This publication addresses the identification, prevention and control of internal parasites in swine and lists characteristics of principle dewormers.
Whether pigs are raised in confinement or on pasture, controlling internal parasites is essential to the overall herd health program. Recent studies by Tom Kennedy of A.E.F. Research, Inc, Waunakee, WI, have shown that worm infestation is prevalent on both a farm and individual pig basis. Of the farms examined, 91 percent raised pigs on concrete, wire or slotted floors, but more than 90 percent of all farms were infested with one or more kinds of worms

Straw, B.E.

English

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University of Nebraska - Lincoln 
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Historical Materials from University of 
Nebraska-Lincoln Extension Extension 
1991 
G91-1049 Controlling Internal Parasites in Swine 
B.E. Straw 
University of Nebraska - Lincoln 
Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist 
 Part of the Agriculture Commons, and the Curriculum and Instruction Commons 
Straw, B.E., "G91-1049 Controlling Internal Parasites in Swine" (1991). Historical Materials from University 
of Nebraska-Lincoln Extension. 1153. 
https://digitalcommons.unl.edu/extensionhist/1153 
This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - 
Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an 
authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
G91-1049-A 
 
Controlling Internal Parasites in Swine 
This publication addresses the identification, prevention and control of internal parasites in swine and 
lists characteristics of principle dewormers. 
B. E. Straw, Professor, Veterinary Science  
? Roundworms  
? Whipworms  
? Lungworms  
? Nodular Worms  
? Anthelmintics for Swine  
? Prevention and Control  
 
