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Full text of "Stomach worms in sheep : prevention and treatment"

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U. . . . GIr. . 47. 



list 1919. 



UC-NRLF 




B 3 101 no 




Agric-.fr ores! library 



BIOLOGY 

LIBRARY 

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STOMACH WORMS IN SHEEP 

PREVENTION AND TREATMENT 



Prepared Jointly by the Animal Husbandry 
and Zoological Divisions 




UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 47 



Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 



Washington, D. C. August, 1919 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1919 



• • . - 



*ioic. 



STOMACH WORMS IN SHEEP: 

PREVENTION AND TREATMENT. 



CONTENTS. 

Page. 

How can one tell when sheep have stomach worms ? 3 

How do the worms injure the sheep ? 4 

How should infested sheep or lamhs be treated ? 4 

How do sheep become infested by stomach worms ? 6 

What methods can be employed to prevent loss from stomach worms ? 8 



ONE of the most serious problems of owners of farm sheep is the 
prevention of injury and loss by stomach worms. This para- 
site (Hxmonchus contortus) has been known in this country for many 
years and is common in farm flocks, particularly during wet summers. 
It has been studied bv the Zoological Division of the Bureau of 
Animal Industry and the principal facts in its life history have been 
determined. Methods of treatment and of prevention are still under 
investigation by that division, and although the methods have not 
yet been perfected, what has been learned is sufficient to show how 
affected sheep or lambs can be treated successfully and, what is of 
greater importance, how they may be raised in such a way as practi- 
cally to overcome the danger. 

What is known of this parasite and the methods of prevention and 
control may be presented as answers to practical questions, as 
follows : 

HOW CAN ONE TELL WHEN SHEEP HAVE STOMACH WORMS? 

Either lambs or old sheep may be affected by stomach worms at 
any time of the year. The trouble may be noticed first in lambs 
about the middle of summer, though it may be earlier, according to 
the part of the country and the temperature and moisture of the 
season. 

In many flocks the first knowledge of the trouble is gained through 
the death of one or more lambs. If the flock is under careful obser- 
vation, however, signs of stomach-worm disease will be noticed 
earlier. Dullness and lack of thrift are among the first indications. 
Scouring is often present. These conditions may result from other 
causes, but when due to stomach worms, they are accompanied with a 
very pale, bloodless appearance of the skin and of the mucous mem- 
branes of the eyes and mouth. The whiteness of the skin has caused 
the trouble to be known in some sections as "paper skin." In many 
cases there is a watery swelling under the jaws. 

120227°— 19 3 

4< 



■ • • 

• ■•■ : :• : • 



4 Departnu'it Cx'r£WdK|f, T$J$. Department of Agriculture. 

Doubt as to the cause of the trouble ran be removed by an exami- 
nation of the fourth stomach. For examination purposes, any one 

unfamiliar with the ailment can well afford to kill an affected lamb. 
If there is any uncertainty as to the position of the fourth stomach 
it can be ascertained by taking hold <»f any part of the -mall intestine 
and following it forward. The fourth stomach is one of the 4 com- 
partments into which the stomach is divided ami i- the portion con- 
tinuous with the forward end of the -mall intestine. When the 
fourth stomach is found, it should be held bo .1- to prevent the 
fluids from leaving it at either end, and an incision made along 
nearly the full length of the upper part. When this is done the 
stomach worms, if present, can be seen, often in large numbers, 
wriggling around in the fluids. They are from one-half to 1} inches 
long, about as thick as an ordinary pin, and spirally striped with 
red and white. It is often necessary to look closely for some time 
in order to distinguish them. When the stomach is emptied some 
of the worms can be seen adhering to the inside walls. 

HOW DO THE WORMS INJURE THE SHEEP? 

The injurious action of the stomach worms may be attributed to 
two things: First, the loss of blood abstracted by the parasites, and 
second, the destruction of red corpuscles by a poisonous substance 
which is secreted by the parasites and taken up by the blood. Evi- 
dently the older, stronger, and larger sheep are better able than the 
lambs to withstand the loss of blood, and can better endure the I 
duo to the destruction of red corpuscles. Furthermore, in the blood 
of adult sheep there may be substances tending to neutralize the 
poisonous matter produced by the parasites that are absenl from the 
blood of lambs, or that, if present, occur in smaller quantities. 
Besides the direct injury caused by stomach worms it is nof unlikely 
that damage is also done by bacterial infection through the wounds 
the worms make in the mucous lining of the stomach. 

HOW SHOULD INFESTED SHEEP OR LAMBS BE TREATED? 

MEDICINAL TKi: A I U INT. 

[f taken in time, most cases of stomach worms can be treated 
successfully according to the following directions: 

Dissolve one-fourth pound (avoirdupois) of the powdered crystals 
of copper Bulphate (bluestone) in I pint of boiling water, using a 
porcelain or enamel-ware di h, as the Milestone corrodes most metals. 

Then add cold Wiiler enough to make the solution up to ;; gallons, 

using Wooden, cart lienw ale, or other iinelallic recept acles. This 

will make approximately a I percent solution and will be enough to 
(lose 1(H) adult sheep, allowing Id per rent u a le. In the preparation 

of the dose use onlj clear-blue crystals of copper sulphate. Crush 

the crystal to a line powder when reads to make up (he solution. 



Stomach V/orms in SJieep. 5 

The doses for lambs and sheep are : 

For lambs under 1 year of age 1| ouncea (50 cubic centimeters). 

