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PUERTO RICO AGRICULTURAL EXPERIMENT STATION
MAYAGUEZ, PUERTO RICO
Under the supervialon of the
UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 38
Washington, D. C. March 1936
PARASITES AND PARASITIC DISEASES OF SWINE
IN PUERTO RICO'
By H. L. VAN VOLKENBERG, Parasitfologist
Introduction------------------------. 1 Internal parasites. _.--------------------.... 5
Occurrence and distribution of parasites.... Protozoa---..----......---....... ......... 5
Damage by parasites..... ---------............ 2 Lungworm--------........- ............. 6
Shade_.-------------.------------------- 2 Kidney worm....----.....------............. 6
Preventive measures ---------------------... 3 Hookworm--.... .....----------.....----.... ... 8
Bare-lot method of raising pigs--............ 4 Thorn-headed worm--...-...---------- 9
Treatment for parasites.....------------------- 5 Pork measles or pepita_ -------.--... -- 10
Other internal parasites_ --.... .-.-.- 11
External parasites...................-...-... 12
The most serious diseases affecting swine in Puerto Rico seem to
be hog cholera, intestinal disorders (enteritis), and parasitic infesta-
tions. The fact that as a rule there are no large herds of swine in
Puerto Rico, and hence no occasion for crowding, tends to restrict
the spread and prevalence of infectious diseases and many parasites.
However, this advantage is largely offset by the lack of care and
attention given to these animals. Some of the problems of swine
raising are to increase the numbers of the animals, improve the
quality of the stock, and to raise a higher percentage to profitable
OCCURRENCE AND DISTRIBUTION OF PARASITES
In many places, especially in the more temperate climates, the
ascarid or large roundworm is a menace to the swine industry. In
Puerto Rico, the kidney worm is probably as injurious to the pig and
potentially as serious to the industry as the ascarid. If many hogs
are raised on a farm or on the same plat of ground, the most careful
control measures are necessary. The ascarid is most common and
injurious among young pigs. Mature hogs do not lose their suscep-
tibility to infection by the kidney worm, and serious infestations
1 Acknowledgment is made especially of the constructive and very helpful criticism of the manuscript
by Maurice C. Hall and F. C. Bishopp of the U. S. Department of Agriculture.
2 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
amoig older animals as well as among the young may occur. The
lungworms also thrive, and where pigs are raised and fed in numbers
for several years in succession, unless precautions are taken, they may
increase sufficiently to cause financial losses instead of profits in this
industry. There are other parasites which on many farms are ob-
stacles to profitable swine production.
Infestations with internal parasites, similar to those in other host
animals, are more or less seasonal in occurrence. Among the animals
slaughtered at Mayaguez worm parasites are most common during
a period of several months beginning with December. One-half or
more of these hogs are obtained from the dry southern coastal plain.
In the dry sections the bulk of the infestations are picked up during
the latter part of the rainy season, whereas in the areas subject to
torrential showers they occur at different times during the so-called
dry season. However, infestations may occur at any time among
pigs closely confined in insanitary, covered pens or heavily shaded
yards where the free-living stages of parasites are less influenced
by the prevailing weather conditions where they would be out in the
open. Other things being equal, the dry areas are superior to other
parts of the island for raising pigs, as the environment is less favor-
able for parasites.
DAMAGE BY PARASITES
Some of the external parasites extract blood from the host and
all of them irritate the skin. The internal parasites of the pig cause
damage by mechanically injuring tissues and organs and in various
other ways. Pigs and young hogs are more susceptible and more
seriously injured than older animals. Parasitism prevents the best
and most rapid development and reduces vitality and resistance so
that infested animals become susceptible to attack by other diseases.
Heavy infestations with worms also indicate that the environment is
insanitary and unsafe, and that other filth-borne diseases are likely
Hogs must have shade, but the kind and extent of the cover is
most important in a climate such as exists in Puerto Rico. A satis-
factory structure for providing both shade and shelter consists of a
framework about 4 feet high made of posts and poles and having the
roof thatched or covered with sheet iron or palm leaves. This
structure should be open on all four sides. Preferably the roof
should be set on rollers and moved back and forth over its own
length every few days, so that the entire area can be exposed periodi-
cally to the direct rays of the sun.