Whether pigs are raised in confinement or on pasture, controlling internal parasites is essential to the overall 
herd health program. Recent studies by Tom Kennedy of A.E.F. Research, Inc, Waunakee, WI, have shown 
that worm infestation is prevalent on both a farm and individual pig basis. Of the farms examined, 91 percent 
raised pigs on concrete, wire or slotted floors, but more than 90 percent of all farms were infested with one or 
more kinds of worms.  
Worms reduce growth rate and feed efficiency, and damage tissues, predisposing pigs to infection by other 
diseases. Hale and Stewart estimated that worm infestation could add $1 to $14 to the feed and maintenance 
cost of finishing a pig (Table I). Economic loss also will be incurred when affected tissues are condemned at 
the slaughter plant.  
Table I. Prevalence and cost of parasites 
 Prevalence of internal parasites in Midwestern hogs
Per pig cost ($) of worm damage at 
three levels of parasite infestation
Parasite % Farms infested
% Pigs infested
at slaughter Light Moderate Heavy
Ascaris suum 
(roundworm) 70% 60% 1.92 3.21 5.56 
Trichuris suis 
(whipworm) 45% 19% 1.44 4.31 13.76 
Oesophagostomum 
(nodular) 33% 4% 1.25 2.09 3.69 
Roundworms 
The large intestinal roundworm, Ascaris suum, is the most common internal parasite of pigs and is found in 
almost every herd in Nebraska. Eggs of Ascaris suum are small--about the diameter of a human hair and 
almost invisible. Eggs can withstand severe cold, dryness, most chemical disinfectants and can live at least 
seven years in soil. The eggs pass from pigs in manure. When they leave the body with the feces, they are in 
an early stage of development and are not infective. Within a few weeks a tiny larva develops inside the egg.  
Pigs become infested by consuming food and water contaminated with infective worm eggs. When a pig 
swallows ascarid eggs, the shells rupture in the intestine and larvae are liberated. The larvae burrow through 
the intestinal wall and enter the blood stream, which carries them to the liver. From the liver, larvae travel in 
the blood through the heart to the lungs where they burrow through lung tissue and enter large air passages. 
The pig coughs and forces worms into the throat where they are swallowed and passed into the small 
intestine--this time to mature and grow to adults. It takes about four days for larvae to reach the liver, nine 
days to reach the lungs and 15 days to complete the trip to the intestine. Worms grow to egg-laying adults in 
about 60 days.  
Clinical signs of roundworm infestation are primarily associated with larval migration through the lungs. Pigs 
have a dry nonproductive cough, loss of appetite and weight, rough hair coat, increased temperature, and an 
increased rate of respiration accompanied by thumping.  
Both young and adult worms cause damage. Young worms destroy liver tissue, causing abscesses and scars. 
In the lungs they penetrate blood vessels, destroy tissue and plug smaller air passages. Damage to the integrity 
of the lung tissue predisposes pigs to pneumonia. Adult worms in the intestine rob the pig of food, block the 
gut and excrete substances which interfere with digestion.  
Diagnosis is made by microscopic identification of eggs in the feces. Adult worms in the intestine and scars in 
the liver are seen on postmortem examination.  
Whipworms 
Trichuris suis, is called the whipworm because it is shaped like a whip. A mature whipworm is 1 1/2 to 2 
inches long. It has one of the simplest life cycles known. Eggs are laid in the large intestine and pass from the 
body in manure. They develop into infective larvae in 21 days. After being swallowed by a pig, the young 
larvae burrow into the wall of the large intestine. Within a few days, the young worms emerge, attach to the 
lining of the large intestine and grow to maturity. A life cycle lasts 70-90 days.  
Whipworms cause considerable inflammation and irritation of the intestine. Whipworm infestation is 
characterized by loose stools which in many cases progresses rapidly to a severe, bloody diarrhea. Diagnosis 
is made by finding worm eggs in the feces or by recovering worms at necropsy. If sexually immature worms 
are causing the damage, eggs may not be found in the feces.  
Lungworms 
Metastrongylus 
(lungworm) 7%     
Stephanurus (kidney 
worm)   3.16 6.09 13.39 
(Adapted from T. Kennedy material, personal communication; and O. M. Hale, and T.B. Stewart, Agri-Practice, April 
1987)
There are three species of Metastrongylus or lungworms. Lungworms are thread-like, white worms up to 2 
1/2 inches long. Female lungworms live in air passages in the lungs where they produce large numbers of 
thick-shelled eggs, which the infected pig coughs up, swallows and passes in manure. Earthworms swallow 
the eggs, which hatch in the earthworm's intestine and become infective in three to four weeks.  
Pigs become infested by eating earthworms which harbor the infective larvae. Lungworm infestation causes 
coughing and shallow breathing. Hemorrhages occur on the surface of the pig's lungs during early stages of 
lungworm invasion. Constant irritation by lungworms can bring about consolidation of lung tissue around 
sites occupied by worms. Tips of lungs become grayish or whitish and very hard in some cases. Secondary 
pneumonias are common. Pigs infected with lungworms tend to go off feed, become unthrifty and fail to 
grow.  
Diagnosis is made by isolating eggs or larvae from feces or by demonstrating larvae in nasal secretions. 
Frothy mucus may be found at necropsy. When it is collected in a dish containing water and examined 
microscopically, the worms are easily observed.  
Prevent lungworm infestation by keeping pigs in lots where they cannot contact earthworms. Earthworms 
thrive in old hog lots in which manure and litter have accumulated, or on permanent pastures and in low fields 
that receive drainage from higher ground.  
Nodular Worms 
The nodular worm, Oesophagostomum dentatum, is a small, whitish worm about 1/3 to 1/2 inch long that 
lives in the large intestine. Worm eggs pass from the pig in manure and under favorable conditions of 
moisture and temperature, develop to form infective larvae in three to seven days. These larvae can survive up 
to 10 months in mild climates but will die in cold temperatures. In the Midwest, these parasites survive by 
wintering in breeding stock. The pig will eat infective larvae with feed or water. The worms encyst in the 
lining of the large intestine and cause nodules to form. This condition is called "pimply gut". Within six to 10 
days after infection, the young worms emerge from the nodules and grow to maturity. The life cycle requires 
50 to 53 days.  
These immature worms can cause loss of appetite, diarrhea or constipation, and anemia. Diagnosis is made by 
microscopically identifying the characteristic worm eggs in the feces, or by recovery and identification of 
adult worms at necropsy.  
Anthelmintics for Swine 
When selecting a dewormer for swine, consider these five factors: efficacy of compound, spectrum of 
activity, mode of administration, margin of safety and cost of treatment. The spectrum of anthelmintic activity 
determines the number of species affected by the dewormer. Certain swine anthelmintic drugs are highly 
effective against only one species. If the herd problem involves several species of parasites, use a dewormer 
that effectively removes many species.  
Prevention and Control 
Since moisture favors the development of worm eggs into larvae and dryness kills them, reduce moisture to 
decrease parasitic contamination. Pastures should be well drained and feeding areas should be raised above 
ground. Many worm eggs can survive for long periods in dirt. Research has shown that ascarid eggs on 
unplowed pasture lots remained infective for seven years--whipworm eggs can remain infective up to six 
years. Rotating hog lots will help prevent infestation.  
Worm eggs are easily carried by the wind or water and have been recovered from soil on roofs, window sills, 
and sides of buildings. 
 
