third being

infective for the next host when ingested.

 

3 . The successful development of these stages outside the host depend

on the climate. Barber pole eggs and larvae love warm, moist

conditions and hate cold or very hot, dry conditions

 

4. Barber pole larvae can also undergo a process called ARRESTED

DEVELOPMENT where they sit quietly in the abomasum (the true stomach

of ruminants) following infection and don't become adults until

several months later. This is an important adaptation for keeping the

worm around through cold winters when eggs and larvae don't survive

well on pasture. As a result, we see an increase in parasite

transmission from spring to fall.

 

5. The worms require about three weeks to complete their life cycle.

However, if large numbers of larvae are inactive and lying in the

lining of the stomach and intestines, severe parasitism can occur

within 7 to 10 days after deworming.

 

6 . Diagnosis is made on symptoms and identification of worm eggs

under a microscope. At NCSU, animals are dewormed when the number of

nematode eggs per gram of feces reaches 600 to 700.

 

Dewormers

 

Little change has occurred in recent years in the dewormers that are

licensed for use in goats. Considering only the " modern dewormers "

which are effective against a number of species and have high safety

margin, there is only 1: thiabendazole. In general, the efficacy of

this product is regarded as low. Several other products have been

shown to have efficacy against barber pole worm and other members of

the same family in experimental situations (see Tables 1,2,3).

 

1.

 

Other benzimidazoles (drugs in the same family as thiabendazole,

i.e. fenbendazole, oxfendazole, albendazole) . There is evidence

indicating that goats metabolize this group of drugs differently and

require higher doses than sheep (2 times the sheep dose) as a result.

Also, oxfendazole and albendazole have been associated with problems

in pregnant sheep. Doses that have been used in sheep include:

fenbendazole, 5-10 mg/kg; oxfendazole, 5 mg/kg; albendazole, 5 mg/kg.

 

When a worm becomes resistant to one product in this group it

becomes resistant to all of them. Resistance to benzimidazoles is

widespread in barber pole worms and once it occurs it will stay around

for years whether you continue to use the drugs or not.

2.

 

Levamisole is another widely used deworming product for

ruminants. In goats, it is usually used at the sheep dose (8 mg/kg or

3.6 mg/lb). Again, goats need a higher dose than the sheep dose and 11

mg/kg (5 mg/lb) has been recommended. The safety margin for this

product is lower than for the other anthelmintics and side effects,

especially salivation, may be seen after treatment especially if the

injectable form is used. The oral form is safer and will be eliminated

from the animal faster. Barber pole worms resistant to levamisole have

been documented, although resistance to this product does not appear

to be as widespread as benzimidazole resistance.

3.

 

Ivermectin is available as an injectable product for cattle and

a drench for sheep (0.2 mg/kg or .09 mg/lb). Experimentally, the oral

form appears to be more effective than the injectable, especially in

goats. The withdrawal time is also shorter when the product is given

orally.

4.

 

Morantel is a product which chemically is very similar to

pyrantel, which is the active compound found in the Strongid® horse

dewormers. Morantel is currently marketed for cattle (Nematel and

Rumatel®) and is useful because it has no milk withdrawal time.

Research has been done with goats and this product appears to be

effective (4.5 mg/lb or 9.9 mg/kg) and not have milk residues.

Formulations of this drug for administration in feed are available for

other species.

 

It is difficult to stress too much the importance of minimizing the

development of drug resistance. Once these products lose their

efficacy, there isn't really much on the horizon to replace them. An

Australian educational program to help reduce the development of

resistance suggests the following steps that owners can take. The

acronym of the program is especially appropriate!

 

Check for resistance

 

If you suspect that a dewormer is not working it is possible to

check for resistance by doing a fecal parasite egg count before and

after treatment.

 

Reduce the frequency of exposure to dewormers.

 

The more frequently the worms are exposed to a drug, the more

likely it is that resistance will develop. Because Haemonchus has a

slightly shorter generation time than other members of its family and

because females produce huge numbers of eggs, parasite populations can

increase to dangerous levels in very short periods of time and many

owners rely on frequent treatments. Reducing treatments by

incorporating pasture management techniques into your control programs

is a practical way to limit use of dewormers.

 

Annually rotate dewormers.

 

It is not a good idea to use the same dewormer year after year. The

best interval for switching dewormers is still a bit controversial,

but most parasitologists now agree that annually is probably best.

 

Check the dose.

 

It is very easy to underdose animals. Even experienced owners may

underestimate average weights. Always dose groups of animals for the

heaviest, not the average goat.

 

Keep resistance off your farm.

 

New goats may bring resistant parasites with them. Never mix new

animals with residents without deworming them first. It has been

recommended that new animals be treated with 2 times the normal dose

of 2 dewormers to make sure that any resistant worms are eliminated

and don' t have an opportunity to infect your pastures with eggs.