Dense, natural shade for yards should be avoided. The common
practice of placing yards and feeding places under mango trees
or other large trees having thick foliage is conducive to heavy infes-
tations with parasitic worms. Sunshine is not only necessary for
growing pigs, but it also acts as an efficient drier and disinfectant
and is very destructive to the eggs and larvae of parasites on the
ground. Also much of the island is exposed to seasonal and almost
daily torrential showers. These rains have a very noticeable effect
in washing and cleansing infective material from the soil. In many
*. ..I.. .
PARASITES AND PARASITIC DISEASES OF SWINE 3
yards both these purifying agencies are shut off by trees. In a loca-
tion open to the trade winds, trees and brush often shield the yard
from the prevailing breezes which are cool and pleasant. With a
high humidity in this climate, evaporation and drying of the soil
is sluggish unless the surrounding air is kept in motion.
The best arrangement as far as sanitation is concerned would be
to eliminate all trees and brush in and around the yard and provide
a roof shelter for protection from the elements. Otherwise a selec-
tion and arrangement of shade trees should be made in order that
the direct rays of the sun can reach all parts of the yard at least
one-half the day. Trees that branch fairly high from the ground
are good for this purpose.
If hogs are confined in yards the ground should be kept dry and
free of growing vegetation. As previously explained, shade is an
important factor in connection with moisture or dryness in hog
FrGURa 1.-A bare yard for hogs located on a sloping hillside. Farrowing pen and yard
yards. Also shade for the microscopic eggs and larvae of parasites
on the ground may be provided by any covering that conserves mois-
ture and prevents the penetration of the direct rays of the sun.
Therefore all accumulations of left-over feed, especially grass, cane,
corn husks, etc., should be cleaned up and removed each day with
On the heavy soils in the wet sections the yards should be placed
on a slope or hillside to insure proper drainage (fig. 1). Otherwise
artificial or subsoil drainage must be provided. Any surface water
accumulations such as mud wallows must be avoided. If the yards
are properly situated the heavy washing rains during one season and
the sunlight during both seasons are very effective in carrying away
........ ------------- -----.-------- -"-------
4 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
or destroying the infective material. In the dry sections or where
the soils are sandy or porous the drainage requirements are leas
exact but in like manner the yards must be kept free of all veget n.
The College of Agriculture at Mayaguez has success used
bare lots with a herd of purebred hogs over a period of several years
and very little attention has been paid to such sanitary measures as
cleaning up manure accumulations and rotation of yards. Examina-
tions have shown that these animals are remarkably free of internal
parasites. Varying somewhat in detail, other farmers are using dry,
bare lots with very little, if any, trouble from parasites. Often this
method has developed on individual premises more by accident than
design owing to the absence of shade trees and the destruction of
the vegetation by the animals themselves.
Yards should not be situated so that one can drain into another.
In all cases, the rotation of yards or pastures is very desirable. Each
year or oftener a fresh lot should be occupied and, unless plowed,
at least 1 year should elapse between successive occupations. Other
aids in disinfection are plowing two or more times a year and fre-
quent applications of air-slaked lime to the yards and feeding places.
Hogs should not be confined in small, covered pens unless the floors
are of tight construction, preferably of concrete, and are kept in a
dry, sanitary condition and free of dust. As parasites among un-
confined pigs which range over a wide territory are less subject to
control by preventive measures, these animals should be confined in
sanitary yards or pastures. Cultivated pastures should receive more
attention, as several valuable crops for hogs can be grown and
pastures can be used during the entire year.
BARE-LOT METHOD OF RAISING PIGS
A special farrowing yard enclosing about 500 square feet should
be provided. This yard should be used for only one purpose and by
one sow with litter at one time. It must be located on a we-
drained, unshaded or properly shaded area. All growing vegetation
should be trimmed close to the ground and removed or plowed
under, and the surface should be kept in this condition during occu-
pancy. A pen consisting of a concrete floor at least 6 by 6 feet in
size, with a roof set on posts, should be constructed in or opening
into the yard. Except for woven wire as a barrier the sides of
this pen should be open. The sanitary features of the yard can
be improved by providing at one end a separate enclosure or feeding
floor for the sow and at the other end a creep with a self-feeder
for the pigs. The pigs should be prevented from entering the feed-
If previously occupied, the floor of the pen should be scrubbed and
disinfected with a 3-percent solution of compound cresol (U. S. P.).