Table II. Approved claims of principle dewormers (listed alphabetically by trade name) 
 Types of worms controlled
 roundworm whipworm nodularworm kidneyworm threadworm lungworm
relative
cost*
Atgard (dichlorvos)
? Mixed in 
feed and fed 
for 1 to 
several days, 
according to 
directions, 
to pigs of any 
age 
adult 
L4 
adult 
L4 
adult 
L4 --- --- --- medium
? Top dressed 
on feed for 1 
day to sows, 
boars, gilts 
adult 
L4 
adult 
L4 
adult 
L4 --- --- --- low 
Banminth (pyrantel tartrate)
? Continuous 
use in feed, 
96 g/ton, or a 
1 day 
treatment in 
feed at 800 
g/ton 
adult 
L3, L4 --- adult --- --- --- high 
? 3 day 
treatment 96 
g/ton 
adult --- --- --- --- --- low 
Hygromycin B
? 12 g/ton 
continuous 
in feed 
adult adult adult --- --- --- medium
Ivomec (ivermectin)
? Subcutaneous 
injection 
300 µg/kg 
adult 
L4 --- 
adult 
L4 adult 
adult 
L3, L4 adult high 
Levasole, Tramisol (levamisole)
? 1 day 
treatment in 
feed, 
water, or oral 
gel 
adult --- adult adult adult adult medium
Piperazine
? 50 mg/lb 
 File G1049 under: SWINE 
C-9, Swine Management 
Issued October 1991; 7,500 printed. 
  
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with 
the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, University of 
Nebraska, Institute of Agriculture and Natural Resources. 
University of Nebraska Cooperative Extension educational programs abide with the non-discrimination 
policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.  
body weight 
1 day, in 
water or feed 
adult --- --- --- --- --- low 
Safe-Guard (fenbendazole)
? 1.36 mg/lb 
body weight 
in feed/day, 3 
to 12 day 
treatment 
adult 
L3, L4 
adult 
L3, L4 adult 
adult 
L3, L4 --- adult medium
TBZ (Thiabendazole)
? Fed 
continuous 
45.4 to 
908 g/ton 
adult --- --- --- --- --- dependson dose 
TBZ paste (Thiabendazole)
 --- --- --- --- adult --- medium
* Relative cost at the time of publication. Low is less than $.15 per 100 lbs body weight, medium is about $.30 to $.50 per 100 
lbs body weight, and high is over $.85 per 100 lbs body weight.  
L3 = Third stage larvae are those that migrate (liver, lungs or within tissue)  
L4 = Fourth stage larvae are those immediately preceding adulthood (in the gastrointestinal tract)  
Atgard is a product of Fermenta Animal Health; Banminth is a registered trademark of Pfizer, Inc; Ivomec and TBZ are 
registered trademarks of Merck and Co.; Levasole is a registered trademark of IMC/Pitman-Moore; Safe-Guard is a registered 
trademark of Hoechst-Roussel Agri-Vet Co; Tramisol is a registered trademark of American Cyanamid