For sheep past 1 year old 3$ ounces (100 cubic centimeters). 

A glass with marks scratched on the side with a file may be used 
for measuring the doses. 

The drenching apparatus consists of (1) a strong rubber tube 
about 3 feet long and three-eighths inch in diameter; (2) a hard rubber, 
porcelain, or enamel-ware funnel, which is fastened to one end of 
the tube; and (3) a brass mouthpiece three-eighths inch in diameter 
and 9 inches long, fastened to the other end. It is preferable that 
the end of this tube should be closed and holes made in the sides of 
about the last two inches of its length. 

Ordinarily the treatment is given after the sheep have been without 
feed overnight, but apparently it may be given with equally good 
results without preliminary fasting, provided the animals are not 
gorged with feed or water when treated. For best results sheep 
should not be watered for 2 hours afterwards. 

While being drenched the sheep should remain on all 4 legs with 
its head held horizontally. This is important, for if the head is 
held above the horizontal (nose higher than the eyes), there is danger 
that some of the fluid will pass into the lungs, thereby causing 
pneumonia and almost certain death. Measure the dose in the 
measuring glass, and after the drenching tube is in position pour the 
dose slowly into the funnel. The metal mouthpiece of the drenching 
tube should be placed between the jaws in the space between the 
teeth at the side of the mouth and directed backward, but should 
not reach farther than the base of the tongue. In order to prevent 
the sheep from stopping up the end of the mouthpiece with its 
tongue and thus interfering with the flow of the liquid, the person 
holding the mouthpiece in the sheep's mouth should give it a rotary 
motion. This tends to keep the sheep swallowing, prevents plugging 
the tube, and also tends to keep the fluid from entering the lungs. 
The fluid should not be administered more rapidly than the sheep 
can swallow comfortably. 

Care in the administration of the dose is highly important, as 
carelessness or any undue haste is liable to have serious results. 
The copper-sulphate treatment, like the administration of medicines 
in general, is safest in the hands of a competent veterinarian. 

CHANGE OF PASTURE NECESSARY FOR BEST RESULTS. 

Although losses from stomach worms in many cases may be 
minimized by repeated medicinal treatment without change of 
pasture, much better results can be obtained if the treated animals 
are placed on ground that is free or practically free from infection. 
It is still better to institute preventive measures before the results 
of stomach-worm infection become evident. A lamb that has been 



. ■ 



■ 



6 DcpartiHi'iU ", '.inuilup 'il , V/S. Department of Agriculture. 

affected sufficiently to show the external effects of stomach worms 
has received a serious setback. Although it may recover and again 
be thrifty it has lost at least a month or 6 weeks of progress toward 
marketable weight and condition. The only safe and economical 
way of raising sheep where stomach worms are a factor is by managing 
the flock and pastures in a way to prevent a serious develop- 
ment of the trouble. In most localities the methods necessary for 
preventing stomach worms are at the same time those that need 
to be employed for most economical production. In order to follow 
these methods, particularly with respect to pasture rotation, the 
shepherd needs to know just how and when infection occurs. 

HOW DO SHEEP BECOME INFESTED BY STOMACH WORMS? 

INFESTED PASTURES. 

In the adult sexual stage stomach worms are able to live and 
carry out their reproductive functions only in the alimentary canal 
of sheep or other ruminants, and practically only in the fourth stom- 
ach. Each female produces thousands of eggs, of microscopic size, 
which do not develop into adult worms in the body of the host in 
which they are deposited, but, without hatching, pass out of the 
intestine in the feces. In a few hours, days, or weeks, according as 
the temperature is high or low, these eggs, if they are not killed by dry- 
ing or freezing (either of which is commonly fatal to them), hatch and 
the tiny embryonic stomach worms then develop to what may be 
termed the final larval or infectious stage. This later development like- 
wise requires days or weeks, according to the temperature, and until 
the young worms have reached the infectious stage they appear to be 
fully as susceptible to freezing and drying as the eggs. Having 
reached the infectious stage, however, the worms are able to with- 
stand long periods of dryness and severe cold, though some of them 
succumb comparatively early. 

In the infectious stage the young worms are very active in the 
presence of moisture, and rapidly orawl up blades of grass and other 
objects whenever the relative humidity of the air is at a maximum, 
provided the temperature is above 40° F. or thereabout; below that 
temperature they are inactive. A decrease in the relative humidity, 
with the consequent evaporation of the moisture from the surface of 
grass blades and oilier objects, Btops (lie migrations of the worms, 
and they become quiesoent and remain in a condition of suspended 
animation \\ herever they happen to be at the time. During (be next 
period of wet weather, dew, rain, or fog, the worms again become 
active ami climb still Idgber on the grass, from winch thej are better 
able to attain their final abode within the stomach of a sheep or row 
than if they remained on the ground. When swallowed by a sheep 
or other ruminant the young stomach worm, if il has reached its fmal 



Stomach Worms in Sheep. 7 

larval stage, whether active at the time or in a state of suspended 
animation, continues its development, and in the course of 2 or 3 
weeks reaches maturity. 

The length of life of individual worms in the stomach has not been 
determined. Infested sheep have been kept in pens with board 
floors, which were kept clean by sweeping and frequent scrubbing — 
the sheep being fed from raised racks and water being supplied in a 
trough which was frequently cleaned — for varying periods up to a 
maximum of 19 months, and at the end of these periods were found 
to be still infested, though the number of worms present was small. 