A few days before farrowing, the sow, if encrusted with mud and
filth, should be scrubbed with a brush, using soap and warm water,
on the. sides, udder, and entire lower portion of the body, and then
placed in the farrowing yard. The bedding must be watched care-
fully and changed when it becomes foul or wet. The manure and
all other accumulations in the yard should be frequently and thor-
oughly removed and properly disposed of. After weaning, the pigs
should be separated from all other hogs and placed in a fresh,
PARASITES AND PARASITIC DISEASES OF SWINE 5
uncontaminated (temporary) pasture or in a yard or yards where
no hogs have been during the last year or on ground that has been
plowed since hogs were there. If pastures are used for hogs the
kidney-worm-control plan (p. 8) should be adopted. These sani-
tary measures cannot be depended on as a preventive of hog cholera,
and immunization should be carried on in accordance with the
approved methods of hog-cholera control.
TREATMENT FOR PARASITES
Preventive measures are more important in controlling the in-
ternal parasites of pigs than the administration of anthelmintics.
There is only one species (ascarid) for which an efficient vermifuge
is known, and this worm is of minor importance. Capsules should be
used with caution on swine as they often lodge in the pharyngeal
pouches and the contents may cause inflammation of the neck, swell-
ing, and suffocation. Also the pig has a comparatively narrow
throat, and liquids must be given slowly and carefully. Worm treat-
ments to be given in feed or as mineral mixtures are not satisfactory.
Drugs for pigs are best administered by a competent veterinarian.
S* The internal parasites consist of protozoa, flukes, tapeworm larvae,
and roundworms. As a group the roundworms are usually more im-
portant than the others. Several of the internal parasites are of
special importance because they may be transferred in some stage
of their development to man and to other animals. Not all the so-
called cosmopolitan species of parasites are known to occur in the
native pig. Among those not known from Puerto Rico are the
Sworms that cause the disease trichinosis and the hydatid, Echinococ-
nus gramulosus, both of which are transmissible to man and which
may be fatal.
Intestinal disorders cause losses and interfere with the growth
and development, especially of pigs and young hogs. Diarrhea is
the most common and characteristic symptom. Some of these
troubles are brought about by improper feeding, but the majority
apparently are caused by one or more groups of bacterial and
parasitic infections and are due to the insanitary environment in
which the animals live. Among the parasites associated with these
disorders are several kinds of worms and protozoa. The intestinal
tract of hogs is frequently infested with protozoa of one kind or
another. Usually these are harmless forms but at times some of
them are pathogenic.
The most common protozoa found in swine are coccidia. These
are microscopic round or oval organisms located in the lining mem-
brane of the large intestine. Coccidia are frequently found in fecal
examinations, but apparently they are usually pathogenic only to
young pigs, causing a lack of appetite and diarrhea. Also the
comparatively large, motile organism, Balont.idium coli, a parasite
of man, is frequently encountered. The balantidia, either alone or
associated with pathogenic bacteria, at times produce diarrhea with
fatalities in young pigs. On autopsy, the large intestine teems with
6 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
this organism and extensive ulcers are found,. especially in the
caecum. Other protozoa, such as amoeba, spirochetes, and tri-
chomonads, are also found in the intestinal tract.
Specific treatments for the protozoan and filth-borne diseases
in pigs are unknown. Pigs should be farrowed and raised in dry
bare lots and careful attention should be given to the details of
sanitation. Food and water should be given in containers that
will not allow contamination of the contents with manure. Scrub-
bing the sow before farrowing, as previously mentioned (p. 4),
may help to prevent infestations by protozoa among sucking pigs.
The lungworms, Metastrongylus elongatus and Choeroetrongylus
pudendotectus (fig. 2, B), are slender white worms varying from 1
to 5 cm (approximately 1/2 to 2 inches) in length. They are found in
the air passages of the lungs.
Life history.-These worms require earthworms as intermediate
hosts. The eggs are coughed up, swallowed, and pass out with the
feces and are ingested by earthworms. Pigs become infested by eating
Importance.-Lungworms are the most common of the more impor-
tant parasites affecting the epig. They are most abundant in pigs
raised in the wet coastal and mountain areas. Pigs on an open rang
often become heavily infested.