G91-1049 Controlling Internal Parasites in Swine

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Historical Materials from University of Nebraska-Lincoln Extension Extension 1991 G91-1049 Controlling Internal Parasites in Swine B.E. Straw University of Nebraska - Lincoln Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist  Part of the Agriculture Commons, and the Curriculum and Instruction Commons Straw, B.E., "G91-1049 Controlling Internal Parasites in Swine" (1991). Historical Materials from University of Nebraska-Lincoln Extension. 1153. https://digitalcommons.unl.edu/extensionhist/1153 This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. G91-1049-A  Controlling Internal Parasites in Swine This publication addresses the identification, prevention and control of internal parasites in swine and lists characteristics of principle dewormers. B. E. Straw, Professor, Veterinary Science  z Roundworms  z Whipworms  z Lungworms  z Nodular Worms  z Anthelmintics for Swine  z Prevention and Control   Whether pigs are raised in confinement or on pasture, controlling internal parasites is essential to the overall herd health program. Recent studies by Tom Kennedy of A.E.F. Research, Inc, Waunakee, WI, have shown that worm infestation is prevalent on both a farm and individual pig basis. Of the farms examined, 91 percent raised pigs on concrete, wire or slotted floors, but more than 90 percent of all farms were infested with one or more kinds of worms.  Worms reduce growth rate and feed efficiency, and damage tissues, predisposing pigs to infection by other diseases. Hale and Stewart estimated that worm infestation could add $1 to $14 to the feed and maintenance cost of finishing a pig (Table I). Economic loss also will be incurred when affected tissues are condemned at the slaughter plant.  Table I. Prevalence and cost of parasites  Prevalence of internal parasites in Midwestern hogsPer pig cost ($) of worm damage at three levels of parasite infestationParasite % Farms infested% Pigs infestedat slaughter Light Moderate HeavyAscaris suum (roundworm) 70% 60% 1.92 3.21 5.56 Trichuris suis (whipworm) 45% 19% 1.44 4.31 13.76 Oesophagostomum (nodular) 33% 4% 1.25 2.09 3.69 Roundworms The large intestinal roundworm, Ascaris suum, is the most common internal parasite of pigs and is found in almost every herd in Nebraska. Eggs of Ascaris suum are small--about the diameter of a human hair and almost invisible. Eggs can withstand severe cold, dryness, most chemical disinfectants and can live at least seven years in soil. The eggs pass from pigs in manure. When they leave the body with the feces, they are in an early stage of development and are not infective. Within a few weeks a tiny larva develops inside the egg.  Pigs become infested by consuming food and water contaminated with infective worm eggs. When a pig swallows ascarid eggs, the shells rupture in the intestine and larvae are liberated. The larvae burrow through the intestinal wall and enter the blood stream, which carries them to the liver. From the liver, larvae travel in the blood through the heart to the lungs where they burrow through lung tissue and enter large air passages. The pig coughs and forces worms into the throat where they are swallowed and passed into the small intestine--this time to mature and grow to adults. It takes about four days for larvae to reach the liver, nine days to reach the lungs and 15 days to complete the trip to the intestine. Worms grow to egg-laying adults in about 60 days.  Clinical signs of roundworm infestation are primarily associated with larval migration through the lungs. Pigs have a dry nonproductive cough, loss of appetite and weight, rough hair coat, increased temperature, and an increased rate of respiration accompanied by thumping.  Both young and adult worms cause damage. Young worms destroy liver tissue, causing abscesses and scars. In the lungs they penetrate blood vessels, destroy tissue and plug smaller air passages. Damage to the integrity of the lung tissue predisposes pigs to pneumonia. Adult worms in the intestine rob the pig of food, block the gut and excrete substances which interfere with digestion.  Diagnosis is made by microscopic identification of eggs in the feces. Adult worms in the intestine and scars in the liver are seen on postmortem examination.  Whipworms Trichuris suis, is called the whipworm because it is shaped like a whip. A mature whipworm is 1 1/2 to 2 inches long. It has one of the simplest life cycles known. Eggs are laid in the large intestine and pass from the body in manure. They develop into infective larvae in 21 days. After being swallowed by a pig, the young larvae burrow into the wall of the large intestine. Within a few days, the young worms emerge, attach to the lining of the large intestine and grow to maturity. A life cycle lasts 70-90 days.  Whipworms cause considerable inflammation and irritation of the intestine. Whipworm infestation is characterized by loose stools which in many cases progresses rapidly to a severe, bloody diarrhea. Diagnosis is made by finding worm eggs in the feces or by recovering worms at necropsy. If sexually immature worms are causing the damage, eggs may not be found in the feces.  Lungworms Metastrongylus (lungworm) 7%     Stephanurus (kidney worm)   3.16 6.09 13.39 (Adapted from T. Kennedy material, personal communication; and O. M. Hale, and T.B. Stewart, Agri-Practice, April 1987)There are three species of Metastrongylus or lungworms. Lungworms are thread-like, white worms up to 2 1/2 inches long. Female lungworms live in air passages in the lungs where they produce large numbers of thick-shelled eggs, which the infected pig coughs up, swallows and passes in manure. Earthworms swallow the eggs, which hatch in the earthworm's intestine and become infective in three to four weeks.  