As the possibility of reinfection by larval worms developing from 
eggs passed in the feces of these sheep was not entirely removed, 
though greatly minimized, the results obtained do not necessarily 
indicate that the worms found at the end of the period of observation 
were all present when the experiment was begun. The experiment, 
however, while it proves nothing as to the length of life of the adult 
stomach worm, demonstrates the futility of attempting to rid sheep 
entirely of stomach worms simply by keeping them away from pas- 
ture. On the other hand, very little infection occurs among sheep 
kept in stables if cleanly conditions are maintained. Lambs have 
been kept with infested sheep in stables for long periods of time, the 
only precautions against infection being the removal of manure about 
once a week. Under such conditions they have continued in good 
health, and acquired only a very few stomach worms and other 
parasites. 

LENGTH OF TIME PASTURES MAY BE INFESTED. 

The maximum period during which the larval stomach worms are 
able to survive on pastures is not definitely known, but it has been 
found that pastures on which infested sheep had grazed were appar- 
ently still infectious after a lapse of nearly 8 months, namely, from 
October 25, when the infested sheep were removed, to June 16, when 
the pastures were tested by placing in them some lambs which had 
been raised under special precautions to avoid previous infestation. 
In cultures made September 14, 1906, from the feces of an infested 
sheep and kept thereafter in the laboratory, most of the larvae were 
dead but some were still alive, though very sluggish, on June 5, 1907, 
nearly 9 months later. Cultures in which the worms were allowed 
to develop to the final larval stage, after they were kept in cold storage 
at a temperature below freezing — in some cases as low as 12° F. — 
still contained some living worms after 2 or 3 months, while in other 
cultures eggs and newly hatched worms not yet developed to the final 
larval stage were killed within a few hours after exposure to tempera- 
tures below freezing. 

These experiments show that pastures may remain infected for 
several months after sheep are removed from them, and that the 



8 Department Circular 47, U. S. Department of Agriculture. 

infection is not destroyed by cold weather. They show, however, 
that during a winter with more or less freezing weather there is 
likely to be little or no increase in the amount of infection in pastures 
occupied by infested sheep. The eggs passed in the feoes of the sheep 
will either be killed at onoe by freezing, or, on account of low tem- 
peratures above freezing, will remain dormant or develop so slowly 
that they are killed later by frost before they have reached the final 
larval stage, which is resistant to cold. At the same time, while the 
infestation of pastures may not be increased during the winter, the 
infestation of the sheep may be added to by their picking up from 
time to time larval worms which, prior to the beginning of cold 
weather, had developed already to the stage in which they are able 
to withstand freezing. 

If sheep, goats, and cattle are kept off a pasture for a year, it is 
fair to assume, upon the basis of our present knowledge, that all, or 
practically all, larval stomach worms will have died within that time. 
There is also little doubt that the period required for the practical 
disinfection of a pasture may be shortened considerably by plowing 
it and placing it under cultivation. 

Thus there are two ways by which a pasture may be freed of infesta- 
tion, one by excluding sheep or other ruminants for at least a year, and 
the other by turning it into a cultivated field. In view of the fact 
that sheep placed on disinfected fields or pastures probably will not 
be entirely free from infestation, it is not of much consequence 
whether every larval stomach worm in the pastures is dead or not. 
The approximation to this point, which is attained by vacating pas- 
tures for a year or by plowing them up, is sufficient for practical 
purposes. 

WHAT METHODS CAN BE EMPLOYED TO PREVENT LOSS FROM 

STOMACH WORMS? 

It is barely possible that some means of artificially producing in 
lambs an immunity against the evil effects of stomach worms may 
be devised, but at the present time it is only a matter for speculation 
and experimental research. Our present knowledge of the stomach 
worm leads us to direct our efforts toward bringing about freedom 
from infestation or, as the next best thing, reducing the amount of 
infestation to a minimum and keeping it there. 

EARLY DEVELOPMENT OF LAMBS. 

One great step toward evading the stomach worm is found in the 
plan of having lambs dropped early and feeding to develop them as 
much as possible before they go to pasture. 

Where sheep graze during winter and spring there is little danger 

of infestation in freezing weather, as the eggs or young larva' are killed 



Stomach Worms in Sheep. 9 

before they are taken up by the lambs. There is but very slight 
danger that young lambs will become affected seriously while running 
with older sheep in barns or yards free from vegetation. Early lamb- 
ing, combined with good feeding of the ewes to make them milk well, 
or of the lambs themselves in a " creep," or with both, brings early 
lambs to marketable weight and finish before the most dangerous 
part of the summer. Where lambs must remain for several months 
on pasture, frequent changing of pasture must be resorted to, to 
keep infestation below the extent that is injurious. 

A PRACTICABLE METHOD OF PASTURE ROTATION. 

The means of preventing the stomach-worm larvae from getting 
into the lambs is suggested by what has been said concerning its 
development and powers of resistance. It was stated that a pasture 
that had been occupied by wormy sheep would need to be for at 
least a year without cattle, sheep, or goats in order to become 
practically free from stomach-worm larvae. 

From 10 to 20 days, according to temperature and moisture, must 
intervene between the dropping of the feces containing stomach- 
worm eggs and the development of many of the larvae to a point 
where they will develop into adult worms after being swallowed. If 
sheep are moved to a fresh pasture before the eggs in their droppings 
develop into mature larvae, complete health can be maintained. The 
practical difficulty lies in always having a fresh pasture available. 
If only permanent grass pasture were used, adequate control would 
call for as many separate pastures as would allow the flock to be 
moved at least every 2 weeks without going on the same ground 
twice within 12 months. The time of grazing during freezing 
weather would not be included in such a plan, as few of the eggs or 
young larvae would survive. It should be observed that it is not 
simply the changing of pastures that is called for, but changing to 
clean ground. Putting infested sheep on pasture in May, removing 
them during June and returning them in July, offers an excellent 
chance for infestation from the eggs dropped during the first pastur- 
ing which would have hatched out into young worms waiting to be 
taken up. 