Symptoms and lesions.-The disease is characterized by a cough.
Heavy infestations may result in pneumonia. Lungworms may be
fatal to young pigs. Infested lungs are conspicuous because of the
whitish colored areas on the surface, usually near the tips of the
Treatment.-Medicinal treatment should not be attempted. Sick
animals should be placed in clean, dry pens and given an abundance
Prevention.-For unconfined pigs the frequent cleaning and proper-
disposal of the manure around the feeding and sleeping quarters or
from any area where the pig is in the habit of depositing its drop-
pings would eliminate much of the infective material. Pigs wander-
ing farther afield would be less subject to a concentration of infection.
Infestations among confined pigs can be largely prevented by
cleaning up all manure accumulations. The concreting of the entire
hog lot would materially aid in eliminating these worms as well as
others but its cost would limit such construction to exceptional cases
only. These worms are unimportant among hogs confined in dry,
bare lots. Pigs should be raised under the kidney-worm-control plan
or by the bare-lot method.
The practice of inserting a wire ring in the nose of the pig to
prevent rooting in the soil is probably an effective control measure
for lungworms and also thorn-headed worms.
The kidney worm, Stephanurus dentatus (fig. 2, A), is a thick,
mottled worm from 2 to 4.5 cm (approximately 8/4 to %l inches)
long. As adults they are located in the abdominal viscera, espe-
cially in the fat surrounding the kidneys.
PARASITES AND PARASITIC DISEASES OF SWINE
Life history.-Unlike most worm parasites, the eggs of this worm
pass out with the urine. The eggs hatch on the ground and infective
larvae develop in a few days. These larvae are swallowed with the
food or they penetrate the skin. After several months of develop-
ment in the liver the young worms migrate through this organ into
the abdominal cavity. Some go astray and enter the lungs and other
FIGURE 2.-Worm parasites of Puerto Rican hogs: A, Kidney worms; B, lungworms; C,
pork measle worms; D, American swine hookworms; E, common hookworms; F, whip-
worms; o, strongyline stomach worms; H, red stomach worms; I, nodular worms; J,
thorn-headed worms; K, ascarid. A to 1 approximately natural size, J and K slightly
tissues. This parasite shows a remarkable adaptation or specializa-
tion. Numbers of the young worms in the abdominal cavity appar-
ently without following any natural body channel, get to the slender
ureters by burrowing through the surrounding fat and puncturing
these tubes, thus providing an artificial opening or avenue of elimina-
tion for the ova.
Importance.-The kidney worm is one of the most serious parasites
of swine in Puerto Rico. Besides the unthriftiness and stunting of
growth, there is considerable damage to carcasses from which wormy
8 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
livers and other parts must be discarded. Usually pigs confined in
dlark, damp, and dirty pens harbor heavy infestations with this
worm. As massive infestations are often found in hogs of the im-
proved breeds, it is believed by some that they are more susceptible
thanIi the native pig. It is probable that as these hogs are more apt
to be closely confined, they are more likely to be exposed to & con-
centration of infection than the native pig, which may have a free
range all or part of the time. However, pigs on a free range do not
Symptoms and ledion.-Loss of appetite, swollen abdomen, and
emaciation are the usual symptoms. Severe infestations may cause
weakness and paralysis of the hindquarters. The liver is injured by
t(le young worms actively migrating through this organ. Most of
the livers of slaughtered pigs show varying degrees of fresh injuries
or scar tissue formation resulting from infestations with these worms.
The mechanical injuries are complicated by bacterial infections and
Treat men t.-Unknown.
Prevent;on.-The eggs a.nd larvae of this worm are readily de-
stroyed by sunlight, heat, and drying and they cannot survive in
the open unless they fall in grass, leaves of trees, corn husks, and
The kidney-worm-control plan as developed by the Bureau of
Animal Industry, United States Department of Agriculture, is ef-
fective in controlling this parasite, where pastures are used. Most
of the infective material is passed in the area around the sleeping
quarters and close to the fences. This plan requires cutting and
cleaning away the grass and weeds in a strip 3 to 5 feet wide along
the fences on the sides of the pasture lot and a strip about 30 feet
wide at the end where the shelters and all other equipment are
placed. These strips must be kept free of trash and litter while the
pasture is in use. Providing separate feeding pens for the sows
and, some distance away, creeps with self-feeders for the pigs also
helps to control other parasites as well as kidney worms. The pigs
are kept in this pen with the sows until weaning and then are
placed on temporary pastures, with only pigs of a similar age raised
under the same system.