Pigs become infested by eating earthworms which harbor the infective larvae. Lungworm infestation causes coughing and shallow breathing. Hemorrhages occur on the surface of the pig's lungs during early stages of lungworm invasion. Constant irritation by lungworms can bring about consolidation of lung tissue around sites occupied by worms. Tips of lungs become grayish or whitish and very hard in some cases. Secondary pneumonias are common. Pigs infected with lungworms tend to go off feed, become unthrifty and fail to grow.  Diagnosis is made by isolating eggs or larvae from feces or by demonstrating larvae in nasal secretions. Frothy mucus may be found at necropsy. When it is collected in a dish containing water and examined microscopically, the worms are easily observed.  Prevent lungworm infestation by keeping pigs in lots where they cannot contact earthworms. Earthworms thrive in old hog lots in which manure and litter have accumulated, or on permanent pastures and in low fields that receive drainage from higher ground.  Nodular Worms The nodular worm, Oesophagostomum dentatum, is a small, whitish worm about 1/3 to 1/2 inch long that lives in the large intestine. Worm eggs pass from the pig in manure and under favorable conditions of moisture and temperature, develop to form infective larvae in three to seven days. These larvae can survive up to 10 months in mild climates but will die in cold temperatures. In the Midwest, these parasites survive by wintering in breeding stock. The pig will eat infective larvae with feed or water. The worms encyst in the lining of the large intestine and cause nodules to form. This condition is called "pimply gut". Within six to 10 days after infection, the young worms emerge from the nodules and grow to maturity. The life cycle requires 50 to 53 days.  These immature worms can cause loss of appetite, diarrhea or constipation, and anemia. Diagnosis is made by microscopically identifying the characteristic worm eggs in the feces, or by recovery and identification of adult worms at necropsy.  Anthelmintics for Swine When selecting a dewormer for swine, consider these five factors: efficacy of compound, spectrum of activity, mode of administration, margin of safety and cost of treatment. The spectrum of anthelmintic activity determines the number of species affected by the dewormer. Certain swine anthelmintic drugs are highly effective against only one species. If the herd problem involves several species of parasites, use a dewormer that effectively removes many species.  Prevention and Control Since moisture favors the development of worm eggs into larvae and dryness kills them, reduce moisture to decrease parasitic contamination. Pastures should be well drained and feeding areas should be raised above ground. Many worm eggs can survive for long periods in dirt. Research has shown that ascarid eggs on unplowed pasture lots remained infective for seven years--whipworm eggs can remain infective up to six years. Rotating hog lots will help prevent infestation.  Worm eggs are easily carried by the wind or water and have been recovered from soil on roofs, window sills, and sides of buildings.  Table II. Approved claims of principle dewormers (listed alphabetically by trade name)  Types of worms controlled roundworm whipworm nodularworm kidneyworm threadworm lungwormrelativecost*Atgard (dichlorvos)z Mixed in feed and fed for 1 to several days, according to directions, to pigs of any age adult L4 adult L4 adult L4 --- --- --- mediumz Top dressed on feed for 1 day to sows, boars, gilts adult L4 adult L4 adult L4 --- --- --- low Banminth (pyrantel tartrate)z Continuous use in feed, 96 g/ton, or a 1 day treatment in feed at 800 g/ton adult L3, L4 --- adult --- --- --- high z 3 day treatment 96 g/ton adult --- --- --- --- --- low Hygromycin Bz 12 g/ton continuous in feed adult adult adult --- --- --- mediumIvomec (ivermectin)z Subcutaneous injection 300 µg/kg adult L4 --- adult L4 adult adult L3, L4 adult high Levasole, Tramisol (levamisole)z 1 day treatment in feed, water, or oral gel adult --- adult adult adult adult mediumPiperazinez 50 mg/lb  File G1049 under: SWINE C-9, Swine Management Issued October 1991; 7,500 printed.   Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources. University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.  body weight 1 day, in water or feed adult --- --- --- --- --- low Safe-Guard (fenbendazole)z 1.36 mg/lb body weight in feed/day, 3 to 12 day treatment adult L3, L4 adult L3, L4 adult adult L3, L4 --- adult mediumTBZ (Thiabendazole)z Fed continuous 45.4 to 908 g/ton adult --- --- --- --- --- dependson dose TBZ paste (Thiabendazole) --- --- --- --- adult --- medium* Relative cost at the time of publication. Low is less than $.15 per 100 lbs body weight, medium is about $.30 to $.50 per 100 lbs body weight, and high is over $.85 per 100 lbs body weight.  L3 = Third stage larvae are those that migrate (liver, lungs or within tissue)  L4 = Fourth stage larvae are those immediately preceding adulthood (in the gastrointestinal tract)  Atgard is a product of Fermenta Animal Health; Banminth is a registered trademark of Pfizer, Inc; Ivomec and TBZ are registered trademarks of Merck and Co.; Levasole is a registered trademark of IMC/Pitman-Moore; Safe-Guard is a registered trademark of Hoechst-Roussel Agri-Vet Co; Tramisol is a registered trademark of American Cyanamid

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G91-1049 Controlling Internal Parasites in Swine

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