Some modifications of such a plan are quite practicable on any 
farm. In the first place, the danger is greatest to the lambs, and after 
they are sold or separated the ewes may go back to pastures used 
earlier in the season with much less danger of injury than would be 
incurred by the lambs. This change, however, would render that 
pasture unsafe for young lambs during the following spring. Hay- 
fields, grain stubble, and cornfields can be utilized in the rotation of 
fields to furnish fresh grazing. 



10 Department Circular 47, U. S. Department of Agriculture. 

Plowing the land infested with the larvae of stomach worms greatly 
reduces the danger of infection. This fact allows the same land to be 
used two or three times for sheep in a season by using forage crops. 
Fall-sown wheat can be used for the earliest period, the land broken 
and resown to peas and oats, rape, or soy beans for a later grazing, 
and in some cases plowed again and sown to wheat to furnish late-fall 
feed. A succession of such crops is particularly desirable for carrying 
over from weaning time until winter the ewe lambs that are to be 
retained in the flock. 

Where sufficient changes of pasture and fresh ground can not be 
provided, preventive dosing may be partially relied upon. The 
danger in depending upon treatment lies in the fact that while cures 
usually can be effected by its proper use, lambs that have been al- 
lowed to reach the point where medicine is needed have at least been 
seriously checked in growth, and unless very carefully watched some 
deaths will occur. 

The treatment can be used as a measure to hold the stomach 
worms in check, in conjunction with rotation of pastures. Many 
successful shepherds dose all the ewes before turning them on the 
spring pastures with the lambs. This greatly lessens the number of 
eggs dropped. Afterwards all the lambs to be kept are similarly 
treated at the time of weaning, and individual cases may be treated 
on the first appearance of symptoms which will be noted if the flock 
receives the attention it really requires. When pasture rotation and 
similar preventive measures are impossible, sheep may be given the 
copper-sulphate treatment, preferably in diminished dosage, every 
month or 6 weeks during the summer season. 

The stomach worm need not be a serious trouble for a good shep- 
herd who has his lambs come early, feeds well, drenches the flock as a 
measure of prevention, and provides a rotation of pastures or pasture 
crops. 



PUBLICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE RELAT- 
ING TO DISEASES OF LIVE STOCK. 

PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION. 

Exterminating the Texas Fever Tick. (Farmers' Bulletin 498.) 

Texas, or Tick Fever. (Farmers' Bulletin 569.) 

Foot-and-Mouth Disease. (Farmers' Bulletin 666.) 

Sheep Scab. (Farmers' Bulletin 713.) 

Tuberculosis of hogs. (Farmers' Bulletin 781.) 

Anthrax, or Charbon. (Farmers' Bulletin 784.) 

The Sheep Tick: Its Eradication by Dipping. (Farmers' Bulletin 798.) 

Screw-worms and Other Maggots. (Farmers' Bulletin 857.) 

Swine Management. (Farmers' Bulletin 874.) 

Cattle Lice and How to Eradicate Them. (Farmers' Bulletin 909.) 

Important Poultry Diseases. (Farmers' Bulletin 957.) 

Spinose Eartick, Treatment for. (Farmers' Bulletin 980.) 

Cattle Scab and Methods of Control. (Farmers' Bulletin 1017.) 

Hemorrhagic Septicemia: Stockyards Fever, Swine Plague, Fowl Cholera, etc. 
(Farmers' Bulletin 1018.) 

Cerebrospinal Meningitis. (Department Bulletin 65.) 

Vesicular Stomatitis of Horses and Cattle. (Department Bulletin 662.) 

Necrotic Stomatitis, with Special Reference to Its Occurrence in Calves, Calf Diph- 
theria, and Pig Sore Mouth. (Bureau of Animal Industry Bulletin 67.) 

Diseases of Stomach and Bowels of Cattle. (Bureau of Animal Industry Circular 68.) 

Actinomycosis, or Lumpy Jaw. (Bureau of Animal Industry Circular 96.) 

PUBLICATIONS FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT 

PRINTING OFFICE, WASHINGTON, D. C. 

Dog as a Carrier of Parasites and Diseases. (Department Bulletin 260.) Price 5 cents. 
Control of Hog Cholera, with Discussion of Results of Field Experiments. (Depart- 
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Laws (Federal, State, and Territorial), Relating to Contagious and Infectious Diseases 

of Animals. (Bureau of Animal Industry Bulletin 54.) Price 5 cents. 
Gid Parasite, Its Presence in American Sheep. (Bureau of Animal Industry Bulletin 

66.) Price 5 cents. 
Studies of Blood and Blood Parasite of American Cattle. (Bureau of Animal Industry 

Bulletin 119.) Price 5 cents. 
Nematodes Parasitic in Alimentary Tract of Cattle, Sheep, and Other Ruminants, 

(Bureau of Animal Industry Bulletin 127.) Price 20 cents. 
A Comparative Study of Methods of Examining Feces for Evidence of Parasitism. 