If the above plan is not followed, pigs should be farrowed in a
dry, bare yard and then placed on fresh ground after weaning.
In a general way, the more dense the shade, the more growing vege-
tation, the poorer the drainage, and the more animals on the same
area the greater is the need for cleaning up manure accumulations,
the rotation of yards, and the adoption of a sanitation system.
The common hookworm, Globocephalus urosublatus (fig. 2, E), is
a slender white worm about 4.5 to 7.5 mm (approximately three*
sixteenths to five-sixteenths inch) long. These worms are found in
the small intestine.
Life history.-Similar to other hookworms; infection probably
takes place by way of the mouth and of the skin.
2 SCHWARTZ, B. CONTROI.LI1N KIDNEY WORMS IN SWINI IN SOUTHERN STASTL.
U. S. Dept. Agr. Leaflet 108, G pp., illus. 1934.
PARASITES AND PARASITIC DISEASES OF SWINE 9
Importance.-This is one of the more common and serious para-
sites. A large percentage of the pigs from the dry southern coastal
area are infested.
Symptoms and lesions.-The worms are closely attached to the
mucosa of the small intestine, but examinations indicate that they
do not have the bloodsucking tendencies and do not produce anemia
to the extent of the common hookworms in other animals. How-
ever, heavy infestations produce a severe catarrhal inflammation
of the intestine, resulting in unthriftiness.
-Treatment.-Either oil of chenopodium or tetrachlorethylene is
indicated. Oil of chenopodium is given at the dose rate of one-half
to 1 fluid dram (approximately 2 to 4 cc) to a 100-pound pig pre-
ceded or followed immediately by 2 fluid ounces .(approximately
60 cc) of castor oil, or given in the oil. As used to destroy ascarids
the smaller dose is less effective but is safer and may be repeated
at shorter intervals.
Tetrachlorethylene may be given at the rate of 21/2 cc (about 3
fluid dram) for pigs 8 weeks old or weighing 40 pounds. A purgative
is not usually necessary, but if pigs are in poor physical condition
because of parasites an adequate dose of a saline purge should be
given with this drug.
Swine should be fasted for 18 to 24 hours before, and not fed or
watered for 3 hours after, treatment for worms.
Prevention.-Sanitation, proper manure disposal, and general
cleanliness about yards, buildings, and feeding places used by swine
The thorn-headed worm, Macra.canthorynchus h irudinaceus (fig.
2, J), varies in length from 21,i to 14 or more inches. It occurs in the
small intestine. The body is white, cylindrical, and gradually tapers
toward the posterior extremity. The body has somewhat the appear-
ance of being segmented, owing to annulations in the cuticle. The
S head has an invaginating, cylindrical proboscis which bears five rows
of backward-projecting hooks.
Life history.-There are several kinds of beetles which are the inter-
mediate hosts of this worm. Among these are the four or five
species of white grubs (gusanos blancos) which are the larvae of the
Phyllophaga (Lac/htosterna) beetles. Also a common water beetle,
Tropisternus collaris, is another and apparently an important inter-
mediate host. The ova are passed in the feces and are swallowed by
beetles or their larvae. The pig becomes infested with this worm by
eating infected beetles or grubs. The water beetle is normally very
active but after infection with this intermediate stage, in which a
comparatively large cyst develops in the body cavity, it becomes
sluggish. Thus it is an easier prey for pigs which may be feeding
on the roots of plants in marshy ground.
Importance.-This worm is of considerable importance because of
its abundance. Pigs on a free range are most likely to pick up this
worm and often harbor heavy infestations.
Symptoms and lesions.-The presence of many thorn-headed worms
causes considerable mechanical injury and obstruction to the intestine.