 

Prevention, rather than cure, is the philosophy used in developing

control programs against gastrointestinal worms. It should be assumed

that worms cannot be eradicated but infections can be limited to the

extent that they will not cause economic loss to the producer. A

combination of treatment and management are strategic use of

anthelmintics. Anthelmintics are used at a time when most of the total

worm population is within the host and not on the pasture, such as

when livestock are moved from a contaminated pasture to a parasite

free or nearly free pasture. Pastures become parasite free when they

have been tilled or given prolonged rest at a suitable time of year or

were grazed by animals which are not satisfactory hosts for the target

parasite species.

 

Strategic treatments aimed at worms that have undergone arrested

development, in winter or in spring kidding females, have proven

effective in controlling worm burdens during the warm weather

transmission season.

 

Tactical treatments when weather conditions have been favorable for

the transmission of parasites, eliminates worms from the

gastrointestinal tract before they have the opportunity to reproduce

and further contaminate the environment. The timing of tactical

deworming may be based on increasing fecal egg counts. Treatment at

this time, especially when accompanied by movement to parasite free

pastures, may prevent an outbreak of disease.

 

Salvage (treatment to save lives, not control parasites) is a

frequently used anthelmintic strategy in small ruminants. This is

treatment in the face of a disease; the animals are frequently anemic,

may have diarrhea, bottle jaw or swelling (edema) along their ventral

abdomen due to blood loss from the parasites.

 

Monitoring resistance

 

It can be difficult sometimes to decide whether you have worms

resistant to a specific drug or whether animals are just becoming

reinfected with parasites so rapidly that it appears that resistance

is present. It is possible to determine if parasites are resistant

using Fecal Egg Count Reduction Test (FECRT). Fecal samples are

collected from goats (10% of the herd or at least 5 animals) which are

then dewormed. Ten to 14 days after deworming a second sample is

collected and the parasite eggs are counted again. If your dewormer is

still effective you should see at least a 90% reduction in fecal egg

counts. It is very important that all goats be dewormed with an

accurate dose when performing the FECRT. It is also important to wait

about 10 days before collecting the second sample because some drugs

may still decrease egg production for several days, even when the

adult worms are resistant and are not killed. By waiting 10 days, you

allow egg production to come back to normal. This is not a highly

sensitive test for resistance and if the results indicate that the

dewormer is no longer very effective you can be assured that there is

widespread resistance in the population of parasites infecting your goats.

 

Animal variation

 

In any herd, certain animals are less resistant than others to

gastrointestinal parasites. The animals prone to have heavy parasite

loads should be culled because a) they are most likely to pass that

trait on to their offsprings and b) they will shed more nematode eggs

through their excreta, therefore increasing the worm population of

their surroundings. In addition, culling these animals is the first

step toward the development of a herd that will have a higher degree

of natural resistance to parasites.

 

Pasture management

 

One of the best ingredients of a parasite control program is reducing

the number of parasites that the goats are exposed to in the first

place. One way to accomplish this is to manage your pasture in a way

that will reduce its parasite load. There are several ways to do this:

 

1.

 

Take a hay crop or plow and reseed. This type of pasture can be

incorporated into a dose and move program in which goats are grazed on

one pasture in the early grazing season and then dewormed and moved to

another goat pasture which was used for a first cutting of hay.

Another move before the end of the grazing season will probably

provide the best parasite control.

2.

 

Graze a contaminated pasture with another species. There is only

one worm species that can infect cattle, sheep, goats, pigs and horses

and for practical purposes it isn't very important. When another

animal species eats the goat parasite larvae they will be killed. THIS

DOES NOT APPLY TO SHEEP, which goat worms find equally delectable.

3.

 

Pasture Rest. Unfortunately, it takes a long time for the worm

eggs and larvae to die off if the pasture is just left empty. A year

or at least an entire grazing season is required. This is usually

impractical and it also means that the kind of rotational grazing at

short intervals used to maximize pasture production usually doesn't

have much impact on parasites.

 

Questions and comments

 

Is there a relationship between worming in late gestation and abortion?

 

Goats seem to be more sensitive than other livestock species in terms

of abortion in late lactation. Abortion cases have been reported.

However, it is not clear whether or not abortion was provoked by the

wormer used or simply by the stress related to animal handling and

deworming.

 

As a general rule, be conservative!! Avoid deworming during early

pregnancy if possible (first 20 to 60 days).

 

Some products are to be avoided. Cases of abortion have been reported,

BUT NOT PROVEN, with levamisole. Albendazole should not be used in

pregnant does.

 

COCCIDIA

 

The symptoms of coccidiosis can vary from some loss of appetite and

slight, shortlived diarrhea to severe cases involving great amounts of

dark, bloody and foul smelling diarrhea, fluid feces containing mucous

and blood, straining, loss of weight, rough hair coat, with up to 15%

dehydration. The primary pathology associated with coccidiosis

involves intestinal cell destruction. Scarring of the intestine

following treatment or recovery may result in a permanently unthrifty

animal. Diagnosis is based on history, symptoms and microscopic

examination.