(Bureau of Animal Industry Bulletin 135.) Price 10 cents. 
Dourine of Horses, Its Cause and Suppression. (Bureau of Animal Industry Bulletin 

142.) Price 15 cents. 
Trypanosoma American, a Common Blood Parasite of American Cattle. (Bureau of 

Animal Industry Bulletin 145.) Price 5 cents. 
The Action of Anthelmintics on Parasites Located Outside of the Alimentary Canal. 

(Bureau of Animal Industry Bulletin 153.) Price 5 cents. 
Roundworms of Domestic Swine, with Special Reference to Two Species Parasitic in 

the Stomach. (Bureau of Animal Industry Bulletin 158.) Price 10 cents. 

11 



12 Department Circular kl, U. S. Department of Agriculture. 

The Life History of Habronema Muscae, a Parasite of the Horse Transmitted by the 

House Fly. (Bureau of Animal Industry Bulletin 163.) Price 10 cents. 
Diseases of the Stomach and Bowels of Cattle. (Bureau of Animal Industry Circular 

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Mycotic Lymphangitis of Horses. (Bureau of Animal Industry Circular 155.) Price 

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Methods for the Eradication of Gid. (Bureau of Animal Industry Circular 165.) 

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Measles in Cattle. (Bureau of Animal Industry Circular 214.) Price 5 cents. 
Special Report on Diseases of Cattle. Price $1. 
Special Report on Diseases of Horses. Price $1. 
Special Report on History and Condition of Sheep Industry of the United States. 

Price $1.40. 

o 



> » O • 9 • 



_» ^-r.,-1. 



xj- 1 — i-^r* — * — • — *~ 



STOMACH WORMS IN SHEEP 

PREVENTION AND TREATMENT 



Prepared Jointly by the Animal Husbandry 
and Zoological Divisions 




UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 47 



Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 



Washington, D. C. August, 1919 



WASHINGTON : GOVERNMENT PRINTING OFFICE I 1919 



• ■ 



STOMACH WORMS IN SHEEP: 

PREVENTION AND TREATMENT. 



CONTENTS. 

Page. 

How can one tell when sheep have stomach worms ? 3 

How do the worms injure the sheep ? 4 

How should infested sheep or lambs be treated ? 4 

How do sheep become infested by stomach worms ? 6 

What methods can be employed to prevent loss from stomach worms? 8 



ONE of the most serious problems of owners of farm sheep is the 
prevention of injury and loss by stomach worms. This para- 
site (Hwmonclius contortus) has been known in this country for many 
years and is common in farm flocks, particularly during wet summers. 
It has been studied by the Zoological Division of the Bureau of 
Animal Industry and the principal facts in its life history have been 
determined. Methods of treatment and of prevention are still under 
investigation by that division, and although the methods have not 
yet been perfected, what has been learned is sufficient to show how 
affected sheep or lambs can be treated successfully and, what is of 
greater importance, how they may be raised in such a way as practi- 
cally to overcome the danger. 

What is known of this parasite and the methods of prevention and 
control may be presented as answers to practical questions, as 
follows : 

HOW CAN ONE TELL WHEN SHEEP HAVE STOMACH WORMS? 

Either lambs or old sheep may be affected by stomach worms at 
any time of the year. The trouble may be noticed first in lambs 
about the middle of summer, though it may be earlier, according to 
the part of the country and the temperature and moisture of the 
season. 

In many flocks the first knowledge of the trouble is gained through 
the death of one or more lambs. If the flock is under careful obser- 
vation, however, signs of stomach-worm disease will be noticed 
earlier. Dullness and lack of thrift are among the first indications. 
Scouring is often present. These conditions may result from other 
causes, but when due to stomach worms, they are accompanied with a 
very pale, bloodless appearance of the skin and of the mucous mem- 
branes of the eyes and mouth. The whiteness of the skin has caused 
the trouble to be known in some sections as "paper skin." In many 
cases there is a watery swelling under the jaws. 

120227°— 19 3 



4 Department Circalor kl \ U. S. Department of Agriculture. 

Doubt as to the cause of the trouble can be removed by an exami- 
nation of the fourth stomach. For examination purposes, any one 
unfamiliar with the ailment can well afford to kill an affected lamb. 
If there is any uncertainty as to the position of the fourth stomach 
it can be ascertained by taking hold of any part of the small intestine 
and following it forward. The fourth stomach is one of the 4 com- 
partments into which the stomach is divided and is the portion con- 
tinuous with the forward end of the small intestine. When the 
fourth stomach is found, it should be held so as to prevent the 
fluids from leaving it at either end, and an incision made along 
nearly the full length of the upper part. When this is done the 
stomach worms, if present, can be seen, often in large numbers, 
wriggling around in the fluids. They are from one-half to \\ inches 
long, about as thick as an ordinary pin, and spirally striped with 
red and white. It is often necessary to look closely for some time 
in order to distinguish them. When the stomach is emptied some 
of the worms can be seen adhering to the inside walls. 

HOW DO THE WORMS INJURE THE SHEEP? 

The injurious action of the stomach worms may be attributed to 
two things: First, the loss of blood abstracted by the parasites, and 
second, the destruction of red corpuscles by a poisonous substance 
which is secreted by the parasites and taken up by the blood. Evi- 
dently the older, stronger, and larger sheep are better able than the 
lambs to withstand the loss of blood, and can better endure the loss 
due to the destruction of red corpuscles. Furthermore, in the blood 
of adult sheep there may be substances tending to neutralize the 
poisonous matter produced by the parasites that are absent from the 
blood of lambs, or that, if present, occur in smaller quantities. 
Besides the direct injury caused by stomach worms it is not unlikely 
that damage is also done by bacterial infection through the wounds 
the worms make in the mucous lining of the stomach. 