SThe head of the worm is attached to and deeply embedded in the wall
of the small intestine. The comparatively large nodules frequently
BULLETIN 38, PUERTO RICO EXPERIMENT STATION
seen on the outside of the intestinal wall usually indicate the location
of the embedded head of the worm. Occasionally deaths are caused
by peritonitis resulting from the head perforating the intestine and
allowing the contents to escape into the abdominal cavity.
Treatment.-There is no specific treatment known.
Prevention.-Hogs should be prevented from feeding in marshes
and along sluggish streams, not only to control infestations of this
worm by means of the water beetle but also infestations with the liver
fluke and the bloodsucking leeches. Infestations with this worm
have not been found among hogs confined in unshaded, bare yards.
Apparently the beetles are not attracted to these yards and there is no
food for the grubs. Aside from the insertion of a ring in the nose of
the pig to prevent rooting the best that can be done for pigs on pas-
tures would be to harbor and protect the large nocturnal toad (Bufo
marines). As this toad has brought white grubs under control over
thousands of acres of cane land, it should be useful in hog lots and
gardens. Before the advent of this toad in 1920, herds of pigs were
maintained in cane fields solely for the purpose of following the plow
and eating the grubs. At present, the welfare of the pig should
receive first consideration.
PORK MEASLES OR PEPITA
The pork bladderworm, CysticercuR cellulosae (fig. 2. C), is the in-
termediate stage of a tapeworm of man. This cysticercus is round or
oval in shape and about as large as a small bean. It consists of a cap-
sule or cyst filled with a watery fluid. Inside the capsule as seen from
the outside is a conspicuous white spot which indicates the location
of the larval head (scolex) of the tapeworm. These cysts are usually
located in the muscles. In a heavily infested animal they may be
found in other tissues and embedded in the fat.
Life histomy.-The eggs produced by the adult tapeworm in the
human intestine are ingested by swine when human feces are not
properly disposed of. As a pig may ingest several gravid segments
of the tapeworm, which have passed at one time, and as each segment
may contain many ripe eggs, heavy infestations may result and are
not uncommon. Many thousands of cysts may occur in one carcass .
Importance.-This parasite is of special importance because of its
relation to public health, as the pork tapeworm is considered a dan-
gerous parasite of man. The number of swine carcasses condemned
at the abattoirs is not an indication of the prevalence of the pork
bladderworm as the buyers of market hogs either avoid the districts
where this disease is most common or inspect the animals for the cysts
Pepita seems to be more common in the region of Ponce and Mayaguez
and most of the infested pigs are obtained from or can be traced to
certain districts in the mountains.
Symptoms and lesions.-The presence of cysticerci is usually not
diagnosed in the live animals. However, a heavily infested pig can
often be detected by palpating or by discerning the cysts underneath
the lining membrane of the under surface of the tongue.
Treatment.-Treatment, which is surgical, is not practical in swine.
Preven tion.-To prevent infestation in swine, proper disposal of
human excrement must be made. The thorough cooking of pork and
PARASITES AND PARASITIC DISEASES OF SWINE 11
pork products is necessary to prevent infestations with the tape-
worm in man.
OTHER INTERNAL PARASITES
Several other worm parasites occur in the pig. As far as is known
they are of relatively less importance in Puerto Rico than those
already described in this bulletin. Usually the common worms of
the pig can be identified from their gross appearance and precise loca-
tion in the intestinal tract or elsewhere in the body. The morpho-
logical differences between two closely allied species, such as the
lungworms or nodular worms, are unimportant from a practical view-
point. Any unusual parasites that are encountered in livestock should
be sent to the experiment station at Mayaguez for identification.
The red stomach worm, Hyostrongylus rubidus (fig. 2, H), is a
small, hairlike, reddish worm. Close examination is necessary to
discern these worms in mucus scraped from the lining of the stomach.
Heavy infestations may produce a catarrhal condition. The mainte-
nance of clean, dry quarters for swine is the indicated control measure.
The strongyline stomach worm, Ascarops strongylina (fig. 2, G),
is a small white worm somewhat larger than the red stomach worm.
It varies from 1 to 2.2 cm (approximately 1/2 to 1 inch) in length.