 

In the presence of appropriate temperature, moisture and oxygen,

coccidia eggs passed in the feces become infective in one to several

days and readily contaminate food and water. Goats become infected

after ingesting the eggs. However, presence of coccidia in the feces

of normal goats does not indicate a disease situation. When an

outbreak begins, only good sanitation and isolation of sick animals

will prevent its spread through the herd. Coccidia eggs are resistant

to disinfectants and may survive more than a year in the environment.

They will stay alive in a pasture as long as they are in a moist, dark

environment but will die when temperatures drop below freezing. Goats

that survive through a disease outbreak are usually immune to future

problems.

 

Important facts to remember about coccidia are the following:

 

1.

 

Coccidia are very host specific. Therefore the species of

coccidia that infect goats infect goats only. Coccidia found in birds,

cattle, dogs or even sheep will NOT infect goats.

2.

 

Virtually every goat has some level of infection, but illness

occurs only in some animals. Fecal samples from virtually any goat of

any age, sex, breed, dry or lactating, etc. will contain coccidia.

3.

 

THE DISEASE IS ALMOST ALWAYS GOING TO OCCUR IN YOUNG ANIMALS.

KIDS LESS THAN 5 MONTHS OF AGE ARE MORE SUSCEPTIBLE. Kids will become

infected early on from the environment. Adults will have immunity to

the parasite that is pretty effective in preventing disease, but not

infection.

4.

 

The primary sign of coccidiosis is diarrhea. Look for disease in

stressed animals. Happy, well nourished kids left with the doe may

show no diarrhea until they are, weaned. THE STRESS OF WEANING MAY

DEPRESS IMMUNITY ENOUGH FOR THE COCCIDIA TO GET THE UPPER HAND AND

CAUSE DISEASE.

5.

 

Control of coccidiosis include removing manure, not feeding off

the ground or letting goats jump into feeders (a real challenge).

Coccidiostats (preventatives) include amprolium (Corid®), decoquinate

(Decox®) and lasalocid (Bovatec®). These products may be used in the

feed or water to prevent the development of the disease.

6.

 

Drugs used to treat clinical cases of coccidiosis include sulfa

drugs and amprolium. The doses to use can be found in the " Goat Health

Handbook " authored by Dr. Thomas R. Thedford and published by Winrock

International. This very handy book can be purchased through NCMGA. At

NCSU, we drench severe cases, for 5 days, at the rate of 22.7 mg

Amprolium per pound body weight, or .25 ml / lb body weight of 9.6%

Corid (Amprolium) solution.

 

Factors to take into consideration about the use of drugs

 

1.

 

Read label carefully - labeling directions change frequently

2.

 

Use the proper dose for the size and species of animal to be

treated.

3.

 

Calculate preslaughter drug withdrawal time accurately. -

withdrawal and discard times begin with the last drug administration

4.

 

Use the correct route of administration - giving drugs

incorrestly can lead to drug ineffectiveness, adverse reactions,

illegal residues, and possible animal deaths.

5.

 

DO NOT DOUBLE DOSE - use of the same drug in the feed and by

injection can cause illegal residues.

6.

 

Select needle size and injection site carefully, if injections

are necessary - misuse can lead to tissue dmage, reduced

effectiveness, and/or illegal residues.

7.

 

Keep accurate records of drugs used and animals dosed - poor

records can be costly if drug residue violations occur.

8.

 

If possible, seek the advice of your veterinarian.

 

GENERAL DEWORMING PROGRAM

 

At NCSU, animals are wormed according to fecal egg count. However, it

is a good idea to deworm prior to or very shortly after kidding to

prevent periparturient rise in parasite egg production. If deworming

takes place before kidding, make sure that the dewormer is safe for

pregnant animals.

 

For dewormer to be effective, it is important to correctly estimate

the weight of the animals. In a group of animals, calculate dose for

the heaviest animal. Underdosing is a problem that can lead to

parasite drug resistance. In addition, for goats, it is recommended to

use 1.5 times the prescribed dose calculated on a body weight basis.

Dewormers should be rotated annually.

 

Coccidia

 

Dose with Corid at 8 wks of age. Preventive treatment around weaning

has proved effective in our situation.

 

ACKNOWLEDGMENTS

 

This article was the result of numerous conversations held with Dr.

Kevin Anderson from the College of Veterinary Medicine, NCSU, Raleigh,

the copilation of articles and short notes written by Dr. Anne Zajac

from the Virginia Polytechnic Institute and State university,

Blacksburg, Drs. Kevin Anderson, Daniel Amaya, Jeff Musser, Sandy

Grant, Dan Moncol and Michael Levy from the College of Veterinary

Medicine, NCSU, Raleigh, and Dr. Thomas Thedford, who wrote the Goat

Health Handbook, and finally the copilation of notes taken during

field days and 'goat meetings'.

Return to EAH Meat Goats Home

Return to Extension Animal Husbandry Home

Return to Department of Animal Science Home Last modified October 1998

EAH Webmaster, Department of Animal Science, NCSU