HOW SHOULD INFESTED SHEEP OR LAMBS BE TREATED? 

MEDICINAL TREATMENT. 

If taken in time, most cases of stomach worms can bo treated 
successfully according to the following directions: 

Dissolve one-fourth pound (avoirdupois) of the powdered crystals 
of copper sulphate (bluestone) in 1 pint of boiling water, using a 
porcelain or enamel-ware dish, as the bluestone corrodes most metals. 
Then add cold water enough to make the solution up to 3 gallons, 
using wooden, earthenware, or other nonmetallic receptacles. This 
will make approximately a 1 per cent solution and will be enough to 
dose 100 adult sheep, allowing 10 per cent waste. In tho preparation 
of the dose use only clear-blue crystals of copper sulphate. Crush 
tho crystals to a line powder when ready to make up tho solution. 



Stomach Worms in Sheep. 5 

The doses for lambs and sheep are : 

For lambs under 1 year of age If ouncea (50 cubic centimeters). 

For sheep past 1 year old 3£ ounces (100 cubic centimeters). 

A glass with marks scratched on the side with a file may be used 
for measuring the doses. 

The drenching apparatus consists of (1) a strong rubber tube 
about 3 feet long and three-eighths inch in diameter; (2) a hard rubber, 
porcelain, or enamel-ware funnel, which is fastened to one end of 
the tube; and (3) a brass mouthpiece three-eighths inch in diameter 
and 9 inches long, fastened to the other end. It is preferable that 
the end of this tube should be closed and holes made in the sides of 
about the last two inches of its length. 

Ordinarily the treatment is given after the sheep have been without 
feed overnight, but apparently it may be given with equally good 
results without preliminary fasting, provided the animals are not 
gorged with feed or water when treated. For best results sheep 
should not be watered for 2 hours afterwards. 

While being drenched the sheep should remain on all 4 legs with 
its head held horizontally. This is important, for if the head is 
held above the horizontal (nose higher than the eyes), there is danger 
that some of the fluid will pass into the lungs, thereby causing 
pneumonia and almost certain death. Measure the dose in the 
measuring glass, and after the drenching tube is in position pour the 
dose slowly into the funnel. The metal mouthpiece of the drenching 
tube should be placed between the jaws in the space between the 
teeth at the side of the mouth and directed backward, but should 
not reach farther than the base of the tongue. In order to prevent 
the sheep from stopping up the end of the mouthpiece with its 
tongue and thus interfering with the flow of the liquid, the person 
holding the mouthpiece in the sheep's mouth should give it a rotary 
motion. This tends to keep the sheep swallowing, prevents plugging 
the tube, and also tends to keep the fluid from entering the lungs. 
The fluid should not be administered more rapidly than the sheep 
can swallow comfortably. 

Care in the administration of the dose is highly important, as 
carelessness or any undue haste is liable to have serious results. 
The copper-sulphate treatment, like the administration of medicines 
in general, is safest in the hands of a competent veterinarian. 

CHANGE OF PASTURE NECESSARY FOR BEST RESULTS. 

Although losses from stomach worms in many cases may be 
minimized by repeated medicinal treatment without change of 
pasture, much better results can be obtained if the treated animals 
are placed on ground that is free or practically free from infection. 
It is still better to institute preventive measures before the results 
of stomach-worm infection become evident. A lamb that has been 



6 Department Circular hi, U. S. Department of Agriculture. 

affected sufficiently to show the external effects of stomach worms 
has received a serious setback. Although it may recover and again 
be thrifty it has lost at least a month or 6 weeks of progress toward 
marketable weight and condition. The only safe and economical 
way of raising sheep where stomach worms are a factor is by managing 
the flock and pastures in a way to prevent a serious develop- 
ment of the trouble. In most localities the methods necessary for 
preventing stomach worms are at the same time those that need 
to be employed for most economical production. In order to follow 
these methods, particularly with respect to pasture rotation, the 
shepherd needs to know just how and when infection occurs. 

HOW DO SHEEP BECOME INFESTED BY STOMACH WORMS? 

INFESTED PASTURES. 

In the adult sexual stage stomach worms are able to live and 
carry out their reproductive functions only in the alimentary canal 
of sheep or other ruminants, and practically only in the fourth stom- 
ach. Each female produces thousands of eggs, of microscopic size, 
which do not develop into adult worms in the body of the host in 
which they are deposited, but, without hatching, pass out of the 
intestine in the feces. In a few hours, days, or weeks, according as 
the temperature is high or low, these eggs, if they are not killed by dry- 
ing or freezing (either of which is commonly fatal to them), hatch and 
the tiny embryonic stomach worms then develop to what may be 
termed the final larval or infectious stage. This later development like- 
wise requires days or weeks, according to the temperature, and until 
the young worms have reached the infectious stage they appear to be 
fully as susceptible to freezing and drying as the eggs. Having 
reached the infectious stage, however, the worms are able to with- 
stand long periods of dryness and severe cold, though some of them 
succumb comparatively early. 