These worms may be embedded in the lining membrane of the stomach
or are sometimes unattached and entangled in a mass in the lumen
of the stomach. Because of the habit of burrowing, they may cause
considerable injury to the stomach. As dung-frequenting beetles are
intermediate hosts of this worm, prevention depends on the frequent
and thorough cleaning out of manure in order to prevent the beetles
from feeding on it. The giant toad might be useful in controlling
these beetles. About 50 percent of pigs slaughtered at Mayaguez
are infested with one or the other or both species of stomach worms.
The roundworm or ascarid, Ascaris lumbricoides (fig. 2, K), is
a thick yellow or pink worm varying from 6 up to 10 or more inches
in length. It is unattached and is usually found in the lumen of the
small intestine. If numerous, these worms are very serious, causing
digestive disturbances, malnutrition, and stunting in young pigs.
In Puerto Rico infestations are uncommon and usually consist of only
a few worms.
The American swine hookworm, Necator swillus (fig. 2, D), located
in the small intestine, is somewhat longer and more robust than the
common hookworm (p. 8). A few pigs lightly infested with this
worm have been found at Mayaguez but further information as to
the economic importance of this worm is lacking. This worm is
common in Trinidad.
The nodular worms, Oesophagostomum dentatulm and 0. longi-
caudun (fig. 2, 1), are roundworms found as adults in the large
intestine. They vary from 8 to 14 mm (approximately 5/8 to 1/ inch)
in length. Some of these worms are white but the majority are of
a grayish-brown color. Heavy infestations of this worm are com-
mon in the wet coastal areas. These worms are not as serious in
pigs as the nodular worms in calves. Control measures depend on
sanitation, proper manure disposal, and general cleanliness about
yards or buildings occupied by swine.
12 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
The whipworm, Trichuris sui (fig. 21 F), is a white worm found
in the caecum and colon. The anterior portion of the body is
long and slender and the posterior portion short and thick. The
anterior portion is embedded in the lining membrane of the intestine.
Whipworns are often found in pigs and calves but usually infes-
tations are light. The control measures are the same as given for
the nodular worms.
The liver fluke, Fasciola hepatica, is a leaflike flatworm found
in the ducts of the liver of cattle, goats, and swine. This worm
is common in pigs that have access to swampy ground. Among
slaughtered animals a loss occurs in that infested livers are con-
demned. Pigs should be prevented from feeding in marshes and
should not be fed grass obtained from these areas. Directions for
fluke control are given in a previous publication of the station.8
The thin-necked bladderworm, Cysticercus tenuicollis, consists of a
spherical cyst about 21/ cm (1 inch) or more in diameter. The ex-
ternal tough membrane encloses a thinner transparent membrane
having a projecting neck and head, the scolex of the tapeworm. This
inner cyst is filled with a watery fluid. These bladderworms are
usually embedded in the liver or attached to other viscera in the
abdominal cavity. The adult tapeworm is found in the intestine
of the dog. In natural infestations, which consist usually of one
or two cysts, no symptoms are observed in the pig. The cysts should
be removed at time of slaughter and destroyed. The deep burying
or destruction by burning or otherwise of carcasses of animals dying
in the field is another indicated control measure.
Although several kinds of arthropods or external parasites occur
on the hog in Puerto Rico, on the whole they are not considered of
much importance. The hardy native pig exposed to plenty, of
sunlight on the open range seems to be remarkably free from external
parasites. However, infestations occur, especially among pigs con-
fined in insanitary quarters, which are detrimental to health and
control measures are necessary.
The hog louse, Haematopinus adventk-ius, causes considerable dam-
age to hogs if present in large numbers. In some herds, especially
of the improved breeds, this louse is commonly present for years.
Under conditions such as exist in Mayaguez this louse is not noticeable
except during the hot weather of April and May before the start of
the regular, torrential showers, when it increases in numbers. It does
not seem to spread and is rarely if ever found on the native hogs
brought to the abattoirs.