In the infectious stage the young worms are very active in the 
presence of moisture, and rapidly crawl up blades of grass and other 
objects whenever the relative humidity of the air is at a maximum, 
provided the temperature is above 40° F. or thereabout; below that 
temperature they are inactive. A decrease in the relative humidity, 
with the consequent evaporation of the moisture from tho surface of 
grass blades and other objects, stops the migrations of the worms, 
and they become quiescent and remain in a condition of suspended 
animation wherever they happen to be at the time. During the next 
period of wet weather, dew, rain, or fog, tho worms again become 
active and climb still higher on the grass, from which they are better 
able to attain their final abode within the stomach of a sheep or cow 
than if they remained on the ground. When swallowed by a sheep 
or other ruminant the young stomach worm, if it has reached its final 



Stomach Worms in Sheep. 7 

larval stage, whether active at the time or in a state of suspended 
animation, continues its development, and in the course of 2 or 3 
weeks reaches maturity. 

The length of life of individual worms in the stomach has not been 
determined. Infested sheep have been kept in pens with board 
floors, which were kept clean by sweeping and frequent scrubbing — ■ 
the sheep being fed from raised racks and water being supplied in a 
trough which was frequently cleaned — for varying periods up to a 
maximum of 19 months, and at the end of these periods were found 
to be still infested, though the number of worms present was small. 

As the possibility of reinfection by larval worms developing from 
eggs passed in the feces of these sheep was not entirely removed, 
though greatly minimized, the results obtained do not necessarily 
indicate that the worms found at the end of the period of observation 
were all present when the experiment was begun. The experiment, 
however, while it proves nothing as to the length of life of the adult 
stomach worm, demonstrates the futility of attempting to rid sheep 
entirely of stomach worms simply by keeping them away from pas- 
ture. On the other hand, very little infection occurs among sheep 
kept in stables if cleanly conditions are maintained. Lambs have 
been kept with infested sheep in stables for long periods of time, the 
only precautions against infection being the removal of manure about 
once a week. Under such conditions they have continued in good 
health, and acquired only a very few stomach worms and other 
parasites. 

LENGTH OF TIME PASTURES MAY BE INFESTED. 

The maximum period during which the larval stomach worms are 
able to survive on pastures is not definitely known, but it has been 
found that pastures on which infested sheep had grazed were appar- 
ently still infectious after a lapse of neariy 8 months, namely, from 
October 25, when the infested sheep were removed, to June 16, when 
the pastures were tested by placing in them some lambs which had 
been raised under special precautions to avoid previous infestation. 
In cultures made September 14, 1906, from the feces of an infested 
sheep and kept thereafter in the laboratory, most of the larvae were 
dead but some were still alive, though very sluggish, on June 5, 1907, 
nearly 9 months later. Cultures in which the worms were allowed 
to develop to the final larval stage, after they were kept in cold storage 
at a temperature below freezing — in some cases as low as 12° F. — 
still contained some living worms after 2 or 3 months, while in other 
cultures eggs and newly hatched worms not yet developed to the final 
larval stage were killed within a few hours after exposure to tempera- 
tures below freezing. 

These experiments show that pastures may remain infected for 
several months after sheep are removed from them, and that the 



8 Department Circular 47, U. S. Department of Agriculture. 

infection is not destroyed by cold weather. They show, however, 
that during a winter with more or less freezing weather there is 
likely to be little or no increase in the amount of infection in pastures 
occupied by infested sheep. The eggs passed in the feces of the sheep 
will either be killed at onoe by freezing, or, on account of low tem- 
peratures above freezing, will remain dormant or develop so slowly 
that they are killed later by frost before they have reached the final 
larval stage, which is resistant to cold. At the same time, while the 
infestation of pastures may not be increased during the winter, the 
infestation of the sheep may be added to by their picking up from 
time to time larval worms which, prior to the beginning of cold 
weather, had developed already to the stage in which they are able 
to withstand freezing. 

If sheep, goats, and cattle are kept off a pasture for a year, it is 
fair to assume, upon the basis of our present knowledge, that all, or 
practically all, larval stomach worms will have died within that time. 
There is also little doubt that the period required for the practical 
disinfection of a pasture may be shortened considerably by plowing 
it and placing it under cultivation. 

Thus there are two ways by which a pasture may be freed of infesta- 
tion, one by excluding sheep or other ruminants for at least a year, and 
the other by turning it into a cultivated field. In view of the fact 
that sheep placed on disinfected fields or pastures probably will not 
be entirely free from infestation, it is not of much consequence 
whether every larval stomach worm in the pastures is dead or not. 
The approximation to this point, which is attained by vacating pas- 
tures for a year or by plowing them up, is sufficient for practical 
purposes. 

WHAT METHODS CAN BE EMPLOYED TO PREVENT LOSS FROM 

STOMACH WORMS? 

It is barely possible that some means of artificially producing in 
lambs an immunity against the evil effects of stomach worms may 
be devised, but at the present time it is only a matter for speculation 
and experimental research. Our present knowledge of the stomach 
worm leads us to direct our efforts toward bringing about freedom 
from infestation or, as the next best thing, reducing the amoimt of 
infestation to a minimum and keeping it there. 

EARLY DEVELOPMENT OF LAMBS. 

One great step toward evading the stomach worm is found in the 
plan of having lambs dropped early and feeding to develop them as 
much as possible before they go to pasture. 

Where sheep graze during winter and spring there is little danger 
of infestation in freezing weather, as the eggs or young larva* are killed 



Stomach Worms in Sheep. 9 

before they are taken up by the lambs. There is but very slight 
danger that young lambs will become affected seriously while running 
with older sheep in barns or yards free from vegetation. Early lamb- 
ing, combined with good feeding of the ewes to make them milk well, 
or of the lambs themselves in a "creep," or with both, brings early 
lambs to marketable weight and finish before the most dangerous 
part of the summer. Where lambs must remain for several months 
on pasture, frequent changing of pasture must be resorted to, to 
keep infestation below the extent that is injurious. 

A PRACTICABLE METHOD OF PASTURE ROTATION. 

The means of preventing the stomach-worm larvae from getting 
into the lambs is suggested by what has been said concerning its 
development and powers of resistance. It was stated that a pasture 
that had been occupied by wormy sheep would need to be for at 
least a year without cattle, sheep, or goats in order to become 
practically free from stomach-worm larvae. 

From 10 to 20 days, according to temperature and moisture, must 
intervene between the dropping of the feces containing stomach- 
worm eggs and the development of many of the larvae to a point 
where they will develop into adult worms after being swallowed. If 
sheep are moved to a fresh pasture before the eggs in their droppings 
develop into mature larvae, complete health can be maintained. The 
practical difficulty lies in always having a fresh pasture available. 
If only permanent grass pasture were used, adequate control would 
call for as many separate pastures as would allow the flock to be 
moved at least every 2 weeks without going on the same ground 
twice within 12 months. The time of grazing during freezing 
weather would not be included in such a plan, as few of the eggs or 
young larvae would survive. It should be observed that it is not 
simply the changing of pastures that is called for, but changing to 
clean ground. Putting infested sheep on pasture in May, removing 
them during June and returning them in July, offers an excellent 
chance for infestation from the eggs dropped during the first pastur- 
ing which would have hatched out into young worms waiting to be 
taken up. 

Some modifications of such a plan are quite practicable on any 
farm. In the first place, the danger is greatest to the lambs, and after 
they are sold or separated the ewes may go back to pastures usod 
earlier in the season with much less danger of injury than would be 
incurred by the lambs. This change, however, would render that 
pasture unsafe for young lambs during the following spring. Hay- 
fields, grain stubble, and cornfields can be utilized in the rotation of 
fields to furnish fresh grazing. 



10 Department Circular 47, U. S. Department of Agriculture. 

Plowing the land infested with the larvae of stomach worms greatly 
reduces the danger of infection. This fact allows the same land to be 
used two or three times for sheep in a season by using forage crops. 
Fall-sown wheat can be used for the earliest period, the land broken 
and resown to peas and oats, rape, or soy beans for a later grazing, 
and in some cases plowed again and sown to wheat to furnish late-fall 
feed. A succession of such crops is particularly desirable for carrying 
over from weaning time until winter the ewe lambs that are to be 
retained in the flock. 

Where sufficient changes of pasture and fresh ground can not be 
provided, preventive dosing may be partially relied upon. The 
danger in depending upon treatment lies in the fact that while cures 
usually can be effected by its proper use, lambs that have been al- 
lowed to reach the point where medicine is needed have at least been 
seriously checked in growth, and unless very carefully watched some 
deaths will occur. 

The treatment can be used as a measure to hold the stomach 
worms in oheok, in conjunction with rotation of pastures. Many 
successful shepherds dose all the ewes before turning them on the 
spring pastures with the lambs. This greatly lessens the number of 
eggs dropped. Afterwards all the lambs to be kept are similarly 
treated at the time of weaning, and individual cases may be treated 
on the first appearance of symptoms which will be noted if the flock 
receives the attention it really requires. When pasture rotation and 
similar preventive measures are impossible, sheep may be given the 
copper-sulphate treatment, preferably in diminished dosage, every 
month or 6 weeks during the summer season. 

The stomaoh worm need not be a serious trouble for a good shep- 
herd who has his lambs come early, feeds well, drenches the flock as a 
measure of prevention, and provides a rotation of pastures or pasture 
crops. 



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Exterminating the Texas Fever Tick. (Farmers' Bulletin 498.) 

Texas, or Tick Fever. (Farmers' Bulletin 569.) 

Foot-and-Mouth Disease. (Farmers' Bulletin 666.) 

Sheep Scab. (Farmers' Bulletin 713.) 

Tuberculosis of hogs. (Farmers' Bulletin 781.) 

Anthrax, or Charbon. (Farmers' Bulletin 784.) 

The Sheep Tick: Its Eradication by Dipping. (Farmers' Bulletin 798.) 

Screw -worms and Other Maggots. (Farmers' Bulletin 857.) 

Swine Management. (Farmers' Bulletin 874.) 

Cattle Lice and How to Eradicate Them. (Farmers' Bulletin 909.) 

Important Poultry Diseases. (Farmers' Bulletin 957.) 

Spinose Eartick, Treatment for. (Farmers' Bulletin 980.) 

Cattle Scab and Methods of Control. (Farmers' Bulletin 1017.) 

Hemorrhagic Septicemia: Stockyards Fever, Swine Plague, Fowl Cholera, etc. 
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Cerebrospinal Meningitis. (Department Bulletin 65.) 

Vesicular Stomatitis of Horses and Cattle. (Department Bulletin 662.) 

Necrotic Stomatitis, with Special Reference to Its Occurrence in Calves, Calf Diph- 
theria, and Pig Sore Mouth. (Bureau of Animal Industry Bulletin 67.) 

Diseases of Stomach and Bowels of Cattle. (Bureau of Animal Industry Circular 68.) 

Actinomycosis, or Lumpy Jaw. (Bureau of Animal Industry Circular 96.) 

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11 






12 Department Circular 47, U. S. Department of Agriculture. 

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