These lice can be eradicated by hand applications, sprays, medicated
hog wallows, or dipping. Hand applications may consist of (1)
crude petroleum, (2) crank-case draiinigs, (3) cottonseed oil and
kerosene, equal parts, or (4) lard 1 pound to one-half pint of kero-
sene. These remedies should be distributed in a thin, even coating
over the entire surface of the head and body, including the inner
surface of the ears and between the thighs. Freshly oiled or greased
VAN VAN LKENBR'RG, I. L. PARASITES AND PARASITIC DISEASES OF CATTLR IN PUIMO
n1o0. I'Putrto Rico .\gr. Expt. Sta. Bull. 36. p. 18. 1934.
ill -- --- .. ........ ---- ....... .. ....... .... .. ..... .....----- -
PARASITES AND PARASITIC DISEASES OF SWINE
hogs should not be moved rapidly and must be kept under shade. The
large fat hogs should be handled or moved only in the evening or early
Demodectic or follicular mange is caused by Denwdex phylloides,
a microscopic, wormlike mite which lives in colonies or groups in
the hair follicles and sebaceous glands. This mange is often found
in market hogs, but infestations are mild and unimportant. This
skin disease is usually not recognized as mange and as being con-
tagious. The lesions usually consist of small, hard nodules the size
of a pinhead, or larger, located on the skin of the head, neck, and
shoulders. If the disease advances, which occurs only occasionally,
these nodules break and discharge pus and suppurating cavities may
form. No effective treatment is known, although frequent dipping
in crude petroleum check the progress of the disease. In badly
infested herds, animals with advanced cases should be destroyed,
the remainder fattened for market and disposed of, and the premises
cleaned and disinfected before being restocked with healthy hogs.
Sarcoptic mange is caused by Sarcoptes suis, a small whitish mite
which burrows into the upper layers of the skin. The mites are
usually easy to find among the lesions on the inside edge near the
base of the ear. They are barely visible to the naked eye if placed
on a dark background. Sarcoptic mange is uncommon and it does
not spread rapidly in this climate, but it is more noticeable and
more serious than demodectic mange. It is usually accompanied by
demodectic mange. Stockmen usually recognize sarcoptic mange
as a contagious parasitic skin disease.
The same remedies and treatments are used for both lice and
mange. Crude petroleum is the most effective known remedy, but
in using it precautions must be taken to prevent burning of the
skin and overheating of the animal. The arsenical solution as used
for cattle ticks is effective if hogs are dipped four times at intervals
of 6 or 7 days. Detailed instructions for the treatment and control
of hog lice and mange are given in a Farmers' Bulletin of the
United States Department of Agriculture.4
The primary screw worm or gusano de la herida, Cochliomyia
americana, is the maggot of a blowfly which may attack any open
wound of pigs and other animals. This fly is more abundant
some years and during certain seasons but no severe outbreaks have
been known to occur. The treatment is to apply a small amount
of commercial benzol or chloroform to the infested wound. Benzol
is preferable; and if it is used, the blood and serum in the wound
should first be swabbed out with cotton. After waiting 3 or 4
minutes a small amount of the material should be introduced into
the pockets of the wound and these should then be plugged with
cotton. When the worms have been killed, the wound should be
lightly covered with commercial pine-tar oil. All wounds should
be treated with pine-tar oil to prevent attack by flies.
The sand flea or nigua, Tunga penetrans, frequently attacks hogs,
especially those that are raised near the seashore. The flea burrows
into the skin between and above the claws and its presence pro-
SIMES, M. HOG LICE AND HOG MANGE: METHODS OF CONTROL AND ERADICATION. I'. S.
Dept. Agr. Farmers' Bull. 1085, 22 pp., illus. 1933. (Revised.)
14 BULLETIN 38, PUERTO RICO EXPERIMENT STATION
duces considerable irritation and inflammation. The infested tis-
sues become swollen and pits or ulcers are produced. In a badly
infested foot the skin appears honeycombed. Providing a concrete :
wallow containing 3 to 5 inches of water with a thin layer of
tcrude oil will control lice and would probably be effective in con-
trolling sand fleas. A hog wallow should be provided with a
roof for shade. The construction and medication of hog wallows
are fully described in a Farmers' Bulletin of the United States
Department of Agriculture.5
Other external parasites that have been found on the pig are:
Mosquitoes; gnats or mimes, Hippelates spp.; fleas other than sand
fleas; horse ticks, Dermaoentor nitens, in the ear; and leeches or
SSee footnote 4.
U. 5 GOVERNMENT PRINTING OFFICE: 196
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UNIVERSITY OF FLORIDA
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